shadowncs said:
And perhaps it is? In the vids you can clearly see both unit 2 and unit 3 lower-level basements are flooded at the stairwell. For unit3 vid the worker spends a large amount of time measuring radioactivity of the stairwell water, outside the torus room, which appears to be a few meters lower than the basement level the torus room door is located. That water comes from somewhere perhaps the most likely being the torus room. Remember those rooms are quite high. As to water in drywell, TEPCO is yet to confirm there is any water at all - see unit 2 endoscope. We simply don't know yet but I tend to agree, if the torus were intact then we'd expect water in drywell.
I'm surprised by the fact the unit 2 door could be opened, that with the "explosive sounds" reported coming from unit 2 torus early on.
Yes I am pretty sure that the water in the stairwell is the same as torus room water, because those stairs lead down to the floor level of the torus room (as opposed to the door they opened to look into the torus room, which is at least half-way up the torus room wall).
If neither the torus or the lower part of the drywell had damage then yes, we would expect to see much more water in the drywell, TEPCOs original drywell flooding plan would not have been abandoned. We can't use this to establish with certainty that the torus is damaged though because if the torus was intact but the bottom or lower walls of the drywell were damaged, we could still expect to see little water in the drywell and lots of water in the torus room.
As for the explosion at reactor 2, this has not been a safe assumption for a long time either. Firstly because the explosion at reactor 4 building happened around the same time, causing confusion, and later when they looked at local plant seismograph readings it looked like reactor 4 was the epicentre, not reactor 2. And the other reason they made a hasty assumption that the reactor 2 suppression chamber went boom, was because for many hours before the explosion they were afraid that the reactor 2 suppression chamber was in trouble. They knew its pressure & temperature was too high, but they failed in their mission to vent it, so they had to release more steam from the reactor into the suppression chamber anyway, because they were desperate to lower reactor vessel pressure so they could get some water pumped in. The site manager had already made plans for an evacuation, hours before the partial site evacuation actually took place. So with this in mind, its no surprise that when an explosive sound was heard and radiation levels on site climbed dramatically, they assumed the suppression chamber had failed.
And it may well have failed, all we can now rule out is that it failed in a manner where the torus was completely mangled, doors deformed etc.
The intriguing mysteries of reactor 2 only grow for me, because as we have seen from past surveys by humans & robots, there aren't the same sorts of highly contaminated areas at various locations within reactor 2 building that we see with reactor 1 (where various bits of equipment are well contaminated) or reactor 3 (where there were some very high levels of contamination to north-east and south-west of the drywell containment near to pipe penetrations and access doors). At reactor 2 we just have the highly contaminated water in the basement, and several hotspots on the refuelling level near to the concrete cap over containment, not much on any of the other reactor building floors with which we may gain clues about emission pathways.
