In January this year, at Unit 4 of Kansai Electric Power's Takahama Nuclear Power Station in Fukui Prefecture, the reactor automatically shut down. It was reported that it was caused by falling into the reactor due to a mechanical failure.
Unit 4 of the Takahama Nuclear Power Plant in Takahama Town, Fukui Prefecture, was in operation, and on January 30, an alarm was issued to notify an abnormality that the amount of neutrons, which indicate the state of nuclear fission in the reactor, had decreased sharply, and the system was automatically shut down. Did.
Regarding this trouble, Kansai Electric Power compiled a report on the 7th and explained it to the Nuclear Regulation Authority.
According to this, it was estimated that one of the 48 control rods had fallen into the reactor, partially suppressing the nuclear fission reaction, reducing the amount of neutrons and triggering the alarm.
During operation, the control rods are lifted above the reactor and held by the force of the electromagnets, but the electromagnets that hold the three control rods, including the one that fell this time, show a phenomenon in which the current value drops. that it has been confirmed.
It is believed that the cables that send current to these electromagnets were causing connection failures due to the weight of other cables that were overlaid from above.
As a countermeasure, Kansai Electric Power will replace the cable with a spare one and cut the excess cable so that it does not take weight.
The regulatory agency will review the report in detail and consider future responses.