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Reactor Containment & Fuel Storage from UCS; (h/t commenter lobster)
It’s Thursday, 6:00 pm EDT: Friday, 7:00 am in Japan.
Today’s update focuses not so much on anything new happening — another quake, near loss of power at another plant, broken power lines — but on further analysis of the range of concerns the Japanese are facing at Fukushima.
The Union of Concerned Scientists held a press briefing with David Lochbaum and Edwin Lyman to help reporters understand the details of the NRC report on reactor conditions at Fukushima Daiichi Nuclear Station. The details explain how dire the conditions are at Units 1-4.
The March 26 NRC report had been the basis of a New York Times story, which we summarized on our Wednesday update, noting that nuclear plant experts had serious concerns about several conditions facing the Japanese as they try to get the three reactors cores and at least two spent fuel storage pools under control.
The entire UCS briefing is worth reading, but here I focus on two aspects: the continuing concern about the spent fuel pools, particularly at Unit 4 but also at Unit 3, and the condition of the reactors in Units 1-3 and the challenge of trying to keep cooling water covering their respective cores.
Why they can’t keep the reactor cores covered.
As explained by UCS, and based on the March 26 NRC analysis, it appears they may not yet have the ability to sustain water over more than about half of the core. And they have limited ability to circulate water over portions that are nominally covered because of salt build up (or core damage).
UCS nuclear scientist Lochbaum first explains the problem created by the salt and other obstruction inside the core. That’s restricting the flow of water into the core and around the fuel rods, leaving them at least partially uncovered.
The fuel that’s or the water that’s being injected is being injected into the reactor vessel outside a device called the core shroud that’s kind of like a can within a can, and the reactor core is within the inner-most can, the core shroud. The water that’s being injected is supposed to flow down through the annulus region between those two pieces of metal, be turned around by the lower dome, and then flow up through the reactor core to cool it. There are pretty clear signs that that’s not happening and the fuel inside the core shroud is not fully covered.
Lochbam further explains that each reactor vessel has, for this discussion, two sets of water injection points where external pumps can inject water into the reactor core to maintain cooling. The pipes are sealed at the point where they enter the reactor vessel, but those seals can break down when exposed to intense heat. If the seals fail, water can leak back out of the reactor vessel, offsetting the ability to inject cooling water in.
Two points then become critical. One injection point where the seals may have failed is about half way down the reactor vessel relative to the height of the core. That means water is leaking from a point that could leave half the core uncovered if not offset.
Moreover, if the pumps available for water injection cannot keep up with the rate water is leaking out, they can never get the core fully covered. That appears to be what’s happening at least at Unit 1 and possibly Units 2 and 3 as well. Here’s Lochbaum:
If [the seals] fail, they’re deliberately designed to limit how much water they leak out through a failed seal to about 60 gallons per minute, more or less. It’s more if the pressure inside of the reactor vessel goes up to squeeze more water through that narrow opening; it’s less if the pressure in the reactor vessel drops down.
But if you assume that both recirculation pumps on each reactor has failed seals, you could have upwards of 100 to 120 gallons per minute leaking out through those failed seals. Their elevations are about half of the reactor vessel core height. If those seals are intact, you should be able to at least flood the vessel back up to two-thirds core height. At that point, water leaks out through what are called the jet pumps. Right now, the fact that they are having trouble get the water level above one-half of core height is telling them that the reactor seals have likely failed.
To answer your question, could they get out of this situation, if they can get flow rate through the reactor core greater than the leakage rate and greater than the boil-off rate, which if that’s the only losses you have, is about 120 gallons per minute for the seals and about 50 gallons per minute for evaporation right now, and if you could get 200 gallons or more makeup and it’s not being blocked or bypassed from the core, then you should be able to refill the entire vessel. Right now, that’s not happening, so water’s going somewhere.
So, to summarize: Water injected at the top and pushed down the annulus inside the reactor may not be circulating back up through the fuel rods. And they can’t keep the fuel in the core covered more than half way because some water is boiling off and other water is leaking out half way down at a rate faster than they can inject it through whatever pumping equipment they have now.
And what about the Unit 3 and 4 spent fuel pools?
As we’ve noted many times, the fact the spent fuel storage pools are outside containment creates additional risks of nuclear materials being dispersed to the environment from any explosion. Here’s Lochbaum:
It’s difficult to determine which is worse, the spent fuel pool situation or the reactor core situation. There are signs that the explosions in the Unit 4 and perhaps also the Unit 3 spent fuel pool have caused irradiated material to leave the building. That could have been the reason for the high or the reports periodically of neutron beams. That actually could be coming from decay from fuel or fuel particles that are now no longer in the spent fuel pool and were carried away by the explosion. That was already known to cause high radiation levels. It caused challenges for the workers, including even the helicopter pilots that were dropping water onto the site a week or so ago.
There’s also a discussion of concerns about other issues, including why they need to be injecting nitrogen into the containment vessel — it was displace by hydrogen and the explosions and must be present to prevent further hydrogen explosions — and the need to expand the evacuation range. As Lyman emphasizes, the zone between 20 and 30 kilometers has been exposed for a month, and there is no sign conditions are improving. Those people (and probably others further out) should have been moved long ago.
Sources:
NHK World
Kyodo News
Hi-res photos
IAEA Updates
Union of Concerned Scientists
fleep Graphing Earthquate, radiation and water readings
54 Comments
Meaning the top half of the fuel rods has melted at least. And at least one spent fuel pool hit hard enough by an explosion to blow material out of the building.
But I don’t think scattered fuel is the cause of the neutron emissions. You need quite a bit of fuel to land at the same place in a favorable configuration.
Boxturtle (Yeah, yeah, I know. ANY source but a melted core)
How far should they evacuate? How far should they evacuate if the they can’t get enough water to cool the reactor?
Korea is a bit too close. China would be better.
New, 7.1-7.4 earthquake hits Japan; tsunami warning issued. (h/t C&L)
Old news. Tsunami was 1 m high.
There are boars in Germany eating fungi that are still radioactive from the Chernobyl blast – and so are the boars. Now, this isn’t all of the boars, but this is over 400 miles away from the source and many years later.
Tokyo is what, less than half that distance from the crippled reactors? Isn’t it about 150 Km?
Where would anyone suggest evacuating the 30 million residents?
There is no safe distance in Japan, Korea or anywhere else.
Radioactivity declines the farther away one goes from the source – and fairly quickly by the square of the distance from the radiation. However, these are particles spread, if by explosion and fire, over a large area, blown by the winds.
Already there are hot spots appearing and disappearing over 30 Km from the site of the disaster.
What we are witnessing is potentially far worse than Chernobyl, which was an explosion in a reactor lacking a sealed containment vessel. The explosion and fire came under control rather quickly compared with this. While the radiation leakage has so far been relatively less, if any of the dire scenarios pan out this will dwarf both prior disasters by quite a bit.
You have potentially 6 Chernobyls at that site (not counting the OTHER site with a 10 Km evacuation zone).
At the moment there is a crisis on top of a disaster on top of another disaster. That crisis may morph into something far worse than the other two if they fail to cool the units. And right now, they are failing.
I appreciated one comment about this where a physicist was quoted as saying it’s like starting a countdown timer. It’s heating. The clock never resets. If you fail to keep the rods cool, the timer keeps ticking down. The utmost priority is not getting the water to stop flowing into the sea, the soil or the groundwater. The utmost priority is stopping the clock.
It’s ticking loudly.
“Already there are hot spots appearing and disappearing”
Umm, and they disappear how? Shovels?
Yes, the evacuation zone should have been expanded weeks ago. The damage the delay has cost won’t be calculable for years, but it could be extensive, heartrending and needless.
Salt build up inside cooling system piping isn’t the only problem generated by having used seawater as an emergency coolant. At temperature and pressure, chlorine from sea salt interacts with the SS, degrading it, making pipes and containment vessels brittle and prone to rupture.
Thanks. I saw that it was hours old but hadn’t been mentioned on this thread. I hope effects of the quake were as modest as the resulting tsunami.
Tokyo, a conurbation more than 50 km across, is about 250 km away from these reactors.
Does anyone have any idea what this train wreak will look like when it finally derails? Or when that’s likely to happen?
I’m assuming a large part of NE Japan will be uninhabitable from here on out but it was rural so that issue will be easier to manage. But I’d imagine even Tokyo’s ground water will become contaminated at some point.
And what about the workers? A week or so ago the NYT, I believe (can’t find the link), had an article specifically about them and stating they were aware that they were dying and had discussed it amongst themselves. It seems these people are sleeping inside the plant, which I had assumed was the case because they either had no home to go to or were too radioactive to be out in public. How long can they last due to both the psychological impact and physiological effects of the radiation? Who will replace them?
Thanks tons for your daily updates Scarecrow. I don’t usually comment but look forward to them.
“that’s kind of like a can within a can, ”
And if you connect the two cans with a string, will that describe Japan’s telephone system.
Wind. The radiation is blown by the wind and collects in an area. They register high radioactivity. The breeze changes directions and sometime later, it drops.
These are particles. They are blown by the wind, and have already circled the globe. Radiation, in very low levels, but definitely from the plants, has been detected from Washington to California and from Maine to Florida. It was detected in Europe.
Large concentrations of particles = large radiation.
Thank you! It’s about 150 miles away and about 35 miles across.
That is not far enough away to escape the radiation from a fire in the “spent” fuel rod pools, ignoring for the moment what the cores are capable of (their rods are more energetic than the ones in the pools).
http://www.wired.co.uk/news/archive/2010-08/06/german-radioactive-boars
Yes, the evacuation zone should have been expanded weeks ago.
I wonder if the evacuation zone issue may have been because the government isn’t up to having to contend with more displaced persons given that they’re not adequately taking care of the ones in the make shift shelters. I”ve been concerned about the problems being compounded because neither the government nor Japan Red Cross and other so-called legitimate disaster relief charities are getting money and resources into the hands of displaced families. I’ve heard reports that they’re having to develop new distribution systems, never mind deciding who is to get amount of money and on what basis.
Sound familiar? I’ve heard reports that very few checks have been given to the Gulf Coast folks who’ve been waiting for almost a year now, but the “distribution boss” I’ve heard got a bonus from BP. And I’ve also read numerous articles about the failure of most of the NGOs operating in Haiti to distribute some, much less all the funds they’ve secured. Red Cross (certainly in America, and possibly elsewhere) has an enormously bad reputation for hoarding money, shifting funds to purposes different from the appeal needs.
I’ve said this before, probably insulting and offending many folks at the Lake, but we really need to be praying for Japan and its people, institutions and the energy company desperately trying to find solutions for their ongoing crises.
Thanks to Scarecrow for your ongoing updating the process there.
Thanks to patrickherveypress for your comments above with new info and perspectives. And to all others who have added so much to our understanding of so many issues in this horrible reality in Japan and elsewhere.
Blessings,
Another nice roundup, Scarecrow.
Sadly, the media doesn’t highlight this horror unless something blows up or they can throw some frightening rad numbers around. The situation continues to deteriorate on a daily basis with no real end in sight. Your reports are timely and thoughtful. I wish more people were being informed about the very real potential for disaster on both a short and long term basis. You are doing an important job in this respect. Thanks.
From http://www.boingboing.net/2011/03/17/scientist-who-studie.html
If workers are unable to get additional cooling water into the reactor vessel, the molten fuel core will collapse into the water in bottom of the vessel. Eventually the heat from the decaying fuel would boil away the water that’s left, leaving the core sitting on the vessel’s lower head made of steel.
Should that happen, “It’ll melt through it like butter,” Allen said.
That, in turn, would cause a “high-pressure melt injection” into the water-filled concrete cavity below the reactor. Because the concrete would likely be unheated, the reaction created by the sudden injection of the reactor’s ultra-hot content would be immense, he said.
“It’ll be like somebody dropped a bomb, and there’ll be a big cloud of very, very radioactive material above the ground,” Allen said, noting that it would contain uranium and plutonium, as well as the fission products.
Should these events happen, the best outcome would be if the winds are blowing east and push the radioactive plume over the Pacific Ocean, he said. “It (the radioactivity) will fall out in the ocean and everything will be fine,” he said.
The worst case, Allen said, would be if winds pushed a radioactive cloud south toward Tokyo and Japan’s highly populated cities. If that were to happen, he said, the consequences would likely be greater than the 1986 accident at Chernobyl, where an entire area of Ukraine had to be evacuated because of the radioactive conditions that increased the risk of developing cancer.
Well said, that pretty much sums up my thoughts as well. Thank you again Scarecrow for keeping us so well updated, I’ve been watching this develop on here since the beginning, and I have to say I’m glad you’ve been working so much to keep coverage on this unfortunate disaster.
Hi php,
The contents of the Unit 4 “spent fuel pond” included the entire non-spent Unit 4 reactor core, which was outside containment for “routine maintenance.” The stuff in the Unit 4 spent fuel pond is essentially the same as the stuff in the cores of reactors 1-3, except that it is already, definitely outside containment.
Thanks for the link.
However, [blockquote]Should these events happen, the best outcome would be if the winds are blowing east and push the radioactive plume over the Pacific Ocean, he said. “It (the radioactivity) will fall out in the ocean and everything will be fine,” he said.[/blockquote] Good for Tokyo but ma nature can only take so much abuse.
where’s preview when you need it?
LOL! I wasn’t even sure blockquotes would work in the diaries.
The water they are injecting is not circulating, it’s going somewhere.
If it is leaving the system as liquid, it will carry some salt with it.
If it is leaving the system as steam, it is leaving the salt behind, concentrating the brine.
At some point the brine could become concentrated enough that the salt precipitates out, encrusting the reactor components.
I submit that fuel rods encrusted with salt will not be properly cooled. Not to mention obstructing flow paths.
This blog gives an interesting perspective to things as well as having information not commonly available to us. He’s Japanese but lives in California. He has family in Tokyo and elsewhere. He can listen to and read Japanese media and then he translates it to English for the rest of us.
Here’s a recent post with numbers I hadn’t seen before. The post before it is very sad as it is about kids going to school in a fairly high radiation zone. The schools wanted to postpone, but the government said no.
http://ex-skf.blogspot.com/2011/04/radiation-in-japan-its-safe-governments.html
The quake last night took out majority of thermal generation plants for Tohoku Electric and also took out two of the three grid feeds to the Onagawa nuclear facility. Onagawa averted the big tsunami earlier by a matter of 80cm. Combination of recovered grid and diesels running the cooling at Onagawa and another nearby nuclear facility for the moment. Fukushima apparently did not get any further damage that can be confirmed (so who knows?).
Failure of the water injection to cover the cores is not news. That’s basically the report that comes out daily in the press conferences. It is also the source of the huge amount of contaminated water, which would otherwise not exist if injection were occurring only to displace loss to steam.
Whether the leak occurs at the bottom of the vessel or elsewhere would be the difference between uninformed fear mongering and uninformed optimism.
I think on the second night of the train crash, recovery crews (what they were recovering, no idea) cut the communications to Fukushima. So they were left with one satellite phone. And presumably flashlights for the night. So we have a can and string going out to a satellite bending around a rubber band and going a can in Tokyo.
That’s 3 out of 4 grid feeds to Onagawa. And apparently there’s been some leak of water from spent fuel pools.
Well, we now have Obama Electric (on unattributed background, of course) telling the public that all is well:
Japan nuclear crisis ebbing, U.S. experts say
“Although the situation at the Fukushima Daiichi nuclear plant is far from stabilized, evidence suggests that a complete meltdown is unlikely, Obama administration experts say.
“Although the damaged Fukushima Daiichi nuclear power plant has not yet been stabilized, there is no evidence that overheating during the last month has resulted in any melting of the reactor vessels or their containment structures, Obama administration officials said Thursday.
“If that assessment is correct, then significant additional releases of radioactivity into the environment will be limited, and emergency crews should have a far better chance of preventing further damage to the plant’s reactors.
“The assessment, provided to The Times on background, suggests that the plant is unlikely to suffer a complete meltdown, in which uranium fuel gets so hot that it melts through the bottom of the reactor and containment vessels, spewing high-level radiation into the plant’s underlying foundation.”
If science could connect that amount of spin to a generator we wouldn’t need nuclear power at all.
Disasters everywhere. Sound like 2012 will completely live up to the hype. I am of course, including the financial train wreck in this country.
NEWS ADVISORY: Water leaks found at Onagawa nuke plant after Thursday quake: Tohoku Electric
Kyodo News Feed, 11:56 8 April
Steve Herman (VOA) tweets:
Tohoku Electric: Water leaks at Onagawa NPP from Reactor 1,2 spent fuel pools.
There may be more than 1 water leak at Onagawa NPP. We’re trying to clarify.
Last night NISA said 2 of 3 ext. power grids to Onagawa were knocked out by aftershock but 3rd line maintained cooling.
Leak referred to now as spillage 2.3 Liters #1, 3.8 L #2
1.8 L #3. Spillage I guess comes from top of container and not from bottom or sides. Lot of shaking though.
There is a silver lining in all this for the nuclear industry. Hitachi/GE and Toshiba/Westinghouse have begun bidding race to un-construct, as it were, the Fukushima facility.
The decommission, mothballing, demolition, and removal are now proposed to be possible in matter of 10+ years as opposed to 30+.
The quake last night managed to pull the extension cord linking Hokkaido supply to electricity starved Honshu. The cord in question is 14 cm diameter running 43km under water and carries 400MW.
This is not good news.
Oops. A nearly 6 inch diameter cable broken. The sea is a tad cold and blustery just now. I hope the cable has lots of sensors that will help teams find the break(s) along that 27 mile run. What no one in Japan needs just now is less access to power.
You notice they DON’T mention if the core melted. And while they say the vessels didn’t melt, they don’t say that the vessels haven’t been breeched. Ditto the containment structures.
And they’re unwilling to put their name on it. Background only.
Boxturtle (The crisis is only ebbing because it’s off the front page)
Ten years would be optimistic if everything was in one piece. And it ain’t. And there’s no way any of those companies have enough information to determine a bid. Unless it’s an open end bid.
Boxturtle (It’ll take 10 years just for things to cool down enough to work)
The longer it takes the more income it will generate, so the short period they are talking about is partly sales talk.
Yeah, true. The nuclear industry has always been about lowballing cost and time estimates at the front end, then screaming for a rate increase to finish the job.
Boxturtle (If this was America, we’d be busy hiring illegal immigrants to do the onsite work)
This is a 12-minute video two Japanese journalists made of their trip TO Fukushima. They took 2 geiger counters (or dosimeters, not sure which) and show the readings they get as they approach. The scenes of devastation mixed with pastoral views is jarring. The numbers they get are frightening.
http://ex-skf.blogspot.com/2011/04/fukushima-i-nuke-plant-video-footage-of.html
It’s time for them to evacuate everyone within a couple hundred miles. Do this within the next two weeks. Move them on to ships if need be. Then let this fucker melt. Abandon the site. It has to be done. I really feel there’s no way to stop this.
I understand the humanitarian crisis this creates. These folks will all have to be relocated somewhere. Japan will be lost for hundreds of years. The global economy will be wrecked (faster).
But if there’s no stopping it, just let it rip. Why continue to waste resources and poison people?
NHK report reminds us of the continuing physical instability:
Headline from Kyodo:
U.S. Marine team conducts drill to prepare for nuke disaster
[That would be preparation for a major release of radiation in the future.]
From the Asahi Shimbun.
And what was in that pool for spent fuel rods? The entire core fuel assembly of the Higashidori reactor — outside most of the available containment, just like Unit 4 of Fukushima Daiichi.
The large earthquake and tsunami was a rare event. Evidently the practice of moving the entire fully loaded fuel assembly outside all the principle containment for extended periods of time is not. WTF?
More details from The Daily Yomiuri
There are a lot of safety features at a modern nuclear reactor; multiple levels of containment. Before the events of the last month, I never knew that all the fissile material associated with a reactor is routinely held outside all that terrific containment for months at a time every year or two.
And the increased attention from the media reveals additional surprising (to me) shortcomings at the Onagawa power plant that surely must be routine shortcomings:
Manual reboots required? Pressure gauges on critical systems that routinely fail?
None of these events were actually consequential, but I link to them because it reveals the human problem of “defense in depth”: With all the confidence that multiple layers of containment bring, each individual layer is not actually maintained at 100% in the face of pressures to be efficient. That efficiency concentrates the risk.
When enough goes wrong, you end up with the situation at Fukushima, where there is hardly any working instrumentation at the four stricken reactors and a major, long-term disaster ongoing. The operators are left flying blind.
After the failures of the defense in depth due to station blackout conditions at Fukushima, Japan is now looking at improvised, long-term approaches which will be much less safe.
Evening news reported that all is fine in Japan. They reported that radiation levels had decreased and people were able to come back home to the areas that had been evacuated. ??? I thought i must be hearing things. They said things had improved so much that people could start looking for dead bodies again. Is all this true? It seemed like a complete and absolute fabrication. One more note of interest. I live in the midwest near a military base. One of my children’s friends Dad was sent home early from Japan, very suddenly. This poor mother was shocked because he was coming home two weeks earlier. She was frantic…cleaning her house for his arrival. Don’t know what it means or where he was stationed or why, but the look on her face as she told me he was suddenly coming home was terror. (perhaps he is a tyrant, but I don’t think that was it). Was he sent home early because the problem is solved or was it because they are evacuating parts of Japan. Given the report on the news it would look like the latter. Was it a special report (it was on our local news) for our area because all these folks are coming home suddenly? Is the propaganda that organized? Or are things really significantly better suddenly? Corn fused.
My guesses for the observed increase in temperature, in decreasing order of likelihood. From the basic setup, keeping in mind I may easily have the order of likelihood gummed up:
o New sections of Zr uncovered by physical rearrangement of the materials inside the RPV. Translation: new heat likely came from oxidation of zircaloy; “cladding fire”. Implications: more hydrogen release, more fuel melt. Probably a small but irreversible increase of corium.
o Blockage of cooling flow somewhere in the RPV. Localized (re)melt. Translation: Decay heat was not actively removed from a localized region of RPV contents and the temperature spiked there. Event would stop mainly due to melt and drip, which evidently brought the hot material back into the cooling flow. Implications: Nothing obvious to me. Just a reminder that there is a lot of potential energy involved that needs to be controlled. Think of a big granite stone held over your head by a thread and a bunch of kindergarteners running around with scissors. Or something like that.
o Existing corium melt dislodged and dripped onto the inside of the RPV. There would be some exchange of energy between the hot melt and the relatively cooler RPV, and the RPV would heat up. Implications: The RPV would also be damaged in the process, increasing the precarious nature of the situation in Unit 1.
o Localized recriticality event. Very unlikely because there would have been a neutron signal and SURELY they have working neutron detectors onsite. Right?
All the radiation monitoring outside the plant (i.e., all around the country) is showing consistent declines in radiation levels. This is true.
It is a result of the decay of Iodine-131, which was a major, major component of all the radioactive stuff that was released. Every 8 days, half of the I-131 in the environment disappears and is no longer a threat to life.
So there is a lessening of the immediate danger. I do not have access to readings from Cs-137 and other isotopes, so I am not qualified to say whether it would actually be safe to reenter particular areas that were evacuated. I suspect there is a lot of Cs-137 on the ground. If true, it could be okay to enter the zone for a short period of time to retrieve items of value and then leave. Items in a person’s home (for example) would not be radioactive and could be saved.
However, the overall situation remains grave. There are still no credible solutions for the problems at Fukushima reactor 1-4. The worst-case scenario remains very bad and the best-case scenario is also still getting worse.
From the already reported levels of Cs-137 outside the 30 km zone, it remains probable that we will see additional evacuations, but we may also see other areas reopened. It all depends on which way the wind was blowing at the times of the major releases, where it rained, etc. It can be measured and determined, though, so it won’t be obviously nutty if they reopen a village.
WTF, indeed.
And 2 of 3 generators were not even available? What kind of planning is that?
Ahhh. Of course the scientific long term concerns were not covered on this local news report. And it’s good to know that there is a kernal of truth in the report. thanks!
I just found some amazing photos of debris floating across the Pacific toward Hawaii and the US mainland’s west coast. One of these floating islands measures 70 miles in length.
http://refreshingnews9.blogspot.com/2011/04/japan-earthquake-and-tsunami-debris.html
A month passes and we have photos..
http://www.yomiuri.co.jp/photonews/article.htm?ge=614&id=108289
http://www.yomiuri.co.jp/photonews/article.htm?ge=614&id=108292
Ughh. See this particular figure.
So there was a big jump in the radiation levels in the Unit 1 RPV immediately after the tremor. And then the monitor that measures this important quantity died.
I do not know enough to say whether this particular radiation field is consistent with a recriticality event. The readings tripled, making it back to levels of 100 Sv / hour.
I think I will shift my attention from the Unit 4 SFP to Unit 1. This was an impressive event.