Japan shuts reactor again at world’s largest nuclear plant

Japan on Thursday suspended operations at a reactor at the Kashiwazaki-Kariwa nuclear power station, the world’s largest nuclear plant, after detecting a technical problem only a day after the unit was brought back online. The shutdown involved the No. 6 reactor at the Niigata Prefecture facility, raising fresh questions over the reliability of Japan’s nuclear restart process.

Control rod malfunction prompts shutdown

Tokyo Electric Power Company Holdings Inc. (TEPCO) said the reactor was halted after engineers identified a fault in electrical components responsible for operating the control rods, a core safety mechanism used to regulate nuclear reactions. According to the operator, attempts to correct the malfunction were unsuccessful, leading to a precautionary shutdown while the cause is examined.

Restart faced earlier delays

The reactor had resumed operations on Wednesday following the completion of inspections, but the restart itself was delayed by a day after an alarm related to the control rods malfunctioned during testing on Tuesday. TEPCO said inspections later confirmed the rods were functioning, allowing the restart to proceed before the latest issue emerged.

Plant idle since Fukushima era

Kashiwazaki-Kariwa, with seven reactors and a combined capacity of 8.2 gigawatts, has remained largely inactive since 2012. Operations were suspended amid public safety concerns following the 2011 Fukushima Daiichi nuclear disaster, which was triggered by a massive earthquake and tsunami and severely damaged confidence in nuclear power and TEPCO’s management practices.

Regulator says safety maintained

Japan’s Nuclear Regulation Authority said the reactor remains in a stable condition and that there are no immediate safety risks. The authority added that it will continue monitoring the situation as investigations into the malfunction proceed, as Japan seeks to balance energy security with public trust in nuclear safety.