The real question — the one you’re not asking — is whether this risk, however small, is necessary or even worthwhile. Since Vermont no longer buys any power from VY, since there is a glut of electrical capacity on the New England grid into the foreseeable future, and since studies show that both VT and the rest of the nation simply waste roughly 20% of the electricity consumed, that question looms considerably larger now than it did just a few years ago.Since you’re demanding details, however, let’s look more deeply at 2 questions:1) “Design basis” is not handed down from on high. Fukushima was designed to resist earthquakes, but its designers did not think that an earthquake as large as the one that occurred was “credible,” and therefore did not design for it. Precisely the same is true for tsunamis, in fact. Fukushima WAS designed to resist CREDIBLE tsunamis, but the one that occurred was larger than deemed credible. More broadly, consider the impact of climate change — not even on the radar screen in the late 1960s when VY and Fukushima were designed — on a plant designed to last for decades. Or the notion that a terrorist would intentionally fly a plane into a target, an idea which would have been laughed at in 1967 when VY was designed. What all these examples show is that the design basis is only as good as the engineers’ ideas of what is credible, and yet these can easily prove false.

2) Even if no eventuality ever exceeds the basis for which nuclear plants are designed, there is little margin for error in their operation either: small mistakes can have major consequences. Yet nuclear plants are run by human beings, who, even under the best of circumstances, make mistakes. Murphy’s law pertains as much to nuclear power as to other human endeavors. One need only look at the twice collapsed cooling towers at VY to see that its operators are not perfect. It is fortunate that the collapse of the cooling towers had no radiological consequence, but that’s good luck, not an indication of infallibility.

What unites VY and Fukushima — besides their substantially identical design — is not the PARTICULAR accidents most likely to occur, but rather their common vulnerability to loss of offsite power which, at Fukushima, led to loss of cooling water, and their inadequate containment design for which, it turns out, hard venting did NOT adequately compensate.

Peruse a list of major nuclear accidents and what leaps off the page is that almost every one of them had a different trigger: neither Chernobyl nor Three Mile Island were subjected to earthquakes or tsunamis, and yet they melted down. The only common cause is the one you folks are intentionally missing: all nuclear plants are designed, built, and run by fallible humans.