Fukushima Nuclear Accident – 17 March update

The crisis at the Fukushima Daiichi nuclear power station is approaching a weeks’ duration. The on-site situation remains extremely serious, with glimmers of hope being shrouded by a shadow of deep uncertainty.

If you’ve not been following the situation on BraveNewClimate, and want to recap, please read these recent updates:

Japan Nuclear Situation – 14 March updates

Further technical information on Fukushima reactors

Fukushima Nuclear Accident – 15 March summary of situation

Fukushima Nuclear Accident – 16 March update

These are assumed knowledge for understanding the rest of this post. The preparation of the material below was aided greatly by the private advice of my acquaintances in the nuclear engineering field.

As predicted yesterday, attention over the last 24 hours has focused on the critical situation with the ponds used for temporary storage of spent nuclear fuel at the individual reactor units, before it is moved to a centralised facility on site. Although this old fuel has lost much of its original radioactivity, the decline is exponential (see this figure) which means that thermal energy must continue to be dissipated for months.

This figure shows the location of the spent fuel ponds:

The problem, as is explained in this updated fact sheet by the NEI, is that as these ponds heat, their deep covering of water (which acts as a radiation shield and a cooling mechanism), starts to evaporate. If they reach boiling point, because of lack of operational maintenance systems, the evaporation rate will accelerate. If exposed, the there is a potential for these old fuel rods and their zirconium cladding to melt, and radiation levels will rise considerably. The heat generated in spent fuel depends on a number of parameters, including: (1) level of build-up of fission products (burn-up) and (2) length of time after having been taken out of the reactor.

The spent fuel pool temperature has been rising gradually since last Friday due to the loss of cooling pump (presumably no power source). As we know from previous updates, the side of the Reactor 4 building has been lost (it’s the left-most of the 4 buildings in the following image):

The Unit 4 reactor was already shut off for periodic maintenance when the earthquake struck. IF the fire was caused by hydrogen,  its only plausible source would be spent fuel degrading in steam. Under this scenario, initial inventory was probably reduced by sloshing during the earthquake, and heat generation and resulting evaporation/boiling would thereafter be more than double that in other pools due to it containing freshly off loaded fuel. Temperature indications in the absence of water would be that of the mixture of steam and air in the location of the thermowell.

Nothing can be confirmed at this stage. As has been the case throughout this crisis, information is hard to come by and must be pieced together.

Are the spent fuel in the pools in Units 3 and 4 are now uncovered? TEPCO claims that NRC Chief Jaczko was wrong in claiming this, that the spent fuel pools in both Units 3 and 4 need some refilling but are NOT dry. (The Japanese authorities are apparently saying they’ve seen water still in the Unit 4 pool.) The big concern here is that unlike the releases from damaged fuel in the reactor cores of Units 1, 2, and 3, which were largely filtered by scrubbing in the containment suppression pools (wetwell torus), releases of volatile fission products (e.g., cesium and iodine) from these spent fuel pools have direct pathways to the environment, if they remain dry for an extended period.

Efforts to deliver water to these pools have proven to be very difficult, and fuel damage may be occurring.  If they are exposed, then the use of the evaporation of salt water as a heat sink over periods of more than a few days is not viable because the quantities of salt deposited as the water evaporates becomes large in volume and plugs the flow paths through the fuel, degrading heat removal. Everything that is cooled becomes a heat sink to condense anything volatilised. Unfortunately, a fresh water supply seems difficult to come by.

One option is to bring fresh water by helicopter, but the amounts needed imply a large number of flights and gamma radiation levels are high above the pools making overflights hazardous. NHK has reported a number of  successful water dumps using helicopters today. If radiation levels on the ground increase further, personnel access will become more challenging. Additional spent fuel is stored in pools in Units 5 and 6 and in a large centralized storage pool. A key issue is how to continue to make up water to these pools in the longer term, particularly if site access becomes more difficult.

It was announced at a press conference that a total of 11 specially-equipped vehicles will be used to spray water on the crippled reactors at Fukushima-1 after an access path is cleared using bulldozers. The big advantages of fire trucks over helicopters is that their water cannons can be better aimed, from the side rather than the top, and their operation is continuous rather than in batches so they can deliver vastly more water. It is clearly an appealing option. An additional 130 personnel have also been moved back on site to help with work.

Some additional key information from NEI:

Crews began aerial water spraying operations from helicopters to cool reactor 3 at Fukushima Daiichi shortly before 9 p.m. EDT on Wednesday, March 16. The operation was planned for the previous day, but was postponed because of high radiation levels at the plant. News sources said temperatures at reactor 3 were rising. Each helicopter is capable of releasing 7.5 tons of water.

Spokesmen for TEPCO and Japan’s regulatory agency, Nuclear and Industry Safety Agency, on March 17 Japan time refuted reports that there was a complete loss of cooling water in the used fuel pool at Fukushima Daiichi reactor 4.

The spokesmen said the situation at reactor 4 has changed little during the day today and water remained in the fuel pool. However, both officials said that the reactor had not been inspected in recent hours.

“We can’t get inside to check, but we’ve been carefully watching the building’s environs, and there has not been any particular problem,” said TEPCO spokesman Hajime Motojuku.

At about 7 p.m. EDT, NISA spokesman Takumi Koyamada said the temperature reading from the used fuel pool on Wednesday was 84 degrees Celsius and that no change had been reported since then. Typically, used uranium fuel rods are stored in deep water pools at temperatures of about 30 degrees Celsius.

Recent radiation levels measured at the boundary of the Fukushima Daiichi plant have been dropping steadily over the past 12 hours, Japan’s Nuclear and Industrial Safety Agency said on Wednesday night (U.S. time).

At 4 a.m. EDT on Wednesday, a radiation level of 75 millirem per hour was recorded at the plant’s main gate. At 4 p.m. EDT, the reading at one plant site gate was 34 millirem per hour. By comparison, the Nuclear Regulatory Commission’s annual radiation dose limit for the public is 100 millirem. Radiation readings are being taken every 30 minutes.

Japan’s Chief Cabinet Secretary, Yukio Edano, said earlier today a radiation level of 33 millirem per hour was measured about 20 kilometers from the Fukushima Daiichi plant earlier this morning. He said that level does not pose an immediate health risk.

Edano said that TEPCO has resumed efforts to spray water into the used fuel pool at the damaged reactor 4.

TEPCO also continues efforts to restore offsite power to the plant, with up to 40 workers seeking to restore electricity to essential plant systems by Thursday morning, March 17.

Based on the information coming out of TEPCO, it appears that units 1,2 and 3 remain critical but stable. Partial melting has almost certainly occurred in all three cores. There was definitely a period of no water injection because of a pressure buildup caused by stuck relief valve — always a potential issue for in high pressure systems. This figure illustrates the current state of play with the reactor units and spent fuel ponds:

The following is the latest status report, with timelines, from the Federation of Electric Power Companies of Japan (FEPC) Washington DC Office.


• Radiation Levels

o At 6:40AM (JST) on March 16, a radiation level of 400 milli sievert per hour was recorded outside the west side of the secondary containment building of the Unit 3 reactor at Fukushima Daiichi Nuclear Power Station.

 At 6:40AM on March 16, a radiation level of 100 milli sievert per hour was recorded outside the west side of the secondary containment building of the Unit 4 reactor at Fukushima Daiichi Nuclear Power Station.

o At 8:47AM on March 16, a radiation level of 150 milli sievert per hour was recorded outside the secondary containment building of Unit 2 reactor of Fukushima Daiichi Nuclear Power Station.

 At 8:47AM on March 16, a radiation level of 300 milli sievert per hour was recorded between the exteriors of the secondary containment buildings of Unit 2 reactor and Unit 3 reactor of Fukushima Daiichi Nuclear Power Station.

 At 8:47AM on March 16, a radiation level of 400 milli sievert per hour was recorded outside the secondary containment building of Unit 3 reactor of Fukushima Daiichi Nuclear Power Station.

 At 8:47AM on March 16, radiation level of 100 milli sievert per hour was recorded outside the secondary containment building of Unit 4 reactor of Fukushima Daiichi Nuclear Power Station.

o At 10:40AM on March 16, a radiation level of 10 milli sievert per hour was recorded at the main gate of the Fukushima Daiichi Nuclear Power Station.

o At 4:10PM on March 16, a radiation level of 1530 micro sievert per hour was recorded at the main gate of the Fukushima Daiichi Nuclear Power Station.

o For comparison, a human receives 2400 micro sievert per year from natural radiation in the form of sunlight, radon, and other sources. One chest CT scan generates 6900 micro sievert per scan.

• Fukushima Daiichi Unit 1 reactor

o At 6:55AM on March 16, the pressure inside the reactor core was measured at 0.17 MPa. The water level inside the reactor core was measured at 1.8 meters below the top of the fuel rods.

• Fukushima Daiichi Unit 2 reactor

o At 6:55AM on March 16, the pressure inside the reactor core was measured at 0.043 MPa. The water level inside the reactor core was measured at 1.4 meters below the top of the fuel rods.

• Fukushima Daiichi Unit 3 reactor

o At 8:37AM on March 16, white smoke was observed emanating from the vicinity of the secondary containment building.

o At 9:55AM on March 16, the pressure inside the reactor core was measured at 0.088 MPa. The water level inside the reactor core was measured at 1.9 meters below the top of the fuel rods.

o At 11:32AM on March 16, the Japanese government announced that the possibility of significant damage to the primary containment vessel was low.

• Fukushima Daiichi Unit 4 reactor

o At 4:08AM on March 15, the temperature of the spent fuel pool was measured at 183 degrees Fahrenheit.

o At 5:45AM on March 16, a fire occurred in the vicinity of the third floor of the secondary containment building.

o At 7:26AM on March 16, no flames or smoke was observed and thus it was concluded that the fire extinguished on its own accord.

• Fukushima Daiichi Unit 5 reactor

o At 4:00AM on March 16, the temperature of the spent fuel pool was measured at 141 degrees Fahrenheit.

• Fukushima Daiichi Unit 6 reactor

o At 4:00AM on March 16, the temperature of the spent fuel pool was measured at 137 degrees Fahrenheit.

• Rokkasho Reprocessing Plant and Accompanying Facilities

o As of 12:00PM on March 15, power generation of all facilities was restored to the commercial electricity grid from backup power generation systems. It was confirmed that no fire, damage to equipment, injuries to personnel occurred. Radiation levels were measured at a normal level of safety.


Further important information can be read at World Nuclear News, especially Problems for units 3 and 4 and Attempts to refill fuel ponds. Some key extracts:

The Japan Atomic Industry Forum reports that the level of water in unit 4’s fuel pond is low and damage to fuel stored there is suspected. Efforts are underway to refill the pool, including an abandoned attempt to douse the building with water from an army helicopter, hoping to get some to go through the damaged building. The temperature of the pond was last known to be 84ºC on 14 and 15 March, said the International Atomic Energy Agency. There was no data for today…

Efforts to cool the partially exposed cores of units 1, 2 and 3 continue. So long as radiological conditions allow, a team of workers pumps seawater into the reactor vessels. This boils away, raising steam pressure which must later be vented. Fuel assemblies are exposed by between one and two metres at the top, but the high thermal conductivity of the zirconium alloy rod casings helps cooling with just the lower portion of the rods submerged. This process is set to continue until the heat produced by the core has reduced so that the entire core can be covered.

The lack of recent temperature data may stem from a broken gauge. Please read the above WNN links for further details.

In sum, this accident is now significantly more severe than Three Mile Island in 1979.  It resulted from a unique combination of failures to plant systems caused by the tsunami, and the broad destruction of infrastructure for water and electricity supply which would normally be reestablished within a day or two following a reactor accident. My initial estimates of the extent of the problem, on March 12, did not anticipate the cascading problems that arose from the extended loss of externally sourced AC power to the site, and my prediction that ‘there is no credible risk of a serious accidenthas been proven quite wrong as a result. It remains to be seen whether my forecast on the possibility of containment breaches and the very low level of danger to the public as a result of this tragic chain of circumstances will be proven correct. For the sake of the people there, I sure hope it does stand the test of time.


  1. This guy talks about the possibility of a catastrophic loss of cooling to the reactor core. Yesterday, you said “…the reactor cores will need significant cooling for at least another 5 days before stability can be ensured.” Is that how long it will take to remove the threat he envisions? Or, will it take longer, or has that danger already subsided? Thanks for the info.


  2. Does anyone have a credible source of monitoring data regarding spread of cesium 137 (etc) particulate level contaminants along the Japan coast?

    NHK TV Japan yesterday interviewed 2 experts who both agreed that amidst all information (factual and hysteric) the most important data is missing – i.e. monitoring presence of slow decay contaminants. NHK stated there is a website with such data but did NOT provide either data or the URL!

    Thanks very much for Barry’s efforts with providing the information to date – much appreciated.


  3. i am also frustrated with the governement and tepco’s inability to release current radiation levels… they are checking them every 30minutes but not telling anyone what they are…
    the situation is clearly running out of control… they could at least be live blogging radiation levels


  4. Drew, I don’t know if this is what you’re asking for but the most recent number I’ve seen is 3.7 mSv/hour (3,700 uSv/hour) at a distance of something like 130-180 meters from unit 3 at the Fukushima Daiichi site. The level was essentially unchanged pre- and post-water-drop.


    Not sure about monitoring levels offsite, haven’t seen anything recent reported.

    Also, it’s worth noting (as it pertains to this most recent update) that further airdrops of water will apparently not happen today. Not particularly surprising, since apparently they haven’t been very effective.


  5. Barry,
    I have found BNC a very useful source of information is a sea of miss-information from media sources.
    I am hoping that these accidents provide lessons that will be applied to a future expanding nuclear power generation rather than result in early closure of existing and cancellation of new nuclear plants. The world needs as much low carbon emission energy as possible, including wind, solar, geothermal and nuclear.


  6. MIke… my problem is those figures are from 10.. it is now 6:35 and the media has said dick all…. its rather frustrating…. as like many people in japan i want to know if its time for me to give up hope and bail south or keep hanging on… hourly updates wouldnt hurt


  7. @Drew FYI there are some non-official rough sources for radiation data in Tokyo such as this:

    The measurements are predictably LOW – which is reassuring at the current time. The levels have varied based on time and wind directions etc obviously. I guess that indicates the site’s monitoring is working.

    That site’s data DOES NOT directly indicate much regarding particulate level contamination.

    The variations of background radiation may provide an indication about long-lived radioisotope (particulate) levels though.

    Note that I’m assuming this because short half-life sources of radiation coming from the Fukushima reactors presumably would decay (fully?) by the time they reach as far as Tokyo.

    The thoughts above are just my own – I’m not an expert.


  8. Thanks again for a nice update.

    Re radiation outside the plant I got this site:
    Unfortunately it lacks the closest area (earthquake/tsunami damage presumably), but is good for reassuring people a bit further away.

    Agree about the need for isotope data – but it is early days yet, and with the extensive damage due to the earthquake/tsunami, I’m not _that_ surprised we don’t have detailed data plotted on a map yet. With the wind being what it has mostly been and the (supposed) leakages not that catastrophic it is probably not seen as that prioritized yet.

    I’m waiting and hoping for good news about getting normal systems operational again once electricity is fully hooked up.


  9. Prof. Brook,

    I also wanted to thank you for this little mea culpa:

    “…my prediction that ‘there is no credible risk of a serious accident‘ has been proven quite wrong as a result. It remains to be seen whether my forecast on the possibility of containment breaches and the very low level of danger to the public as a result of this tragic chain of circumstances will be proven correct.”

    I’m not a fan of fear-mongering but I’m definitely a fan of data, and the data seem rather clear on the point of a “serious accident”. It’s nice to see someone in this day and age (and on the Internet, even) actually acknowledge even the possibility that they might have been incorrect. Perhaps I shall have to reassess my recent estimate of your site’s credibility (though I’m not so sure about your last guest poster’s piece).


  10. Nothing can be confirmed at this stage. As has been the case throughout this crisis, information is hard to come by and must be pieced together.

    I’ll echo that. It is rather frustrating. And while it is really important not to spread panic, FUD will spread even more if people distrust the agencies and information is sparse or confusing. The nuclear industry has a horrible track record in terms of transparency in general, here in Germany it is commonplace that accidents and events that would have required notification only come out years later.

    As for Tepco’s track record…

    Tokyo Electric Power Co injected air into the containment vessel of Fukushima reactor No 1 to artificially “lower the leak rate”. When caught, the company expressed its “sincere apologies for conducting dishonest practices”.

    This was in 2002. It goes on and on like that. The Japanese quoted say they don’t really trust the information policy. I trust the engineers to make honest judgements, but how much worth is that if the company is overriding safety precautions (and subsequently blaming it on the engineers)?

    Fukushima nuclear plant owner falsified inspection records (The Australian)
    Bungling, cover-ups define Japanese nuclear power (AP)

    Another good source of real-time updates: http://gakuranman.com/great-tohoku-earthquake/#live


  11. thank you for keeping us as updated as possible. i’ve been sharing your posts around, because i have been finding them very informative and devoid of hysterics. i really appreciate it.


  12. Japan’s Chief Cabinet Secretary, Yukio Edano, said earlier today a radiation level of 33 millirem per hour was measured about 20 kilometers from the Fukushima Daiichi plant earlier this morning. He said that level does not pose an immediate health risk.

    Surely that millirems unit is wrong. Such a level at 20km would imply a colossal level local to the plant. Microrems, surely.


  13. Prof Brook, there are reports of external AC power supply being restored as we speak…any opinion on that? Will that lead to quicker resolution of the problem? Or we have crossed a point where it matters much?


  14. My initial estimates of the extent of the problem, on March 12, did not anticipate the cascading problems that arose from the extended loss of externally sourced AC power to the site, and my prediction that ‘there is no credible risk of a serious accident‘ has been proven quite wrong as a result. It remains to be seen whether my forecast on the possibility of containment breaches and the very low level of danger to the public as a result of this tragic chain of circumstances will be proven correct. For the sake of the people there, I sure hope it does stand the test of time.

    Kudos to you, Prof. Brook. That took guts. And thanks for the update.


  15. I know the Japanese Government has many grave problems to deal with but the lack of timely and accurate information can ony lead to speculation & rumour. I know they too were frustated by the lack of info they were getting from TEPCO but they have the ultimate authority and responsiblity to inform their people. I hope they can be” encouraged” to imrprove,

    The power company TEPCO and the saftey regulators NISA’s public disclosure however have been risible and I hope that after the crisis is resolved senior people in these organisations are held to account for this failure.


  16. When Cyclone Yasi was forecasted to tear along the Queensland coast, Queensland’s Premier clearly and bluntly told people that there would be substantial deaths if people did not take relevant precautions. No mass panic ensued, people simply did as they were advised and sat tight. Fortunately the cyclone was less damaging than expected and no lives were lost. Ultimately, people were able to make informed choices for themselves and the Queensland Premier has been praised for her handling of the situation.

    Fukushima is admittedly a more complex situation; however it is now starting to seem like the same old mistakes, specifically involving corporations/governments, are being made. Confusion, misinformation, and some would say outright lies – is this really the ideal situation for the people of Japan who have to deal with this crisis?


  17. On current NHK TV live news, it was stated that at an altitude of 90 metres above the No. 3 reactor radiation there was measured around 86 mSv/h when the helicopters were dispersing water on the reactor. Also there was a mention that there is more than 700 fuel rods in the No. 3 reactor SFP and the rods are exposed to the air, meaning the water level is too low.

    On the status of the No. 3 reactor, I have a theory of what happened: On wednesday there was a white smoke coming from No. 3 reactor building. It is suspected, that the smoke was most likely water vapour from SFP there. I think, as the reactor core or parts of it were melting, the temperature around reactor core and reactor containment vessel rose to the point of actually heating the SFP to over 100°C and subsequently the water level in the pool quickly went down and exposed the fuel rods in SFP which were continuing to heat not only from their residual nuclear activity, but also from the near reactor core melting.


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  21. Reported by NHK, as of now, the police have aborted the operation of cooling the SFPs by water cannons due to high radiation levels and are seeking shelter now.

    As I see it, the external AC power is the most crucial thing that could stabilize the situation.


  22. Barry – I said previously that those who know you personally can vouch for your integrity and honesty. You have proved this to be true. Thankyou for the informative post updating the situation so honestly. We can continue to rely on you to give us the truth, as you understand it, of the current situation just as you have been doing throughout this crisis.


  23. I am reading you bulletins with interest because my Japanese wife is determined to visit her sister near Tokyo on Saturday. Of course this is a worry.

    I have heard that these reactors are 1960 cheap design and the containment is not as strong as they might be, so assumptions that they would contain a total melt down may be optimistic?

    I find it extraudinary that they cannot get a hose into each of these ponds, but then seeing the ponds are situated on a high level floor explains that. Seems like a design fault.


  24. What about the boric acid drop they were considering?
    They have been reports they were trying to buy it from South Korea.

    It appears odd that they didn’t try to procure first just in case it would be necessary to use it.


  25. Delivery of water via high velocity stream looks pretty crude. Isn’t the splashing and possible pool overflow going to spread active fission products?
    Wouldn’t a snorkel truck or even a repurposed concrete pump be a more precisely targeted tool for refilling the spent fuel ponds? Is a spray preferred to a stream for some sort of physical reason involving fuel rod cooling?
    A video camera for operator aiming and better situation assessment would be a nice option to add if one doesn’t come on the standard model.


  26. Is there any chance someone can answer this:

    Are the doses being bandied around in mSv actually properly weighted dose readings, or has it just been shorthanded with 1 rem = 1 Sv?

    It makes a big difference if the dose readings include beta decays or not, which appear to make up at least 50% of the energy in the daughter decay cycles.

    At the very least if it does include betas, the workers are protected from that portion of the stated doses by their suits. If it is only gammas then they will get the stated dose.

    Insights from Dr Brook or others would be appreciated.


  27. Woo! trucks are spraying according to NHK as of 19:35 (40 minutes ago).

    And w/ that i need to get some sleep. If when i wake up the power-line is connected, i’m going to do a little dance.


  28. You know, it says a lot about the ‘blogosphere’ when a mea culpa such as Barry’s is considered remarkable. :-(

    The updates are certainly appreciated, in any event.

    Regarding the water cannons – can they not be “set and forget”? I.e. set up to fire water into the reactor building, then personnel evacuate to a safer distance while it continues to spray water into the building for a while?

    And if they have Chinooks there – couldn’t they have flown in half a dozen diesel-powered generators by now to provide a few MW of electricity? Surely that would be enough to get some of the pumps running again, until the main AC supply could be restored? (a quick search reveals 0.5MW skid-mount generators at about 3 tonnes, which is well within the capabilities of a Chinook)


  29. Well done for admitting that ‘you have been proven quite wrong. I will keep reading your updates.

    I still feel that there is hiding of information from the authorities. What is the potential outcome of all this for the world?


  30. Are the doses being bandied around in mSv actually properly weighted dose readings, or has it just been shorthanded with 1 rem = 1 Sv?

    1 rem is not 1 Sv, it’s 0,01 Sv or 10 mSv.

    Some of the published readings are given in grays, while others in sieverts. It’s possible, or even likely, that some direct measurements are made in CPS with simple GM meters and converted to grays with meter spesific efficiency factors and then to sieverts with a Q factor of 1.

    That would actually result in underestimation of actual doses for persons not wearing any protective clothing, but relatively accurate doses for persons with breathing protection and some kind of garments preventing direct skin contact of contaminated dust.

    However, the national network and other thin window proportional gas counters spesifically designed for exact dose rate measurements of nuclear accident or weapon detonation fallout will give you accurate sieverts also taking into account beta and alpha components. There must be such portable equipment at the site also.


  31. Prof Brook,
    I echo the sentiments of others and honour your humility in correcting your earlier assertions about the gravity of the situation.
    Your clear explanation of the facts that do appear to be hard and fast (with caveats where necessary)have been useful to me to attempt to piece together the story of what is happening! Ignoring the pro/anti flaming and trolling on your blog threads the remainder has been an informative insight into the many challenges and technical difficulties that must be overcome in a crisis such as this.
    I remain aggrieved that we are so easily minded to forget the rest of the human tragedy in Japan which hasn’t disappeared overnight – whatever the outcome we should remember in our hearts the plight of those who have lost all and more.
    Thanks again.


  32. Red_Blue, thanks for that. Sorry for messing the units, I dont use rem much and got mixed up with the Q factor.

    So … if they are using a normal GM meter it will be a good estimation at the site, but bad for regular folks, and if they are using sensitive equipment it will be a good estimation for people downwind, but an over-estimation for the workers (by a fairly big factor)

    Is there anyway to know what they are doing the measurements on?

    I have heard them talk about dosimeter readings from the workers, which are probably all GM counters, and thus accurate in what they are trying to measure yeah?


  33. DrD, it IS a crude effort. But as I understand it, they are battling for access at the moment, radiation is presumably too high for anyone to go close enough to put a pipe up there. Measurements by the helicopters showed 4,130 microSievert/h 300m above ground and 87,700 microSievert/h at 100m.

    It is not clear if the regular cooling systems still work at the damaged reactors (they look a bit too beaten up for my taste though), but AC power would certainly be a great progress, be it only to hook up the cooling in the currently undamaged reactors.
    The worst case scenario, IMHO, is now that they would further loose access to the facility, e.g. due radiation from a fire in untit 4’s spent fuel pool – at which point they will have problems with keeping the currently heating up, but still not boiling SFP’s in units 5 & 6 in check. I also wonder what is going on in Unit 1 & 2 SFP’s (“no info”).


  34. I have heard them talk about dosimeter readings from the workers, which are probably all GM counters, and thus accurate in what they are trying to measure yeah?

    Personal dosimetry for an exposed person after exposure is entirely different from measuring effective dose rates to prevent “overexposure” (as in exceedance of certain regulatory limits or for evacuations/withdrawals on encountering health damaging levels). If a person is exposed very high radiation doses requiring medical attention, dosimetry can be accomplished from bloodwork.

    Nuclear workers usually wear dosimetry devices (either badges or recording units) that keep track of their personal doses. However, at least the badge type devices are usually designed for quite low total doses encountered in normal plant operations. The digital recording units on the other hand are capable of recording accident levels.

    Simple badges are also made for rescue personnel that have very high doses marked (usually with alert colors or authorized doses for different types of operations marked in simple termps), but whether there will be enough stocked to distribute to every worker in a disaster this large with possibly hundreds of people working at the accident site for a week, is a nother question. I hope they do have them and don’t have to rely on health physics personnel with portable counters following every “fire fighting attack” done in the heavy radiation zone.


  35. According to the Tokyo data, at 10 am on March 15 there was an alarming spike in airborne I-132 levels (281Bq/m3) and Cs-137 levels (60Bq/m3).
    Both have gone down since then with the latest readings (3/17) showing none to negligible amounts.
    Before leaving my home in Tokyo I will be checking these numbers – can anyone give me a rough level above which it would be advisable to stay indoors?


  36. No, that is what I was saying, they have mentioned personal dosimetry devices (I called them dosimeters – thats what we call them at work)

    The digital recording units (we have some at work too) – do they only record photonic radiation or alphas and betas too?


  37. My reactions and suggestions are deeply colored by my ignorance of the specific facts on the ground. Radiation levels, access to the foot of the building and simple availability of the equipment may all dictate the use of the water cannons rather than alternative equipment.
    A benefit of the concrete pump is its ability to cantilever into the space above the spent fuel pool without there being a human at the top of the building.


  38. I think one of the major tragedies to come from this nuclear accident (getting away from the arguments over safety and the future of nuclear power) is the fact that after such a devastating natural disaster, rather than concentrating on relief to those who are injured, homeless, hungry, etc., all efforts and attention seems to be on the nuclear danger. The nuclear aspect has created such a danger and possibility of further future dangers that everything else has been sidelined. Can such a situation be acceptable, just for the sake of having nuclear power ? Can AGW only be tackled in such a way that we create other problems relating to nuclear contamination ?

    For me, nuclear power must only be a temporary stop-gap towards the ultimate aim of total reliance on renewables, and I think we need to divert money and resources to this aim, while making sure that the nuclear resources we have or plan to have (temporarily, hopefully) are as safe and secure as possible – i.e. MORE safeguards, not less.

    Hopefully the world can learn from this tragedy that not only must we get away from carbon-based sources of energy but we must also move away from ALL sources of energy which endanger whole populations and the environment. And the sooner the better.


  39. Is there anyone who can do the math as to when the sediment of solids in the seawater now used for cooling will block the cooling effect to the extend that the decay heat can no longer be sufficiantly influenced by this process?


  40. @bchtd1parrot It would be nearly impossibly to even perform even a crude calculation of the decay in heat transfer.

    Usually if the water temperature rises above 60 C you can expect to start having fouling issues after some months. But that is the case on turbulent flow in heat exchangers, quite a different scenario than this one.


  41. Some promising updates from WNN on perimeter radiation levels:

    Radiation at site border
    Despite high levels of radiation close to the units, levels detected at the edge of the power plant site have been steadily decreasing.

    17 March, 4.00pm
    0.64 millisieverts per hour

    17 March, 9.00am
    1.47 millisieverts per hour

    16 March, 7.00pm
    1.93 millisieverts per hour

    16 March, 12.30pm
    3.39 millisieverts per hour


  42. Before leaving my home in Tokyo I will be checking these numbers – can anyone give me a rough level above which it would be advisable to stay indoors?

    Becquerels are extremely small units of activity and m^3 of air is a huge amount of air.

    Occupational limit for Cs-137 is about 2,200 Bq in m^3 and 740 Bq in m^3 for I-131. Remember, these are occupational limits, which have a very high buffer against health effects.

    For short term exposure, you should be safe even with levels much higher than these. I would also expect even P1 particulate filtration face masks to provide a high degree of protection against inhaling any particles with Cs-137 or I-132 (protection factor of x4 for work use). A P3 half mask should give a protection factor of about x30.


  43. Also, to give you an idea of what kind of Cs-137 and I-131 levels would require staying indoors by European standards:

    Breathing air with Cs-137 concentration resulting in 10,000 Bq/m^3 for 10 hours results in a dose of 1 mSv (less than average yearly dose of background). If the same air has I-131 concentration of also 10,000 Bq/m^3, dose to the thyroid is 14 mGy for an adult = 0,7 mSv.

    Sheltering inside is indicated if the effective dose so avoidable exceeds 10 mSv during two days. So accordingly, by government estimates you should be just fine staying outside even if the concentration is on the order of 50,000 Bq/m^3 for both Cs-137 and I-131.

    For comparison, the threshold for acute radiation poisoning would be about 1 hour spent in 100,000,000 Bq/m^3 of Cs-137 (or 100 MBq/m^3). However, at that high levels of fallout you should really take shelter in spaces deep underground or at the center rooms of large concrete buildings.


  44. I think that admission (below) is very welcome. I would urge some of the other people on this blog that seem to be in a state of semi denial about the seroiusness of this incident could take a leaf from Barry’s book. My concern is that some of the more extreme positions taken by some of the pro nuclear boosters have severley undermined the credibility of their positions. I think we are all agreed though that this shocking situation is only making the circumstances worse for those Japanese who need our support.

    From Barry Brook
    “My initial estimates of the extent of the problem, on March 12, did not anticipate the cascading problems that arose from the extended loss of externally sourced AC power to the site, and my prediction that ‘there is no credible risk of a serious accident‘ has been proven quite wrong as a result. It remains to be seen whether my forecast on the possibility of containment breaches and the very low level of danger to the public as a result of this tragic chain of circumstances will be proven correct. For the sake of the people there, I sure hope it does stand the test of time.’


  45. To be fair Barry’s comments were far more based on reality than most of the crazy anti-nuke crowd… who will get away for a month of Sundays saying 100,000, or 1 million people were killed at Chernobyl.


  46. Kyodo reports:

    NEWS ADVISORY: TEPCO says water shots effective in cooling fuel pool as steam rose (21:21)

    Earlier Metropolitan Police Department crowd control water cannon vehicle failed, but the attempt was followed by two other, GSDF controlled vehicles. This is supposed to be reactor 3, since helicopter recon of reactor 4 building detected some water in that pool.


  47. The Chernobyl situation seems to be hotly debated. Certainly the statements of only 50 people seriously injured/dead as a result seem to lack all credibility. I think the central point here is that early predictions of the triviality of this event have clearly been proven wrong. I think the fact that Barry has acknowledged this is to his credit, showing that the pro-nuclear side of the argument is equally capable of arguing from an emotive point of view as any other. A point worth remembering in future discussion.


  48. Barry – the admission is to your very great credit. Its part of a much better tone here over the last few days with people from initially very polarised and distant positions coming together as the evolving realities of the situation have broken down many of the barriers. Its a terrible situation to witness and I hope that the university, your peers, your sources and yes your previous detractors will take great pride in the signficant public service being performed here (with our tax dollars.)
    [Moderator – Blog host runs this site in his own time with his own money – no tax dollars needed]
    Who knows at this stage what this means for the future (wholly inappropriate to progress now), but we have all for sure learnt some very real and hopefully persistence lessons. I personally hope that the barriers to respectful, openminded, balanced and suitably critical communications within and between different groups in the climate solution space can persist.


  49. A friend of mine at Areva believes that as you allude Barry, salt may well be becoming the problem.

    She thinks that if the pool is simply cracked and the water is “flowing” out as fast as it flows in there is a chance that some salt is being carried away. If however the pools are indeed intact and the contents are boiling off quickly then, well, that’s it….

    Additionally, she believes the ~6MW (BWR1-designs) coolant pumps run with salt water will either not work or not last, or are damaged already and will need overhauling/repair. Restoring the power to pump more salt-water via salt-damaged pumps may not be an answer either.

    She also believes the usual idle flow mass is ~1-2/tonnes of water per minute. That ain’t coming from trucks on the ground and definitely not from helicopters.


  50. All six reactors are having cooling problems. If one of the units becomes impossible to control and all six units are impossible to get near to, what would the outcome be? I would imagine that all remote control systems are not available anymore.


  51. Reports on Twitter that power cable just got connected on Daiichi 1. Can this be confirmed?

    Where is the information coming from? Kyodo reports that connection work will continue Friday (it’s 2221 in Japan at the moment, still over 1.5 hours until Friday).

    All six reactors are having cooling problems.

    Who is reporting this?


  52. is “hotly debated” similar claims that global warming is all cosmic rays, or contravenes the 2nd law of thermodynamics, in opposition to the tireless work of the IPCC. UNSCEAR report on Chernobyl is pretty clear. That is not to say Chernobyl wasn’t a bad incident but some claims are absurd.


  53. @Red_Blue: None on my end. Their previous tweets seemed to be in concordance with actual confirmed reports so I wanted to confirm the information.

    As there’s no official confirmation I will treat it it as speculation for now.


  54. @Red_Blue No idea, its been setup recently that account. First twitt was 14 hours ago only:

    > “There is problem at the Fukushima Daiichi Nuclear Power Station. “We deeply apologies for the anxiety and inconvenience caused”.”


  55. Regarding the spent fuel pools (SFPs), the most critical question appears to be whether they are leaking, either from damage to piping or from cracks in the reinforced concrete (they are above ground level).

    Damage could have been caused by the earthquake’s ground acceleration or by nearby explosion or fire.

    Are there credible reports that address this?

    If an SFP has a big enough leak, adding water will not keep the fuel rods covered. What then?

    Is it better to add water to damaged assemblies, cooling them somewhat, but causing steam with heavy nuclides (e.g. Cs, I, Sr) to enter the atmosphere?

    Or is it better to let them overheat, dry, and possibly try to smother any resulting zirconium fire Chernobyl-style, with sand?

    If there is no major leak, it would seem that one strategy would be to set up a fire hose to pour in water. There must not be access to any nearby river or other freshwater source, as all reports refer to the use of seawater. If unattended, the pool would overflow, and radioactive water would spill down on the side of the containment, contaminating it. The water would run to the basement, onto the plant grounds, perhaps into the ocean.

    But even if personnel were withdrawn from the site, this would keep the SFP full, as long as the pump ran. It would also address the problem Barry discussed, of salt accumulating in the pool.

    It seems as though TEPCO has avoided approaches like this, with high costs but higher net benefits.


  56. What is the worst case scenario in case of spent rods in #4 ? What kind of radiation hazard are we talking about if those rods melt – without any containment structure …

    The other thing is – even if the grid power is restored – will the controls and plunbing still work ? If the blasts have taken them out – grid power may not be that useful.


  57. Der Spiegel reports that TEPCO expects power to come online “this evening” – probably refering to CET, which would mean within the next 6 hours or so. Power will be restored to Units 1 and 2 then. It also says a provisional power generator is going to be operational ‘soon.’


  58. W_Nuclear_News World Nuclear News
    UPDATE 3: 1.41pm GMT Fire trucks in action: Attempts to refill fuel ponds http://bit.ly/fVRvaD

    After clearing heavy explosion debris from tsunami and the various explosions across the site over the last six days, eleven high pressure fire trucks are now showering the reactors. It is thought they are targeting unit 3. Tackling that first may lower the high radiation levels on the ground near that unit, allowing more flexibility and speed when tackling unit 4 or any subsequent units whose fuel pools may get into trouble.


  59. 10 mSv is micro-sieverts or milli-sieverts?

    Sievert is a SI system unit, where universally “m” is the prefix for milli, as in one thousandth. The universal prefix for micro (one millionth) is “µ”, often substituted with “u”.

    The radiation measurements around the evacuation zones show most increases towards nort west from Fukushima Daiichi, in the direction of Fukushima City. Highest measurements as of 1400 JST today are 170 µSv/h (measuring station 32, situated 30 km from the plant along road 399.


  60. What volatile fission products are of concern in the spent fuel bays (that have fuel at least several months old)? In the main article there is this comment

    releases of volatile fission products (e.g., cesium and iodine) from these spent fuel pools have direct pathways to the environment, if they remain dry for an extended period.

    But would there actually be any iodine to worry about any more (8 day half life)? Is there secondary production from another decay chain? I know there will be some Iodine 131 but that has a million year half life so virtually harmless.

    How much cesium might be release from these spent fuel bays and how much of a concern would they be? Is cesium only mobile by its precursor Xenon which would also be stable by now in the spent fuel bays.

    Am I missing something or is there very little volatile fission product danger here and with the low heat rate also very little chance of zirconium producing hydrogen?

    David L.


  61. Can anyone speculate as to the best and worst case scenarios from here?

    Worst case is that a fire breaks out and is not controlled due to high radiation levels and is left to burn for weeks, spreading to one reactor unit to the next, ultimately reaching the external spent fuel pool building and the separate dry storage, releasing the maximum estimated 70% of the activity remaining in the fuel rods at the site (4000 tons). Compare this to Chernobyl where 150 tons were at stake and 4% was released.

    So the absolute worst case, that is only realizable if all efforts to control the situation are stopped not reconstituted for weeks, is much worse than Chernobyl.

    The best scenario is that
    1) external power is connected in a couple hours, plant RHR and emergency core cooling pumps are restarted, there is no siginificant damage to them, 2) reactor containment breaches can be plugged or otherwise dealt with in the coming days,
    3) spent fuel pools on top of the reactor buildings are first filled by the trucks to such levels that the water provides enough radiation protection to approach the reactor buildings to restart their makeup line and heat exchanger pumps and
    4) effective containment and further treatment of the tens of thousands of tons of contaminated water already pumped to the reactor buildings is achieved during the coming weeks.

    In the best scenario the worst radiation release is already over with only negligible releases to come and protection measures for most of the 20-30 km zone (except to the direction of Fukushima City) can be lifted wihin days and for areas about 5-20 km within a weeks.


  62. As someone who understands electronics and a little bit about power generation, I really fail to understand why external AC power took this long to restore (assuming it’s being restored soon).

    Lets assume worst-case, the plant’s cooling systems use some non-standard voltage, with multiple phases. This is an electric power generation plant, so you cannot convince me that they do not have someone on staff who knows how to splice together an appropriate plug for a “good enough” temporary solution. It is true that depending on how your cooling systems run (likely use pumping motors), you don’t want to use bad power or you’ll burn them out and leave yourself in a worse situation. However, again, this is a power generation plant, someone on site *must* be experienced enough to solve this issue given materials at hand.

    Also, portable generators of the size/capacity that they would likely need would be quite useless indeed if they could *only* provide one type of AC power. I find it quite inconceivable that people trucked-in or flew-in generators of sufficient capacity only to discover “oh, our plugs don’t fit, and we can’t change the power signal to match what is needed…, oh well lets throw our hands up and pour water in.”

    There has to be some other major logistical nightmare contributing to the lack of AC power, such as large amounts of debris to clear from the tsunami, or a damaged external-power circuit/breaker at the plant itself.


  63. Red_Blue, I don’t think there are significant containment breaches. My understanding, sparse as it is given the data to hand, is that there is damage to the concrete containment (perhaps only external) and fractures in the wetwell torus of Units 2 and 3. I have seen no evidence to indicate that the drywell or reactor vessels of any of the units has yet been breached.


  64. I know there will be some Iodine 131 but that has a million year half life so virtually harmless.

    I think you meant I-129 which has a 15 million year half life, I-131 is the one with 8 days. I think you’re right that for iodine, the spent fuel pool situation is not dangerous, or in other words, cesium would start to dominate after about 50 days since last criticality.

    My understanding is that Cs-137 is the major or even key concern because it would be released in such small particles (aerosol size) and spread effectively by winds. Zirconium-95 and niobium-95 are also in the same activity range after a couple hundred days (applicable at least to reactors 4, 5 and 6, I still haven’t seen data on when 1 2 and 3 were last refuelled and how fresh the fuel in their pools could be), but their expected particle size would be much bigger, hence less spread.

    Somebody must have already calculated what difference MOX in reactor 3 could have to the situation, but this data is probably only available to the Japanese government at this stage.


  65. Red_Blue,

    > Highest measurements as of 1400 JST today are 170 µSv/h (measuring station 32, situated 30 km from the plant along road 399).

    Wikipedia says 1 μSv = 0.1 mrem. With a US DoD reference, “An acute whole-body dose of under 50 rem [500 mSv] is typically subclinical… 50 to 200 rem [500 to 2,000 mSv] may cause illness but will rarely be fatal. Doses of 200 to 1,000 rem [2 to 10 Sv] will probably cause serious illness… Doses of more than 1,000 rem [10 Sv] are almost invariably fatal.”

    A steady 170 µSv/h dose means ~4 mSv/day or ~120 mSv/month.

    For on-site readings, Attempts to refill fuel ponds ( 17 march 2011 0425 GMT) has:

    “Radiation at ground level near units 3 and 4 is high: peaking at 400 mSv/hr on the inland side of unit 3, and 100 mSv/hr on the inland side of unit 4.”

    To likely avoid dose that would mean radiation sickness, a worker might accept a cumulative exposure of 500 mSv. That would be a bit more than one hour at the unit 3 reading, and five hours at the unit 4 reading. High likelihood of radiation sickness (but not death) at 2 Sv would mean four hours/twenty hours.

    That would mean a very large number of people rotating through the site, to keep even a small constant presence. Is that happening?…

    Brave men.


  66. …any chance of assigning probabilities to those scenarios?

    Without very detailed data, which is lacking at this moment, such probabilities would have extremely low confidence factors and as such of not much use.

    Let’s say that the best scenario is still several orders of magnitude more likely than the worst scenario and that the most likely consequence is much closer to no further releases than massively expanded release.


  67. NHK reports results of the high pressure spraying as inclusive. “Five fire engines loaded with 30 tonnes of water”.

    It’s not stated explicitly, but I think they arrived with the (fresh) water, which would tend to suggest salt build-up is (now) part of the issue at hand.

    30 tonnes of water is not going to significantly cool anything in that plant. The mass of water is fractional compared to the sources of heat.


  68. According to the N.Y. Times the spent fuel ponds are 40′ x 40′ x 45′ deep. That would require 2,000 tons of water to fill completely. One helicopter load is 7.5 tons.



  69. amac78,

    ‘That would mean a very large number of people rotating through the site’

    I don’t know about a ‘large number’ but workers are being rotated from other nuclear facilities according to Tepco as of 9AM Tokyo time.


  70. What about all the water that they pour on the reactors and pools? Will it be contaminated with radioactive materials and flush it into the ground, ocean etc.? Is that an issue or not?


  71. Barry Brook

    What is the basis for the NEI information cited above that says the spent fuel pond in Reactor 4 could take “a few weeks” before evaporating?

    Yesterday I calculated and posted that a spent fuel pond 12m by 12m with a 8m water freeboard above the rods would evaporate in ~ 5 days. I used IAEA info that said all Reactor 4 fuel had been loaded into the pond on Nov 30 2010 and MIT NSE decay heat for Reactor 3 (same size as 4) at 4 months postshutdown 6.3 MW . See mitnse.com/2011/03/16/what-is-decay-heat?


  72. Can anyone speculate as to what all of this means (best case vs. worst case scenarios) to those of us here in the States and in other parts of the world? What if any impact will this have on us healthwise? Experts have been quoted as saying any sort of health risk outside of Japan is highly unlikely, but I have been following another forum and one post said something about the UN producing a model that shows a plume of “low-level” radiation reaching the west coast of the USA on Friday (am assuming that means tomorrow the 18th). Just not sure what to make of it all.


  73. A lot of Russians and Ukrainians survived long term who were on duty the night of the Chernobyl disaster, although most of the firefighters on the roof were to die horrible deaths (Previk, the Lieutenant died fast but his superior, the guy in charge of the whole fire brigade, lived to 2004 and then died of stomach cancer IIRC). Both he and Previk were awarded Hero of the Soviet Union. Of 8000 workers, I think about 6500 ran away permanently during the night or on Saturday the 26th of April, 1986.

    Speaking of brave men (no women?) in Japan, what efforts are underway to find volunteers for working on the site and what countries besides Japan are trying to find them? Should Obama make a call for brave Americans over 65 to volunteer, resulting in medical care for the rest of their lives and medals plus the gratitude of the Japanese (and the world’s) people? I would imagine that volunteers should come from mainly those over 65 because they might expect more to die of natural causes before any cancer hit.

    I’ve seen no mention of US or even Japanese military incentives to volunteer. Rapid promotion and medals? If I were a leader, I might have publicized something to incentivize a large volunteer force so that specific individuals would be subject to less radiation via dilution.

    It might help to publish the full names of some of the helicopter pilots, calling them heroes specifically. What gamma radiation are they probably facing?

    Back to Chernobyl, the two top managers IIRC were convicted and sent to jail for 10 years each. One was released after 5 years. The other was released sooner because he went insane.

    I think the person or person who recently pushed to use the MOX fuel need(s) to be put on trial and possibly sent to jail.

    I would like to see more on this site regarding indicators that plutonium might have been released into the atmosphere.

    Is the US Navy still monitoring the plume out at sea?


  74. > Jeremy, on 18 March 2011 at 12:56 AM said:
    > I really fail to understand why external AC power
    > took this long to restore

    As I recall all the switching and connection panels are located below ground level and that whole area was flooded right at the beginning; that was one of the early problems.


  75. What about all the water that they pour on the reactors and pools? Will it be contaminated with radioactive materials and flush it into the ground, ocean etc.? Is that an issue or not?

    The plant has facilities for treating contaminated reactor coolant water, but these facilities are designed for fresh water. Some changes are probably necessary for sea water treatment.

    SFP or reactor cooling water is only extremely slightly active and usually it could be discharged directly to sea without any treatment or to a river after just some delay (in a pond to let most contaminants settle on the bottom sediment).

    However, since fuel damage has been confirmed by Cs-137 counts for 3 reactors and suspected for SFP 4, any water used to cool these would likely be high or medium activity nuclear waste and not desirable to dump it directly to the Pacific Ocean.

    However, considering population effects, dilluting it to a vast ocean is much, much better than letting the same amount of contaminants get airborne and spread on land.

    It’s likely that some radioactive water has already leaked from the plant, but measuring the activity in nearby waters will probably take some time to arrange. Such measurements would probably be only insituted when the immediate crisis has passed and various options for cleaning the reactor buildings are formulated.


  76. Appreciate the lower key coverage and discussions here. In contrast the hysteria on CNN last night was amazing.

    I’m amazed that with all the defense in depth put into these reactors, at the cost of vast millions of dollars, that apparently no external facility to refill the SFPs was put in place. You would think a simple backup pipe would have been rigged up, from the top of the pool down to the ground and then back a good safe distance.

    They should have figured this out 30 years ago, from TMI, when access to the containment building was lost for over a year due to radiation levels. The idea of not having access to the interior of the reactor building (or the immediate exterior) should have been considered and this seems such a simple safety device. All this strife for want of a simple pipe…


  77. “and my prediction that ‘there is no credible risk of a serious accident‘ has been proven quite wrong as a result. It remains to be seen whether my forecast on the possibility of containment breaches and the very low level of danger to the public as a result of this tragic chain of circumstances will be proven correct. For the sake of the people there, I sure hope it does stand the test of time.”

    I really appreciate your candour Barry, which is why I’ll be basing a lot of my decisions on this blog (I live about 100km from the Fukushima Plants).

    I have a question – what with what we know now – what are the news best-case and worse-case scenarios, disregarding further tsunamis?


  78. It seems a lot of people don’t understand why water is such a good coolant. Water doesn’t reach 100C and then suddenly turn into steam. To turn water into steam takes a very large amount of energy. This is true for pretty much everything though, but water has a particularly high value for changing states.

    To go from 100C liquid water to 100C steam takes 2270KJ (2.27 MJ) per kilogram.
    To heat water from 0C (liquid) to 100C(liquid) takes 418.7 KJ per kilogram.

    1 Kilogram of water is 1 liter. 1000 liters is one cubic meter of water.

    As you can see it takes significantly more energy to turn water from liquid to steam than simply heating the water up. This process is not commonly understood. If the water temperature is less than 100C then it can still absorb a lot more heat before disappearing. (Assuming no cracks)


  79. How about getting an old tanker (ship) and filling that up with a lot of the radioactive water and getting that out to sea? Does the design of new reactors include the ability to airlift the core out to the deep ocean and sink it? What are the parameters there?


  80. Kudos to BNC and Barry for a fact-filled website and a stubborn streak to focus on facts and physics vs. political agendas and personalities.

    I still hunger for fact-based, physics-bounded worse case scenarios.

    1. If a spent-fuel pool is permitted to go dry indefinitely, what happens? Certainly there has been credible research and modelling into this scenario over the years.

    2. Specifically, are there conceivable (AND within the constraints of physics!) mechanisms for nasty radionucleides to get lifted high enough above the SFP and the site to become widely dispersed by winds?

    I’ve read enough to understand this is not Cherenobyl. I’ve even read some posit that there is no way any nasty particles get above 1500 feet, and therefore do not get spread past a ~10km perimeter; (see for example Prof. John Eddington’s comments to British embassy personnel at http://ukinjapan.fco.gov.uk/en/news/?view=News&id=566799182.) But I haven’t seen really compelling arguments based on physics. Anyone?


  81. UN producing a model that shows a plume of “low-level” radiation reaching the west coast of the USA on Friday (am assuming that means tomorrow the 18th). Just not sure what to make of it all.

    That model was just to showcase the weather modelling of hypothetical fallout spread and contained no dose or dose rate estimates. All of the maps with dose rates extending outside of Japan so far have been crude fakes.

    Even should a very large release of radiation occur, health effects in the US would be minimal due to the distances involved. And with minimal I mean that the only result would be such a small increase in cancer rates that it could never be actually proven by the state of science today (due to cancer being such a common cause of death being caused by myriad of other causes and also because diagnosis is unable to show why it did develop for any one patient).

    If the amount of isotopes released can be accurately measured or estimated, then low dose calculations can be performed. From those very low dose estimates one can draw speculative cancer incidence numbers based on the LNT model (which is not scientifically proven, but used as the “worst case estimate” to base protection measures on) and then spread them to very large populations.

    Even if the LNT model was right, the more relevant health effect as a result of such small exposure would be psychological, in other words the total loss of quality of life due to fear than actual physical disease, spread over a large population.


  82. Susanne, on 18 March 2011 at 1:40 AM said:

    >Can anyone speculate as to what all of this means >(best case vs. worst case scenarios) to those of us >here in the States and in other parts of the world?’

    There is an old saying, the solution to pollution is dilution. There is going to be a lot of dilution traveling across 6,000 miles of ocean.


  83. Btw, in reference to my questions ~5 minutes ago, I’ve read the updated NEI factsheet (http://resources.nei.org/documents/japan/Used_Fuel_Pools_Key_Facts_March_16_Update.pdf) and find it still lacking. This leads a reasonable person to wonder if the worse-case scenario is bad enough they simply do not want to communicate it, i.e., if the SFP is not covered the zirconium cladding deteriorates (melts?) and a fire or explosion sends radionucleides high, far, and wide. Why can’t there be more discussion of this scenario in a physics/engineering context?


  84. >Hank Roberts, on 18 March 2011 at 1:42 AM said:
    >As I recall all the switching and connection panels are >located below ground level and that whole area was >flooded right at the beginning; that was one of the early >problems.

    Seawater flooding in that sort of equipment is death. I’m surprised it wasn’t designed to be above potential tsunami height considering that risk.


  85. > coalburner
    Remember the ocean around the plant, from which they’re apparently pumping salt water, is full of debris. They don’t have a port to bring in a tanker and don’t have pumps to remove water; they’re flooding the site.

    > bobash
    Google Scholar is a much better place to paste questions than ordinary Google; here’s yours:


  86. Shielding. What can be done?

    I know this sounds hokey, but can shielding be manufactured that would protect people in those pumper trucks? I’m sure the military NBC vehicles must be somewhat shielded to be able to survive.


  87. Dr. Brook writes,

    … Although this old fuel has lost much of its original radioactivity, the decline is exponential (see this figure)

    It’s not easy to characterize mathematically. However, in the early days, it’s the sum of many beta decays occurring at different rates, and although each individual beta-decay component is exponential in time, collectively they are a polynomial — I think — anyway, they add up, fairly closely, to the Untermeyer and Weill equation, which can be found on this site in previous postings of mine.

    Megawatts of residual power equals the need to evaporate gallons per minute of water. So adding tonnes of water is indeed very helpful.


  88. From a 2002 report concerning terrorism:

    “On average, spent fuel ponds hold five to 10 times more long-lived radioactivity than a reactor core.
    Particularly worrisome is the large amount of cesium 137 in fuel ponds, which contain anywhere from
    20 to 50 million curies of this dangerous isotope. With a half-life of 30 years, cesium 137 gives off
    highly penetrating radiation and is absorbed in the food chain as if it were potassium. According to
    the NRC, as much as 100 percent of a pool’s cesium 137 would be released into the environment in
    a fire.”

    Click to access alvarezarticle2002.pdf



  89. I’m failing to understand one thing.
    Red_Blue said that on the worst case, it can be worse than Chernobyl, so, in this case hole Japan would be infected, right?

    With this information that we have, its going well?
    Or it’s looking like the tendence is to get worse?
    I know about that status, but I can’t understand what is primordial there.


  90. > bobash
    > what if …

    Take some time to read in Google Scholar on your questions; much of this has been worried about and studied for 40 years, using many different scenarios, and there is no simple short bloggable answer.

    The people who can answer this kind of question will not be coming by here any time soon, I’d bet.

    This is something we need to educate ourselves about, that we’re all very new at.

    Examples just as places to start reading; look at the citing papers — it will give you an idea of what people know and an appreciation for how this is studied, in very detailed papers looking at individual variables, slowly accumulating information.


    Go back a few years at bravenewclimate and read up on the Gen4 reactor design, which incorporates a fuel reprocessing plant right on the site and can burn up leftover fuel rods from these Generation I, II, and III reactors.

    I wonder how the reprocessing plant that Japan is in the process of building came through the earthquake and how its design specs look now; anyone know?


  91. We seem to be entering the final stages of what can be done to bring this back under control. If the spent fuel ponds (especially the MOX rods in the #3 pond and the large stockpile of rods in #4) are exposed much longer, radiation around the site will be too high for workers to stand even for a few minutes. Let’s hope those power lines get there in time and the electrical systems of the plants are able to be brought back online. Direct pumping of seawater and boric acid must begin very soon or it will be too late. If that happens they will have to pull out all workers and the reactor / ponds will most likely meltdown and could even cause criticality. Pure water is actually very dangerous and could help cause criticality. Whatever the outcome it will be known in the next 24 hours.


  92. I am so glad that I found this site (rather by accident) and I appreciate your updates and insights, Dr. Brook. It’s much better than what’s on the MSM in the US right now.

    And kudos to you for your mea culpa–it took courage to say that, but in my eyes, you’re a hell of a lot better than most on the web.

    If this is possibly worse than TMI…well, let’s hope that things are able to be brought under control. The Japanese people have enough tragedy and heartbreak with the twin blows of the earthquake and tsunami…something that the media has all but pushed off the desk.


  93. We know that there is a full core-load of used fuel in the Unit 4 defueling pool, which was put there after the reactor was shut down for inspection on November 30. (Earlier on, I was not aware that this was the case, but I was wrong.)

    (Assumption I’ve made which may possibly be wrong: That that single core-load of fuel is the only fuel in the pool.)

    That fuel has been cooling for the last 3.5 months, or approximately 9.2 * 10^6 s.

    After this time, the radiothermal power output of the used fuel is small. Looking at Kirk Sorensen’s decay heat chart, we read that the decay heat is approximately 2 MWt. However, this chart is for a power reactor with a thermal power rating of
    3000 MW. (And I’ve done a not-really-precise job of eyeballing that chart.)

    But the Fukushima-I Unit 4 reactor has an electrical power capacity of 784 MW; that’s about 2352 MW thermal. So, we need to scale back the above figure commensurately; it’s approximately 1.6 MWt, from the entire core load of fuel.

    The latent heat of vaporisation of water, at 100 C, is 2260 kJ/kg.

    (Let’s assume, conservatively, that the water in the pool is boiling; it’s at 100 degrees C, and the only route of energy dissipation from the system is through vaporisation of the water. This also assumes that none of the energy released is stored in the water by means of a rise in the water’s temperature, because it’s already at boiling point, and that there is no functioning mechanism for otherwise cooling that water.)

    1.6 MW / (2260 kJ/kg * 1000 g/L) = 0.7 litres per second. 61 cubic meters per day.

    The used fuel pool at Vermont Yankee, which is also a GE BWR-4, is 40 feet long, 26 feet wide and 39 feet deep, and is normally filled with 35,000 cubic feet of water.
    (I found those numbers in one of the old NRC studies on fuel-pool LOCAs.)

    I will make an assumption that the Fukushima I Unit 4 used fuel pool has the
    same dimensions. (Aside: Given that it is a similar GE BWR of about the same age, the Fukushima incident really isn’t going to do any favors for the campaign to support the continued operation of Vermont Yankee.)

    The level of water in the used fuel pool is normally 16 feet above the top of the fuel assemblies. With the water level evaporating at the rate described above, the water level will drop by 2 feet per day.

    Uncovery of the fuel assemblies will take eight days. (Beginning from the point where the water level reached boiling point, after active cooling ceased.)

    (Working assumption which you may subject to some skepticism: That there is no form of leakage or other water loss pathway from the used fuel pool.)

    It seems plausible that a fire hose or something can be used to add water to the pool at a rate equal to this loss rate of 700 ml per second. The Chernobyl-style helicopter drops seem like overkill, and they are doing an effective job of whipping up “Chernobyl again” fear.


  94. Something not known yet (because the pools are too “hot” to get a visual inspection) is whether explosions in #3 or #4 buildings have caused cracks in their spent fuel containment pools. The pools are much closer to the explosion area than the reactor vessels. The top of #3 and especially #4 looks to have sustained serious concussion damage from the explosions around the area of the fuel ponds.


  95. I don’t know where Forbes.com got their information as to the technical layout of the plant site at Fukushima but the following article (with picture) is quite ominous.


    The picture shows two vertical tanks that were placed right at the water’s edge – completely destroyed and washed away by the tsunami. The article identifies them as the diesel fuel tanks that supply the generators. It seems plausible as there is something that looks (to me) like an oil sheen on the water in the “after” picture.

    If this is true it represents a critical error in planning the site; while the tanks are within the confines of the artificial harbor there is nothing protecting them in the event a wave overtops the seawalls.


  96. Since we all love the facts / numbers.

    “Figures provided by Tokyo Electric Power on Thursday show that most of the dangerous uranium at the power plant is actually in the spent fuel rods, not the reactor cores themselves. The electric utility said that a total of 11,195 spent fuel rod assemblies were stored at the site.”

    So, the worst case, in the event of an explosion and fire that cascades throughout the plant, is multiplied by 11,195 spent fuel rods, all stored in ponds and buildings that offer zero containment protection.

    Note; America and Japan store tens of thousands of so called “spent” fuel rods in these unprotected on site fuel ponds.
    [ad hom deleted]


  97. Japanese authorities have informed the IAEA that engineers were able to lay an external grid power line cable to unit 2. The operation was completed at 08:30 UTC.

    They plan to reconnect power to unit 2 once the spraying of water on the unit 3 reactor building is completed.


  98. Luke, I’m continuing to be curious why you assume things we’ve been told by the authorities are overly pessimistic. The ministry official interviewed some days ago said the new fuel planned for loading into Unit 4 is in the pool on the roof — you assume otherwise, but why? And you are assuming there’s no damate to the rooftop pool and calculating that the water in it can’t be boiling, but we’ve had observations that it is boiling, and the interview about the crack in the roof. The cites for those are in the earlier threads.

    I am _delighted_ that your assumptions are more optimistic than the news reports, and I really hope you are correct. Citations to the sources you are relying on — even if it’s “personal communication from insider who has to remain anonmyous” — would be helpful.

    Here’s the roof crack report. Again, I hope it’s wrong; if you are willing to give us sources you are trusting, citing your reason for assuming it’s wrong would help:

    “Japan safety agency: roof cracked at Fukushima No 4 reactor
    Tue Mar 15, 2011 8:46pm GMT
    TOKYO, March 16 (Reuters) – Two workers are missing after Tuesday’s explosion at one of the reactors … the No.4 reactor at the Fukushima nuclear plant …. Agency official also told a news conference there was a crack in the roof of the reactor building. ”

    If you are doing this on the basis of assumptions and logic rather than observations from the site, please do say that.


  99. @Luke Weston:

    Why do you persist in assuming minimal spent fuel in the reactor building pools when you were supplied with solid evidence to the contrary in your post yesterday?

    Here is the link again:

    Click to access 6-1_powerpoint.pdf

    Slide 9 says that as of November 2010, there were a total of 3450 spent fuel assemblies distributed among the reactor building ponds. And note that would not include the fuel from the building #4 core, since servicing had not begun in early November. There is absolutely no reason to think any significant amount of that spent fuel has been removed in the interim, since the common pool was already almost filled to capacity (6291 assemblies, total capacity 6840.)

    And since we are told approximately 700 spent fuel assemblies are produced each year and a total 10149 were being stored on site, it’s clear spent fuel was not being transported elsewhere at any appreciable rate.

    Note also, the dry cask facility was at capacity, so no fuel could have been moved there either.


  100. The level of water in the used fuel pool is normally 16 feet above the top of the fuel assemblies. With the water level evaporating at the rate described above, the water level will drop by 2 feet per day.

    Assuming your calculation is correct, then the consequence would be that the pool loses water not only by evaporation, but also by some other routes, a damaged pipe for example.


  101. I don’t think you can truthfully say that “there is a crack” in the roof of reactor building 4. More like partial collapse of the roof, with only frames remaining and some of those also bent. And we don’t have to rely on statements about it either, because we have public helicopter and satellite imagery available, such as this:


  102. Another issue which just occurred to me:

    We are told (http://www.iaea.org/newscenter/news/tsunamiupdate01.html) that the temperature in the Unit #4 spent fuel pool was 84 ˚C on 14 March, 10utc and still 84 ˚C one full day later (no data for the following day.)

    Laying aside the fact that it hardly seems credible the temperature would increase some 59 ˚C or so over four days and then completely stabilize, it’s also important to note the temperature in the pool is certainly not uniform as it is heating. I don’t know where the sensors are located, but unless they’re directly adjacent to the spent fuel assemblies it’s likely the temperature at the surface of those assemblies were substantially higher. Just as a pot of water heating on a stove forms water vapor bubbles on the bottom long before the pot boils, so there were surely such bubbles forming on the fuel rods by the time the pool temperature was as high as 84 ˚C.

    At that point, it seems possible to me that some oxidation of the zirconium cladding could begin even though the rods are not yet exposed above the water surface, adding more heat to the total. How much that might be is beyond my capacity to calculate. It might be negligible, it might not.


  103. On NHK, officials stated that the SFPs need 50 tons of water added per day to keep them topped off (the ponds hold 2000 tons of H2O). 30 tons of water was sprayed into the SFP at unit #3, and they are somewhat optimistic about that. Spraying operations will resume in the morning when it gets light. If we see less steam coming from #3 in the morning, that might be an indication of some success.

    There is absolutely no reason to think any of the SFPs are cracked or leaking. They are heating up, and losing water to evaporation. There is another week before they have to worry about getting water into SFPs at #5 and #6.

    While spraying operations continue, they are working to restore high voltage power to the facility. It would be nice to see that happen on Friday. They still have to hook some temporary pumps up because the on-site pumps were damaged by seawater (from the tsunami I suppose).

    They are doing a tremendous job of working to get this under control in a calm, deliberate manner.

    Note that there were only 4 helicopter passes, at varying heights (and they didn’t slow down for the drops). These may have been test runs for the most part, to gauge the exposure to the flight crews. More helicopter water drops may not be needed if the water cannons work.


  104. Looking at the way the water spread out as it was dropped from the helicopters, i’d be absolutely amazed if even a tenth of it made it into the pool.

    I’m sure the water cannons are substantially more accurate, but there’s likely some loss there as well.


  105. @Jan R.
    This is unrealistic, it would asume difference in temperature of over a thousand degree Celsius between the pool surface and the rod surface. That kind of difference creates a turbulence big enough to rip the construction apart. Even a few degrees in difference is enough to cause a quite violent circulation. As far as i understand it the whole idea of the fuel in cladding in water containment is that it puts a rather definite lid on the matter. Even rods partially exposed to air would receive sufficient cooling from conduction to stay solid, wouldn’t they?


  106. Although late on this thread, I would like to apologize to Barry Brook for writing such a flame-like comment on his early “nothing serious will happen” assessment.

    I should have used more respect, considering the years of good info Barry has put out (for free!) on this blog.

    However, I also appreciate Barry regaining his credibility by his admission he was wrong on several points that I raised.

    Both of us spoke in the “heat of the moment” (and what a hot moment, that first realization of nuclear tragedy in Japan …)

    Now I find Barry back at work, passing on useful information. I continue to learn from this blog, even though we fundamentally disagree on the role of nuclear power.

    I know I also make mistakes. We are human. And that is part of my problem with nuclear power over-all. With this technology, the price of mistakes is too high, in my opinion.

    Keep going Barry.

    Alex Smith
    Radio Ecoshock


  107. Kyodo:

    Hidehiko Nishiyama, [METI] spokesman, also said efforts to bring electricity back to the plant by using outside power lines accelerated Thursday.

    Electricity could be restored Friday or Saturday to recover the lost cooling functions at the No. 2 reactor building, which he said takes priority over other the troubled reactors as it cannot be doused since the roof of its building is still intact.


  108. @bchtd1parrot:

    I didn’t realize it took such extreme temperature to cause any oxidation. If it’s true that no oxidation would occur in the presence of steam at temperatures less than, say, 200 ˚C then I’ll agree it’s a non-issue.


  109. My working assumption is that the helicopter drops (which failed) and the pumper trucks (mixed reports) are trying to get more water into the SFP’s, NOT as even a semi-permanent solution, but INSTEAD to get the radiation down long enough to repair/install pump/pipe-based solutions that are more longstanding.

    All efforts seem to be still bound by the working assumption, “we need to get the radiation near these SFP’s down to levels that allow workers to get close enough to implement further stabilizing measures.”

    I don’t know what they would be do once they conclude one or more of the SFP’s is empty and compromised to a degree we can’t ever hope to get humans close enough to effect further solutions.

    The failure of TEPCO and the Japanese government to outline a worse-case scenario by which their progress (or lack thereof) can be measured has left the world to fill the void with their imaginations. And where radiation is concerned, laypersons (especially) have pretty rich imaginations.


  110. @seamus wrote:

    There is absolutely no reason to think any of the SFPs are cracked or leaking.

    The lower walls on unit 4 show evidence of being blown off with explosive force. Note some rebar bent out 90degrees from the building. The roof however has collapsed inwards. Perhaps an explosion happening lower down in the building w/o the weaker roof structure providing an easy escape for the pressure?

    Explosive structural dammage to the pool(s) seems reasonable especially after the 9.0 quake and aftershocks.

    Is there a secondary containment / liner on the pools that would prevent leaks from the primary concrete structure of the pools?

    Have there been any official explanations for the damage to unit 4?


  111. @Jan R.
    There is corrosion and there is burning. Both involve oxidization. Corrosion is not significant in this case and if i recall correctly even slightly reduces with rise of temperature. Burning requires way higher temperatures.


  112. New satellite image from DigitalGlobe shows how reactors 2 and 3 are still constantly steaming and how the explosion in 3 has clearly been the most energetic, with remains deposited on the turbine hall roof as well as 100 meters west even past the spent fuel wet storage building (this building apparently also has one wall panel damaged in the east face of the south wing according to previous imagery).


  113. What I’m starting to sense is that while the TV media is making ratings at the expense of my nervous system.
    Reading the last few posts, makes me wonder that maybe, while things may be bad, the operators are in control of themselves and doing things in a methodical fashion. For example, if things were really all that bad in SFP 4, why stop dropping water or using water cannons till tomorrow (their time) And the comment about getting power to reactor 2 first kind of puts the SFP issue in perspective.
    Contributing to this problem may be the cultural differences. As a media culture the US tends to over-hype things. Remember all the hype about 30,000 body bags going to the gulf before GWI ?
    Perhaps the Japanese operators are going about the business of solving problems just without the hype.


  114. > Jason
    > … The lower walls on unit 4 show evidence
    > of being blown off with explosive force….

    Yeah, I’ve been looking at that, and thinking the same thing. That explosion was underneath rather than above the fuel loading deck. On the diagrams those are shown as solid concrete, continuous with the whole inner concrete structure. But clearly wall panels blew out leaving a grid of columns and beams.

    I read that Units 3 and 4 shared a common control room. Anyone know where it is?


  115. @Jason
    The explanation for the blowout at nr 4 is condensation of diluting gas components on the cold inside of the roof, creating a mixture able to selfignite. That would speak against an explosion in lower parts. (i should start mass storing linx) Besides that the exploding substance is a relatively mild explosive, its the lot of it that made the bang big. Still you are right about the quake being the least unlikely reason for any crack. That being so, the position of the pond makes it less vunrable to quake influence. Static wise that is.


  116. Is there a secondary containment / liner on the pools that would prevent leaks from the primary concrete structure of the pools?

    Yes, a steel liner. According to NEI sourcing TEPCO, the steel liner is assessed as being intact even in the worst damaged reactor 3.

    Have there been any official explanations for the damage to unit 4?

    I don’t have a source at hand, but TEPCO representatives have speculated along the lines of the only reasonable explanation, which is zirconium/steam hydrogen production from the SFP rods and subsequent explosions.

    The reason being that since there are no rods in the reactor, there could be no hydrogen production there. Also, even though they attributed the first fire in reactor building 4 to an “oil pump”, clearly there are no materials with enough energy to blow up the building to such extent, so hydrogen is the only possible explanation.

    I’ve been somewhat sceptical of the explanation for the explosions of reactors 1, 2 and 3 as being caused by hydrogen vented from inside the reactors, because they should have vented it through the stack, filtered or not, instead of releasing it to the secondary containment where there was no actual facility to deal with it.

    We might eventually find out that the hydrogen explosions were all caused by hydrogen released from the SFPs. The reason why it hasn’t happened to reactor building 2 may be the whole punctured in it by the biggest explosion in 3. For the hydrogen to explode with sufficient force for breaking up concrete and steel structures, there needs to be proper air/hydrogen mixture, which isn’t going to happen if slowly generated hydrogen leaks out of a building (being lighter than air).


  117. Alex Smith wrote:

    “Although late on this thread, I would like to apologize to Barry Brook for writing such a flame-like comment on his early “nothing serious will happen” assessment.”

    What earlier “flame-like” comment?

    Oh yeah, it must have been deleted, unlike the ones praising Professor Brook.

    Seems like what’s “personal” *is* allowed here, but only in one direction. Just as with what’s allowed substantively here too.

    Apparently striving for TedCo level of credibility….

    Has any comment even made it here and not been deleted noting that TedCo has been blacking out many of the radiation readings in the immediate vicinity of the plant? So not allowing, for instance, the U.S. to do computer modeling of fallout patterns and exposures?

    What is this site anyway? At first it seemed open, and now it seems … embarrassed. A shame.
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  118. Says this is someone’s translation of a TEPCO Twitter feed that’s being written originally in Japanese.

    OfficialTEPCO is assumed to be the account for TEPCO proper, but currently it includes only Japanese references to their corporate website and not much more (general reference to the power shortage and the need for rationing and how they ask people to cooperate in saving power).


  119. > it takes significantly more energy to turn water
    > from liquid to steam than simply heating the water up

    Remember that a white plume doesn’t have to mean “steam” nor “boiling” — you get what looks the same from a distance from having a pool of warm water under cold and relatively dry air. The warm moist air blowing off the water gets carried out into cold environment and water vapor condenses making the white cloud.

    The local site temperature has been near freezing; if it’s been below freezing for long, that will make it relatively dryer air.


  120. I wouldn’t be too quick to recant your prediction as to the seriousness of the accident. This has been a disaster to the utility, and some workers are incurring relatively hight doses (certainly not life threatening). Personal opinion: The defining parameter will be dose to the public.

    I’m a little stumped by the report of 33 mR/hr at the 20 kilometer boundary, if the dose rate at the site boundary has been less than 100 mR/hr recently. That could be a hefty plume that hasn’t dispersed (which I doubt), or mistaken increments (should that have been mircoR/hr?). At any rate, if the public gets by with no more than 100 mrem, or even twice that, we should all agree it could have been a lot worse. I haven’t given up guarded optimism yet.


  121. > massive quantities of ‘dry ice’ in peanut form might
    > help control the temperature problems?

    It’s not available; no power, no refrigeration.

    There are some plant designs, not as old as this one but still antiquated, that actually use big blocks of ice in normal routine operation. They’ve had problems, e.g. here where “plant personnel questioned whether plant systems used to cool the reactor and containment during a postulated accident would function on a long-term basis ….” — good question.


    “Cook Nuclear Plant To Thaw Ice In Unit 2 Ice Condenser … April 1, 1998 — “… additional inspections of ice condenser systems. The purpose of an ice condenser is to absorb rapidly the thermal energy released to the containment in the event of a loss of coolant accident or steam line break in order to reduce pressure in the containment building. The ice condensers also must provide water for long-term cooling. In each of the two units, there are more than 2.5 million pounds of ice held in 1,944 48-foot-long cylindrical baskets. The primary maintenance issues relating to the ice condensers are basket ice weight, basket damage, missing fasteners in basket couplings, and debris contained in the ice. The units have been off-line since Sept. 9, 1997 when plant personnel questioned whether plant systems used to cool the reactor and containment during a postulated accident would function on a long-term basis. On Sept. 19, 1997, the Nuclear Regulatory Commission (NRC) issued a Confirmatory Action Letter which detailed the issues raised during an August 1997 NRC design inspection. …”


  122. “@American
    This aint Reuters and you didn’t get deleted did you?”

    Perhaps because the moderators are sleeping :P

    I am amazed at the quality (or lack thereof) of the evidence being used to support the “there is still water in the unit 4 pool” argument, though of course they could be 100% correct. But in terms of direct evidence of water in the pool, a little bright section (that “might” be water) of the frame of a shaky overhead flight video seems less than conclusive.

    Still, I suppose one operates with the best information one can get. Shaky or not, that’s why they have decided to focus their efforts on unit 3–hopefully that was a good decision.


  123. The statement about there still being (any) water in the pool was not an initiative, but a reaction on an earlier statement of there being no water in the pool, which can be rejected on basis of several indications besides visual observation. This rejection has relevance as the pool being dry would have permanent consequences.


  124. I would think that the best evidence for there being water in the unit 4 pool would be the radiation levels near the plant. Without water shielding the fuel, the radiation levels would be horrendus, probably hundreds to thousands of sieverts per hour. Since the radiation levels reported so far have been much less than this, I believe it is evidence that there must be water in the pool.


  125. nkinnear wrote,
    “Without water shielding the fuel, the radiation levels would be horrendus, probably hundreds to thousands of sieverts per hour.”

    Really? I haven’t checked the references, but others here have mentioned that the dose rate at the edge of a dry pool might be hundreds of Sv per hour…Or perhaps it was hundreds of Sv per minute, which would indeed mean thousands or tens of thousands of Sv per hour at the pool edge. Certainly not a good place for one’s honeymoon.

    I agree that it is another reasonable line of evidence, though. Still, 100 mSv/hour at the building exterior on the 16th is nothing to sniff at.


  126. One thing i would still like to know:
    The relative stability of the current situation is due to an enormous extend to the use of seawater as a coolant. Is this SOB? If not, why not? The reason i ask is because it would take an installation of no more than 50,000$ to have the pool levels guaranteed tsunami and earthquake proof if it was.


  127. Considering that much of the emergency systems stopped working soon after the quake and subsequently there was damage all around, and eventually radiation levels became too high for a detailed inspection – is there a damage assessment for the emergency equipment?

    I’m thinking about turbine blades and other things that could turn into an unpleasant surprise if power is restored and systems wound up again.

    Not that ignorance of the situation would prevent power from being restored. This is not a situation where there is much choice. But it would be reassuring to know they know that nothing will go up in sparks or pieces of turbine blade will suddenly start flying as soon as they wind up systems again.

    Any such assessment would probably be from Sat/Sun, so it would long be out of the news.

    In any case, their data seems to indicate that the risk of SFP evaporation in I-3/I-4 is low enough to justify trying to put power back to I-2 (and eventually I-1). Because they will have to stop splashing around water, particularly seawater, at least at I-3 (this is why the electricity hookup was postponed).

    As far as I can tell from the data at hand, I-1 is the only of the 4 that can be considered reasonably stable. The others have made too much trouble in the last 2 days to be considered anything other than in equilibrium, but precarious. E.g. even a light aftershock could displace the spent fuel in I-3/I-4 so that it will heat up or cool down.

    NOTE: there is AFAIK no MOX yet in the I-3 SFP. The current load of I-3 is the first MOX fuel used in Fukushima Daiichi.


  128. @nkinnear
    Evaporation of the pool water causes a gradual increase of radiation, but the instant the water is gone the temperature goes up dramaticly and with it the radiation of simple heat. An event that could be observed easily at great distance. Ever left any milk on the stove?


  129. @nkinnear: Above the plant. Too little is known about the conditions inside to make a reasonable assessment as regards radiation that has to pass through all this mess.

    @bchtd1parrot: “guaranteed”? “tsunami AND earthquake proof”? How?
    Earthquakes tend to produce a phenomenon known as “subsidence”; you should read up on it because it tends to render calculations on height of protective measures somewhat spurious. E.g. for Daiichi you can subtract half a meter or more from the height of the seawall relative to sea level.


  130. Mike:

    Yes, I believe so. I did a quick estimate for just Cs-137, and estimated that there is between 1 and 10 million curies of that isotope alone in a core’s worth of fuel. I agree that 100 mSv/hr is not good, things could get a whole lot worse if all the water was gone.


  131. From NEI March 17 11:35 EDT

    TEPCO officials say that although one side of the concrete wall of the reactor 4 fuel pool structure has collapsed, the steel liner of the pool remains intact, based on aerial photos of the reactor taken on March 17. The pool still has water providing some cooling for the fuel; however, helicopters dropped water on the reactor four times during the morning (Japan time) on March 17. Water also was sprayed at reactor 4 using high-pressure water cannons.


  132. I would think that the best evidence for there being water in the unit 4 pool would be the radiation levels near the plant. Without water shielding the fuel, the radiation levels would be horrendus, probably hundreds to thousands of sieverts per hour.

    When NRC studied this in 1997, they calculated that the dose rate at the edge of a pool with exposed rods would be 140 Sv/h. However, assuming the 400 mSv/h reading from the service road on the west side of unit 4 (and I must note that this 400 mSv/h is probably the maximum reading they would attempt to measure, in other words they would not send anyone closer than the dose rate where this was measured, even if they actually could get closer physically), that’s after about 50 m of air and shielding of the pool steel liner, concrete wall of the pool (and what remains) of the reactor building wall.

    If you calculated those shielding factor and then gave some consideration for local fallout, I would not be surprised if the numbers matched rather nicely. In other words, the radiation environment supports much more the hypothesis that the water level is at least way below the top of the rods and possibly even gone, since there have not been much steam or other visible discharge from reactor 4.


  133. Do people think the accident sequences involved:
    1. Loss of power after generator flooding, with operation of HPCI/RCIC systems on battery backup
    2. Exhaustion of battery backup, with failure of DC-dependant valve operation and turbine governors. Safety relief valves fail closed.
    3. Reactor vessel injection is lost, and cores degrade
    4. Drywells are flooded to above the level of the core, but reactor vessels fail in 1&3, either at penetrations or via creep.
    5. #2 experiences a very rapid failure, perhaps from core melt and water entering the control rod room, with pressure increase and release of hydrogen, steam and N2 into the reator building and turbine hall. Building damage ensues, etc.


  134. The turbine blades will not be spun up ever again on the damaged units. The reactors are defunct and will be forever…. The turbines installed will never spin again on this site for the damaged units….

    Issues do exist with repowering essential pumps as reports of distribution center floodings during the tsunami make them unusable to get the power to the pumps. This was actually the reason for the fire in the reactor MG set area on one of the units. A lube oil leak was ignited by efforts to restore power.

    Getting water to the fuel pools, containments and reactor vessels is still the priorities. One for cooling and 2 for shielding to allow access for further needed operations. After that establishing normal cooling methods will be pursued.


  135. Problem with normal at the boundary estimates is they assume only one unit issue. Multiple units are experiencing issues with shielding, fuel coverage and cooling…. It’s bad don’t get me wrong and likely multiple things are not good for water coverage…


  136. In my 6:15 AM post above, I think if one side of concrete pool wall has collapsed, it is possible that there would be tears in an intact steel liner.

    Water would leak to the level of bottommost tear and evaporate from there. Luke Weston estimated above that at 1.6 MW, evap is 61 m3/d (If different MW is used evap rate is 61 x (MW/1.6) m3/d. I’ve seen estimates of 1.6, 3.9 and 6.3 MW.

    7.5 ton helicopter drop is 7.5 m3 if all hit pool.


  137. Red_Blue, on 18 March 2011 at 6:18 AM said:

    > that’s after about 50 m of air and shielding of the >pool steel liner, concrete wall of the pool

    According to NEI.org one concrete wall of the pool is gone. Only the steel liner remains.


  138. @Paul
    Sparks may fly left and tight but the routine is not to simply put the plug back in. You check every component you can check before putting juice on it. Thats what i would do and i do that stuff for a living.


  139. According to NEI.org one concrete wall of the pool is gone. Only the steel liner remains.

    I don’t think that’s a correct interpretation of either NEI’s statements or the photos. The wall is gone in _one place_, but not all around the pool. The building wall on the other hand appears to have been damaged from all sides to a certain level and completely collapsed in some places up to different floors.


  140. >>Hank Roberts, on 18 March 2011 at 2:27 AM

    Some have been using Google Scholar to find relevant articles, and I believe I’ve found one:


    “Severe fuel damage experiments performed in the QUENCH facility with 21-rod bundles of LWR-type”
    L Sepold, W Hering, G Schanz… – … Engineering and Design, 2007 – Elsevier

    I was able to access the full article though a university library I have a subscription to. I’ll quote the relevant sections, perhaps people can help analyze it.

    The objective of the QUENCH experimental program at the Karlsruhe Research Center is to investigate core degradation and the hydrogen
    source term that results from quenching/flooding an uncovered core, to examine the physical/chemical behavior of overheated fuel elements under
    different flooding conditions, and to create a data base for model development and improvement of severe fuel damage (SFD) code systems….

    Test QUENCH-10 was
    to investigate the behavior of a fuel bundle during air ingress
    (simulating, e.g. a ****spent fuel pool accident****) with respect to oxidation
    and Zr nitride formation (Sepold et al., 2005).

    Test date Quench medium Injection rate
    Initial temperature
    H2 release
    before/during reflood

    QUENCH-10 July 21, 2004 Water 50 ∼2180 47/5 EC LACOMERA air ingress

    Zr + 2H2O → ZrO2 +2H2 +595 kJ/mol(Zr)1 (2)
    Further sources of hydrogen production are the steel–steam
    reaction and the oxidation of absorber material, e.g. B4C, as
    shown in Eqs. (3)–(5):
    B4C + 7H2O(g) = 2B2O3+CO(g) + 7H2(g) + 738 kJ/mol
    B4C + 8H2O(g) = 2B2O3+CO2(g) + 8H2(g) + 768 kJ/mol
    B4C + 6H2O(g) = 2B2O3 +CH4(g) + 4H2(g) + 965 kJ/mol
    The rate of the Zr–H2O reaction increases with temperature
    and is described by Arrhenius’ law.

    The QUENCH-10 experiment (Sepold et al., 2005) which
    was to simulate a storage-pool accident included an air ingress
    phase before quench did not cause an excursion of temperatures
    and hydrogen production during reflood, but a strong embrittlement
    of the cladding (Fig. 5). The small H2 release in the
    quench phase is the consequence of the especially strong oxidative
    metal consumption during the preceding test phases and fast
    flooding with water. Furthermore, the results of the QUENCH
    bundle experiment on air ingress demonstrate in accordance with
    ongoing separate-effects tests (Steinbr¨uck, 2005) the importance
    of nitrogen during Zr oxidation in air: favored by local
    Fig. 6. Embedded ZrN cells within the ZrO2 oxide scale at the 850mmelevation
    of rod 12 after quenching of the QUENCH-10 test bundle.
    defects ZrN phases form under consumption of ZrO2 leading
    to severe bundle degradation. Radially, Zr nitride is found
    between the surface of the -Zr(O) layer at the inside and the
    (spalled) zirconium oxide scale at the outside. Under the oxygen
    starvation conditions prior to quenching, the oxide scale is
    converted to a continuous nitride top layer. It is assumed that
    during quenching, this layer is partially re-converted into fragile
    ZrO2 except for some embedded nitride cells depicted in
    Fig. 6.


  141. @Paul
    A Tsunami is a magnitude of substance in motion. In most cases the phenomena is being opposed by tackling the magnitude. However, if you make a construct that can for itself deal with the substance and the motion, the magnitude is irrelevant. Or to put it otherwise. If i were to get caught in a tsunami, i would probably die, but my swiss watch would definitely suvive intact.


  142. Madison the issue plays out this way to me and it’s based on screening reports for facts.

    Normal ECCS cooling and makeup was lost either through the station blackout from the tsnumai or final loss of steam driven systems on multiple units. Each plant in deep trouble experienced this in some way.

    Then the trump card. Due to the station blackout, loss of power, efforts to lower primary containment pressure to prevent complete irreversable damage resulted in attempted controlled vents to the associated reactor buildings (secondary containment).

    These vents contained the hydrogen which ultimately collected in the upper elevations of the reacor building. Ultimately exploded destroying the refueling areas which are not hardened.

    Lack of power prevented ventilation dilution from the reactor building structure to the exhaust stack, creating the explosive concentrations.

    Beyond that, lack of ability to provide makeup and or unsubstantiated damage induced leaks to the fuel pools have increased local radiation levels even more as days passed.

    This is predicted and expected due to loss of shielding and potentially uncovering of stored fuel…. either through direct leaks and/or evaporation.

    This is making access for efforts to restore pool levels along with the explosion damage extremely difficult to say at least. Levels at the refueling floor if water is low prevent any human activity…..


  143. Red Blue I would tend to believe that Unit 4 pool with the full core offload is significantly low even if intact without makeup for this long. Unit 3 pool seems to be the focus though by the efforts…. which means something… reading between the lines it may be damaged and also leaking? Have to have on the ground real time information to make that kind of assessment though.

    Based on unconfirmed information to date here or publicly there are issues with both pools affecting water level significantly….. I suspect both pools have structural leaks, extent yet defined.


  144. “The concern with reactor 3 appears to stem from an explosion on Monday that is thought to have damaged the primary containment facility around the reactor’s core. If the storage pool at the reactor runs dry, radiation levels could soar so high that engineers cannot approach the reactor to try and bring it under control. David Lochbaum, a nuclear physicist for the Union of Concerned Scientists and a former Nuclear Regulatory Commission safety instructor, said the level of radiation beside the exposed rods would deliver a fatal dose in 16 seconds.

    The frantic attempts to refill the leaking storage pool came as engineers installed a kilometre-long power cable to replace those destroyed in last Friday’s earthquake and reconnect the power plant to the grid. Engineers said the power supply would first provide electricity to reactor 2. Japan’s Nuclear and Industrial Safety Agency (Nisa) said three of the plant’s six reactors – numbers 1, 5 and 6 – were relatively stable.

    The fresh power supply will be used to drive pumps that are needed at three of the reactors to circulate seawater and prevent their nuclear cores from going into meltdown. The water levels in all three reactors are dangerously low, exposing between 1.4m and 2.3m of the fuel rods, according to Nisa. The fuel rods should be covered with water at all times to prevent meltdown.

    The UN nuclear watchdog said engineers were able to lay an external grid power cable to reactor 2 and would reconnect it “once the spraying of water on the unit 3 reactor building is completed”.


  145. Red Blue, do you have technical knowledge of the Mark 1 Containment vent modification or subsequent BWR containment vent designs?

    If the ultimate primary containment vent path is not directly to the stack it goes through Reactor Building ventilation in later designs standby gas (non operational in a blackout due to loss of ventilation fans).

    Ventilation ducts leak…. without fans to provide dilution air due to station blackout….. hydrogen migrates to the upper elevations. It seems quite credible to me…


  146. I know there is a lot of chaos right now but I thought I’d toss this in. Would it be viable to drag via robot or fly and drop via heli -hoses that are connected to pumps pulling water from a refillable pool outside the plant. Or drive the hose trucks up there with a long feeder hose from this refillable reservoir aim the stream and get out of there?


  147. Shelby, do you have a solid report of a leaking fuel pool at 3. I knew they had a potential torus breach due to hydrogen explosion. Obviously they are concerned with vessel cooling based on that along with containment. Please link if you have any public data on actual fuel pool liner damage too.


  148. @Paul
    Did the homework on the subsidence and thanks for the picture. Its probably me, but i fail to see where that would become a problem. Little if any point to make it survive more than the pond would, right? Still, do you know if the seawater thing is SOB? Thats really what i wanted to know.


  149. I’ve found the gold star article (Free online at link) that others reference in regards to spent fuel pool dranage which is relevant since it seems the crticial issue now is what is happening with the spent fuel pools @ reactors 3 and 4.

    Spent fuel heatup following loss of water during storage. [PWR; BWR]
    Benjamin, A.S. ; McCloskey, D.J. ; Powers, D.A. ; Dupree, S.A.


    It’s rather long so I’m reading it now, they have a lot of data and go through many scenarios since how long the fuel has been in the pool is of course a critical factor long with others. They seem to look at it all systematically.


  150. Well I see my earlier comment seems to have survived here and thus must give credit where credit is due.

    Still don’t seem to see much here on TedCo’s blacking out of level readings from around the plant, which is indeed being reported in the U.S. media. Is that in fact the case? And, to be fair, is there any good reason for same, esp. given that the immediate area already seems evacuated?


  151. Although the NYT article is somewhat hyped, it is worse case as far as spent fuel cladding fire etc…

    Where we are now in this event is the spent fuel pools through loss of level are now inhibiting critical access due to radiation levels to address the situation.

    This could be another lessons learned from this event for the industry.


  152. http://tinyurl.com/3ot79

    A factual alternative to the media panic about the Japanese nuclear problems

    Radiation released is no danger to public health. The fact that CNN, FoxNews and other TV broadcasters continue to promote fear is simply a drive for ratings, and should be ignored.

    By Zbigniew Jaworowski, M.D., Ph.D., D. Sc. (He has been a member of the United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR)since 1973, and served as its chairman from 1980-1982.

    Japan, perched on the so-called Pacific “Ring of Fire,” is one of the most seismically unstable countries. In the 20th Century, about 158,280 persons died there in nine major earthquakes, with Richter magnitude 6 and above. The Japanese had that in mind when building 55 nuclear reactors for 17 nuclear power plants, which supply the country with 34.5% of its electricity. They made them sturdy enough not to release any dangerous radioactivity outside the plant limits, even due to the worst earthquakes. The quake of March 11 2011, of magnitude 9.0, the greatest in the Japan history, proved that the plants operated almost as expected. No dangerous radioactivity was reported to escape from the destroyed Fukushima nuclear power plants into the environment outside the plants’ limits, and nobody was seriously harmed by radiation among the public.

    However, even though the power plants evidently withstood the 9.0 magnitude earthquake, they appeared to be sensitive to the enormous tsunami, with the waves up to 7 meters high, which flooded their emergency diesel power generators, intended to provide back-up power for the pumps that cooled the reactor core. This was evidently an effect of the poor original design of the 40-year-old power plant, as the generators were located just behind a sea wall on low-lying coastal ground. The tsunami overwhelmed the 6-meter high barrier. The result was an overheating of the cores of the reactors. Like Chernobyl 25 years ago, Fukushima now brings important lessons for the only 56-years-old nuclear power.

    In the heavily affected prefectures of Miyagi, Fukushima, and Ibaraki, there are 11 nuclear power reactors. Those which operated during the earthquake were automatically shut down when tremors started, and the crews started standard procedures of cooling the “residual heat,” i.e., pumping the water to the pressure vessels of the reactors. However, after an hour, the emergency power generators at Fukushima Daiichi plant were destroyed by the tsunami; the high pressure emergency cooling was lost, and before the mobile generators were supplied, the temperature of the core in the Unit 1 reactor increased to a level where the zirconium cladding of the fuel rods reacted with water, producing hydrogen gas. When the gas was released from the pressure vessel on 12 March, outside the primary containment, a hydrogen explosion occurred in the reactor building, outside the primary containment vessel, which remained intact. This technically aggravated situation injured several persons, but did not cause a large release of radioactivity to the environment. Cesium-137 and iodine-131 levels increased initially after the explosion, but these levels have been observed to lessen a few hours later.

    On 14 March, this was repeated with an explosion at the Unit 3 reactor at the Fukushima Daiichi plant. The reactor building was destroyed, but again, the primary containment vessel remained intact and kept inside the radioactivity released from reactor fuel. And on 15th March at 6 a.m. local time, a third hydrogen explosion occurred inside the plant’s Unit 2 reactor. Pressure readings indicated that the reactor’s containment vessel may have been damaged.

    In addition to these three hydrogen explosions in four days, radiation has also spread into the atmosphere from the spent fuel pond at the Unit 4 reactor at this plant. A dose of up to 400 mSv per hour has been reported from a single location between reactor 3 and 4; later this dropped to 11.9 mSv per hour, and after six hours, to 0.6 mSv. The fire was probably caused by a hydrogen explosion. As a precaution, the workers have been evacuated from the vicinity of this reactor. The fire was extinguished early on 15th March, and according to a spokesman for the Prime Minister, the fuel in the pond did not cause the fire.

    All four reactors in the Fukushima Daini nuclear plant have now achieved cold shutdown, where coolant water is at less than 100oC, with full operation of the cooling system. Water levels are now stable in all four reactors and offsite power is available. According to Metropolitan Government’s Office in Charge of Health and Safety the radiation readings in Tokyo were by 11 a.m. on 15 March 0.147 microSv, i.e. at natural level. This was in agreement with the data reported by American 7th Fleet operating in the Tokyo area showing very low levels of airborne radiation.

    Precautionary Measures

    Several precautionary measures were taken by the authorities. More important among them were evacuation of about 200,000 residents of ten towns near the affected nuclear plants, and distribution of 230,000 units of stable iodine to evacuation centers from the area around the Fukushima Daiichi and Fukushima Daini nuclear power plants. The iodine has not been yet administered to residents, as this measure is not necessary.

    The situation at the Fukushima nuclear plants is still unpredictable. However, one may imagine what would happen in the (rather improbable) case of a total reactor meltdown of all Fukushima Daiichi and Fukushima Daini power plants. We know what happened after a partial reactor meltdown in 1979 Three Mile Island event and a full meltdown in the 1986 Chernobyl catastrophe. In Japan, the result would be probably similar as in the Three Mile Island power plant accident, where the reactor was protected by a thick concrete containment which efficiently retained fission products: There was almost no emission of radionuclides into the atmosphere, except innocuous radioactive noble gases, and practically zero radiation exposure of population.

    There is a zero possibility of repeating in Japan the scenario from the Chernobyl nuclear power plant. The Chernobyl plant, an engineering pathology – a hybrid of a military plutonium factory and a power station, was not fitted with a containment vessel, and for ten days the radioactivity was freely escaping from the melted reactor, roasting in the burning graphite used for its construction. But even if by a magic miracle the containments of the Japanese plants perished completely in the quake or tsunami, the residents around them would not be harmed by radiation.

    This is what we learned from the Chernobyl disaster, in which not a single person died among the affected populations of Ukraine, Belarus, and Russia, as according to a recent report of United Nations Scientific Committee on the Effects of Atomic Radiation, a body most authoritative in radiation matters (UNSCEAR 2011), the radiation doses from Chernobyl fallout (of about 1 mSv per year) were below the natural radiation, too small to produce any effect. Even after ten times higher doses, the result would be the same.

    See: UNSCEAR. 2011. Sources and Effects of Ionizing Radiation. Vol. II. Annex D. “Health effects due to radiation from the Chernobyl accident”, pp. 1-173. United Nations


  153. > American
    redo that with “TEPCO” — still can’t support your reading; I’d bet you searched on the typo, or were seeing referrals to the electrical power rolling blackouts. If you do have a source for what you say you found, please post it and why you think it reliable if it’s second hand.

    > Pool wall/liner
    Apparently someone’s interpretation from that helicopter overflight; does the cooling pool share a common wall with the outside of the building at any point? As I read this I think it probably means:
    ——- begin interpretation by me ———-
    The _building_ _outside_ _wall_ collapsed (as we know) and the pool is not visible from the helicopter; no flood of water was observed, so by inference the steel liner is intact — even IF the concrete around it is damaged.
    ——– end interpretation —-

    The original text I’m trying to interpret is:

    “TEPCO officials say that although one side of the concrete wall of the reactor 4 fuel pool structure has collapsed, the steel liner of the pool remains intact, based on aerial photos of the reactor taken on March 17. The pool still has water providing some cooling for the fuel;


  154. Is it possible for TEPCO to have used SF Pool water for emergency reactor cooling. It seems to me they would been reluctant in the early stages to use sea water in the pressure vessel. Just a thought.

    The IRSN French post did compute 4 days to uncover the fuel in the No 4 pool. So maybe vaporization is enough by itself, as would be major crack/leaks.


  155. I know of no other current alternatives and the following is based on my knowledge only. I could be wrong….

    You have to move exposed fuel under water from the core to the spent fuel pool. Due to radiation shielding etc.

    Current guidelines in the US require that it must stay there for 5 years for radioactive decay under water before it can be safely loaded into dry inerted fuel canisters for land based, called dry fuel storage.

    There is alot of things involved with land based dry storage that I will omit here as they are not relevent to the current situation….

    Bottom line is dry fuel storage of bundles less than 5 years is not approved or analyzed…. in the US at least. Which is equivalent to the issue we are seeing with loss of fuel pool levels in a laymens terms.


  156. Pingback: Comparing Fukushima to Chernobyl, Three Mile Island, Forsmark, and Tokaimura — The Good Men Project Magazine

  157. Thanks hank, I hope what you reported is true. I read it as the concrete walls are damaged, Spent Fuel Pool liner questionable but visable level observed… Correct me if I am wrong….
    I have struggled all day with media reports that level was lost in unit 4 spent fuel pool, the one with the full core offload…. I hope your report is correct…


  158. So the CH-47 air drops aren’t doing it. Not least because they’re dropping from comically ineffectual altitudes.

    Let’s brainstorm a bit.

    Build a large rectangular frame of metal pipe dotted with nozzles. Any good industrial supply house would have everything you would need.

    Place numerous nozzle crossbars within the frame. Plumb it for a fire hose connection.

    Trained men could do this in a single afternoon: pipefitters, machinists, welders, any of these disciplines could handle the rather simple assembly job. If it leaks a bit, no one will care.

    Attach a long hose to the nozzle frame from one of the onsite fire engines.

    Use a CH-47 to carry the nozzle frame, dry, trailing the hose, to the top of a reactor building. Drop it on top. Precise positioning and close approach not required.

    You may also want to trail some long steel cables from the nozzle frame. These could be secured by vehicles on the ground in order to tug the frame back and forth, and to secure it in place once the hose fills and becomes heavy.

    Turn on the water from the fire engine.

    This should flood the entire rooftop.

    Most of the water will presumably be lost down the sides of the building (inter alia carrying some fission products down to ground level).

    But if you have a high enough density of nozzles per square meter of roof, you will end up putting some of that water effectually into the interior and presumably into the spent fuel pool.

    This scheme only exposes the helo crew to roof proximity once. And it does not rely on offsite grid power showing up.

    Plus it provides continuous delivery of water to compensate for ongoing boiloff and leakage, unlike the previous air drop scheme.


  159. Joe, there are no accicent managment strategies I know of that tell you to add water via lowering the spent fuel pool to a BWR containment or vessel. That’s all I can add on that and it’s doubtful that any knowlegable operator would consider that as a success path …


  160. >Hank Roberts, on 18 March 2011 at 2:13 AM said:
    >Their seawall was sized to protect them from the >“potential tsunami” — reality exceeded design spec.

    That’s potentially forgivable. But putting power circuits that are critical to operation below ground so near the ocean… Seems fishy. Even if you don’t suspect a Tsunami will breach your wall, it’s still below ground, a significant flood could cause problems. Perhaps there are reasons I’m not aware of to do this. Seems like you’d put your backups above the tsunami wall though, just in case.


  161. Jeremy there will be lessons learned from this event about the importance of water intrusion below ground level before this is over. Either from flooding or tsunami…. Hardened structures are no good if there are leaks allowing water intrusion….


  162. >Hank Roberts
    My experience with concrete is that it doesn’t ‘collapse’, meaning if it is partially no longer there, it must have been blown out by explosive force. The odds of the steel liner surviving a blast strong enough to rip a hole in the concrete are slim to my estimation. The idea of the combination of concrete and steel liner it merely to ensure that a crack in the concrete does not result in a leak. Its like blowing a hole in a brick wall and leave the wallpaper intact. Its a liner, the literal meaning of the quote doesn’t make sense.


  163. Hank Roberts:

    Yes, USA Today newspapers is saying that here:


    Oddly they did not attribute this alleged news even to any unnamed source, but did then talk about some U.S. guy complaining about a general lack of info coming from the Japanese. Not good reporting, for sure, but it’s a little much to expect footnotes to every statement given the nature of the situation, no?

    For what it’s worth some other reporting I found interesting:

    It is said there’s kind of a disagreement between the Japanese on the one hand and the U.S. and the Brits on the other concerning the Japanese claimed primary focus on the storage pool at #3, and the other countries saying that no, the concentration ought to be on the pool at #4 which they believe is either dry or terribly low.


    Further interesting then is the report from an Atlanta paper saying that TepCo has “moved closer” to agreeing with the assessment that water in #4 is low if not gone:


    From the paper: “‘Considering the amount of radiation released in the area, the fuel rods are more likely to be exposed than to be covered,’ Yuichi Sato [from TepCo] said.”

    One question that may have been discussed here that I may have missed: Aren’t lots if not all of the proposed solutions to the holding tank problems assuming that the tanks are indeed still intact? (And thus can still hold significant water at all?) So, anyone have any idea of how good that assumption is?

    Wonder if that has any relation to the news that GB seems to be shipping tons and tons of boron over.


  164. From ParetoJ’s post at 7:16 AM, the document

    “Spent fuel heatup following loss of water during storage. [PWR; BWR] Benjamin, A.S. ; McCloskey, D.J. ; Powers, D.A. ; Dupree, S.A.


    indicates that the typical thickness of the SS liner is 1/4″. Collapse of a concrete wall during explosion could well tear a liner this thick at attachment points.

    Importantly, reading the documents introduction & conclusion section seems to indicate that there is a “decay time” of 5 to 150 days after the BWR fuel assemblies are put in the spent fuel pond, after which the fuel assemblies do not reach the critical 850-950C following a complete water drain.

    Would somebody else please read and verify my interpretation.


  165. That was an interesting read, ParetoJ.

    It seems that natural air convection is enough to keep the fuel from melting. I wonder if the guidlines for improving cooling in partial drainage were followed as a completely dry pool was said to be better than a partially filled pool.

    Though they did talk about spraying the fuel as being highly effective and a rate of about 100 gallons per minute (tiny!) asuming 70% spray efficiency was enough to keep temps under 500C.

    As long as the fuel hasn’t fallen into a critical configuration there really shouldn’t be any problems other than the massive unshielded radiation. ie things shoudln’t get worse.


  166. > bchtd1parrot

    I agree, the literal text we see doesn’t make sense.

    > em1ss
    You’re reading me right, and that is just my guess, from reading the English original and — stand back, I’m attempting to use logic — I don’t see a wall that’s common to both the outside and the tank.

    There must be little spy helicopters on the US Navy ships if not in the Japanese police and military — someone should be trying to get a better view in here.

    I have the sad thought that the agencies are always reluctant to publicly reveal how good their imagery can be — remember this confusion: http://www.nytimes.com/2003/03/13/us/shuttle-team-sought-view-from-satellite-nasa-official-says.html

    But if there’s a tool out there that can buzz in an open window and photograph what’s on someone’s desk (I’m making this up, people, not disclosing something, just wishful thinking) — if there is anything like that, it should be used.


  167. http://www.iaea.org/press/?p=1374
    Briefing on the Fukushima Nuclear Emergency (17 March 14:00 UTC)

    “… Radiation Monitoring

    We are now receiving dose rate information from 47 Japanese cities regularly. This is a positive development. In Tokyo, there has been no significant change in radiation levels since yesterday. They remain well below levels which are dangerous to human health.

    As far as on-site radiation levels at the Fukushima Daiichi and Daini nuclear power plants are concerned, we have received no new information since the last report.

    In some locations at around 30km from the Fukushima plant, the dose rates rose significantly in the last 24 hours (in one location from 80 to 170 microsievert per hour and in another from 26 to 95 microsievert per hour). But this was not the case at all locations at this distance from the plants.

    Dose rates to the north-west of the nuclear power plants, were observed in the range 3 to 170 microsievert per hour, with the higher levels observed around 30 km from the plant.

    Dose rates in other directions are in the 1 to 5 microsievert per hour range…..”


  168. My understanding was that they were concentrating on SNP #3 because it was open at the top, and not on #4 because most of the roof is still there. The roof obviously gets in the way of dropping water from above.

    Is this not correct? Is the roof no longer over the SNP of #4 ?


  169. Importantly, reading the documents introduction & conclusion section seems to indicate that there is a “decay time” of 5 to 150 days after the BWR fuel assemblies are put in the spent fuel pond, after which the fuel assemblies do not reach the critical 850-950C following a complete water drain.
    Would somebody else please read and verify my interpretation.

    Unfortunately Unit 4 pool’s fuel is not “spent”. The fuel was waiting for reinsertion into the core following maintenance.


  170. I do not understand how a hydrogen explosion blew out a concrete wall in the spent fuel pond. That sounds more like you would need high explosives. The sheet metal of the building around all this mess, sure, but not concrete. Could the tsunami have undercut the wall? Don’t know enough about the layout, but that doesn’t seem that possible either. The concrete wall that has colapsed may not be the SFP wall. The building wall? That would not be as thick.


  171. BBC is reporting Unit 4 cooling pool as empty, but it’s not clear on what basis. “Official confusion” … “too radioactive to check” … “an American drone flying over … concluding it was now empty … extremely dangerous …”


  172. @Jason: To the extent that reactor 4’s fuel assemblies are not fully”spent” or may have some fresh rods, isn’t that a good thing? I thought the fuel assembly heat was generated more by radioactive decay of fission byproducts instead of the U235. Am I right?


  173. Jason, on 18 March 2011 at 8:29 AM said:
    “Unfortunately Unit 4 pool’s fuel is not “spent”. The fuel was waiting for reinsertion into the core following maintenance.”

    Is this fresh fuel or partly burnt fuel? If fresh there would be no fission products, you could pick it up in your hand. Even if partially burnt the radionuclide load would be much less than fully burnt which would be good. There may be a mixture of fuel waiting to go in and spent fuel from the last unloading. Maybe this is where the confussion is.


  174. @Steven Moss
    There is at least something between open air and the structure at nr4. On Sat pics this is clearly visable. The units number sequence seen from sea is 432165 with only the roof of unit 2 intact day before yesterday.

    Putting a camera on a buzzer of some sort is no problem. Its the controling of it so close to so much radiation thats challenging. Otherwise it would have been done already. It takes one trip to a radio shack and a toystore to get what it takes.
    @Geoff Russell
    170mSv at 30 miles. Where would that put the reading at the plant? If that reading is true it would support the story on the empty pool, but it would make any human presence on the site itself impossible.


  175. One thing I don’t think they should have done is throw buckets of salt water at the reactor. Unlikely to get much in the SPF and from that height you may destroy more required infrastructure from kinetic impact and now you have radioactive water running who knows where. They didn’t do this that much before they tried the firehoses. Why did they bother?

    On the same topic. Is there no way to get to the heat exchangers or pumps for the SPF and pore water in there. I believe all that infrastructure is above the top of the pool. Gravity would do the rest of the work. I assume it is just too radioactive there as well.


  176. Now we get the recognition:

    …my prediction that ‘there is no credible risk of a serious accident‘ has been proven quite wrong as a result.

    [unsubstantiated personal opinion deleted]

    Now we must consider the flow of information.

    If at 6:55 on 16 march the water level inside the reactor cores of units 1, 2, and 3 were all at least 1.4 metres below the top of the fuel rods, when was this information provided by TECO, the Japanese government or IAEA?

    Anyway, it is all over now, I suppose the only useful thing we wait for now is news that power has been connected to all pumps and all pumps and pipes are functioning.

    Notice too, how we get reports of radiation readings but never accompanied with wind direction. Off course you will get low readings by moving your monitoring west, if the breeze blows east.

    Again the access to, and flow of, information is the key determinate and one of the key reasons (along with commercial competitive pressures) this form of energy production must be closed down.
    [unsubstantiated personal opinon deleted]


  177. Hasn’t it already been said that a complete unloading of core #4 was done Nov. 30? That means some or all of the fuel is not spent — had been destined to go back in, after spring inspections were done — and all of it has been irradiated. None is new. If it were, as above said, it would not be part of the problem at all. Indeed, they wouldn’t keep it in the SFP.


  178. A quick scan of the Morse paper suggests the dose rate should allow someone to quickly advance a fire hose into the pool if they crouch down and don’t get too close. Ergo, there are other, extreme sources of radioactivity en route to the SFP besides (potentially) exposed fuel rods.


  179. @William Fairholm,
    @Leo Hansen

    Good questions about the specific Unit 4 fuel load.

    I’m sorry I can’t find the post with the specific link to unit 4’s fuel load, the comments here have grown unwieldy. Other posters have been repeating this information and basing calculations on it.

    I’m sorry if i’m repeating inaccurate information. Moderators feel free to delete my original post if inaccurate.


  180. @bchtd1parrot, on 18 March 2011 at 9:00 AM said:

    >170mSv at 30 miles. Where would that put the reading at the plant?

    The units are uSv/h.

    It’s a mountainous region. Some areas will be like wind tunnels.


  181. harrywr2, on 18 March 2011 at 9:24 AM said:
    “@bchtd1parrot, on 18 March 2011 at 9:00 AM said:

    >170mSv at 30 miles. Where would that put the reading at the plant?

    The units are uSv/h.

    It’s a mountainous region. Some areas will be like wind tunnels.”

    Any radioactive plumes from the reactor are going to come down in a very patchy manner, depending on wind patterns, local geography and precipitation. A few hundred meters could make quite a difference. That is why I take all these radiation measurements with a grain of salt. They are spot measurements and may or may not give some idea of the average contamination in an area. They will have to eventually do a detailed survey of the radiation pattern. Not going to happen any time soon.


  182. I think that anyone observing the events of the past six days would have to acknowledge that the design assumptions and technology involved are never the sum total of what makes a catastrophic accident. There are people, institutions, culture, and circumstances, which all factor in; human frailty should be accounted for in the design.

    Clearly, there is weak independent oversight over Tepco — just observe the government’s frustration with the company’s almost total lack of candor.
    Second, there is the Tepco culture, clearly one of secrecy, non-disclosure, and closed doors. In 2002, Tepco suffered a system-wide shutdown (17 plants) , according to Wikipedia:
    “TEPCO was guilty of false reporting in routine governmental inspection of its nuclear plants and systematic concealment of plant safety incidents. All seventeen of its boiling-water reactors were shut down for inspection as a result….. The utility “eventually admitted to two hundred occasions over more than two decades between 1977 and 2002, involving the submission of false technical data to authorities”

    Regular deception over a quarter of a century. You don’t cure that merely by firing executives. In 2005, Tepco disclosed more false reporting. The 17 plants in question were closed for three years.

    In 2007, ” a severe earthquake (measuring 6.8 on the Richter scale) hit the region where Tokyo Electric’s Kashiwazaki-Kariwa Nuclear Power Plant …and radioactive water spilled into the Sea of Japan; as of March 2009, all of the reactors remain shut down for damage verification and repairs; the plant with seven units was the largest single nuclear power station in the world.[8]”

    According to the Wikipedia article I got this from there seems to have been another earthquake generated incident, to a cooling tower, in 2008, but there was no additional info on where it was. Bottom line: no one can claim that such events — earthquakes impacting NPPs — are unexpected in Japan.

    [unsubstantiated personal opinion deleted]
    Another thing: what does it matter if these reactors are nearing the end of their design lives? So what? Do you think their licenses would not have been renewed had they not self-imploded? Has their safety not been upgraded over the 30+ years they have been in operation to meet growing knowledge and understanding of what is needed? Do you suggest that regulators would let them continue if they were not safe? In the US, most reactors that have reached the end of their 40 year licenses have had them renewed for another 20 years, and no doubt, if they are proved worthy, they will be renewed again. Saying that the future of nuclear safety is in new designs is nonsense — we have 100 of the old designs, and they are the only reactors we are certain to have in 20 years, and not one of the new plants that has been propsoed will replace them. To suggest otherwise is dishonest.

    This is not a time where any kind of hubris looks good. To suggest that it was unreasonable to plan for a 9.0 earthquake is hubris. How long have we measured earthquakes? How long have they happened? What is the frequency of big ones? Do we know whether smaller ones (the 2007 one was “only” 6.8) can do more damage. Damage in earthquakes is very catch as catch can, depending on many factors, and what falls and doesn’t is due to a lot of factors, the most significant being that we cannot predict with any accuracy where an earthquake will strike, forget about when.

    I love the info you have provided, but find the defensiveness of many commenters detrimental to understanding theis unprecedented accident (multiple meltdowns), which ironically helping to explain the incompetence of Tepco to manage a disaster of this magnitude, a disaster which has cost them three or four reactors. All we know is what they tell us, and when they tell us that there was a loud noise and a bang while we watch a building blowing up, their credibility sinks to new lows.

    I hope it doesn’t get worse, mostly for the sake of the people whose health long- and short-term will be impacted by human decisions over which they had no control or input. But if we have seen the worst already, can the promoters hold off on braying about how everything came out ok?


  183. Interesting to learn that the US has been overflying the Fukushima plant with an “Aerial Measuring System.” I guess because the key isotopes emit photons of fairly distinct peak energy, this device overlay the emissions data on an aerial photograph and map each isotope. Given a known altitude from the flight instruments, they can even get a semi-quantitative assessment of Ci amounts.


  184. Thanks for admitting that you were wrong previously. That takes courage and really helps with credibility. You are a far better source than all the folks who are simply saying that everything is okay.


  185. I read at kyodo news that power lines are prepared to bring power to the pumps at the reactor 3.
    Can anyone have more actual data about this?
    Seems to me that this is the only solution that can calm down that monsters.


  186. Madisonian suggests that someone crawling quickly and low enough could get a firehose close enough to the reactor. Rather you than me!

    I’m much more curious why no robots have been used? I understand the lack of power could be a problem, but.. still, this doesn’t seem to be too hard! If Mythbusters can convert a full sized car into remote control then surely the Japanese can so that and strap a firehose to the roof?


  187. If the ultimate primary containment vent path is not directly to the stack it goes through Reactor Building ventilation in later designs standby gas (non operational in a blackout due to loss of ventilation fans).

    The normal secondary containment (reactor building) air circulation system has inlet filters, and exhaus processing flow which normally requires grid or emergency bus power for the fans and heaters, as well as and some particulate filters, then the stack.

    I don’t believe you need the exhaust fans in a situation where high pressure steam and hydrogen is vented from pressurized primary containment directly to this exhaust filtration plant. The most important function would be the particulate and active carbon filters to screen the steam/hydrogen and those don’t require power. I guess without the dryer you would get some damage from steam though eventually.

    The valves in the containment vent lines should work from the battery bus on control room command, like the valves of the vent lines to secondary containment, but there are obviously some other valves before the stack that might be on other buses. However, all of them should be operable with pressurised air or as the final backup by turning a wheel manually.

    Just as a comparison, in most European plants this functionality of secondary containment overpressure protection is achieved by overpressure disk valves (that open automatically and then stay open until replaced) and a filtration system before the stack which is spesifically designed to handle high pressure steam, requiring no controlled valve operation whatsoever.

    I don’t think anyone except TEPCO know exactly how the modification was implemented in Japan, but I have read some recent US reports (probably coming from GE) that they did implement it somehow.


  188. There is an important difference between the two problem areas in these nuclear power plants.

    The radioactivity from the reactor core is from the release of steam containing gaseous fission products and particles from the primary containment. The primary containment concrete provides shielding from direct gamma radiation from the fuel assemblies in the core.

    The water in the spent fuel ponds within the secondary containment provides cooling and shielding. The bottom and walls of the ponds are part of the concrete section of the containment but the top is open. As the water level in the ponds falls, as well as reduced cooling, the shielding is reduced. The concrete bottom and walls will prevent gamma radiation towards the reactor area but there will be a direct shine path of gamma radiation upwards. This is probably the main contribution to the high radiation levels above the reactors detected by the helicopters.

    Dose rates decrease proportionally to the square of the distance (inverse square law) .

    My estimates of the number of fuel assemblies in the reactor SF ponds, based on Te figures and ~ 170kg U in BWR FA;

    Unit 1 – 294
    Unit 2 – 581
    Unit 3 – 523
    Unit 4 – 756
    Unit 5 – 872
    Unit 6 – 1503

    With an estimate of 6291 in the common poll and 408 in dry casks this gives a total of 11,229 – close to the recent figure of 11,195 stored on site.

    The unit 4 includes the 548 FA full core unload during the current Unit 4 maintenance. This will have a range of burnup from 1-3 years.
    In common with many power plants, SF capacity is nearing full (common pool capacity 6840 FA), therefore more SF have to be stored in the reactor SF ponds – not just the last few unloads.
    There will be a time limit for decay before SF is transported from the reactor SF pool to the common fuel because of transport cask limitations.
    Fuel weight is normally given in TeHM – heavy metal – ie the uranium content.


  189. There is now some interesting additional information available:

    Reactor 1 has last refueled 357 days ago (I believe that’s the day of last criticality of the hottest fuel in the SFP)
    Reactor 2 has last refueled 182 days ago
    Reactor 3 has last refueled 268 days ago (34 MOX assemblies then added)
    Reactor 4 was last refueled 107 days ago (entire core in the pool)
    No data about reactor 5 and 6 refuelings, but pool temperatures around 60 C and can take more week from today without boiling even if no water added (and the water that is there is being cooled with diesel backup power, just that no water has been added)


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  191. duh, still trying to master inserting graphics here

    NCRP data (National Council on Radiation Protection, set up by Congress to gather and provide radiation data to the public, etc.)

    Average American’s exposure to radiation, including background, medical, occupational, the works, 1980s

    360 millirem

    Average, all sources, by 2009

    620 millirem

    Almost 1/2 of which, i.e. 300 millirem is medical imaging. Medical imaging increases so fast NCRP has announced it now exceeds 1/2 of all exposure, i.e. it more than equals what used to be called normal background on average.

    NCRP was displaying a report I think it was Massachusetts indicating around 100 millirem of the 300 millirem that is medical was “defensive medicine”.

    We’re glowing in the dark because our doctors are afraid of our lawyers.

    Well, not actually, these are low levels, but it alarms the NCRP that they are rising so quickly. Prehistoric humans would have gotten close to the dose we got in the 1980s.

    Consider that 100 millirem that has been added unnecessarily to the received average dose of the entire US population due to defensive medicine when the dose rates start being announced for whatever someone says you are exposed to. Call for getting rid of the lawyers, keep the doctors and nuclear power.

    Someone who says a plume coming from Japan that makes it over the US causes some cancer will have to admit that flying to Copenhagen to attend that climate conference also causes cancer by the same reasoning, i.e. you get a dose up there in a plane, said to be in the 2 to 5 millirem range, said to be 1/2 a chest xray per transcontinental flight.

    And saying experts have trouble finding the cases and come up with calculated numbers of cases may even be proven to have been a wrong idea one day. A lab is said to be going into a very low radiation area where a guy Gomez is looking for answers.


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  193. This is for Barry if he is awake or when he gets up. In the link https://bravenewclimate.com/2011/03/17/fukushima-redux-design-basis-godzilla/

    you claim that they are not injecting salt water into the reactor pressure vessel and the primary heat transport system and I think your source is TEPCO. However, when I look at the JAIF pdf on reactor status

    Click to access ENGNEWS01_1300368041P.pdf

    it says they are continuing to inject seawater into the Core AND the Containment Vessel. What am I missing here? What is the Core, but the pressure vessel? And if they are not putting seawater into the pressure vessel where is the makeup water coming from as the water in there is turning to steam and being periodically vented?

    If you have a explaination, please provide it.


  194. William, this is actually Luke’s claim (he was the author of this article). I think you are right, it is my understanding that they have been injecting salt water into the reactor vessel itself due to a chronic lack of onsite fresh water. This also explains the use of the boric acid, as a neutron poison and heat dissipater.


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  196. Importantly, reading the documents introduction & conclusion section seems to indicate that there is a “decay time” of 5 to 150 days after the BWR fuel assemblies are put in the spent fuel pond, after which the fuel assemblies do not reach the critical 850-950C following a complete water drain.

    Would somebody else please read and verify my interpretation.

    There is some delay of several days after a shutdown before the unloading operation starts, but probably never 150 days for scheduled reloading, instead of stop for maintenance issues and the expedited reloading as a result.

    Also, I think the concern of Alvarez, Lochbaum et all is that since the NRC studies about this in the 1990s, the packing densities and used capacity in SFPs have gone up, excarberating the problem.

    I think this may be relevant to the Fukushima situation because TEPCO had to build a secondary wet storage facility because they couldn’t get spent fuel to dry storage or to reprocessing fast enough. So even without exact knowledge of how many and how old rods they have in those pools, evidence points more to the direction of more than the NRC 1997 numbers would assume for a typical BWR/3/4 plant.


  197. Luke Weston wrote:

    The level of water in the used fuel pool is normally 16 feet above the top of the fuel assemblies. With the water level evaporating at the rate described above, the water level will drop by 2 feet per day.

    Uncovery of the fuel assemblies will take eight days. (Beginning from the point where the water level reached boiling point, after active cooling ceased.)

    (Working assumption which you may subject to some skepticism: That there is no form of leakage or other water loss pathway from the used fuel pool.)

    Additional assumption: the spent fuel pool didn’t lose a significant amount of water due to sloshing during the quake. I note this from the NYT article:

    Mr. Lahey said that much of the water may have sloshed out during the earthquake. Much smaller earthquakes in California have produced heavy water losses from sloshing at storage pools there, partly because the pools are located high in reactor buildings.

    “It’s like being at the top of a flagpole, and once you start ground motion, you can easily slosh it,” he said.


  198. I know one probably could have gathered this from all the previous tech talk here, but while I gather that “radiation” is measured in some consistent way I also know that there’s different kinds of radiation, and that gamma rays especially are very bad, right?

    So anyway I then read this from a Guardian (U.K.) paper concerning those holding ponds:

    “Richard Wakeford, an expert in epidemiology and radiation at Manchester University’s Dalton nuclear institute. ‘If the water goes you’ve got no shielding and it’s like having a great gamma-ray searchlight shining into the sky and that is presumably what the helicopters are seeing.'”


    So, for instance, are all “millisieverts” or whatever just … “millisieverts” so that all are equally dangerous? Or are there “non-gamma-ray” millisieverts and then “gamma-ray” millisieverts, so that the latter are much worse than the former?

    Even just articulating it I guess it seems a dumb question because it would seem dumb for them to mean different things, but, still, I’ll ask.


  199. Sorry, had things to attend to but will try and answer a couple questions based on knowledge and experience, not necessary specific design facts of the multiple units involved ….

    First, adding any kind of water is a strategy in an accident like this…. When normal clean makeup is unavailable.

    Second, I believe the thickness of the concrete and the steel liner of the typical spent fuel pool is about as hardened as it gets, inside the secondary containment structure called the reactor building.

    I also don’t believe the hydrogen generated and that collected there was from the spent fuel pool proper. It was from primary containment venting operations…. Meaning the pool was initially full and cool when the events occurred. This is supported by how many days we are into this event without makeup or cooling to the pool….

    Decay heat eventually wins though in the core or the pool….

    Based only on knowledge of the typical designs, level the fuel pool would at most leak, not completely fail due to the hydrogen explosion.

    This is based on failure of alot more less hardened walls at that elevation of the typical design as seen in the photos. Essentially blow out and failure of the weakest saves the strongest.

    There is a significant thickness (approximately 5 feet) of concrete around that steel liner for the pool. A lot less for many of the building walls, especially at the refueling floor elevation…

    Keep on pumping water and try to make up to those pools…. Radiation levels should drop allowing access to determine the next strategy.


  200. So, points to Mr. Lahey for knowing what to look up, and knowing what actually happens

    He also says:
    Richard T. Lahey Jr., a retired nuclear engineer who oversaw General Electric’s safety research in the early 1970s for the kind of nuclear reactors used in Fukushima, said that the zirconium cladding on the fuel rods could burst into flames if exposed to air for hours when a storage pool lost its water.

    Zirconium, once ignited, burns extremely hot and is difficult to extinguish, added Mr. Lahey, who helped write a classified report for the United States government several years ago on the vulnerabilities of storage pools at American nuclear reactors.

    That report has been much mentioned and its existence discussed but apparently the content is still classified


  201. American: my understanding is that the millisieverts reflect alpha, beta and gamma rays as absorbed by the body – i’d like to know how the mixture is calculated from fallout or if it can be. anyone know?


  202. What is the absolutely worst case possible scenario? Why is it so bad to discuss that subject? Because people are afraid. Fear can motivate us to save our lives. If the fear of tsunami was greater this may not be happening. Randomness and anarchy are a part of nature and we are not apart from nature.


  203. …I think the concern of Alvarez, Lochbaum et all is that since the NRC studies about this in the 1990s, the packing densities and used capacity in SFPs have gone up, excarberating the problem.

    The anti nukes, i.e. Nader et.al. vowed to “constipate” the nuclear industry by finding a way to demonize waste repositories to stop creation of them or delay. This resulted in increased packing densities in the SFPs in the US. I’m not sure what’s happening in Japan.


  204. That report has been much mentioned and its existence discussed but apparently the content is still classified

    That report which Lahey indeed did help write is available online http://www.nap.edu/catalog.php?record_id=11263#toc Its an online searchable and readable thing, not a pdf you can download.

    Quoting from itt: “This report is based on a classified report that was developed at the request of the U.S. Congress with sponsorship from the Nuclear Regulatory Commission and the Department of Homeland … . This report contains all of the findings and recommendations that appear in the classified report. Some have been slightly reworded and other sensitive information that might allow terrorists to exploit potential vulnerabilities has been … security. Nevertheless, the National Research Council and the authoring committee believe that this report provides an accurate summary of the classified report, including its findings and recommendations…”


  205. Here is an analysis of loss of water in spent fuel pool from 2000.

    Click to access secnrcsfpstudy102000.pdf

    It is primarily a risk assesment for decomissioned olants but it does discuss the risks of this king of accedent.

    One issue it brings up is the potential for criticality to occur. This is dependent on the types of racks used, whether there are boron plates in the storage racks and if the geometry of the fuel rods changed due to crush or melting.

    The one configuration that criticality is not ruled out for is a low density rack configuration ( no boron plates or plated degraded by gamma radiation) where the geometry has been changed and nonborated water is used to refill the pool.

    Is there any information about the configuration of the SFPs?


  206. @bchtd1parrot

    “If i were to get caught in a tsunami, i would probably die, but my swiss watch would definitely suvive intact.”

    You have no background in geosciences, am I right?

    @David Lewis As long as no permanent way of disposal exists, the problem would exist anyway.


  207. David Lewis, on 18 March 2011 at 12:46 PM said:

    “”Some have been slightly reworded and other sensitive information that might allow terrorists to exploit potential vulnerabilities has been””

    So I guess we should classify this tsunami as the terrorist tsunami? Bad joke sorry.


  208. One last observation. The fact that radiation levels have been dropping at the NPS border and that people are still alive near the reactors mean that doomsday senarios are not playing out. So on that cheerful note, good night.


  209. NHK summary: SFP water level decreasing in I-1 and I-4, critical in I-3. As per JAIF, status of SFP in I-2 unknown, temp increasing in I-5 and I-6.

    Re SFP calculations: do not forget to figure in incoming radiation from outside the SFP. The appropriate figures are not easy to assess; it is obvious that the parameter figure is roughly accurate for I-5 and I-6 but too low (one order of magnitude or two) for the SFPs if I-1 to I-4.

    I suspect that the situation in the I-5/I-6 SFPs is mainly due to the radiation released by I-1 to I-4.


  210. When I look at the closeup photo of reactor 4 building’s wall, in the right hand side of this picture…

    I see panels of concrete between concrete beams. Those panels are made of concrete on a rectangular grid of rebar.

    Around the edges of two panels, the concrete has crumbled away exposing the rebar.

    I can’t imagine what kind of explosion would leave the center of an edge-mounted concrete panel intact, while crumbling away concrete all around the edges, while leaving the panel hanging from its rebar.

    On the other hand, I can easily imagine that repeatedly twisting the beams into a parallelogram would have exactly this effect on the panels.

    What if the damaged walls in building 4 are actually mainly from earthquake damage, rather than explosions?

    Are there any structural engineers here, who can estimate how close that building might have come to collapse? How vulnerable it might be to aftershocks? (That might be a reason not to refill the pool all the way.)



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  212. “Engineers had said on Thursday that a rip in the stainless steel lining of the pool at Reactor No. 4 and the concrete base underneath it was possible as a result of earthquake damage. The steel gates at either end of the storage pool are also vulnerable to damage during an earthquake and could leak water if they no longer close tightly.

    The senior executive, who asked not to be identified because his comments could damage business relationships, said Friday that a leak had not been located but that engineers had concluded that it must exist because water sprayed on the storage pool has been disappearing much more quickly than would be consistent with evaporation.”



  213. “the decline is exponential (see this figure)”

    If only! Check your figure again, that’s not what an exponential looks like on a log-linear plot. The total decay heat goes roughly like a power law until you hit very long timescales (> half a year)


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  215. Here’s a chart I haven’t seen mentioned here — rate of decrease in radioactivity and heat in used fuel assemblies; upper two charts are for BWR (boiling water reactors); lower two are for pressurized water reactors:


  216. “The UN Atomic agency at least said the situation in Japan was not deteriorating despite remaining “very serious”.

    Radiation levels currently detected in Japan and beyond do not pose any harm to human health, an International Atomic Energy Agency (IAEA) expert said.

    “Regular dose information is now being received from 47 Japanese cities,” International Atomic Energy Agency scientific adviser Graham Andrew said.

    “Dose rates in Tokyo and other cities remain far from levels which would require action. In other words, they are not dangerous to human health.”

    Minuscule amounts of radioactive particles believed to have come from the Fukushima plant have now been detected on the US west coast, diplomatic sources said. But the level of radioactivity was far too low to cause any harm to humans.”

    Some more comforting information for those worried about radiation levels/releases and how it may affect them and their families.



  217. @ Ryan 234
    You said :
    “The post also praised the workers, but stated that theey should not be placed in such a horrible position of having to put their own health at risk to save the health of others, and that this is the intractable issue with nuclear when things go wrong.”
    Perhaps it was your personal opinion that the workers were in fact putting their own health at risk (I assume without relevant authoratative references)that got your post removed.
    If I had my husband/son/brother etc working there I would not want to read your doomsday scenario. Remember there are many Japanese residents using this site for real information not conjecture.


  218. why can we not get access to nasa thermal imaging satellite pictures showing the real deal about what is being released,and why not reposition some satellites right over the area to see for sure what spent rods have water,and which ones do not. unless someone wants to climb on up there and take a look…


  219. from BBC site: “0227: Japan has started using a cooling pump at the Fukushima plant’s stricken reactor 5, according to several reports quoting the Japanese government. It is thought to be a diesel-powered pump, rather than a device powered by the still-to-be-reconnected electricity supply.” HOOOORAYYY


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