clancy688 said:
Two things I discovered by skimming through the report:
Unit 2 - If I read the section about Unit 2 correctly (and I'm not really sure I did, perhaps NUCENG could look over the sections regarding Units 1-3? There's a certain emphasis on venting valves), then Unit 2 never vented. The workers established a vent path, but a rupture disc never failed, even though the pressure was higher than the pressure needed to break it.
So when Unit 2 finally depressurized, it wasn't done through venting - but through containment failure.
Unit 3 - RCIC didn't fail on March 14th, it failed on March 12th at 11:36 local time, HPCI provided core cooling until the morning of March 14th. Was that fact known before?
It does not seem to me like there is much in the way of new information in this report, but it is presented in a way that makes it easier to spot such details. We already knew that they had numerous problems trying to vent reactor 2, and although I am not sure we spent much time talking about it. The fact that venting never happened does not strike me as new, although prior to this latest report I am not sure it was ever specifically stated that rupture disc never failed.
Checking the info from that report with a couple of other sources such as NISA analysis of events, my brief summary of venting details for the three reactors is as follows:
Reactor 1
RPV fell to PCV pressure levels without any mention of SRV valves having been deliberately opened
PCV pressure fell somewhat, and radiation levels at plant increased, before there was any venting.
Early venting attempts were only partially successful or not successful at all for hours on the 12th.
Venting was eventually confirmed, backed up by visual evidence of venting via stack.
Reactor 2
Numerous problems when trying to get various vent paths opened.
SRV's opened on more than one occasion.
PCV pressure didn't rise significantly when RPV pressure first fell, suggesting PCV leak.
RPV pressure increased several times after initial SRV opening, requiring further SRV opening activity to be performed.
PCV pressure then went higher, but the indicated drywell pressures went much higher than the suppression chamber ones.
Venting still didn't work.
Tried to vent directly from drywell to get round the issue of lower s/c pressure compared to d/w pressure, but there was still no indication of success.
Sound near suppression chamber, pressure indication for s/c went to 0, drywell pressure fell over the next few hours.
Reactor 3
RPV pressure fell when HPCI started.
RPV pressure increased when HPCI failed.
Attempts to vent not successful.
PCV containment leaking may have occurred.
Venting succeeded, with visual confirmation of venting via stack. SRV opened at about the same time and RPV pressure fell as expected.
Problems keeping vent path open at certain times in the subsequent days, which sometimes affected ability to continuously inject enough water.
