Saturday, March 12, 2011

Understanding a Nuclear Meltdown

A nuclear meltdown occurs when a reactor’s cooling system fails, allowing the nuclear fuel to overheat and melt. If the container is damaged, the melting fuel could release radioactive substances into the air.

Japanese Chief Cabinet Secretary Yukio Edano said at a press conference that the blast didn’t damage the reactor container, only the structure outside it, and that there was no major radiation leakage with the explosion.

“I think we can get this under control” by cooling the reactor with seawater, Edano said, a process he said could take five to ten hours.

Japanese national broadcaster NHK earlier cited Fukushima authorities as saying that the ceiling of the reactor building had collapsed. It said radioactivity at the site was rising to 20 times normal levels. Other reports said the walls of the building that housed the reactor had been blown away.



  1. Question to any experts out there:

    I thought the control rods could be inserted to stop the radiation flux and thus stop the heat production. Is that the case? If so, how long does that process take?

  2. The reactor doesn't stop immediately after the rods were inserted (it continues to produce decreasing amounts of heat over days). So to shut it down normally continuing flow of coolant is needed, which requires electricity.

    (Even in "stopped" mode the reactors continue to generate some heat due to residual radioactive decay).