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Sunday, March 13, 2011

Hydrogen gas burn - Fukushima vs. TMI-2

Many sources have -- quite inaccurately -- compared the accidents at Fukushima Daiichi to other accidents. (See our earlier FACTS post on Core Damage.) For whatever it is worth, the hydrogen gas accumulation and explosion is in fact similar to one of the many events that occurred during the Three Mile Island accident.

Here are the simple facts: 9.5 hours into the accident time line at Three Mile Island, hydrogen gas which had accumulated inside the containment reached explosive levels and there was a hydrogen burn. Instantaneous pressure inside the containment pulsed to 28 pounds per square inch. However, the nature of the containment of pressurized water reactor plants is, in general, different and while there was some shock damage there was no external evidence of the explosion. None of the reactor containment or any building was destroyed or collapsed as we are seeing at Fukushima Daiichi No. 1 and No. 3. The containment at TMI-2 had withstood stress quite advanced from that for which it was designed.

In comparison though the similarity with TMI appears to end there, since about five feet in linear measurement of the fuel rods in the upper part of the TMI-2 reactor plant core were destroyed. Rad levels, and known releases at Daiichi No. 1 and No. 3 are not comparable. This is NOT.. repeat NOT.. to say that the event sequence is over and not to imply that core damage has not occurred at both plants. It has; scroll down for further information in many earlier posts. My point here is to counter some of the hyperbole beginning to appear in the general press.

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