In terms of news from the plant itself that I haven't bothered to mention here recently, there have been various bits and bobs, but probably the most significant was a preliminary survey down in the torus room basements of reactors 2 & 3. This is where the suppression chamber lives and the room and the stairs leading to it are partially filled with the highly contaminated water. They didn't hang around there long and the photos aren't very good quality, but they did get a picture of part of the reactor 2 suppression chamber. It wasn't totally mangled which has caused them to further step away from the idea that an explosive event happened in this area om March 15th 2012. However at reactor 3 the door was damaged and they could not get in, so it may yet turn out that there was more going on with the suppression chamber or torus room of reactor 3 than reactor 2.
http://www.tepco.co.jp/en/nu/fukushima-np/images/handouts_120314_01-e.pdf
It also means that attention has occasionally turned again as to why radioactive release for reactor 2 has been estimated to be so much higher than the other reactors, despite lack of explosion of the building. People used to think it was something to do with the suppression chamber explosion, but as that explosion seems less likely we must search for other answers. My tentative conclusion at this stage is that it was because they failed to wet vent reactor 2 containment. At reactors 1 & 3 they managed to vent much of the contents of containment out through the emissions stacks, which releases radioactive material into the environment but at least some of the substances get scrubbed by the water in the suppression chamber, and will remain in that water rather than getting out into the air. But at reactor 2 they did not manage to perform this operation. They may have managed a very brief dry vent (just a few minutes) which doesn't go via the suppression chamber and so doesn't get scrubbed, but in any case hours later the containment failed and it is quite likely that lots of stuff came out directly from the drywell containment to the upper part of the building and then the air. You'd think this detail might feature heavily in any discussion of the disaster but for some reason it lurks, not exactly off the radar, but not in the limelight either. I've not been overwhelmed by the depth of journalism about Fukushima, so I will be interested to see whether these possibilities find much of a place in Fukushima history over the longterm.
Anyway regardless of what actually happened at reactor 2, we know that the day it got real bad at that reactor was the day that the worst land contamination occurred. It was real bad timing because just as the emission on site rose dramatically, the weather changed late on the 14th/early on the 15th and wind took stuff south, and then shifted clockwise over the next hours. By the time the wind was taking stuff to the north-west of the plant, there was rain or snow which caused a lot of the contamination in this area, in the same way that the parts of England most affected by Chernobyl were caused by the timing & location of wind & rain. Tokyo got some contamination on this date, but apparently they were very lucky because the rain didn't quite make it to Tokyo then, which would have deposited far more long-lasting radioactive nasties and caused a far worse situation for humans. Tokyo did get hit again days later on the 20th/21st and I don't know if they were lucky with the rain that time, but at least it was not happening on the date of peak emissions from the plant.
Now its also possible that these weather phenomenon have enabled them to underestimate the releases on other days and from other reactors, because for much of the disaster the wind was blowing stuff out to sea, and so there is far less data. But either way its the events of the 15th March 2011 which had the biggest impact on land contamination in Japan, the bulk of the contamination, regardless of the detail of which reactor it came from that I get interested in.
Anyway probably not too many more detailed posts from me from now on, the above is my area of special interest and thats pretty much all I've got to say about it until some unknown future date when we learn something concrete about the state of the reactors. Any day now they will have another go at sticking an endoscope into reactor 2 containment, a longer one this time so they can try to discover the level of water at the bottom of containment (if any), since last time the water was not at the higher level they expected. But I will be surprised if this stuff gives us many more clues as to what happened.
This will count as a separate nuclear incident which I believe has received a provisional 1 rating on the INES scale (the main Fukushima disaster and Chernobyl being a 7 rating).
