I guess their need to prioritise and the numerous ways they became overwhelmed by the situation would explain the lack of measurements. Perhaps there was a specific difficulty with getting these measurements in particular, although I don't remember reading about it in reports, mostly it was just criticism of their failure to monitor it.
And yes you are right in that I cannot determine whether the state of the S/C made much difference, they had plenty of other problems that hampered venting and SRV operations.
I've now been looking at the detailed documents that form part of the other 'final report' that I was waiting forever to be translated and then forgot about until recently. One of them does go along a path that's been pursued on this thread from time to time, the failure to vent and why this lead to the idea that reactor 2's containment failure was especially bad for the environment.
Pages 34-40 of this one:
http://warp.da.ndl.go.jp/info:ndljp...nt/uploads/2012/08/NAIIC_Eng_Chapter2_web.pdf
They make it pretty clear that since reactor 3 was vented on numerous occasions, containment did not remain at high pressures for extended periods of time. They make the point that reactor 2 drywell pressure was way too high for seven straight hours, and that containment then failed in more than a minor way, leading to depressurisation without venting. The report is somewhat inconsistent in its discussions though, since they also talk about reactor 1 and from the data they've used the containment pressure for 1 was very high for even longer, 12+ hours, but they don't really dwell on that using the same narrative they used for reactors 2 & 3. I think that's because in the case of reactor 1 a large failure of containment sufficient to decrease pressure significantly didnt occur during this time, so despite the lengthy delay in venting it was still the vent that was eventually responsible for massively reducing pressure at that stage.
So despite the fact that containment ultimately failed in some manner at all three reactors, this does leave me with questions such as 'why did reactor 2 containment fail in a dramatic way more quickly than reactor 1 containment?' or to put it another way 'how did reactor 1 containment last so long under high pressure?'.
Of course to answer this we need to know more about the damage that has been done, and may be waiting a long time for that, especially as TEPCO & government agencies do not seem very keen to highlight every detail of containment damage that they have observed at any point. Mostly what we have learned so far is more about what did not happen, ie the suppression chamber of reactor 2 and the surrounding area does not sem to be damaged in a way people originally thought, and these days the s/c low pressure is assumed to be due to sensor failure.
Please note that I am only speaking of containment failure on a scale necessary to rapidly and significantly reduce pressure, and only about the first meltdown events at each reactor. Clearly there were more minor containment leaks at the reactors at early stages, and potentially further significant releases of radioactive material on subsequent days that haven't received enough attention.
Regardless, the areas I've drawn attention to support the earlier discussions on this thread regarding the reactor 2 release. Large quantities of containment atmosphere, including radioactive material from the initial melting stages left reactor 2 containment in a vigorous manner, at a time when the containment was at a high pressure. At the other reactors, despite some lesser containment leakage, broadly equivalent releases happened via wet-venting.
However I should be careful not to ignore later events at all three reactors, since these reports also touch on the possibilities that further melting events happened at 1 & 3 and venting was not the only release path for these. For example there is talk of reactor 1 doing bad things some days after it first melted, and with regards to reactor 3 in addition to various smoke events that people talked about on these forums at a lot at the time, both these reactors had periods where water injection was temporarily halted long after their original meltdowns. For this reason i would like to better understand how much radioactive material can get from the fuel into containment atmosphere and ultimately the environment at later stages, compared to the amount that can be generated and released during the initial melt. This is one way to better understand how much the failure to take into account later events may have distorted the picture that reactor 2 was responsible for the bulk of the environmental release.
