Japan Nuclear Risk Low

The nuclear meltdown situation is hard to understand, with government saying it’s under control but having also said that prior to the big explosion. The most dire warnings describe the worst-case scenario as being a hydrogen-bomb-like explosion that spreads radioactivity over a large area.

Scientists dismiss that out of hand, however. The most encouraging piece I’ve seen on this came from Dr. Josef Oehmen, a research scientist at MIT, who wrote that “there was and will *not* be any significant release of radioactivity from the damaged Japanese reactors.”

He’s disappointed to find in media reports “blatant errors regarding physics and natural law, as well as gross misinterpretation of facts, due to an obvious lack of fundamental and basic understanding of the way nuclear reactors are build and operated.” He offers the following reassurance:

The entire “hardware” of the nuclear reactor – the pressure vessel and all pipes, pumps, coolant (water) reserves, are then encased in the third containment. The third containment is a hermetically (air tight) sealed, very thick bubble of the strongest steel. The third containment is designed, built and tested for one single purpose: To contain, indefinitely, a complete core meltdown. For that purpose, a large and thick concrete basin is cast under the pressure vessel (the second containment), which is filled with graphite, all inside the third containment. This is the so-called “core catcher”. If the core melts and the pressure vessel bursts (and eventually melts), it will catch the molten fuel and everything else. It is built in such a way that the nuclear fuel will be spread out, so it can cool down.

The [Fukushima] plant came close to a core meltdown. Here is the worst-case scenario that was avoided: If the seawater could not have been used for treatment, the operators would have continued to vent the water steam to avoid pressure buildup. The third containment would then have been completely sealed to allow the core meltdown to happen without releasing radioactive material. After the meltdown, there would have been a waiting period for the intermediate radioactive materials to decay inside the reactor, and all radioactive particles to settle on a surface inside the containment. The cooling system would have been restored eventually, and the molten core cooled to a manageable temperature. The containment would have been cleaned up on the inside. Then a messy job of removing the molten core from the containment would have begun, packing the (now solid again) fuel bit by bit into transportation containers to be shipped to processing plants. Depending on the damage, the block of the plant would then either be repaired or dismantled.

That’s more encouraging than media and government reports!

Hat tip to Anne Groden, et al. for the article.

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