Kashiwazaki-Kariwa Nuclear Plant: Reactor Shut Down After Malfunction

The Japanese electric company TEPCO (Tokyo Electric Power Company) halted restart procedures for reactor number 6 at the Kashiwazaki Kariwa (KK) nuclear power plant – the world’s largest by capacity – and subsequently ordered its shutdown this Thursday. This action followed the detection of an alarm within the control rod monitoring system, just one day after the installation was reactivated.

Restart Interrupted

According to a company statement, “During the operation of withdrawing the control rods, an alarm was issued in the monitoring system (…) for one of the control rods, and the operation was suspended.” TEPCO attempted to replace electrical components within the panel operating the control rods – essential for regulating reactor power and ensuring safety – but the issue persisted, prompting a full investigation.

Did You Know? The Kashiwazaki-Kariwa plant has a capacity exceeding 8,000 megawatts (MW), making it a key component of TEPCO’s energy supply plan.

TEPCO has affirmed that “the plant is in a stable condition and there is no radioactive impact to the outside.” Shortly after the alarm, the company announced its decision to shut down the reactor while investigating the cause, promising to release findings as soon as available.

“While the investigation is underway, given that determining the cause is expected to take time, we have decided to temporarily shut down the plant today and inspect the affected area,” the company stated in a subsequent communication.

Recent Reactivation and Prior Issues

This incident occurred just one day after TEPCO restarted the plant on Wednesday afternoon, fifteen years after its closure in 2011 following the Fukushima nuclear plant accident – also managed by TEPCO. The assembly of the Niigata prefecture, where the KK plant is located, approved the reactivation of reactor number 6 in December, after national nuclear regulators approved the restart of two of the complex’s seven reactors.

Expert Insight: The rapid shutdown following restart highlights the stringent safety protocols in place for nuclear facilities, even after extensive reviews and approvals. This demonstrates a commitment to prioritizing safety over immediate energy production.

Reactors 6 and 7 had passed reviews for reactivation in 2017, but were subsequently ordered to remain offline due to security concerns regarding potential terrorist attacks. Approval for the security measures was granted in December 2023, paving the way for TEPCO to proceed with the restart process.

Potential Next Steps

The immediate priority is for TEPCO to determine the cause of the alarm in the control rod monitoring system. Depending on the findings, the restart process could be delayed significantly. It is possible that further inspections and modifications will be required before regulators will allow the reactor to be brought back online. Analysts expect a thorough review of safety procedures following this event.

Frequently Asked Questions

What caused the shutdown of the Kashiwazaki-Kariwa reactor?

The shutdown was triggered by an alarm in the control rod monitoring system during the process of withdrawing the control rods.

Was there a release of radiation?

TEPCO has assured that the plant is in a stable condition and there has been no radioactive impact to the outside.

When was the Kashiwazaki-Kariwa plant last operational?

The plant was last operational fifteen years ago, before being closed in 2011 following the accident at the Fukushima nuclear plant.

How might this incident impact Japan’s reliance on nuclear power as a key energy source?