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Mar19-11, 09:35 AM
TCups's Avatar
P: 494
Quote Quote by AntonL View Post
Possible cause of hydrogen explosion of reactors 1 and 3 is published by UCS here - an excellent article

What bothers me is quote "A little-known test performed decades ago at the Brunswick nuclear plant in North Carolina may hold the key to answering that question." - why little-known - this is a design limitation/fault common to many nuclear power stations. If this had been common knowledge in the nuke industry safety manuals and emergency procedures may have been rewritten - I am sure they are now being re-drafted.

Now at Fukushima containment vessel pressure has been reported *1) to be steady at .140 to .150 MPa_abs which is about the same as 70PSI Gauge. Now reactor vessels 2 and 3 are reported near 0 pressure Guage that is the pressure inside the the reactor vessel is the same as the pressure in the containment vessel leading to the conclusion that the reactor vessel is breached and the containment vessel 'auto-vents' as described in the article.

It is also reported that sea water flooding into the reactor cores is taking place continually one of two things can happen
1- worst case it boils of and steam is vented as above then slowly a massive NaCl crust must be developing
2- best case the reactors have cooled and the containment vessel slowly filling with water

*1) Reactor 3 CV pressure 0.045MPa_abs must be a typo as it is a vacuum and I think should read as 0.145MPa_abs as in previous reports

Edit: As pointed out later pressure conversion is wrong hence wrong part struck out
This proposed explanation seems quite plausible but in retrospect, even more worrisome to me.

If the hydrogen gas were leaking at the drywell head, then that leak was inside the concrete containment, and so presumably was at least part of the explosion. I am wondering about the likelihood that the concrete shield plug(s) were blown off the top of the secondary (concrete wall) containment.

Although, in retrospect, a lay person would have to conclude that any hydrogen arising from a reaction involving the fuel rods would have to arise from within the reactor vessel, I had considered it got from there to the building's interior by a controlled venting process, not leakage from the drywell head, then concrete containment.

One must assume, for this mechanism to be the cause, that the concrete shield plug would not be fitted tightly enough to prevent leakage of H2. It also seems a reasonable assumption, in retrospect, that the concentration of H2 might be significantly higher under than over the concrete shield plug.

Has anyone made an assessment of the probability that the H2 explosions at Units 1, 2, and 3 blew the concrete containment plugs off like the cork on a bottle of cheap champaign?

If the diagram is accurate, it also gives a bit more insight of a hypothetical course any molten material might take from the floor of the SFP to the building's exterior.

Also, in the videos of the explosion of unit 3, I seem to remember something large and heavy falling from the vertical plume just to the side, and that someone pointed out that the blast at (unit 3?) was more vertically directed, like a cannon shooting straight upward. I have to review that video again.

Yes -- here --

Something large and heavy (who knows what), curls off to the left and comes down over the left hand tower in the video. What are the odds if it were the plug, it might be reasonably intact and visible among the debris on the ground. Back to the satellite images . . .

Hmmm. No way to tell, but it gives pause to think what might have fallen through the roof of the building in front of unit 3, doesn't it?

Here's a link to the video:

I understand this is, again, all speculative, but I am compelled to try to understand what my eyes are telling me.