Looking at the timelines, we get this partial information:
15:30 IC trains A and B manually secured, loss of all cooling to Unit 1
18:18 to 18:25 partial operation of train A
18:45 earliest start of Unit 1 core damage per TEPCO November 2011 analysis
March 11 Unit 1 and 2 MCR instrumentation...
These are quite interesting studies. The Japanese Fukushima reports also mention two papers on hydrogen explosions outside of primary containment, which they consider obscure (one modelling Olkiluoto NPP in Finland and the other Browns Ferry NPP). It appears a lot of theoretical work on severe...
I think the correct phrasing is that nobody knew the incoming tsunami would be high enough to inundate the entire seaside of the site, until a few minutes before it was too late.
Obviously, at that point they didn't know they were going to have a SBO, just suspected it.
This is later clarified...
There's no need to bring in straw men in the form of fictional action heroes. We already know the plant operators did many unconventional, hazardous and even unprecedented things when they had adapted to the realisation that they were managing a very severe accident with life threatening...
They were using SCBA gear with 20 minute tanks and full body suits to enter other parts of the reactor buildings due to radiological conditions already after midnight of March 12th. That equipment must have been present onsite and not brought in, as such external supplies started to only arrive...
They were lining up make up water to the IC pool from the fire protection system tank through the DDFP that was already running in idle. I believe there were 3 valves outside primary containment that would have needed manual opening for this to work. This plan was only changed to core injection...
Unit 1 did have HPCI, it was lacking RCIC. However, there is no evidence of any attempt to start HPCI in unit 1 during the accident.
I'm not at all convinced IC was inherently a worse design than RCIC+HPCI for high pressure cooling. In fact, it is making a comeback in ESBWR. It appears more...
The what-if questions are very interesting from the human performance standpoint. In transportation safety investigations it's standard practise to try to evaluate what would have been the optimal human response and most of the time to also try to validate that performance model with human...
Going back to March 11th 2011 about 15:50 and the SBO of unit 1, is it a correct conclusion from current understanding that the four AC operated internal containment isolation valves of the isolation condenser (MO-1A, MO-1B, MO-4A and MO-4B) inside the PCV were partially closed (April 1, 2011...