March 19th, 2011 – Risk of further explosions in SPFs – Should SFP be removed to temporary storage?

Sent: Saturday, March 19, 2011 1:01 AM
To: Tinkler, Charles; Lee, Richard
Cc: Basu, Sudhamay; Gavrilas, Mirela
Subject: FW: Update

Hi Charlie and Richard,

Good or bad, I’ve asked INL/DOE to talk to you about the spent fuel state in Japan. If that is problematic you can write me off as yet another out of control lab guy/contractor and fire me the next time you see me. Wait: Farouk already did that.

Mitch

—O-ri-gi nal Message —–
From: Farmer, Mitchell T.
Sent: Friday, March 18, 2011 11:15 PM
To: ‘Binder, Jeffrey L.’
Cc: Busby, Jeremy Todd; Grandy, Christopher; Peters, Mark T.; ‘Douglas E Burns’; Peters, Mark
Subject: RE: Update

Hi Jeff,

I’ve taken a look at the viewgraphs and would like to offer a few comments.

1) The opening vg describes large-scale H2 explosions in the vicinity of the SPFs that would make the already dry pools catch fire releasing FPs.

I believe the pools of concern for running dry are 3-4. The hydrogen accumulations and subsequent detonations in these buildings have already removed roof structure and so there is no place for the H2 to accumulate. Secondly, given what little data we have indicates that these pools have been dry for extended periods of time. Zr (from the zircaloy cladding) is an exceptional 0 getter, and so there is probably little cladding left to oxidize to form
additional H2. At this point, the fuel is probably highly degraded, and may be in the form of a rubble bed. I doubt there is little cladding left, and even if there is there is no place to accumulate H2 that would be a concern. Also, if the cladding is highly oxidized then I would guess that most of the Cs and I are already gone. The extent of Ru release, which is a really bad actor in terms of radiotoxicity under air ingress scenarios such as this, is
roughly proportional to the extent of U02 reduction to U308 (going on memory on this), and so it is highly desirable to get these pools quenched again to stop the release of RUOx as well as less volatile fission products.

Note: the NRC and Sandia have substantial experitse, with R&D going on for years in this area and I would try to get them engaged ASAP. Please contact Charlie Tinkler and Richard Lee to get additional input on this; these folks (especially Charlie) have been working on this intensively for years and under the conditions I would really seek their input.

Frankly, in my opinion, the ball has already been dropped on SPF’s number 3-4 and I would just try to get water in there ASAP to try to mitigate additional releases. I think a lot of the bad actors (Cs, I) have already left the house and now it is best to try to quench these beds and mitigate the damage. I wouldn’t be worried about H2 from the SPFs in Units 1, 3 and 4 as there’s no building left to accumulate it. I think for Unit 2 that might not be true but I have access to no information other than CNN.

2) The vgs also talk about H2 from ex-vessel core melt progression, specifically FCIs. What I know is that the cores in Units 1-3 have been have been cooled by seawater injection for several days, and if this was not the case, I would expect that there would have been additional core degradation, H2 release, H2 detonations, and possible RPV failure. 3-4 days is too long to go @ 6 MW decay heat level (what I calculate for Units 2-3) w/o something
giving way inside the primary system without cooling. So, based on the steady cooling process, I have to conclude that Units 1-3 are stable and, whatever the extent of core degradation, Units 1-3 are in coolable configurations. Based on this same reasoning, I stopped worrying about H2 production from in-vessel interactions from these units several days ago.

I’ve also heard concerns about salt deposits in the core and in the SPFs. In the cores, in these degraded states, I’m just really happy right now that they are staying cool regardless of salt deposits that I agree are a concern. If there’s evidence that the degree of core coolability is degrading, then folks can start to worry. However, right now the only course of action is to: a) get fresh water back in (don’t know when that will happen) or b) keep it
up w/ the salt water until (?) the core plugs w/ salt deposits. The one thing we know is that you have to keep the core cooling or (@ 6 MW decay heat level) the core will melt and then one needs to start discussing ex-vessel scenarios.

With regard to salt deposits in the SFPs, the amount of salt water that has been successfully dropped into these pools compared to what has been pumped through units 1-3 is paltry. Since Units 1-3 have not plugged due to salt water, I think that the chances of significant salt accumulation in the SFPs is completely negligible.

Finally, I’ve heard in other areas that there are worries about steam explosions if, e.g, the vesssel were to fail with the drywell flooded. In my opinion, this is not at all a concern. It’s been 7 days now since the incident, and if there is any core melt around the site it will be stiff and viscous because decay heat has dropped considerably. The chances of this exploding on drop into water are, in my opinion, nill. Certainly more detail can be added here and I can do that if you like but that is my opinion.

I hope this is somehow helpful. If someone wants to discuss this please let me know.

Mitch

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