Japan Suspends Restart of World’s Largest Nuclear Reactor After Technical Glitch

Japan has suspended the restart of a reactor at the Kashiwazaki-Kariwa nuclear power plant the world’s largest by capacity just a day after the process began, according to its operator, Tokyo Electric Power Company Holdings (TEPCO). The company said the reactor remains le and there is no safety risk.

The No. 6 reactor at the plant in Niigata prefecture, which has been shut down since the 2011 Fukushima nuclear disaster, was reactivated on Wednesday when workers began withdrawing neutron absorbing control rods to initiate a le nuclear fission reaction. However, the process was halted hours later due to a malfunction involving electrical equipment linked to the control rods.

The issue posed no safety threat and confirmed there had been no release of radiation. The company later decided to place the reactor back into shutdown mode to allow for a more thorough inspection. A spokesperson said investigations into the malfunction were ongoing and the duration of the suspension remains unclear.

Control rods play a critical role in managing nuclear reactions, allowing operators to accelerate, slow, or completely stop fission inside a reactor. The restart had already been delayed from its original schedule after a separate technical issue involving the rods was detected last weekend and resolved earlier this week.

Kashiwazaki-Kariwa, which has seven reactors, was taken offline after Japan shut down its nuclear fleet following the earthquake and tsunami that triggered meltdowns at the Fukushima Daiichi plant in 2011. Only one reactor at the facility was involved in the latest restart attempt.

Japan, which lacks natural energy resources, has been gradually reviving nuclear power to cut dependence on fossil fuels, meet rising electricity demand including from artificial intelligence and achieve carbon neutrality by 2050. Fourteen reactors nationwide have resumed operations since 2011, but this would have been the first TEPCO operated reactor to restart.

If fully operational, the No. 6 reactor could supply about 1.35 million kilowatts of electricity, enough to power more than one million households in the Tokyo area. However, public opinion in Niigata remains sharply divided, with a majority opposing the restart over safety concerns, particularly due to the plant’s location near an active seismic fault line.