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Sunday, March 27, 2011

A few bothersome facts

I have been consistently non-alarmist on this blog because I myself understand what is going on at Fukushima Daiichi, at least in the big picture. There is one assemblage of fact, however, that surrounds No. 2 plant and seems quite troubling at the moment. I will relate this clearly -- and I invite you to go back in the blog and check the facts.

About 24 hours ago or so we reported right here, from TEPCO and JAIF sources that the water injection to the Number 2 plant was borated. This struck me as odd, since no boron has been added to the water being injected to No. 1 or No. 3 plants. If it was, it wasn't noted but I'd doubt this kind of omission given the thoroughness of the documentation the Japanese are releasing.

We also had at least one report of high radiation fields in the No. 2 plant days ago although we never did get a solid breakdown on what type of radiation this was.. one would have to assume gamma with possibly some neutron.

We now have reports of contaminated water in the turbine building at No. 2 plant that is ten million times the normal activity of primary coolant.

One of the isotopes being found in this water is reportedly Iodine-134. I-134 has a half life of 53 minutes.

If you put this all together you arrive at the fact that uncontained fissions in Uranium fuel are occurring in the plant. (And that the water being used to cool the core right now is getting out.)

If there is a significantly damaged core, and some of this core has melted down into a lump or pile, it's possible that this material (a melted mixture of uranium, and zirconium, and other metals that in the industry is referred to in accident discussions and predictions and calculations as "corium," or all sorts of core metals melted together into a non-homogeneous mixture) may not necessarily be overall and throughout in what you would call a shutdown configuration. Normally the core being fully shut down depends upon the relation of the fuel rods (or plates in some designs) and the fully inserted control rods which absorb neutrons to stop the fission process. When a core melts and fails, the exact orientation of all these materials is lost and if enough fuel material can move away from enough neutron absorbing material in the corium, an increased rate of fissions per unit time in the Uranium fuel could theoretically result. Of course, one major problem is moderating the neutrons -- normally the water in the core 'moderates' or slows down the neutrons to thermal energies. It takes thermal neutrons to trigger fission in the U-235 in the fuel. However, if enough corium metals of other types are melted into the pile it's conceivable that you could have a higher fission rate .. all the while being unable to attain any sort of recriticality since there is no good geometry and not enough moderation.

Is this happening at No. 2 plant? It sure sounds like it; the giveaway to me that at least TEPCO or else NISA suspects that it is or may be is the injection of borated water.

This is speculation based upon the facts already released and mentioned previously here, which I've also delineated in this post. We will surely keep on top of this nagging detail and follow it to see what happens.

5:35 AM Eastern Sunday 3/27
ATOMIC POWER REVIEW

UPDATE: TEPCO seems to be hedging their bet on this.. indicating that there is no credible proof yet of how the material is presently exiting the core. Calculations will have to be done to determine the I-134 inventory in the core at this time, very many days after shutdown. The best I have here at hand is the old TID-14844 at the moment. As noted before we will keep looking at this possibility and hope that it is indeed remote.

7 comments:

  1. does the fuel have to melt? If the zirconium is exposed the cans can fail and solids will fall away from the presumably metal incased boron carbide control rods. There are 140 tons of fuel there and not much % has to move somewhere else via boiling?

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  2. I concur that there is fission happening somewhere down in no. 2.

    I blogged as much here:
    http://www.moonofalabama.org/2011/03/march-27-fukushima-updates.html

    What I do not understand is your definition of "recriticality" - we have obviously some sustained fission in no. 2. Isn't that criticality? (Sorry I am largely an amateur in this)

    Also isn't corium a composition lava of melted fuel and melted concrete? Do you thereby mean that the core already escaped the reactor pressure vessel and is burning through the containment?

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  3. I don't see how a high concentration of I134 could exist without some fission and therefore some criticality happening. It looks like Murphy's law applies and that they have an "Oklo" phenomena on their hands ! It is reasonable to expect that borated water will fix this, but cold shut down of Reactor #2 is going to take longer than expected...

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  4. Looks like they want to redo the measurements... http://www.nytimes.com/2011/03/28/world/asia/28japan.html?pagewanted=1&ref=global-home

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  5. Why is there a confusion in announcing the radiation,i just now heard they retracted the earlier announced radiation measurement.i think if things are not measured correctly ,it will be too late,even for prevention extensive damage.atleast provide pottasium iodide pills to areas nearer to affected region.i have one question ,there was an animation of satilite data of radiation propogation from fukusima to california,whic i saw this week,why cant the present situation be analysed thru satillite data,to know the extent of radiation propogated.

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  6. Hi Will,

    Thanks for the clear and concise ongoing analysis. I wish I'd found your blog much sooner. I've been so frustrated with the press's simplistic repeating of bland facts I could hear myself on NHK, with no analysis or understanding. I expect party line from a state run channel, but hoped for better elsewhere. Perhaps I am naive, or perhaps this situation is too technical for reporters, and yet the press agencies don't hire experts to provide analysis. And here you are, providing it free. Thank you.

    Could you please elaborate on what it would mean if uncontained fission is occurring? It sounds very bad, but I'm not clear on why/how.
    Thanks.
    Laura

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  7. Thanks for all of your comments!

    Corium is the generic term for melted together core materials. It will chemically react with concrete, yes, and theoretically continue to move down... but no deeper than 60 to 90 feet, if at all, even for the biggest reactor.

    "Criticality" is a self sustaining chain reaction. A reactor can have an increase in fission rate (fissions per second) and still be nowhere near critical. We're not implying recriticality here, just an increased fission rate both from the evidence and the proof of TEPCO's reaction... see newest post on the blog!

    There is a post on this site to the AQMD page which monitors airborne contamination near Los Angeles. While specially made equipment might detect tiny traces of elements from Fukushima Daiichi in many places, the exposure from such tiny amounts is zero. Zip. Nada.

    "Uncontained fission" means that fission is occurring in material in which the fission products aren't kept inside what they're supposed to be inside.. the fuel material, be it fuel pellets or fuel plates. They might get right into the water being used to cool the plant or even into air above the water level. This isn't a true technical term -- I'm using it to try to relate what's going on, or could be going on, in clear and understandable terms. Thanks for the compliment, Laura! And thanks to the rest of you too!

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