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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.

By Barry Brook

Barry Brook is an ARC Laureate Fellow and Chair of Environmental Sustainability at the University of Tasmania. He researches global change, ecology and energy.

334 replies on “Fukushima Nuclear Accident – 17 March update”

Spent nuclear fuel rods contain 5% fission products. Could a chemical reaction between these elements facilitated by the high temperatures be responsible for some of the fire at reactor 4?

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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.

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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.

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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

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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.

http://www3.nhk.or.jp/news/html/20110317/k10014733231000.html

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.

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I keep hearing chatter about an explosion at 4, is there any confirmation (I can’t find any right now) or has this been debunked?

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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.

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On a side note, the March 16 8:47 am dose rate measurements around the reactor buildings are kind of hardcore. 100-400 mSv/hour. No loitering.

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Press information still not precise?
Today’ entry here scares me a bit, my father just leaved Myiagi with my family.
Stil impossible to this reach chernobyl level, right?

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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

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@Drew FYI there are some non-official rough sources for radiation data in Tokyo such as this:
http://park18.wakwak.com/~weather/geiger_index.html

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.

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Thanks again for a nice update.

Re radiation outside the plant I got this site:
http://www.bousai.ne.jp/vis/index.php
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.

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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).

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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

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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.

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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.

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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?

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Robert, they’ve been talking about the external power all day. They are definitely stringing a new line to the plant with great pace. Finger’s crossed that I have this to report tomorrow! It still matters — a lot — to get external AC power restored.

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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.

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Thanks Barry. Just watched 7.30 report on ABC.tv Interview with “independent” nuclear expert left a lot to be desired.BNC rules !

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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.

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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?

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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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Invaluable update yet again Barry, and your stocks only rise by having the courage to remind us of your previous expectations and why circumstances have not played out that way.

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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.

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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.

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I wonder why the JAIF reports have stopped displaying the International Nuclear and Radiological Event Scale (INES) level.

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NHK just reported that the water pump vehicle could not reach a position close enough for deployment and had to be withdrawn due to radiation levels.

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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.

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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.

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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.

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The highest reading from the country wide radiation monitoring network at this time is 877 nGy/h (nanograys per hour) from Hitachinaka (Ibaraki), about 80 miles south of Fukushima Daiichi.

That is still a very low dose rate, only about 20 times background at that area.

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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.

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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.

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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)

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A lot of people are working on that External AC Power, they need to rush a bit more. The system is already damaged. It can get more damaged without a new explosion?

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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?

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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.

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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.
Jon.

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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?

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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”).

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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.

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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).
http://www.sangyo-rodo.metro.tokyo.jp/whats-new/measurement.html
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?

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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?

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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.

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Thank you Berry for this honest and thoughtful update. Keep up the good work.
Following your blog every day from Germany, lets hope everything turns out fine.

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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.

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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?

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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

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@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.

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I would just like to say thank you for your honesty Dr. Brook. I can now rest assured that the words you say on this site are the truth as you know it.

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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.

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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.

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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.’

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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.

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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.

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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.

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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.

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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.

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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.

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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?

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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.

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@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.

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@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”.”

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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.

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10 mSv is micro-sieverts or milli-sieverts? And isn’t that measured as per hour?

Thanks Dr. Brooks for the mea culpa. It seriously raised the value and credibility of this site.

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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.

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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.

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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.’

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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.

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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).

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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.

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David, one of the concerns, as I understand it, is the accumulated residual particles, shed in trace amounts from the SNF, that remain in the point as a result of >30 years of use. On reflection, I think you make a good point about the iodine.

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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.

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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.

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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.

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David LeBlanc, the spent fuel pools are cesium rich. I recall discussions of these pools in 2002 in connection with terrorist attacks.

–bks

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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.

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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.

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…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.

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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.

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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.

–bks

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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.

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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?

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