John Denker is certainly correct that we are having difficulty getting any reliable information about the nuclear power facilities in Japan. Some of the regular news channels such as network TV and on-line sources such as CNN and New York Times contradict each other as well as contradict themselves.
Perhaps some list members can help me as I try to figure out whether the efforts at the nuclear facilities are perhaps making things worse rather than better. Here is my thinking...
First, I have to admit that I don't know the details of the containment engineering in these troubled plants. However, I have worked at some boiling-water reactors in the US (research reactors, not power reactors) and it seems to me that at some point it would have been better to walk away from it and let it melt.
Early on, if cooling water could have been maintained, it would certainly be worth doing, because that would result in the "graceful shutdown" with little or no damage to the reactor. However, once it becomes clear that you have had some core damage, and you're trying desperate measures to keep from totally losing it, your desperate measures can make things worse. We've already seen this. (1) To get cooling water into the reactor vessel, the vessel had to be vented. That released some long-lived radiation such as 137-Cs (30 years) that was otherwise contained. (2) Venting also released hydrogen gas which ultimately exploded and blew away the outer shell of the facility, and maybe caused some other internal damage.
What would happen if these desperate measure were not undertaken and the vessel was not vented? Presumably there would be total core meltdown which may or may not breach the reactor vessel, but it is not supposed to breach the primary containment. Thus, if meltdown occurred and did not breach the primary containment, it would be a mess to eventually clean it up, but there should be no atmospheric release, and there would have been no hydrogen explosion between the primary containment and the outer shell of the building.
I am assuming there is a substantial primary containment structure (something Chernobyl did not have) and I am assuming it would contain the meltdown because it was designed properly and it was not structurally damaged by the quake. These may not be good assumptions for this particular facility under these circumstances, but these are supposedly the assumptions for nuclear facilities in the USA. A core meltdown should not breach the primary containment.
So perhaps once they knew they had no chance of restoring the cooling loops in time to prevent damage to the core, why didn't they just give up?
Another question involves the spent-fuel storage ponds. There should be no trouble keeping these full of water. If loss of water in one of these occurred, why? Were they not paying attention to it? These storage ponds do require some water circulation through heat exchangers, especially early in the storage period. Without power, that circulation would have been lost. But there are supposed to be tanks of water that can gravity feed the ponds if necessary, and last-ditch methods include bringing in water from fire hydrants or from the nearby river or lake or ocean. That could have been pumped with fire trucks because high pressure is not needed. Therefore, if they indeed had a problem at a spent fuel storage pond, how did this come to happen?
Michael D. Edmiston, PhD.
Professor of Chemistry and Physics
Chair, Division of Natural and Applied Sciences
Bluffton University
Bluffton, OH 45817
Office 419-358-3270
Cell 419-230-9657