Japan shut down the worldʼs largest nuclear power plant just hours after restarting it. It had not been operating since the Fukushima disaster

Tokyo Electric Power Company (TEPCO) has shut down reactor number 6 at the Kashiwazaki-Kariwa nuclear power plant the day after the unit was restarted for the first time in 14 years.

Reuters and Japan Times write about this.

This reactor was restarted on the evening of January 21. It had not been operating since 2011, when the Fukushima-1 nuclear power plant accident occurred in Japan and all nuclear power plants in the country were shut down.

Within hours of the start-up, an alarm went off in the reactor regarding one of the control rods. About 16 hours later, TEPCO reported a “planned temporary shutdown” and took the reactor out of service again for a full investigation.

"We do not expect the investigation and related work to be completed in one or two days. At this stage, we cannot say at all how long it will take," station director Takeyuki Inagaki said at a press conference on the night of January 22.

According to the company, the insertion of control rods began at 11:56 PM on Thursday, and the reactor was officially shut down early Friday morning.

TEPCO said the fault signal came from the control panel of the motor that drives the control rod, indicating a problem with that panel. A separate alarm also indicated a malfunction in the inverter.

Control rods regulate the nuclear reaction in a reactor: they are extended to start nuclear fission and lowered to slow or stop the reaction.

Fukushima accident

In 2011, the “Fukushima-1” nuclear power plant suffered an accident due to an earthquake and tsunami. 150 000–200 000 people were evacuated due to radiation leaks.

In September 2019, the Tokyo District Court acquitted former executives of Tokyo Electric Power Company (TEPCO), the operator and owner of the Fukushima-1 nuclear power plant, in the 2011 accident case.

In 2019, Japanese authorities warned that there was a lack of space in tanks to store the material, so they had “no other option” but to release the diluted water into the ocean.

Japan spent 3.45 billion yen ($320 million) to build a wall to keep groundwater from entering the damaged reactor areas. This has reduced the daily groundwater leakage from about 500 to 100 tons. In 2021, the “ice wall” was found to be melting at Fukushima.

On August 24, 2023, Japan began dumping treated radioactive water from the Fukushima Daiichi Nuclear Power Plant into the Pacific Ocean to free up space at the damaged nuclear power plant.

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