Fukushima-Daiichi Spent Fuel Pools Likely Contain Water

Recent satellite images and helicopter crews flying over Fukushima-Daiichi indicate that the spent fuel pools contain boiling water (which is not surprising, and boiling is a very effective way to shed heat) but that there is water. This means that the fuel can’t be nearly as hot as feared. This is a Very Good Thing!

UPDATE: The IAEA is reporting that the temperatures in the spent fuel pools at units 5 and 6 measured on 3/17 are around 62 to 65 deg C, significantly below boiling temp of 100 deg C. The last measurement of the temperature in the spent fuel pool at unit 4 was on 3/13 and was 84 deg C.



7 Replies to "Fukushima-Daiichi Spent Fuel Pools Likely Contain Water"

  • Paul C from Austin
    March 17, 2011 (9:23 pm)

    Thanks for these updates, Kirk. I have always appreciated your site for it's championing of LFTR- but now appreciate your expertise on the Japanese disaster, and keeping what is occurring with these older nukes in perspective- and you are right- the earthquake and resultant tsunami are what have wreaked such terrible havoc so far, and this should not be obscured by what is happening with these nukes- at least not yet.

    Keep up the good work!

  • Patrick
    March 17, 2011 (11:59 pm)

    Kirk, do you have a reference for this? Not that I don't believe you, but I'd like to post a link to it on my facebook page. Thanks!

  • ET
    March 18, 2011 (1:00 am)

    I too appreciate the updates. It's made me wonder though.

    Since these reactors got stung by Murphy's law, I was wondering about what could happen to a LFTR. Their safety system is a kind of freeze plug. So, naturally, what if Murphy strikes here and the freeze plug clogs somehow? Suppose a quake cracks the emergency storage container below? It seems that every time there's a problem, it's because of something unforeseen.

    I also was wondering if the freeze plug idea was ever tested in the prototypes of the 60s or 70s. I wonder if any nuclear reactor actually tests disaster shutdowns. Don't these tend to destroy the reactors? Simulations don't test the real thing. But Nature does.

    I'm just a retired computer programmer. But during my long career I saw many a program spit out "can't happen" statements.

    LFTR, from your talks and interviews sounds like a true solution, but I'm betting this Japan disaster will probably curtail LFTRs as people will never trust the engineers that claim to have failsafe systems. I'm afraid I'm too old to ever see them in my lifetime.

  • Chris Crowe
    March 18, 2011 (4:19 am)

    If you took a LFTR, picked it up, shook it around, banged it against a rock, set it down for a while and then covered it in water – it too would be a disaster. Thats what a magnitude 9 earthquake is like. The biggest lesson for me in this tragedy is that there is a limit to what ANY structure can withstand. Don't build reactors in known earthquake zones or where there are Tsunami. Also, if you know a reactor is obsolete and old – retire it.

    I see the freeze plug as basically the feature that positively turns off the fission reaction by draining the reactor into a tank at the bottom whose shape and structure doesn't allow fision to occur. This is fail safe in the sense that you need to cool the plug to keep it closed. Loss of coolant empties the reactor into the tank. The molten salt would still have the decay heat that would make it get hotter over time, and presumably this would normally be treated by pumping it to a heat exchanger with water or steam on the other side. Alternatively, you could make the drain tank large and full of solid salt, which would just melt and dilute the fuel and slow the heat rise. In the event that you cannot get cooling water to it, you might have better luck dumping in more salt.

    The big benefit I see is that neither the LFTR reactor and tank operate at high pressure unlike boiling water reactors. The salts are molten and do not have any noticable vapour pressure until they are many thousand degrees, so there is no equivalent to the steam venting, hydrogen explosion, helicopter raids etc that we have seen.

    Instead, substitute other risks: Molten salts are all water soluble, so very important that they be contained. Even though it is not a high pressure environment, recent events have shown that they absolutely will have a containment structure just like modern reactors (before this one of the benefits of the LFTR was that it didn't need a containment structure); There would also be a chemical plant that takes the molten salt and distills off the uranium from the thorium using hydrogen and fluorine. These H2 and F2 are very dangerous gases to handle (but not impossible), but if earthquake ruptured a F bullet, that would instantly kill people.

    And yes, the LFTR frozen plug was trialled successfully on the LFTR Demo plant. I believe it was the preferred way to shut down the reactor by turning off the cooling water to the plug.

    If I may rephrase your question: Does anyone know what the decay heat is of a LFTR reactor expressed as a % of its fissioning heat?

  • Rob Morse
    March 18, 2011 (11:57 pm)

    Chris, you are supporting Kirk's favorite design; a floating or submerged nuclear plant. They are immune from earthquakes. A submerged plant is immune from waves, and the floating plant can be made immune from Tsunami with a tall breakwater. The wall at our local nuc plant is over 30 feet above sea level for that very reason.
    Rob Morse

  • Komoel
    March 19, 2011 (7:19 am)

    I have a (probably dumb) question reqarding visual access to the reactor buildings. Please elaborate for a layman, if you can.

    Looking at the information coming from the Fukushima incident, one gets the impression as if the crew of the plant cannot see into the buildings. For example, it is said that "the helicopter crew was able see a glimpse of water in the used fuel pool".

    I'm wondering, would it not be possible to use a remote-controlled miniature helicopter, with a video camera attached, or even a cellphone with a video call on? One would also think the police and the army have remote-controlled crawler robots that could go into the plant. Even further, some of the airport de-icing spray trucks are remote-controlled, surely it would be possible to rig one for radio-controlled operation?

    Or, are these simple tools used because of a risk of a hydrogen explosion? Then again, one could fly a mini helicopter high above the plant and lower a camera into the building. Or other instruments.

    This really bewilders me, why it is so difficult to see into the buildings.

  • 34mind
    March 19, 2011 (10:31 am)

    Los Angeles Times considers options if cooling cannot be restored to power plants and spent fuel pools. They report U.S. surveillance aircraft have confirmed cracks in containment pool on Friday. Radiation in control room has reached 20 millisieverts per hour. They also cite French nuclear agency report suggesting "the Fukushima Daiichi plant had already released 10% as much radioactivity as Chernobyl." It's worth noting much of this has blown out to sea, and high radiation levels continue to make it difficult for workers to get to many areas of the site.

Leave a Reply