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 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.
Brave New Climate 
334 replies on “Fukushima Nuclear Accident – 17 March update”
Interesting article by Leo Dirac on using reactor decay heat after shutdown to power electric generators for continued cooling when electric grid is not available.
He says this is what Chernobyl operators were trying to accomplish but it failed catastrophically in the third and final attempt.
http://www.embracingchaos.com/2011/03/the-ironic-challenge-of-nuclear-power-safety-and-a-possible-solution.html
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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?
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Red_Blue, what about a mid term? If they do not stop working there, but something goes wrong?
In this case It will be far inferior in comparsion with Chernobyl, right?
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A video taken during an overflight. Very bad image, but perhaps someone here might make sense of it.
http://www.ustream.tv/channel/iwj7
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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.
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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?
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> 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.
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Fly-over from 16 march.
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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.
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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…
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“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?
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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)
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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?
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Need a big crane wouldn’t you?
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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?
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If you understand Japanese this “Independent Web Journal” video site may be helpful:
http://www.ustream.tv/channel/iwakamiyasumi
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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.
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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.
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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?
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>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.
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> 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:
http://scholar.google.com/scholar?q=If+a+spent-fuel+pool+is+permitted+to+go+dry+indefinitely%2C+what+happens%3F
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> Jeremy
> potential tsunami height
Their seawall was sized to protect them from the “potential tsunami” — reality exceeded design spec.
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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.
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“NRC requires the spent fuel to be cooled in the spent fuel pool for at least five years before being transferred to dry casks.” (that’s the US requirement)
from: http://www.nrc.gov/reading-rm/doc-collections/fact-sheets/dry-cask-storage.html
hat tip to the Maddow blog; good info there in some of the main posts (comments are often off the wall as with most blogs on this)
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Is there any way that massive quantities of ‘dry ice’ in peanut form might help control the temperature problems? — assuming that such material might somehow be available.
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Dr. Brook writes,
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.
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Also — what figure?
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Sorry, the figure in Luke Weston’s post of earlier today. I’ll add th at hyperlink when I’m not on my iPhone.
I’m off to bed now, as are my other moderators, so sorry to some new commenters who will be held in the moderation queue for the next half dozen hours.
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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
–bks
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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.
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@Hank Roberts, re google scholar: Thank you!
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> 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.
http://dx.doi.org/10.1016/j.tca.2006.11.021
http://dx.doi.org/10.1016/0022-3115(91)90502-X
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?
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There is a video taken from a helicopter flying over the power central :
http://t.co/L63M9Lu
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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.
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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.
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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.
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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.
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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.
http://blogs.forbes.com/bruceupbin/2011/03/16/idiotic-placement-of-back-up-power-doomed-fukushima/
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.
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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]
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Thanks for the updates and the honest assesment of your own coverage.
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I have found a very large amount of radiological monitoring data that everyone will find very useful. The sites are in Japanese but google translate gets you most of the way there
http://113.35.73.180/monitoring/index.html
also search on
http://www.tokyo~eiken.go.jp/monitoring/index.html
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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.
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@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.
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@ Luke Weston : Am i correctly reading your calculations as an indicator that nr.4 pool must be leaking?
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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.
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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:
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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.
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larger size
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More images spesifically of the current reactor 4 building damage:
Helicopter image from another angle
Helicopter image from yet another angle
Satellite image from yesterday
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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.
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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.
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@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?
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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
host
Radio Ecoshock
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Kyodo:
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@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.
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Can anyone tell me if the possibility of pumping in seawater to cool the ponds is in any way intergrated in normal training scenarios?
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> they could at least be live blogging radiation levels
Drew, they are pulling people out of debris piles, they are short on food and water, they are _busy_ dammit.
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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.
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@seamus wrote:
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?
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Possibly better quality video from the helicopter flight here:
http://t.co/L63M9Lu
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Oops, didn’t realize that would embed a link, hope it’s ok. Hosts feel free to disable if it bogs you down.
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@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.
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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).
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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.
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http://twitter.com/#!/search?q=%23Officialtepco
Says this is someone’s translation of a TEPCO Twitter feed that’s being written originally in Japanese.
Twitter’s also overcapacity and hanging right now for me.
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> 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?
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@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.
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Yes, a steel liner. According to NEI sourcing TEPCO, the steel liner is assessed as being intact even in the worst damaged reactor 3.
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).
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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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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).
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In other words, that Twitter account has not yet posted anything about the situation in Fukushima.
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> 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.
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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.
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> 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.
http://www.aep.com/newsroom/newsreleases/?id=408
“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. …”
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@American
This aint Reuters and you didn’t get deleted did you?
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“@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.
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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.
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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.
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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.
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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.
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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.
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@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?
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@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.
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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.
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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.
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FWIW, IRSN status assessment of SFPs and reactors from today evening (GMT 19:00 I presume): http://bit.ly/gic3f6
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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.
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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.
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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.
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Fairly good-quality (as good as they get) photo of Daiichi-4 interior: http://blogs.aljazeera.net/sites/default/files/imagecache/FeaturedImagePost/images/nuclear_rtr.jpg680.jpg
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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…
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@em1ss, thanks for the correction. I meant pump blades (or do the pumps use another technology?)
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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.
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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.
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@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.
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Any comments, corrections, additions to the New York Times story?
“Danger of Spent Fuel Outweighs Reactor Threat”
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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.
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>>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:
http://scholar.google.com/scholar?q=related:E-7v64r1bv8J:scholar.google.com/&hl=en&as_sdt=0,5
“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.
Abstract
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).
Table:
Test date Quench medium Injection rate
(g/s)
Initial temperature
(K)
H2 release
before/during reflood
(g)a
Remarks
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
(3)
B4C + 8H2O(g) = 2B2O3+CO2(g) + 8H2(g) + 768 kJ/mol
(4)
B4C + 6H2O(g) = 2B2O3 +CH4(g) + 4H2(g) + 965 kJ/mol
(5)
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.
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@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.
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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…..
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