China Syndrome – Update

The New York Times takes up the report which I commented on yesterday about the possibility of the China Syndrome.

Molten nuclear fuel may have bored into the floor of at least one of the reactors at the stricken Fukushima Daiichi nuclear power plant, the complex’s operator said Wednesday, citing a new simulation of the accident that crippled the plant in March. …

Soon after an earthquake and a tsunami on March 11 knocked out cooling systems at the power plant, nuclear fuel rods in three of its six reactors overheated and slumped, the operator, the Tokyo Electric Power Company, has said.

In the No. 1 reactor, the overheated fuel may have eroded the primary containment vessel’s thick concrete floor, and it may have gotten almost within a foot of a crucial steel barrier, the utility said the new simulation suggested. Beneath that steel layer is a concrete basement, which is the last barrier before the fuel would have begun to penetrate the earth.

I note that this is the result of a simulation, and that (as far as we know) NO ONE has yet gone into the basements and found evidence of leakage. But, we know with a good degree of faith that Tepco has be underestimating the disaster throughout.

“This is still an overly optimistic simulation,” said Hiroaki Koide, an assistant professor of physics at the Kyoto University Research Reactor Institute, who has been a vocal critic of Tepco’s lack of disclosure of details of the disaster. Tepco would very much like to say that the outermost containment is not completely compromised and that the meltdown stopped before the outer steel barrier, he said, “but even by their own simulation, it’s very borderline.”

“I have always argued that the containment is broken, and that there is the danger of a wider radiation leak,” Mr. Koide said. “In reality, it’s impossible to look inside the reactor, and most measurement instruments have been knocked out. So nobody really knows how bad it is.”

Tepco based the simulation on projections of decay heat released by the nuclear fuel and other estimates. The results suggest that the uranium fuel rods at the No. 1 reactor were most badly damaged, Mr. Matsumoto said, because it lost cooling water before the other two reactors did. The fuel rods were exposed for several hours before fire trucks could pump in emergency seawater.

Because the simulation suggests that heat released as a result of radioactive decay “far overwhelmed” the effect of the cooling water, he said, and because temperatures in the inner pressure vessel that originally housed the fuel are thought to have dropped quickly, Tepco now assumes that “100 percent of the fuel at Unit 1 has slumped” into the outer primary containment vessel.

In addition, the simulation suggests that the fuel bored more than two feet into the concrete, Mr. Matsumoto said.

Not good news. I would still hope a robot can get in there and take a look with cameras.

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