TollandRCR wrote:
An independent, informed perspective on what is happening at the nuclear power plants in Japan. Emphasis mine.
It's probably an independent perspective, and one of the scientists quoted is a legitimate expert on air pollution. He is not, however, an expert on reactors, nuclear physics, or nuclear power. The other is an expert on nuclear power, but although he gave good information on the dangers of the isotopes released into the atmosphere, he wasn't quoted at all on either the likelihood of a catastrophic explosion, core breach, or total meltdown - just on the danger of released isotopes and information failure.
One of the things I've noticed is that the experts that the media has been able to find to comment almost all seem to be coming from groups with well-established positions on nuclear power. I've seen Friends of the Earth, the Institute for Policy Studies, and the Heartland Institute all represented. The opinions of the experts provided by these groups are all remarkably consonant with the groups' already established positions on nuclear power. What I haven't seen much of are opinions from truly independent and informed experts on the possibility of a core breach.
What that suggests to me is that there is a shortage of independent and informed experts who are willing to provide a definite opinion on that matter. There are several reasons that this could be the case: not enough information has been provided to reliably gage the probability, not enough information is known by anyone to reliably gage the probability, a situation like this hasn't happened before making people unwilling to speculate on the record as to how well the models will match reality, or (most likely) a combination of all of the above.
One thing that I have noticed is that Chernobyl is being thrown around a lot, and understandably so. I do not want to understate the dangers of what is happening now, but it's important for people to understand the differences between the reactor there and the BWRs in Japan.
Chernobyl was a 1000MW graphite-moderated reactor. The top of the reactor vessel was a 3 meter thick biological shield, which supported the floor of the central hall of the reactor building, but there was no separate containment structure. At the time of the incident, it was being operated at power, and in an unsafe and unstable configuration. In other words, the nuclear chain reaction was ongoing at the time. When the reactor vessel was breached, there was nothing else to contain the explosion, and a large quantity of the reactor core itself exploded and was spread into the atmosphere and over a wide area. This process was aided by the graphite, which was on fire at the time.
Fukishima I-1 is a 460MW reactor at the end of it's service life (it was scheduled for shutdown in about 2 weeks). It's a boiling water reactor, and uses water to moderate the rections. It was successfully placed into shutdown (SCRAMmed) when the earthquake hit, and as far as anyone seems to know there is no ongoing nuclear chain reaction. There is, however, a great deal of residual decay heat that needs to be distributed after a shutdown, and this is the area where there are major problems. One of the issues that the engineers are dealing with is a rise in pressure within the vessel. To keep the reactor vessel and containment from over-pressurizing and blowing up, they have released radioactive steam from the reactor and containment. This is not good, but not nearly as bad as a pressure explosion inside the containment. Some of the gasses released include hydrogen, and that is what caused the explosion that was seen.
The building that blew out is not the primary containment surrounding the reactor vessel. It's a secondary building that sits over the primary containment structure, that in turn sits on top of the reactor vessel. The explosion took place outside the primary containment but inside the secondary building. The secondary building is designed to be much weaker than the primary containment, and pressure from explosions takes the path of least resistance, so the explosion should have done little to no damage to the primary containment and none to the core.
There is still a great deal of danger, and they still need to continue cooling the reactor. It's entirely possible that there has been a partial meltdown of some of the core, but there's still a great deal that would need to go wrong for there to be a Chernobyl-type disaster. At present, the main threat is still the need to release contaminated gasses in order to maintain core pressures at safe levels. That's bad, particularly if there's a lot of cesium-137 in the gas mix, but it's nowhere near as bad as having the core spread across a large area.
Right now, I'd say there's cause for concern and worry, but not panic.
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