Patterico's Pontifications


N.Y. Times: Japanese Officials Presume Two Partial Meltdowns Have Occurred

Filed under: General — Patterico @ 12:10 am

And that’s not the only problem:

Japanese officials struggled on Sunday to contain a widening nuclear crisis in the aftermath of a devastating earthquake and tsunami, saying they presumed that partial meltdowns had occurred at two crippled reactors and that they were facing serious cooling problems at three more.

The emergency appeared to be the worst involving a nuclear plant since the Chernobyl disaster 25 years ago. The developments at two separate nuclear plants prompted the evacuation of more than 200,000 people. Japanese officials said they had also ordered up the largest mobilization of their Self-Defense Forces since World War II to assist in the relief effort.

Robert Stacy McCain has been energetically aggregating the news, and has eschewed any partisan extremes, neither wringing his hands in panic, nor (as some have done) rushing to declare everything is OK in advance of the facts. He has been appropriately suspicious of official reports and entertaining as usual. You could do worse than to pay close attention to his blog for the rest of the weekend, as well as my perennial favorite Hot Air.

Understand that “partial meltdown” does not mean “deadly plume of radiation headed for U.S.”:

A meltdown occurs when there is insufficient cooling of the reactor core, and it is the most dangerous kind of a nuclear power accident because of the risk of radiation releases. The radiation levels reported so far by the Japanese authorities are far above normal but still too small to pose a hazard to human health if the exposure continued for a brief period. The fear was that more core damage would bring bigger releases.

The Japanese Nuclear and Industrial Safety Agency said that as many as 160 people may have been exposed to radiation around the plant, and Japanese news media said that three workers at the facility were suffering from full-on radiation sickness.

Viewed in perspective, this is hardly the biggest problem to come out of the double disaster, by a longshot. At least so far. The casualties of the earthquake (now upgraded to 9.0) and tsunami have yet to be measured, but will certainly be in the tens of thousands. Nobody has died as a result of the likely meltdowns.

And again: nothing is definite in a situation like this. Saying something is “presumed” does not mean it is true. As always, appropriate skepticism is the watchword.

UPDATE: This piece appears to have a good explanation of the mechanics behind a reactor such as the one at Fukushima, together with an explanation of all the controls in place. I can’t really vouch for the accuracy of the piece, so take it with a grain of salt. If you believe the piece, it provides reassurance that there is no Grand Disaster in the works, as there are numerous backup systems in place to prevent anything catastrophic, even in the face of numerous unexpected events like the earthquake, tsunami, and explosion. The author’s conclusions about the current state of affairs:

# The plant is safe now and will stay safe.
# Japan is looking at an INES Level 4 Accident: Nuclear accident with local consequences. That is bad for the company that owns the plant, but not for anyone else.
# Some radiation was released when the pressure vessel was vented. All radioactive isotopes from the activated steam have gone (decayed). A very small amount of Cesium was released, as well as Iodine. If you were sitting on top of the plants’ chimney when they were venting, you should probably give up smoking to return to your former life expectancy. The Cesium and Iodine isotopes were carried out to the sea and will never be seen again.
# There was some limited damage to the first containment. That means that some amounts of radioactive Cesium and Iodine will also be released into the cooling water, but no Uranium or other nasty stuff (the Uranium oxide does not “dissolve” in the water). There are facilities for treating the cooling water inside the third containment. The radioactive Cesium and Iodine will be removed there and eventually stored as radioactive waste in terminal storage.
# The seawater used as cooling water will be activated to some degree. Because the control rods are fully inserted, the Uranium chain reaction is not happening. That means the “main” nuclear reaction is not happening, thus not contributing to the activation. The intermediate radioactive materials (Cesium and Iodine) are also almost gone at this stage, because the Uranium decay was stopped a long time ago. This further reduces the activation. The bottom line is that there will be some low level of activation of the seawater, which will also be removed by the treatment facilities.

Under this analysis, what was the “meltdown” that occurred, if it occurred? If I’m reading it right, the author claims that there has been limited melting of the Zircaloy tubes that house the fuel pellets, but no melting of the fuel itself. Is that inconsistent with the reports of “meltdowns”? Depends on the terminology. The press should probably spend more time educating people about the mechanics and less time throwing around undefined terms like “meltdown,” huh?

One question: the author claims of the radiation outside the fuel rods: “if these radioactive materials are released into the environment, yes, radioactivity was released, but no, it is not dangerous, at all.” But if that’s right, how do we reconcile that assertion with the reports above of radiation sickness for three of the workers?

I’m sticking with my previous stance. We don’t really know what is going on and making any positive declarations about anything is premature.

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