This is an update of the situation as of 10 am JST Wednesday 16 March. (For background on events of 15 March and earlier, start with this post and its included links.) Note that this is a blog, not a news website, and thus the following analysis, like all others on BraveNewClimate, is a mixture of news and opinion — but facts remain paramount.
First, the situation is clearly (but slowly) stabilising. As each day passes, the amount of thermal heat (caused by radioactive decay of the fission products) that remains in the reactor fuel assemblies decreases exponentially. When the reactors SCRAMed on 11 March after the earthquake, and went sub-critical, their power levels dropped by about 95 % of peak output (the nuclear fission process was no longer self-sustaining). Over the past 5 days, the energy in the fuel rods dropped by another ~97 %, such that the heat dissipation situation is getting more and more manageable. But we’re not out of the woods yet, and the reactor cores will need significant cooling for at least another 5 days before stability can be ensured.
Yesterday there appears to have been a fracture in the wetwell torus (see diagram: that circular structure below and to the side of the reactor vessel) in Unit 2, caused by a hydrogen explosion, which led to a rapid venting of highly radioactive fission product gases (mostly noble [chemically unreactive] gases, the majority of which had a half-life of seconds to minutes). It also caused a drop in pressure in the supression pool, which made the cooling process more challenging. However, despite some earlier concerns, it is now clear that containment was not breached. Even under this situation of extreme physical duress, the multiple containment barriers have held firm. This is an issue to be revisited, when the dust finally settles.
Units 1 and 3, the other two operating reactors at Fukushima Daiichi when the earthquake struck, continue to be cooled by sea water. Containment is secure in both units. However, like Unit 2, there is a high probability that the fuel assemblies have likely suffered damage due to temporary exposure (out of water), as the engineers struggled over the last few days to maintain core coolant levels. Whether there has been any melting of the clad or rods remains unclear, and probably will continue to be shrouded in a cloud of uncertainty for some time yet.
The other ongoing serious issue is with managing the heat dissipation in the spent fuel ponds. These contain old fuel rods from previous reactor operation that are cooling down, on site, immersed in water, which also provides radiation shielding. After a few years of pond cooling, these are transferred to dry storage. The heat in these rods is much less than those of the in-core assemblies, but it is still significant enough as to cause concern for maintaining adequate coverage of the stored fuel and to avoid boiling the unpressurised water. There have been two fires in Unit 4, the first tentatively linked to a failed oil pump, and the second, being of (currently) unknown cause, but the likelihood is that it was linked to hydrogen gas bubbling.
There appears to have been some exposure of this spent fuel, and radiation levels around this area remain high — making access in order to maintain water levels particularly troublesome. Note that apart from short-lived fission product gases, these radiation sources are otherwise contained within the rods and not particularised in a way that facilitates dispersion. Again, the problems encountered here can be linked to the critical lack of on-site power, with the mains grid still being out of action. As a further precaution, TEPCO is considering spraying the pool with boric acid to minimise the probability of ‘prompt criticality’ events. This is the news item we should be watching most closely today.
An excellent 2-page fact sheet on the spent fuel pool issues has been produced by the NEI, which can be read here: Used Nuclear Fuel Storage at the Fukushima Daiichi Nuclear Power Plant (this includes an explanation of what might happen under various scenarios).
This figure illustrates the current reported state of the Daiichi and Daini reactors, last updated 1230 on 16 March (click to enlarge):
The status report from the The Federation of Electric Power Companies of Japan (FEPC) is given below:
• Radiation Levels
o At 10:22AM (JST) on March 15, a radiation level of 400 milli sievert per hour was recorded outside secondary containment building of the Unit 3 reactor at Fukushima Daiichi Nuclear Power Station.
o At 3:30PM on March 15, a radiation level of 596 micro sievert per hour was recorded at the main gate of Fukushima Daiichi Nuclear Power Station.
o At 4:30PM on March 15, a radiation level of 489 micro sievert per hour was recorded on the site 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 As of 10:00PM on March 14, the pressure inside the reactor core was measured at 0.05 MPa. The water level inside the reactor was measured at 1.7 meters below the top of the fuel rods.
• Fukushima Daiichi Unit 2 reactor
o At 6:14AM on March 15, an explosion was heard in the secondary containment building. TEPCO assumes that the suppression chamber, which holds water and stream released from the reactor core, was damaged.
o At 1:00PM on March 15, the pressure inside the reactor core was measured at 0.608 MPa. The water level inside the reactor was measured at 1.7 meters below the top of the fuel rods.
• Fukushima Daiichi Unit 3 reactor
o At 6:14AM on March 15, smoke was discovered emanating from the damaged secondary containment building.
• Fukushima Daiichi Unit 4 reactor
o At 9:38AM on March 15, a fire was discovered on the third floor of the secondary containment building.
o At 12:29PM on March 15, TEPCO confirmed extinguishing of the fire.
• Fukushima Daini Units 1 to 4 reactors: all now in cold shutdown, TEPCO continues to cool each reactor core.
This indicates a peak radiation level of 400 mSv/hr, which has come down to about 0.5 mSv/hr by the afternoon. This ‘spot’ radiation level was measured at a location between Unit 3 and 4. It was attributted to a hydrogen explosion in the spent fuel pool of Unit 4 — but this is still under debate. The radiation level at the site boundary is expected to have been much lower and, to date, there is no risk to the general public.
Two other useful sources of information are from the WNN: Radiation decreasing, fuel ponds warming and Second fire reported at unit 4. ANS Nuclear Cafe continues to be a great collator of key official channels and top news stories.
Finally, this is a useful perspective from an MIT staffer that is well worth reading:
Kirk Sorenson, from Energy from Thorium blog, also has this very interesting piece: Thoughts on Fukushima-Daiichi. A concluding excerpt:
What is known is that this is a situation very different than Chernobyl or Three Mile Island. There was no operator error involved at Fukushima-Daiichi, and each reactor was successfully shut down within moments of detecting the quake. The situation has evolved slowly but in a manner that was not anticipated by designers who had not assumed that electrical power to run emergency pumps would be unavailable for days after the shutdown. They built an impressive array of redundant pumps and power generating equipment to preclude against this problem. Unfortunately, the tsunami destroyed it.
There are some characteristics of a nuclear fission reactor that will be common to every nuclear fission reactor. They will always have to contend with decay heat. They will always have to produce heat at high temperatures to generate electricity. But they do not have to use coolant fluids like water that must operate at high pressures in order to achieve high temperatures. Other fluids like fluoride salts can operate at high temperatures yet at the same pressures as the outside. Fluoride salts are impervious to radiation damage, unlike water, and don’t evolve hydrogen gas which can lead to an explosion. Solid nuclear fuel like that used at Fukushima-Daiichi can melt and release radioactive materials if not cooled consistently during shutdown. Fluoride salts can carry fuel in chemically-stable forms that can be passively cooled without pumps driven by emergency power generation. There are solutions to the extreme situation that was encountered at Fukushima-Daiichi, and it may be in our best interest to pursue them.
More updates as further information comes to hand. Otherwise, for me, it’s back to the mad TV and radio media circus.
UPDATE: From World Nuclear News: Problems for units 3 and 4
Chief Cabinet Secretary Yukio Edano had outlined problems that had occured on the morning of 16 March with Fukushima Daiichi 3 and 4.
At 8:34am local time white smoke was seen billowing out of Fukushima Daiichi 3. Efforts to determine the cause of this development were interrupted as all workers had evacuated to a safe area due to rising radiation readings. Readings from a sensor near the front gate had fluctuated for some time, although Edano said that on the whole there was no health hazard. Earlier in the morning readings had ranged between 600-800 microsieverts per hour, but at 10am readings rose to 1000 microsieverts per hour. Readings began to fall again from around 10:54.
Edano said that one possibility being considered was that the unit 3 reactor had suffered a similar failure to that suffered by unit 2 yesterday, although there had been no reported blast or loud sound, which had been the case for unit 2. The immediate focus, said Edano was on monitoring of levels and checking pumping operations.
Edano also outlined plans for units 4-6. Preparations were being made to inject water into unit 4, however the high levels of radiation from unit 3 were imparing those preparations. When possible, the water injection would be done gradually as there were safety concerns over pouring a large amount of water at once. The water will be pumped into the reactor building from the ground, plans to drop water from a helicopter having been abandoned. Although he said that “all things were possible” Edano did not believe that recriticality at unit 4 was a realistic risk
Second fire at unit 4
Earlier, the Nuclear and Industrial Safety Agency said that a blaze was spotted in the reactor building of Fukushima Daiichi 4 at 5.45am local time this morning.
Attempts to extinguish it were reportedly delayed due to high levels of radiation in the area. A spokesperson for TEPCO said that by around 6:15am there were no flames to be seen.
The incident at unit 4 is believed to be in the region of a used fuel pond in the upper portion of the reactor building.
Origins
Tokyo Electric Power Company issued a notice of an explosion at unit 4 at 6am on 15 March. This was followed by the company’s confirmation of damage around the fifth floor rooftop area of the reactor building.
On that day, a fire was discovered but investigations concluded it had died down by around 11am.
At present it is not clear whether today’s fire was a completely new blaze, or if the fire reported yesterday had flared up again.
Brave New Climate 
485 replies on “Fukushima Nuclear Accident – 16 March update”
IAEA:
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For a BWR refueling a full core off load is the most decay heat limiting event for a spent fuel pool. Which is likely why the loss of level water level occurred first, even if only due to evaporation, when cooling and makeup to the fuel pool was stopped.
The radiation levels tell the tale…. Have to cover that pool to get back in and combat the other issues…..
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William,
Sea water may be corrocive, over a period of months plus. Demineralised water, which I have some experience with over years of involvement with maintenance of demineralised water plants in operating power stations, is at least as aggressive. Surprisingly, it is precisely the purity of demin water that makes this so.
Let’s not worry about salt Vs demin water, when the issue is bulk cooling.
BTW, for those who wondered about blowing the roof above the storage pool(s) away, in my time as a volunteer bushfire fighter, there have been instances where water dropped from a bucket has been used to punch right through hayshed roofs in order to get at the burning hay inside.
A chopper with a 1300 litre bucket, about the size which hung beneath the chopper in yesterday’s photo, might easily do the same. High explosives are not the only way to destroy the roof… HOWEVER, what about the covers?
The sliding covers on the top of the storage pool are probably closed. They would be much stronger. The problem may not be the roof, per se, but the covers.
Barry, your energy amazes me. Many thanks for maintaining this blog under trying circumstances.
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Back of envelope calculation based on spent fuel pond estimated dimensions 12 m wide by 12 m long with 8 m water freeboard above top of spent fuel = 1152 m3 or 1,152,000 kg water. Heat of evaporation is 2257 kJ/kg. The total heat required to evaporate all this water is 2.6 x 10^9 kJ.
From MIT NSE site, full Reactor 4 heat load after 3 months is about 6.3 MW or 6.3 x 10^3 kJ/s. Time to evaporate all the water is then 4.8 days, just about now.
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No problem Seamus, you just confirmed what I knew but couldn’t link either…. Too much information and disinformation to track anymore….
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Leo, you are a mathamagician… :) I just rely on experience and previously analyzed scenarios… Thanks!
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Problems for units 3 and 4
http://www.world-nuclear-news.org/RS_Second_fire_reported_at_unit_4_1603111.html
contains updates 3 & 4 which clarify many of the points raised in recent comments.
Korea sends boric acid supplies
http://www.world-nuclear-news.org/IT-Korea_sends_boric_acid_supplies-1603117.html
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Take note that no data about reactors 1, 2 and 3, which could be almost as much cause for concern due to the following facts:
1) They also have been without normal cooling since the tsunami at least
2) Like unit 4, the floors where the pools are located have suffered major damage from hydrogen explosions
3) Their control rooms have been inaccessible and may still be inaccessible due to high radiation
4) Temperature measurements by instrumentation may be damaged or battery power to use it unavailable (they were attempting to bring new batteries to the control room of units 3 and 4 when the crews were evacuated last time due to explosions, fire and climbing dose rates)
5) Escaping steam has been recently observed at least from units 2 and 3 and there is no conclusive evidence of where it’s originating from (could be from breaches of reactor containment, could be from the SFP or even both).
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George Monbiot: Japan nuclear crisis should not carry weight in atomic energy debate
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> no reference
For em1ss and seamus, it seems to me you all know some of this stuff from personal experience or from contacts you can’t cite.
Most of us have only second-hand and often unreliable information, so knowing the source is all we can do to verify it.
But if you can’t identify your sources (or yourself or your position) to the public, but can in confidence to Barry, perhaps he can act as a journalist protecting known reliable sources?
Like science discussions — people who have real knowledge and are known to the hosts, can be relied on for facts even without cites, using a consistent pseudonym.
Just sayin’ there — so few people who know the field are posting in public — more would be welcome.
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I thought this would be common knowledge for anybody closely following the situation, at this point. I’m actually a little bit stunned at your question.
I was familiar with the concerns about spent fuel pool #4. It was the bit about storing fresh fuel which threw me. The reporting on this whole situation has been sufficiently confusing I’m beginning to doubt just about everything I’ve heard so far.
So there is indeed spent fuel being stored there. Very well. And they also store fresh fuel there. Which I’d say would be a fairly minor concern all told.
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Boron at this point is a feel good issue in my opinion. Water is what is needed period for the vessels and the pools…. Cover it in water, reduce the rad levels through cooling and shielding. It’s doubtful the reaction it can restart under almost any credible situation.
That statement is based on experience from the other two worst accidents that have occurred previously in the commercial industry, TMI and Chernobyl, where a second critical mass even after core melt was never achieved….
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EVERYONE SHOULDWatch NHK LIVE IN ENGLISH For yourself
http://www.ustream.tv/channel/nhk-world-tv
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Hank, the sources of which core was fully offloaded are available to all. It’s just a tremendous amount of information I am surfing the net for and screening based on my experience. You can choose to believe my comments or not. I try to link if it’s fresh information I just found…
As my wife said tonight, if this happended here I would be still there…. She cried too…
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@ Hank Roberts.
Two points.
One, there is more than one fuel assembly in a BWR (!!!). There are many pellets forming one rod, but that’s not what I talked about. There are many rods per assembly and many assemblies per full core loading. If you multiply the number of fuel assemblies with the number of fuel rods per assembly, you will find a number in the tens of thousands of rods in the reactor. Notice the difference between pellets, rods, fuel assemblies, and the full core loading. Bigger steps of clusters.
Two, the fast decaying isotopes indeed take months to decay – and the spent fuel in the fuel point is months old. That’s exactly my point, and why the spent fuel pool is a different radiological hazard than the reactor core assemblies.
I don’t know how many fuel assemblies are present in the spent fuel ponds. Anyone know how much spent fuel in the smaller reactor containments and how much in the big central pool?
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If radiation exposure remains at or below the new limits, I am not that concerned for radiation workers as there are natural background levels at this levels. I can’t see how they are going to do that with just 50 workers. Why are they not bringing other workers in from other sites especially Fukushima #2 Nuclear Power Station which is in cold shut down or are they already doing this? I have seen no reports on this. Do they have a remote control robot to bring in the hose to start refilling the SFP? I doubt a human would make it. But maybe they would with a very quick death sentence. What happens when that cold water hits those very hot fuel bundles? There are lots of problems here. It seems in the realm of take a guess.
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http://www.elpais.com/graficos/internacional/Alerta/radiacion/central/Fukushima/I/elpepuint/20110316elpepuint_1/Ges/
Also highly interesting: http://i.dailymail.co.uk/i/pix/2011/03/16/article-1366670-0B33232400000578-824_964x703.jpg
Not so much the reactor buildings; the office(?) building in front, in particular its windows.
People who think about laying pipes, cooling the SFPs with firehoses, and generally believing that anything is normal in the reactor buildings should take a long hard look at that before they type any more nonsense.
With the possible exception of I-2, the buildings’ interior is trashed, judging from the force of the explosions as per explosion damage and spread of debris as well as what is visible inside.
There is no factual basis for assuming that conditions will be as if someone had simply pulled the plug in a squeaky clean fuel pool.
Tackling any problem in these wrecks will be as easy as extinguishing fires in WTC1 in the late morning of 2001-09-11… if it had been a plane that carried a lot of uranium that hit the tower, that is.
How would a molten-salt thorium reactor perform assuming all-out failure?
Assuming for example containment starting to fail while the entire building is structurally unsound and full of the trash of an average workday as well as assorted structural elements?
Because it is clear that people will demand answers to the question “assuming an all-out Fukushima-type failure, what would happen to a particular NPP design?”
Not: “Will it stay safe?”
This is the new reality: thinking of what will happen if it DOESN’T stay safe.
[edited personal opinion off topic]
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Finally getting us news press (ABC News), as identified early in this event here, the spent fuel pools are the worst concern right now. The rad levels as the pools empty inhibit any other damage control operations.
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The US Army has Fox vehicles that are used for NBC warfare. I’d think the Japanese probably do too. These vehicles should be able to operate in this environment. I would think they could use them to punch a few holes in the outer building and get a hose or two on the SFP.
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Also, since nobody has answered for like 12 hours, I repeat the question:
Do we have HARD DATA that refutes the hypothesis that one or more reactors didn’t SCRAM?
E.g. are the radiation/isotope measurements in line with the Untermeyer/Weill rule, or do they provide evidence for energy levels exceeding the predictions?
My impression is that the energy output until seawater injection differed markedly in I-1 and I-2… I-2 took a longer time to wind up while I-1 was problematic from the start. Yet I-1 has the smallest power output of all the reactors at Daiichi.
Now, one can think of ways how this can happen (different dimensions of RV create different thermodynamic conditions, I-2 already running low when quake struck), but the gut level suspicion would be “I-1 cannot have SCRAMmed completely”.
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@ew-3: JSDF NBC training is lacklustre. Vehicles are useless without competent crews.
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So what is the“Defense in Depth.” of a dry spent fuel pool. I think everyone knows the answer to this.
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The prevailing view is that a disaster of almost unimaginable proportions is in the process of unfolding. MSNBC national news chief science reporter Robert Bozell calmly explained that “some say” 1 million people died or will die as a result of what happened at Chernobyl.
People are being told that something very much like the Chernobyl event may happen anytime from now. It is possible the wind could be blowing in the direction of Tokyo when this greatly feared disastrous release of a Chernobyl 1 million death cloud happens.
I’m saying, I’m noticing that a website I’ve posted to in the past is delaying posting the opinion of Dr. Ted Rockwell, Rickover’s Technical Director when under the Eisenhower Atoms for Peace Program they caused the first commercial nuclear power plant to be built.
Ted’s opinion is that the fear of radiation is greatly overstated, that the fears of massive radiation release even after containment failure are greatly overstated, and he has issued a prediction that when the dust settles we’re going to see that in the end the damage to the surrounding region and general population is about what happened at Three Mile Island, because the situations are in essence, similar.
I’m saying it’s getting very weird out there if it has come to the point where people look at an opinion like that coming from a source like that in a situation like this and see it as so controversial the normal posting process has to be modified, as it appears to have been. I expect them to eventually post. I’m just saying it appears to be getting very weird.
That site publishes climate deniers who have no qualifications at all with their optimistic view that a far bigger disaster than anything happening in Japan at the moment, i.e. climate change, cannot happen because they say so, and if you happen to describe such types, not even individuals, but such types, as for instance, “devolving Neanderthals” they won’t post it.
I think it is vital that panic be avoided. Many have said the biggest effect of Chernobyl was psychological. Just one example: a very large number of women all over the EU aborted in fear.
Anyway, just putting in my two bits worth.
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@American
Don’t forget that we’re talking about Japan here. Self-surrender runs deep in their history and mythology.
I must admit that the thought of the 47 Ronin crossed my mind when I heard that it was 50 men working at the plant.
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@Leo: thanks for the maths, that was very substantial and enlightening.
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Problem is the elevation level at the typical BWR refueling floor level. It’s not as easy as you think to provide enough pump head or even physically reach to punch that hole….
Pumping the water to that elevation can be done and many US facilities have already staged portable pumpers than can achieve the necessary head to reach the refuel floor should all other systems fail (ie 911/station blackout)……… But someone still has to get there to finish the job……
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Deaths from this event no matter how bad it gets over time will not likely exceed those in Cherobyl. The Tsunami has wiped most of the local area out and they are already deceased or evacuated since the event started… The water preceeded the events unfolding may have been a blessing…
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To answer Amadeus and others here who are questioning, Dr. Jaczko has a Doctorate in Physics and has been a member of the U.S. NRC since 2005. His primary emphasis as Chairman has been on nuclear safety according to the U.S. NRC website. President Obama elevated him to chairman in 2009. I would afford him a lot more credibility than I do to Wikipedia, which some commenters here are turning to for expertise.
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A blessing in that it evacuated most early….
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I have to believe Jackzo, for him to make a statement of that nature was significant…
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Killing millions, we’ve been told that for decades. So far 0 radiation related deaths by the nuclear plants in Japan, all primary drywell containments intact, decay heat down to 0.2 percent full power.
Chernobyl has no full containment, had a bad reactor design that caused 10000% power, and a graphite chemical burning on top of that. That’s some serious drive of radionuclides into the environment, which by design and by physics simply arent there in the Japanese situation.
Update on Daiichi unit 4 spent fuel pond: water temperature rising, but not yet to boiling point. So it appears the trouble is at reactor 3 then?
http://atomicinsights.blogspot.com/2011/03/fepc-information-sheet-for-fukushima.html
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@John: well you are correct insofar as that if bulk cooling does not work, the seawater’s corrosiveness is not a relevant issue anymore.
However, a more correct way to put it is: there won’t be any problems less significant than those caused by seawater corrosion.
Until the cores have cooled and/or until the facility has been physically cleaned up and decontaminated and repaired to a modicum of functionality, corrosion will occur.
The real “fun” stuff will be waste disposal.
It would be much easier if as much corium/NF would escape into the atmosphere. Particularly regarding any RVs that remain intact, as long as heat and pressure have not bled off. If you have ever found an egg that had been left in the sun for a few weeks and shaken it, you’ll know what I mean.
The next 3-4 months, a lot of people will be facing a lot of tough questions
[edited personal opinion off topic]
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@rpl: only fools use Wikipedia as a source of reference. Smart people use it as a source FOR references, which tend to collectively outweigh the experience of one single scientist, no matter how eminent.
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to clarify radiation effects on humans –
in the short term (for the radiation workers in hazmat suits)
1) we can ignore alphas, which are heavy particles (essentially a helium nucleus) and can’t penetrate well. The only way these become dangerous is if ingested. Then they are the worst of all types, because they have so much energy, and deposit it all to a small areas.
2) beta negative decays (electron produced) can penetrate a bit more (like 1 cm of people) so in a suit, it shouldnt have a great effect. The suit itself plus the air gap inside the suit should make up for it.
3) beta positive decays (positron release) create gammas almost immediately
4) gamma rays are highly energetic and highly penetrating. There is no way to protect against these. If they are more energetic than low end Xrays, lead wont do much either. If I am right, these will largely be formed by beta positive decays, plus some isomeric transitions.
5) The interactions of some of these particles with other matter will probably generate xrays via various mechanisms – bremsstrahlung and compton scatters of gammas etc. Xrays of high energy can penetrate very well. If this makes a large component of the radiation then lead vests would help a lot, if the energies were low enough.
So for the workers at the plant.we need to know what % is alpha/beta negative, and what percentage is a gamma source. We also need to know what amount of xrays there are and what energy they are
Then, we get to the other side of things. For the public, long term, it flips. The alphas generators are long lived so they can bioaccumulate, meaning they can contaminate food and get inside people. This is the major public health risk. The other risks (betas, gammas, xrays) are significantly less, although still present.
It means that you have a different apporach. For the workers, they are safe from alphas if they wear suits and masks (with oxygen). The public later need uncontaminated food and water to stay safe, and if there is radioactive substances spread around it is almost impossible to stop it getting in people.
If some nuclear scientist (I only know the effects on humans well) could answer the question as to the percentage make up at this stage of the radiation levels by alphas, betas and gammas, and xrays, that would be great. 100mSv might effectively only be 10mSv for the workers, or it could be 90 mSv.
cheers
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@Mike – Please read what I wrote on radiation again. Prompt radiation can be in the form of gamma OR fast heavy particles is what I wrote.
Also please, if you are going to make remarks or ask questions about radiation, stop and learn about it before posting
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@emi1ss: they are still working on evacuating the 20km zone.
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Good news reported today a few minutes ago:
http://www.reuters.com/article/2011/03/16/japan-quake-level-idUSLJE7ED00X20110316
“(Reuters) – The level of radiation detected at the Tokyo Electric Power Co Fukushima plant has fallen steadily over the past 12 hours, an official at Japan’s Nuclear and Industrial Safety Agency said on Thursday.
A level of 752 microsieverts per hour was recorded at the plant’s main gate at 5 p.m. (0800 GMT) on Wednesday, said the official, Tetsuo Ohmura. The monitoring point was then changed to the plant’s west gate and readings were taken every 30 minutes, he said. At 5 a.m. the reading was 338 microsieverts per hour.
That level was still much higher then it should be, but was not dangerous, and that by comparison absorption of a level of 400 was normal from being outside over the course of a year, Ohmura said. (Reporting by Terril Jones)”
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William Fairholm wrote,
“If radiation exposure remains at or below the new limits, I am not that concerned for radiation workers as there are natural background levels at this levels. I can’t see how they are going to do that with just 50 workers.”
Well, with dose rates at the _front gate_ of the site at 3+ mSv/hour, presumably higher closer to the source, it seems like there is an issue. If they were already close to 100 mSv when the limit was raised (so that they could continue working), that gives them 50 hours at 3 mSv/hour before being legally “dosed” again. A “suicide charge” would probably result in much higher doses, and render the term an apt description.
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More recent updates: power line to Daiichi almost ready, workers return to plant, radiation levels falling:
http://newsblogged.com/fukushima-nuclear-power-plant-reactor-latest-news-real-time-updates
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I watched an interview earlier of a volunteer firefighter from the site. We all need to keep in perspective what has happened overall there. He was finally being pulled back, he was in complete tears and said his home and entire family was lost/missing from the tsunami. How many days has this man been there fighting the battle, yet he stayed….
Those are the people we should pray for tonight….
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Bowing in Cyril R’s direction, you’ve got the terminology right, here’s a cite supporting your terms and numbers:
“… Only the General Electric design has survived. … GE BWR Fuel Assembly. Fuel Assembly: 8 ´ 8 array; Number of Assemblies: 746 … BWR control rods are always placed at the bottom of the reactor rather than at the top as in the case of …”
http://classes.engr.oregonstate.edu/ne/fall2001/ne116/Bwr.ppt
So the long skinny cylindrical thing we’ve seen pictured isn’t a “fuel rod” — it’s an assembly of fuel rods? Or can the terms be cleared up further?
No individual “rod” is handled by the equipment apart from the framework it’s in?
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DV82XL wrote,
“Also please, if you are going to make remarks or ask questions about radiation, stop and learn about it before posting”
Oh, please. Picture me rolling my eyes. I think your ego is showing. For reference, I routinely work with high-energy ionizing radiation and radioactive materials (though nothing transuranic–too nasty on my nasty-stuff-o-meter). Please don’t lecture me, and thanks in advance. I’m only trying to contribute to the discussion.
“Please read what I wrote on radiation again. Prompt radiation can be in the form of gamma OR fast heavy particles is what I wrote.”
Okay, now I understand what you wrote. I read it as, “gamma (which are) fast heavy particles”. Which, as you and I know, is not correct.
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Oh Dear – Matt Fry on the BBC just talked about the terrible whims of nuclear “fusion” *sigh*
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@ David Lewis, 17 March 2011 at 9:12 AM:
Affirmation that a million died as a result of Chernobyl immediately consigns the remainder of David’s contribution to the waste basket. I can understand people relying on WHO reports (for example) of the order of 5000 deaths, but where is a citation for 200 times that?
This thread benefits nothing from wild statements… the actual facts as they evolve have been sufficiently confronting and surprising. There’s no need to make stuff up.
To then refer to TMI and its zero deaths as being comparable, Ted Rockwell or no Ted Rockwell, is confusing in the other direction. David, was your message meant to be that the Japanese struggles will lead to no significant contamination beyond the power station fence and no radiation-induced deaths at all?
I’d be interested to read informed opinion about what is actually happening (facts as they evolve); analysis (explanation of those evolving facts in order to understand the current situation); and further analysis, as Barry and some others have provided, to indicate where they believe this might be heading and how fast – scenario outlines, if you will.
What we do not need is an uncited extreme minority opinion about an imaginary Chernobyl head count.
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As regards the brave men and perhaps women working at the plant right now em1ss wrote:
“Those are the people we should pray for tonight….”
Hear hear.
As regards DV82XL comment saying people should “learn” before making any remarks or even asking any questions about radiation, wrote Mike wrote:
“Oh, please. Picture me rolling my eyes.”
Hear hear again.
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Hank, I have to comment here…
A fuel assembly is an array of fuel rods, the design of that assembly, the loading of the fuel rods or moderator rods (water) and actually burnable neutron poisons is an art.
Trust me on this if you can, fuel assembly or rod design is not the concern now. To fully explain this would require a complete understanding of reactor kinetics and fissionable or non fissionable material.
Let alone critcal geometry…. Way beyond most that are reading this blog….
Fission product decay heat remains the enemy imediately, fissionable products or their production daughters is secondary for now…. Cooling and shielding is paramount.
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American, I am not sure what you mean by your post. Should we not pray for those that are trying to protect the japanese public at their own personal danger?
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During my reading of the latest JAIF pdf which is now quite old, trying to find if they are injecting salt water directly into the core pressure vessel I did not look at the statis of the all the spent fuel pools. Number 3 spent pool is also low (or dry, who knows). 5 and 6 temp is increasing and they have no imformation on 1 and 2. I would guess evaporation has dropped their levels too. So we may eventually have 6 dry spent fuel pools.
Click to access ENGNEWS01_1300273535P.pdf
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Slide 12 of that Oregon State ppt has the individual fuel rod shown — no scale provided but the fuel rod is shown as containing six or seven pellets each about 1cm tall. Tiny things. The image is cited to “WASH-1250” and the text on the page says:
GE Fuel Rod
Fuel Pellet Diameter: 1.04 cm
Fuel Pellet Height: 1.04 cm
Fuel Material: UO2
Cladding Diameter (O.D.): 1.23 cm
Cladding Thickness: 0.81 mm
Cladding Material: Zircaloy
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http://af.reuters.com/article/energyOilNews/idAFLJE7ED00X20110316
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and following that up:
“USAEC Report WASH-1250, July 1973—discusses safety of reactors, and provides … The fuel pin (or rod) is welded shut to prevent escape of radioactivity …
http://www.osti.gov/bridge/servlets/purl/7262735-PGJ6j7/ …”
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Hank,
Fuel pellets are small in the early days they encapulated fuel pellets in lucite and passed them out as trinkets to utility executives….
Of course that stopped over time as even unexposed, low grade enriched uranium fuel pellets as contained in lucite blocks were radioactive….
But then again was some of the dinnerware being sold commercially around the world…
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Compared to yesterday, less steam coming from unit 4, according to the reporter narrating onboard the helicopter.
http://www3.nhk.or.jp/news/html/20110317/t10014728311000.html
Presumably that means it’s either cooled down or the water has boiled off.
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typing failing again, encapsulated in lucite….
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The oregon state reactor is a test facility, BWR fuel rods and assemblys are significantly higher and contain alot more fuel pellets. That information is available, but not going to take the time to link it now as it is relatively unimportant….
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@Joffan – “Jaczko is no friend to nuclear power”
Absolutely right. No real world experience strictly government and academia.
He’s an Obama appointee From his bio –
“Immediately prior to assuming the post of Commissioner, Dr. Jaczko served as appropriations director for U.S. Sen. Harry Reid and also served as the Senator’s science policy advisor. He began his Washington, D.C., career as a congressional science fellow in the office of U.S. Rep. Edward Markey. In addition, he has been an adjunct professor at Georgetown University teaching science and policy.”
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Japanese Police are getting ready to use vehicles with water cannons mounted to spray water into spent pool in reactor 4.
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em1ss: No, it’s an … Englishism I guess. I was absolutely seconding your post about how our prayers should go out for those fighting at the plant. Thought it was a fine thing for you to disentangle us a bit from the … mechanics of what’s going on and remember the human.
So hear hear again!
(Was originally “Hear him!, hear him!” back in the 1800’s I guess. Is now just a general cheer of hearty support.)
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I analysed a bit the situation of the housing of reactor 3, as it can be seen in the photos of the 16.th of march 2011.
I made a sketch about it, with a photo and a cross-section of a Mark 1 reactor.
You can see it here:
What is interesting is that, in the photo, on the left, there is a dome that can be seen between the debris of the roof metal structure. The big question is: what is that dome? if it is “A” (concrete lid of the concrete confinement) it is ok, if it is “B” (metal dome of the upper part of the metal confinement of the reactor) than it is… bad.
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You know in my wildest imagination I would not have believed that during a loss of cooling event (actually events), that the main concern may be the spent fuel pond and primarily one for a reactor that was not even running and has no loss of cooling. Murphy, Murphy, Murphy, you have certainly gone into overdrive in this one. Sorry, but I’m a little dumbstruck and certainly hope I’m overreacting (pun not intended).
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@Cyril, I followed your link and the Reuters stories were both framed as “Tokyo Electric Power Co. spokesman said”. I sincerely hope the information is correct as the source seems to have been serially unreliable throughout this event.
@Mike, you should listen to @DV82XL, who isprobably a perfectly reasonable guy in person who just has an unfortunate tendency to make personal attacks on people on Websites. By all means take his advice and study up on radiation thoroughly by reading Wikipedia. Only dare comment on Websites if you can follow his exemplary path and agree with him in all things.
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Yes, these docs aren’t describing that teaching reactor, they’re describing the early boiling water power reactors. Quote from that last link I posted, which is “A Guidebook to Nuclear Reactors, Anthony V. Nero Jr., May 1976, Lawrence Berkeley Laboratory”
“There are two types of ECCS available. As soon as the water level drops below a preset minimum, a high-pressure injection system driven by steam turbines is activated. Backing this up are low-pressure electrically- driven core-spray and coolant-injection systems, which would become operative after failure of the high-pressure system to cope and subsequent depressurization
(through pressure relief valves) into the dry well and downcomer arrangement. The low-pressure systems are sized to handle the reactor decay heat without damage to the core.
The steel dry well, and the reinforced concrete structure immediately surrounding it, are enclosed by a secondary containment building (Fig. 2-12). Gas exhausting from this building passes through multiple filtration systems for trapping volatile radioactive species. In addition to an altered suppression pool arrangement, as mentioned above, more recent BWR systems have another leak-tight containment structure between the primary containment and the reactor building.
In more current models, a suppression pool is still used, but it does not take the form of the downcomer-torus arrangement….”
This is about the same vintage, but paywalled:
http://rmp.aps.org/abstract/RMP/v47/iS1/pS1_1
Rev. Mod. Phys. 47, S1–S123 (1975)
Report to the American Physical Society by the study group on light-water reactor safety
“The issue of light-water reactor (LWR) safety has been the subject of a part-time, year-long study sponsored by the American Physical Society. The goal of the study was the assessment of some of the technical aspects of the safety of large light-water nuclear power reactors typical of present commercial practice in the Unted States. The report examines issues related to safe operation of LWRs; the research and development program responsible for establishing and enhancing safety; and the consequences of accidents for public health and welfare. The report in no way deals with the need for nuclear power or its benefits, and should not be considered as a net assessment of the risks versus the benefits of nuclear reactors. Since the risks of ecological impacts of other energy technologies are not addressed, no recommendations are made concerning the specific reactor program which should be followed in the immediate future. Among the areas covered in the report are primary pressure-vessel integrity; quality assurance; accident initiation from operator error, transients, and sabotage; the adequacy of present emergency core-cooling system designs; the calculation of long-term consequences to health of one particular low-probability accidental release of radioactivity; and the experimental and calculational (computer-code-development) aspects of the present reactor safety research program. A number of recommendations are contained with the report, mainly addressed to ways in which the safety of the present LWRs can be improved or better understood.”
© 1975 American Physical Society
http://link.aps.org/doi/10.1103/RevModPhys.47.S1
DOI: 10.1103/RevModPhys.47.S1
———
This very old material is about exactly this vintage reactor we’re all looking at.
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Apparently there are some indications the floor of the SFP on I-4 has cracked (n-tv via unspecified Japanese media).
US is gonna deploy a Global Hawk RPV.
Russia preparing evacuation of diplomatic personnel.
Elsewhere, the first tsunami/quake evacuees are returning home. In fact, it may be that 30% of the non-Fukushima evacuees are already leaving the emergency shelters from the figures I have seen today.
Cleanup in the hardest-hit areas is stalling due to a general lack of personnel, material and infrastructure. In the less seriously affected areas, the shaky power supply is the biggest problem remaining.
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Aerial water drop on unit 3 pool (cancelled the first time due to high dose rates) in the works again. SDF firetrucks also on the way for a “ground assault”.
http://www3.nhk.or.jp/news/html/20110317/t10014728561000.html
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As I understand matters (please correct me if I am wrong)
1) When the earthquake struck the reactors automatically started to shut down (control rods fully insterted)
2) All OK until tsunami struck when mains power lost and diesel backup did not work, so affecting the cooling.
3) Batteries then kept cooling going until they went flat.
4) All the problems resulted from lack of power which affected the cooling. So if mains power had been maintained there would have been no problems.
Therefore once it was known reactors OK after quake, but no power after tsunami, would it not have been an idea to restart one reactor so as to provide power to the whole complex? Surely this could have kept all the cooling going and prevented many if not all the problems now faced?
I am layman in all this so sorry if this is a silly question, but I am interested to learn and comments from the learned folk here would be appreciated.
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“I can understand people relying on WHO reports (for example) of the order of 5000 deaths, but where is a citation for 200 times that?”
Do you know the methodologies used to arrive at that numbers? Check them out.
Mass calamities are always liable to methodological distortion due to political interest; in this case this was not different.
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Nikkei, on 17 March 2011 at 10:03 AM said:
Japanese Police are getting ready to use vehicles with water cannons mounted to spray water into spent pool in reactor 4.
If this is not done initially as a fine mist to evaporatively cool the fuel rod there is going to a lot of stress cracking. But maybe the bundles are hot enough to react with the water for another hydrogen explosion. Already happened when it was going dry so even more likely now as they would be hotter. Has to be done, but there is going to be a significant release of radiation.
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@ew3, you seem to want to drag American Politics into the discussion. While I don’t think it is fit for prolonged discussion here, you must be aware that the Obama administration has remained supportive of Nuclear power throughout this Japanese crisis, even while disappointing the left fringe of his political base. It has been the U.S. Republican party and House Speaker Boehner who are having trouble freeing themselves and their hands from the pockets of Big Oil, who have been publically Anti-Nuke lately.
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Hello, I live in Tokyo, around 250kms away from Fukushima.
Again, I would like to ask your opinion on how dangerous it is to stay here. I understand the worst-case scenario for me would be a fire or explosion exposing the rods, releasing a large amount of radioactive particles into the air, and a wind carrying those particles to Tokyo. If this happens, what is the probable level of hazard to my health?
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Cyril R, on 17 March 2011 at 9:29 AM said:
This is an example of false reporting. If you follow the actual link you will find that Reuters reported a fall in radiation readings BUT this was between after moving the monitoring report.
As the wind was blowing radiation easterly over the Pacific, it is natural to get less radiation if you deliberately move your monitoring point west – as in this case.
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Friend or Foe to Nuclear power, I have to believe what Jazko said for now, more than I believe media reports from Japan….
Don’t take this as fact, it’s just my analysis of how we got to where we are….
People also should realize that the entire nuclear industry is scrambling right now because of this event. Checking things are in place for similar events and trying to figure where this all went wrong.
Problem still remains that a beyond design basis accident (DBA) occurred in the earthquake followed by a beyond DBA tsunami which caused a beyond DBA station blackout (complete loss of AC power).
It should be evident that the early designs of these reactors would not have consider these events to occur together. Station blackout is a relatively new concern with respect to when they were designed.
An obvious weak link so far from this event is the need to be able to direct vent any BWR containment design directly to the exhaust stack. This is needed to reduce containment pressure and prevent primary containment failure. The observed hydrogen generation during a loss of power without injection seems to be underestimated by design.
Because of it’s limited size, volume and heat removal capability, the Mark 1 Containment was already predicted to be the most suceptable to failure due to heat generation and pressure rise. Again, the hydrogen pressure rise may have not been fully anayzed for the concurrent events experienced….
All other previous methods to address hydrogen generation require power or emergency power. In severe accident management procedures venting it to the secondary containment (reactor building) is proscribed.
The intent here was to holdup the fission product gasses for decay prior to release to the atmosphere. They would be somewhat scrubbed by venting steam below the water line in the suppression area and decay in the Reactor Building volume would only help prior to release.
These methods may have worked, if power was available for ventilation fan operation in the secondary containment (reactor building) facilitating dilution of the hydrogen generated without design comp measures due to loss of power…
It appears in this case, it resulted in hydrogen explosions in the secondary containment (reactor buildings), possibly in the primary containments (torus) which now exposed the final weakness we are seeing in that of spent fuel pool cooling.
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William
I don’t know what they are waiting for, apparently they talking about starting it last night.
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@em1ss note that among the acutely affected reactors (fuel pool temps do not seem to be stable in I-5 and I-6 either) only I-1 – the least problematic at present – is a BWR-3. The reactors in the most serious condition are all BWR-4 (which is still a 1960s design).
But as it looks, the 1970s BWR-5 design of I-6 does not seem to be much less susceptible to the SFP problem.
Where does the unstable water temperature in the I-5 and I-6 SFPs come from? Ambient radiation? We know it’s there, but is it sufficient or would it heat the SFP contents less than their capacity to bleed off excess heat? Probably can be roughly calculated if the composition of ambient radiation is known.
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Thanks to em1ss and other informed contributors. I thoroughly appreciate your input and I’m sure others feel the same.
There will be a lot of learnings out of this event no matter what our individual views on nuclear power. I salute the herous on the ground trying to bring the situation under control.
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@Nikkei: first, the question of feasibility. As the remote-sensing and ground-based imagery shows, it is a mess all around the SFPs of I-4.
So it is not obvious whether the water cannons can actually reach anything worth reaching.
Second, the question of SFP integrity. If I understand it correctly, the temps are not high enough and there was not enough “white smoke” (read: water vapor) to explain the low water levels in the I-4 SFP by boiling-off.
So if the SFP is structurally damaged, watercannons are not much help.
And third, the problem of unclear fuel status. Putting water on top of fuel rods whose zircaloy cladding is already buckling and breaking is dangerous enough; spraying it on top of them with a high-pressure nozzle is liable to create a situation which according to many eminent scientists are “impossible”.
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Barry thanks again for your blog.
I’m out, it’s time to sleep and deal with addressing the emergent industry wide issues tomorrow… In perspective, that’s still a whole lot easier than what those that are fighting the fight in Japan currently are dealing with.
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@em1ss
I fail to understand how the designers could not have considered that these events would happen together, since one is caused by the other.
Moreover, the world had already witnessed a 9.5 quake followed by a 25 meter tsunami in 1960 of the coast of Chile, seven years before construction started on this plant.
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Do we have data on the amount of fuel in the SFPs? Was some of it transported offsite or are there indeed 30 years’ worth of fuel elements stacked (or probably not really stacked well anymore) up there?
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> a beyond design basis accident (DBA)
> a beyond DBA tsunami
> a beyond DBA station blackout
And don’t forget the other problem the 1960s designers wouldn’t have thought about
— human factors issues with these old plants, well documented and fixed in newer installations
— these plants as tired old equipment due to be taken out of service, Unit 1 _this_month_.
— operation during an unimagined crisis by human beings many of whom don’t even know where their families are.
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I, too, am off. Thanks em1ss, Prof. Brooks (P.S. my post above that received the edit-stick was not intended as an ad hominem attack, for the record–I try to keep things respectful), and all. I learned a lot from this discussion, but unfortunately pressing matters will keep me away until after the immediate incident is (hopefully) resolved.
The only other thing that I’ve been thinking about is, even once (if) power and pumping are restored, even once water is in the storage pools, the incident is still not over. That seems to be only the beginning of the end, with more releases of steam (at best) inevitable as the cooling process proceeds. I certainly hope for nothing worse than we’ve already seen.
So long, and thanks for all the fish!
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@mike – I only know you from what you write, and don’t tell me that these threads haven’t been full of many that don’t have the faintest idea what the difference is between prompt radiation, and radioactive contamination.
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I don’t know if this has been already discussed, but why are we not making more of a point of the fact that nearby (newer) nukes did not suffer problems?
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Apparently live feed of helicopter dumping water on #3/#4 reactors:
http://live.nicovideo.jp/watch/lv43483520
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Follow developments live on this Japanese news channel:
http://www3.nhk.or.jp/nhkworld/
I believe this is being accurately reported. Levels must be down over the plants because water is now being dumped by helicopters.
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> Huw
> nearby (newer) nukes did not suffer problems?
You’d need a list of other power plants washed over by the tsunami and how they did — and how they’re doing.
Likely there are more technicians struggling to keep various other operations together, dealing with problems that would rate as emergencies under other circumstances.
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Helicopter drops now commencing on I-3 and I-4
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Quite strong westerly wind
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Latest JAIF report out. Little change from last. Pressure unknown in unit 2 pressure vessel instead of fluxtuating and slight drop in radiation at NPS boundary.
Click to access ENGNEWS01_1300322727P.pdf
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Hank the second plant had the same tsunami issues as it a little to the south of Fukushima Daiichi.
They had problems with keeping power to the cooling but they were able to fix the issues.
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From searching:
Nuclear Power Plant Safety
by H.J.Otway
… probability of large-scale accidents. This article will limit itself to a discussion of the latter item, consistent with space limitations, based largely
upon a summary of material from the USAEC report WASH-1250 [ 1] “The Safety of Nuclear Power Reactors (Light Water Cooled) and Related Facilities”…. an up-dating of the WASH-740 material, also presents the basic design philosophy for assuring nuclear power plant safety —”defence in depth”.
This philosophy defines three levels of safety:
The first level is to design and build …
The second level … to prevent or minimise the effects of an incident. Such devices include an emergency core cooling system (ECCS) to provide adequate core cooling in event of a loss of coolant accident, …. an independent supply of off-site power.
The third level of safety supplements the first two by features which add design margin by assuring protection of the public even if seemingly remote and unlikely events occur. … such as the assumed independent failures of redundant protective systems simultaneously with occurrence of the accident they were designed to control. … Other third level design features include protection against (among others) seismic events, tornados, floods, component failures.
It should be mentioned that there has been a controversy surrounding emergency core cooling systems since semi-scale tests in 1969 indicated deficiencies in the evaluation models and computer codes used in their design. … ECC systems must satisfy required performance criteria under conservative assumptions regarding simultaneous component malfunctions…”
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Injuries or Contamination at Fukushima Daiichi Nuclear Power Plant
Based on a press release from the Japanese Chief Cabinet Secretary dated 16 March 2011, the IAEA can confirm the following information about human injuries or contamination at the Fukushima Daiichi nuclear power plant.
Please note that this list provides a snapshot of the latest information made available to the IAEA by Japanese authorities. Given the fluid situation at the plant, this information is subject to change.
Injuries
* 2 TEPCO employees have minor injuries
* 2 subcontractor employees are injured, one person suffered broken legs and one person whose condition is unknown was transported to the hospital
* 2 people are missing
* 2 people were ‘suddenly taken ill’
* 2 TEPCO employees were transported to hospital during the time of donning respiratory protection in the control centre
* 4 people (2 TEPCO employees, 2 subcontractor employees) sustained minor injuries due to the explosion at unit 1 on 11 March and were transported to the hospital
* 11 people (4 TEPCO employees, 3 subcontractor employees and 4 Japanese civil defense workers) were injured due to the explosion at unit 3 on 14 March
Radiological Contamination
* 17 people (9 TEPCO employees, 8 subcontractor employees) suffered from deposition of radioactive material to their faces, but were not taken to the hospital because of low levels of exposure
* One worker suffered from significant exposure during ‘vent work,’ and was transported to an offsite center
* 2 policemen who were exposed to radiation were decontaminated
* Firemen who were exposed to radiation are under investigation
The IAEA continues to seek information from Japanese authorities about all aspects of the Fukushima Daiichi nuclear plant.
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Helicopters leave and the water cannon trucks come in.
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Annotated satellite picture, buildings identified:
“The angle of this new image, however, shows what appears to be more extensive damage to the Unit 3 reactor building than can be seen in previous satellite imagery. The image also shows damage to the reactor building for Unit 4 from an explosion. Steam can be seen venting out of a hole in the side of the reactor building for Unit 2. Workers likely removed a panel in the side of the building to vent the steam.”
“Figure 1. DigitalGlobe commercial satellite image of the Fukushima Daiichi nuclear site taken at 9:35AM local time on March 16, 2011.”
From: http://isis-online.org/isis-reports/detail/new-satellite-image-of-fukushima-daiichi-nuclear-site-in-japan-from-march-1/
Figure 2 shows the reactor buildings for Units 5 and 6. The side and roof of the buildings appear intact and there is no sign of steam venting from the building.
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Comments from Sir John Beddington and Hilary Walker
These people are the UK Govt’s Chief Scientific Advisor and deputy director for emergency preparedness at the Department of Health respectively, and I think their words deserve more prominence:
“Unequivocally, Tokyo will not be affected by the radiation fallout of explosions that have occurred or may occur at the Fukushima nuclear power stations.”
— Copied from James Annan’s ‘Empty Blog’ (He lives in Kamakura.)
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Watching live feed on Japanese news channel. Yen hits all time high. I know not relevant, but not what I would have expected. Selling of overseas assets is given as the explaination.
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[…] – a simple and accurate explanationFukushima Nuclear Accident – 15 March summary of situationFukushima Nuclear Accident – 16 March updateDiscussion Thread – Japanese nuclear reactors and the 11 March 2011 earthquakeTEPCO reactor by […]
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Nikkei, on 17 March 2011 at 11:43 AM said:
“Hank the second plant had the same tsunami issues as it a little to the south of Fukushima Daiichi.
They had problems with keeping power to the cooling but they were able to fix the issues.”
I think the main factor is they did not lose links to outside power. Would be somewhat interesting to know if they lost their backup generators, but I doubt they did. Most likely the tsunami was not as large due to local sea bottom characteristics, otherwise outside power would have been lost.
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@em1ss
“A fuel assembly is an array of fuel rods, the design of that assembly, the loading of the fuel rods or moderator rods (water) and actually burnable neutron poisons is an art.
Trust me on this if you can, fuel assembly or rod design is not the concern now. To fully explain this would require a complete understanding of reactor kinetics and fissionable or non fissionable material.
Let alone critcal geometry…. Way beyond most that are reading this blog….
Fission product decay heat remains the enemy imediately, fissionable products or their production daughters is secondary for now…. Cooling and shielding is paramount.”
===
I agree to some extent. But its an interesting discussion on a blog with many nuclear engineers reading and posting.
I’m wondering about reports that say criticality in is still a possibility in one or more of the cores. How may that happen and how unlikely? U-235 needs a flux of thermal neutrons as well as proper geometry to sustain a chain reaction. Heat (which we obviously have) causes doppler broadening of the U-235 cross section to increase the probability of neutron absorption. Water is a good moderator to slow the neutrons, which allows some new fission reactions of the U-235. So it must be the control rods that prevent enough thermal neutrons from being available to sustain the reaction??? I’m interested in a technical discussion about why criticality may or may not be possible.
I’m not trying to make the case for possible criticality, I’m just technically interested in the reason why its so unlikely.
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Barry, aren’t these sentences contradictory?:
Yours:’Even under this situation of extreme physical duress, the multiple containment barriers have held firm.’
‘• Fukushima Daiichi Unit 3 reactor
o At 6:14AM on March 15, smoke was discovered emanating from the damaged secondary containment building.’
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evcricket, secondary containment is the ‘shell’ building surrounding primary containment (which in this context is the concrete shell, drywell and reactor vessel).
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SFT temp in I-4 on Mon/Tue: 84°C. Source: IAEA (which has no data yet for Wed.)
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