Wednesday, August 31, 2011

Now It's "We Dodged A Bullet"

We are, it seems, still hyperventilating about nuclear Armageddon based on earthquakes. The Independent headlines “Why the Fukushima disaster is worse than Chernobyl,” except that having read the article twice to be sure I didn’t miss anything, I don’t see actual evidence that it’s even anywhere near as bad as Chernobyl. That’s not to say that it isn’t bad, or that it is not imposing terrible tragedy on the people in that part of Japan, but…

Then Balloon Juice headlines “We Dodged a Bullet” and cites one article which bleats that the Virginia reactor was “only” designed to withstand a 5.9-6.1 earthquake, and another which says that the 5.8 earthquake, which was eleven miles away, “may have exceeded design limits” of that reactor. That one says, further, that,

As in Japan, all U.S. power nuclear power plant spent fuel pools do not have steel lined, concrete barriers that cover reactor vessels to prevent the escape of radioactivity.

Actually, the spent fuel is submerged in water to prevent the escape of radioactivity as well as for cooling, and if that water is lost any kind of cover on the container is not going to do much good when the fuel overheats and explodes. That cover would be in pieces and/or in the neighboring state.

Unlike Japan, in any case, the spent fuel pool at North Anna site is at ground level, not 30’ or so in the air, which makes a rather dramatic difference in an earthquake. Nothing in either article comes within proverbial hand grenade distance of actually suggesting that spent fuel was at risk in this earthquake event.

Also, the Japanese reactors which failed are of the boiling water design, while North Anna’s are pressurized water reactors which are several orders of magnitude safer. Again, there is no suggestion in either article that the reactors were ever within any reasonable distance of being at risk of overheating, let alone melting.

The article which says the quake “may have exceeded design limits” of the reactors offers no explanation for that given that they were designed for a 5.9-6.1 quake and experienced a 5.8. The Richter scale is logarithmic, so the 5.8 actual quake is quite a lot smaller than the 5.9 lower limit of the maximum for which the reactors were designed, not the tiny margin that is implied in most writing on this topic. The epicenter was eleven miles away, as well; close, but still far enough to reduce the effects to some degree. The article even says that no damage has been found other than some minor insulation shaken off of pipes, so the statement about “exceeding design limits” sounds a bit ludicrous.

The 5.8 earthquake was the largest on that side of the continent on some sixty years, so the design criteria sounds like it was reasonable, and with no damage other than insulation it sounds like the criteria was adequate as well, so the “We dodged a bullet” headline sounds a bit silly to me.

1 comment:

Arthur said...

Hey... "a miss is as good as a mile". Especially when the miss is BY a mile; or several miles, as in this case.
Several miles, given that the coastal geology is all wring for tsunamis, which is what killed the (damaged, but safe) Fukushima reactors. And that the spent fuel is stored in open "swimming pools" because that is the safest way. That would be why everyone does it, including the most safety-conscious.

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