Ishikawa earthquake
Ishikawa prefecture had a strong earthquake on Sunday morning, but luckily, the two nuclear reactors there were not functional at the time, according to NHK.
One of its reactors have been in the news recently, as Hokuriku Electric Power Co., known as Hokurikuden, failed to report a criticality accident in 1999 at its nuclear power plant in which there was an uncontrollable chain reaction for 15 minutes:
On June 18, 1999, three of the 89 control rods inserted from underneath into the reactor core suddenly slipped out during a regular checkup at Shika Nuclear Power Station, causing the reactor to reactivate. The reactor was not automatically stopped and the chain reaction lasted for 15 minutes. But the company did not sufficiently inspect the cause, and failed to keep records of the accident or report it to the government.
I wrote about the cover up just a couple of days ago... I'm so glad these two reactors were off-line Sunday morning. Who knows what might have happened with a 6.9 earthquake nearby.
(Photo and quote from Yomiuri Shimbun)
Comments
Criticality is the state when the number of neutrons released by fission is exactly balanced by the neutrons being absorbed. A reactor is said to be "critical" when it achieves a self-sustaining nuclear chain reaction, as when the reactor is operating. It is not a "runaway" situation.
Supercriticality is when the chain reaction is accelerating, and that was not happening in this instance.
Apparently, they inadvertantly started up the reactor. While I agree that this was a serious incident, the most disturbing aspect of it to me was the cover up.
Japan will have to reconsider its official position that nuclear power is 100% safe, and catch up with the view in other countries, that it is "probably safe".