NUCENG said:
And their alternatives are what?
You are absolutely justified in your concerns about potential additional problems. Keep watching and questioning.
Alternatives... I am concerned that the site is still not instrumented properly. We should know most everything by now, or at least all that matters. Water flows, state of piping. Thanks for the encouragement, there is not much I can do from the sidelines, except ask questions.
Are there any indications that corium can still be in a molten state after 2 years?
At one point a few months ago there have been some changes - thermometers failing mostly - that suggested new paths for the water, or corium shifting, or both. We don't know. Just looking at the thermal power that it can still make, there shouldn't be any of it that is still molten though, no? I mean, barring odd situations, such as a hot bubble in a very efficiently insulating ceramic foam or something? When I said "corium flows" I mostly meant in the past - the paths it took are assumed, not known.
Has any radiological evidence of reactivity changes indicated an impending recriticality?
We don't know. There are to my knowledge no neutron detectors anywhere near the reactor buildings. I haven't read any mention of anything like that. The (enormous amount) of assorted metallic debris that has already been removed has not been checked for neutron activation. And so on.
They are injecting water through both feedwater and spray piping. Adjustments in these flows seem to demonstrate that at least some of the flow from both paths is getting where it belongs.
I am not disputing that, evidently there is some water (a lot actually). We don't know how exactly it gets to where it is and we don't really know where it goes when it goes (well, to the sea eventually but...) and so the cooling loop is not really closed. That should be a cause of great concern, due to contamination issues. Yet it somehow isn't.
Operating pressures of piping systems still in use are significantly lower that design conditions.
There's that at least, yes.
Leaks or additional cracks are possible or even probable due to damage, corrosion, and poor chemistry, but required flows are fairly small and there are additional paths available. Time to respond is in terms of days, not hours as it was in 2011.
Small blessings.
I can think of at least one practical reason to FINALLY do a thorough check of the piping system - the water processing/storage facility is overloaded as it is, flows could probably be reduced even further, much further in fact if we (TEPCO really) actually knew where the water is needed and how to get it there.
