ScribbleLive

If the sudden and final (fatal) pressure drop in RVP 3 was caused by a Safety Relief Valve, not corium penetration, just citing that fact alone begs the question as to why the core was never able to regain its pressure. Other ventings didn't result in permanent depressurization. The fact that the pressure drop is exactly as predicted by Ott et al. (ie, the degree of the drop is just about a perfect match to Ott et al.), is, imo, compelling evidence that that's what happened in light of the inability of the core to ever recover pressure again.

@Edano, it looked like we had gotten some clarity, and then a swap of new information, argh!!

swamp

@Ian , the safety valves close automatically when the pressure drops. The hardened vents to relieve pressure from the wet well closed by themselves somehow after crew had openened them. This was unintended. Tepco just does not know how long these valves stayed open. They had to send crew in repeatedly to find out whether they were closed and reopen the valves.

@Edano, the safety-valve doc is all Peter's fault. ;-) teasing!
The data by itself looks obvious for melt-through.

@I should add that also safety valves may fail open, if they are used too much.

@Peter, thanks for your expertise! It sounds like from the press releases of the 13th that they say they opened the SRV.

A curious note is that they add to each press release on the 13th about Unit 3 "Currently, we do not believe there is any reactor coolant leakage inside the reactor containment vessel." Oh really now?!! What an interesting thing to say when that's exactly what is could seem was happening (what I'm confident was happening that led to a huge mushroom cloud of vaporized seawater). I mean, it's like why state that if there wasn't at least the suspicion that the water was leaking. It's almost like you lie only when you realize you need to. I don't accuse even Tepco lightly (in fact, I think I'm a rare case of never having accused Tepco of lying), but here I'm getting suspicious!

I checked the history for unit 1 in the NISA doc. There is an explicit statement that the HPCI malfunctioned.

@Ian , must be legal like let's not confess anything we do not have to.

@es, brilliant observation!!! They say they don't believe it's leaking out of the reactor containment vessel, that's not the reactor pressure vessel! OMG! That's like an admission that they believed it was leaking out of the RPV!

@Ian , that complies with the philosophy: the containment contains the lot no matter what the rpv does. As long as everything is contained, nothing comes out, no sweat. Only it did not work that way.

Remember the PM had to order the hardened venting. Had it been for tepco leaders in Tokyo venting might not have happened, because otherwise they would have been responsible for letting the Jinni out of the bottle.

@Edano , this something I still wanted to mention. When the safety valves open, pressure is relieved from the rpv into the wet well, where it is supposed to be diminished in the pool of water. However, that diminution only works with steam, not with gases like noble gases, hydrogen and iodine. If the relieved pressure from the rpv brings a lot of those to the wet well, the pressure in the wet well will rise. That is when we must resort to hardened venting. Futhermore, if there is a hole in the rpv, pressure will rise in the dry well. Tepco also had hardened vent for the dry wells, but never used them. I guess the idea was that they could relieve the pressure in the dry well via the breaches in the rpv through the water of the suppression pool which was supposed to filter out plenty radioactivity. Regardless and despite venting, pressure built up in the dry well of unit 3 until the lid blew.

Too much undiminished pressure for the suppression pool to handle. There was a statement around then (can't remember which reactor) talking about using the condenser chamber of the suppression pool for extra fluid storage.