How Much Spent Nuclear Fuel Does the Fukushima Daiichi Facility Hold?

As Japan attempts to cool overheating nuclear fuel with seawater, experts worry that the damaged spent-fuel pools pose the greatest threat

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Fukushima Daiichi nuclear power plant reactors spent nuclear fuel pool

INTACT REACTORS: Several of the reactors (pictured here before the March 11 earthquake) at the Fukushima Daiichi nuclear power plant have sustained damage, making it difficult for crews to get close enough to stem the spread of radioactive material. Image: Wikimedia Commons/Japan Ministry of Land, Infrastructure and Transport

Helicopters and fire trucks proved unsuccessful at replenishing damaged nuclear fuel pools at Japan's Fukushima Daiichi plant on Thursday. The spent-fuel pools contain a large amount of radioactive material that is not contained as well as that in the reactor cores. And although information has been spotty, nuclear experts worry that this fuel—which should be submerged in circulating water to keep it from overheating—has been at least partly exposed in the pools belonging to reactor Nos. 3 and 4.



As of 10 P.M. local time on Thursday, the JAIF listed the following status of the six Fukushima Daiichi reactors:

•    Buildings around reactor Nos. 1, 3 and 4 were "severely damaged"; the building housing reactor No. 2 was "slightly damaged";
•    Cooling was not working for reactor Nos. 1, or 3;
•    Water levels were covering more than half of the fuel in reactor No. 2; reactor Nos. 1 and 3 water levels were covering only about half of the fuel.
•    Structural integrity of the spent fuel pools was unknown for reactor Nos. 1 and 2;
•    Reactor Nos. 3 and 4 had low water levels; pool temperature was continuing to rise for reactor Nos. 5 and 6.


•    Reactor No. 1: 50 tons of nuclear fuel
•    Reactor No. 2: 81 tons
•    Reactor No. 3: 88 tons
•    Reactor No. 4: 135 tons
•    Reactor No. 5: 142 tons
•    Reactor No. 6: 151 tons


The fuel had been moved from reactor No. 4's core to its spent-fuel pool recently, so "that fuel is relatively fresh and hotter, thermally," Resnikoff explained. "So it's not surprising that when the water [was] no longer circulating that the water was actually boiled off in a zirconium exothermic reaction, that the zirconium burned" (occurring at about 1,800 degrees Celsius).

Scientists are not confident that they will be able to assess just how much radioactive material will have been released as this event unfolds, David Richardson, an epidemiologist at the University of North Carolina at Chapel Hill's School of Public Health, said in the press briefing. It might not be until people can safely take stock of all of the fuel that is left, and then only "by that we can make a reckoning of what was lost," he said.

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  1. 1. YetAnotherBob 09:07 PM 3/17/11

    So, the folks in Washington who don't know what is what in Japan are issuing press releases recommending panic.

    I liked the quote from the man who oversaw the Three Mile Island cleanup. That five days into it, they didn't know what they had yet. That is probably true here in spades.

    It will take a couple of years to clean up, and probably several months just to find out what the conditions are. Right now, they are just trying to get rough control of the site.

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  2. 2. BFC 12:13 AM 3/18/11

    Ms. Harmon's article confirms there were storage pools in Units 1 & 3. So what happened to the spent fuel in Units 1 and 3? If you review a diagram of the reactors, those storage pools could not have survived the explosions of the buildings.

    If they are not worried about the spent fuel pool in Unit 1 but are worried about cooling the reactor - does that mean the spent fuel went up in the explosion? Otherwise there would be a concern to cool the storage pool.

    Look at the pictures of Unit 3 - where exactly is the spent fuel storage pool in what is left of the building? Did that go up in that tremendous explosion?

    And just what happened to the building around Unit 4. If you watch the video of the explosion of Unit 3, the explosion does not indicate the kind of damage to the Unit 4 building that appears now. There is substantial damage to the side of the Unit 4 building that is on the opposite side from Unit 3. What happened? If Unit 4 was shut down, then what happened to the Unit 4 building?

    Bottom line - it looks like the storage pool in Unit 3 went up with the building explosion - in which case the plutonium mix in the stored fuel was exploded. If so, that would be a major, major contamination problem.

    Why isn't anyone asking about the storage pools in Unit 1 and 3?

    The top floor and roofs of the Unit buildings was nothing more than corrugated steel on a steel frame - certainly not airtight enough to hold in hydrogen in enough quantity or long enough to create a bubble for a hydrogen explosion. Give the nature of the explosions, is anyone even asking if the explosions were actually the result of attempts to cool the storage pools with seawater, and that went badly wrong producing explosions of the stored fuel?

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  3. 3. BFC in reply to Vendicar Decarian 12:25 AM 3/18/11

    Your numbers are a bit exaggerated. But as to TMI, they didn't know the core had melted until 15 years later when they finally were able to access the reactor vessel with a remote camera as part of the cleanup.

    But at TMI they had a fully functioning reactor and cooling system, it was a combination of equipment failure compounded by operator error that produced the problem. They did know there was a collection of hyrdogen inside the reactor containment - which at TMI was considerably larger than the Japanese design. The bled off the hydrogen and avoided catastrophe.

    But all through TMI the people on site managing the reactor and problems knew what was going on - it was the press that couldn't get it straight - and that is the problem in Japan as well.

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  4. 4. ChazInMT 01:14 AM 3/18/11

    I like how people point out the MOX with plutonium having a lower melting point, I'd be surprised if the difference was more than 100°F. But when you're talking 2,200-2,400°F it's like, if the train is flying off the rails, what's the diff between 50MPH and 55MPH? The MOX has 3-5% plutonium built in from the beginning, and spent fuel has 1% plutonium by virtue of having been produced when the fuel was utilized in the core. So, the scary plutonium gets mentioned here for splash & wow, in reality, the difference in MOX/No MOX is probably trivial in the grand scheme of things.

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  5. 5. FaradayFan 08:44 AM 3/18/11

    This may be an idiotic idea, since the radiation may mess with electronic devices, but why not use a robot (controlled remotely) to spray water/do what the humans must do around the radiation. Yeah, it probably won't be able to be used again, but it would put fewer people in danger and would be able to work for longer times uninterrupted carrying heavier loads, such as lead shielding to protect the electronics. It probably wouldn't take much time to modify.

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  6. 6. HertzianContact in reply to Vendicar Decarian 12:49 PM 3/18/11

    Always find statements like this funny:

    "An economy powered entirely by Nuclear power will require the construction of approximately 200,000 new nuclear reactors.

    Given the current track record, this number can be expected to suffer about 50 core melts per year."

    You are merely emphasizing the safety of nuclear plants with this statement. Aside from the fact that by the time 200,000 new plants were built the technology and safety associated with them would far surpass what is currently available, and aside from the fact that the vast majority of plants in the US that you are basing your numbers on broke ground in the early 70s, your frequency of events is 50/200,000 per year. Compared to the 104 active plants in the US, this equates to 0.026 events per year. Meaning in 100 years we could expect to see 2.6 melts on average if we kept the same technology used on plants like TMI (where operator error led to the melt, not the plant itself). What was the radiation dose on surrounding areas from that incident? Equivalent to that of an x-ray scanning.

    I will admit to that simple truth any day.

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  7. 7. Carlyle in reply to Vendicar Decarian 04:24 PM 3/18/11

    Keep up the good work. Your comments are invaluable. To your oposition:)

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  8. 8. In-Tokyo 08:36 PM 3/18/11

    @Vendicar Decarian

    Your comment on the "typical pattern in Japanese culture" is wrong.

    Take for example the only known survivor of both Atomic bombs. After the first bombing, that survivor who'd been on a business trip went back to his office and in fact was giving his boss the news of what happened at the very moment the second bomb detonated.

    The tendency in Japanese culture is not really to hide things, but to be accurate. This means that in times of uncertainty, less will be said as Japanese people tend to err on the side of being accurate.

    It is unfortunate that people mis-understand Japanese culture to the degree they do.

    Of course too, there is an ability of being able to decipher from context but in terms of communication, it is a cultural thing to evaluate that as undesirable. Take for example commonly expressed western sentiment that this is "chernobyl on steroids" or "armageddon". Or take for example Rush Limbaugh's statement that this is all exaggerated. You are seeing a wider variety of reactions from Western commentary as Westerners have more freedom to be wrong.

    Of course all people try to hide things that are not favorable to them and I do not mean to suggest the Japanese are any different.

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  9. 9. BFC in reply to ChazInMT 10:15 PM 3/18/11

    Except that even 1% plutonium released into the environment is deadly.

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  10. 10. BFC in reply to Vendicar Decarian 10:24 PM 3/18/11

    At TMI they knew that the core probably had begun to melt, but there was no way in 1979, or now for that matter, to put a camera in a live operating nuclear reactor. So I don't see that you have any point.

    TMI did not explode because they knew there was a hydrogen bubble in the containment, and they took steps to prevent it. I am all but certain that as the true facts of Fukashima come out over the next several years, we will see that different than TMI, the Japanese made the wrong decisions. This will ultimately be a story about cascading human error.

    You will probably be ultimately proven correct on the "lowballing" by the operators/utility. Same thing happened at TMI, the difference was then Gov Thornberg made sure to get someone in there who would not sugar coat things, along with Pres Carter being a nuclear engineer who sent Harold Denton in in response to Thornberg's pleas for help. The real hero of TMI was Denton, who took over managing the plant and the interface with the public and government.

    Bottom line, this will ultimately be an indictment of the operators and the company utility, not the technology itself. What difference that will make we'll all have to wait and see.

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  11. 11. BFC in reply to HertzianContact 10:27 PM 3/18/11

    No one to this day knows how much radiation was released by TMI when they vented on the first two days. So the assertion that it was nothing more than an x-ray is more opinion than fact. The radiation monitor on the stack that released the gas was broken, and since no one knew what was going on there was no monitoring until days later. The arguments in support of low levels is the lack of scientifically documented effects. No one knows how much radiation escaped and never will.

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  12. 12. BFC 10:35 PM 3/18/11

    WILL SOMEONE IN THE PRESS PLEASE ASK ABOUT WHETHER THERE IS EVEN A STORAGE POOL LEFT IN THE REMAINS OF UNIT 3? The building is gone almost to the ground, and the smoke coming from the middle of the building is clearly from the reactor containment vessel. If you say the video of Unit 3 exploding, that was more than just some hydrogen collecting at the top of the reactor building. If the Unit 3 storage pool went up in the explosion it is a very serious contamination - will somebody in the press please ask the questions!

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  13. 13. ashanson 01:05 AM 3/19/11

    In a reasonably accurate article, Ms. Harman unfortunately repeats inaccurate and exaggerated statements from so-called experts about MOX fuel. Here are the facts. There are exactly 32 MOX fuel assemblies in the core of Unit 3 which contains a total of 548 assemblies. Some simple arithmetic will show that the MOX fuel represents somewhere between 5 and 6% of the fuel in that reactor. Furthermore, the MOX assemblies were put in the reactor for the first time late last year and have been burned for only a few months. What this means is that those MOX assemblies are among the coolest in the reactor. Furthermore, upon shutdown the MOX assemblies actually generate less heat from radioactive decay than the UOX assemblies and thus have a higher safety margin. The author of the article should be aware that every single assembly in that reactor contains Plutonium, not just the MOX fuel. It should also be obvious then that the MOX assemblies do not contribute to the problem in Unit 3 in any significant way.

    I would add that the melting point of the MOX cladding and the fuel pellets do not differ significantly from the other UOX assemblies.

    Finally, the fact is that there are no MOX assemblies in any of the other reactors at Fukushima, and there is not even one MOX assembly in any of the 6 reactor used fuel pools.

    I would suggest that the author seek out real experts in nuclear engineering to do fact checking instead of repeating the mis-informed opinion of anti-nuclear zealots.

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  14. 14. lakota2012 in reply to YetAnotherBob 02:49 PM 3/19/11

    bob says," Right now, they are just trying to get rough control of the site."

    Simply suggesting that there is even a remote possibility of getting a "rough control" of a situation that has been completely out-of-control since the very beginning, hardly makes any sense at all.

    This only clarifies the need to lessen our spent fuel rod quantities at each of our aging LWR's, not by a repository in Nevada, but by building new Gen IV IFR's to replace our aging reactors, that would use the waste as fuel.

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  15. 15. lakota2012 in reply to Vendicar Decarian 02:56 PM 3/19/11

    vendicar says,"It is clear that the Japanese operator has been lowballing the severity of the disaster from day 1."

    While this is probably true, and that the current level is at least 6 instead of 5, in this type of situation, when the authorities in power finally tell us it's a very bad situation, it's most likely even much worse with no chance of getting any better any time soon.

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  16. 16. In-Tokyo in reply to Vendicar Decarian 07:01 PM 3/19/11

    From the evidence you posted about the lies of the Japanese Nuclear Industry, you can hardly state that it is a Japanese trait to not tell the truth.

    What you can and should conclude is that industry will not regulate itself and that industry will attempt to evade regulation.

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  17. 17. In-Tokyo 07:18 AM 3/20/11

    I simply state the truth that you can not conclude it is an American trait to lie just because Reagan and friends did it to fund insurgency in Nicaragua.

    I am no more to blame for the rape and murder of nuns in Central America, than I am to blame for any corruption in the Japanese Nuclear industry.

    That you suggest I am shows just how tentative your grasp on actual facts is.

    You stated it is a Japanese trait to lie. I assert that your evidence of that is lacking.

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  18. 18. eco-steve 07:18 PM 3/20/11

    We obviously need to be very careful with this MOX fuel, "Some of which might have escaped". This contains plutonium with a "half-life of 24,000 years". That is, after 24,000 years any radioactive contamination will only be divided by two, meaning hundreds of thousands of years will be required to reach safe levels...

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  19. 19. HertzianContact 01:52 PM 3/21/11

    "One core melt per week can only be viewed as a good thing by the truly ignorant."

    There are about 450 commercial nuclear power plants around the world. Lets say that took 40 years to get to. So in the 17 thousand years it takes to throw up another 199550 that you think we should have, I will gladly tell you again that 50 core melts per 200000 plants per year is still safe.

    In comparison there were 272 fatal aviation accidents in 2009. That is 5.2 accidents per week!! AND that was 2009, not even 17 thousand years in the future! Clearly flying is way more dangerous now than operating 200000 nuclear reactors will ever be in the future.

    Take the time to learn some statistic based risk analysis and then try and build something that carries 0% risk from human error. Until then don't waste everyone's time with foolish math.

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  20. 20. HertzianContact in reply to BFC 02:05 PM 3/21/11

    "No one knows how much radiation escaped and never will."

    If you read my post i say "radiation dose".

    Here is some light reading for you.

    Just skip to the "Health Effects" Section.

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  21. 21. Jan Cosgrove 07:21 PM 3/25/11

    Remember, this was a situation which could never happen, or a one in a billion chance etc etc. Whilst we have been focused on Japan, anyone notice what's been afoot at Chernobyl? The new sarcophagus, to be moved into place on rails by remote control. How long will it last? How long has it got to last? Replacing the original concrete structure now degrading and leaking. Given that reality, what measures will have to be taken, if indeed they can be, to contain the Japanese site?

    Arrogance is a nasty vice, it is a very dangerous one in this case. The very existence of these plants sited where they are has to be mind-boggling stupidity. Those who are not techno-phobe but who recognised the special case of nuclear for the most extreme caution are finding small comfort in "we told you so". What is developing is worse than any nightmare scenario dreamed up by opponents of nuclear.

    That it happened in Japan is perhaps the worst irony of all.

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