Nuclear News by Region
Tokyo, Oct. 15 — “The Japanese nuclear safety agency secretly calculated the possibility of a worst-case meltdown at Tokyo Electric Power Co.’s Fukushima No. 1 power plant,” reports the Yomiuri Simbun.
The agency began working on this report in late March, as Tepco was saying the nuclear fuel was only “slightly damaged.” It wasn’t until April 18 that the Japanese government acknowledged the fuel had begun to melt. Tepco did not acknowledge this until April 20.
In one scenario, all reactor cores dropped out at the same time. In another, melted fuel jetted out of the vessels.
The calculations were premised on nuclear fuel at Reactors No. 1, 2 and 3 would melt down entirely, developing into a so-called “China syndrome,” the worst-possible scenario.
“Coined in the United States, the term China syndrome refers to an imagined worst-case meltdown of nuclear fuel that burns through the bottom of a containment vessel and eventually through the Earth’s crust until finally reaching China,” reports Yomiuri.
The agency’s calculations indicated that if water could not be injected, erosion could badly damage the reactor containment vessels’ 10-foot thick concrete walls.
The agency said it had roughly gauged the extent to which the pedestals (floor) of the containment vessels would be eroded should all the melted fuel drop through the pressure vessel of the three reactors.
The erosion could “possibly” stop after vessel wall was eroded to a depth of around 6 feet in eight days.