TEPCO’s Cautious Restart: Nuclear Energy’s Measured Return in Japan

The Tokyo Electric Power Co. Holdings (TEPCO) has partially restarted Reactor No. 6 at the Kashiwazaki-Kariwa Nuclear Power Plant in Niigata Prefecture. This marks the company’s first reactor restart since the Fukushima Daiichi incident in 2011. The activation of the 1.35 GW reactor is a significant step in Japan’s cautious return to nuclear energy as the country prepares for peak summer energy demand.

The Nuclear Regulation Authority (NRA) of Japan has granted permission for “test use” of Reactor No. 6. TEPCO plans to gradually increase the reactor’s output to 50% within a week, after which it will be temporarily shut down for inspections before further power escalation. The company aims to resume commercial operations by the end of February, pending final regulatory approvals.

Kashiwazaki-Kariwa, located 220 kilometers northwest of Tokyo, is the world’s largest nuclear power station. When all seven reactors are operational, they generate a total capacity of 8.2 GW. The electricity produced primarily serves the Tokyo region.

Originally, TEPCO planned to launch Unit No. 6 on January 20, but postponed due to a fault detected in the alarm system during pre-start tests. Following additional checks, the NRA authorized test usage, allowing TEPCO to initiate rod extraction and start the nuclear reaction.

In December, the Niigata Prefecture assembly supported the governor’s consent to restart Reactors No. 6 and No. 7. Reactor No. 7 is expected to resume operations later, following the completion of a facility required by Japanese standards established post-Fukushima.

Since the 2011 earthquake and tsunami caused meltdowns at Fukushima Daiichi, Japan halted all 54 nuclear reactors. Prior to this, nuclear energy accounted for about 30% of the country’s electricity. Now, Japan has 33 operational reactors, but only 15 are currently online, including Kashiwazaki-Kariwa. In the 2023 fiscal year, nuclear energy provided only 8.5% of Japan’s electricity. The government aims to increase this share to 20% by the 2040 fiscal year as part of its energy security and decarbonization strategy.

Despite regulatory approvals, the restart process remains politically and socially sensitive. Public trust in nuclear power is slowly rebuilding, with ongoing concerns about seismic risks, evacuation planning, and safety oversight reliability. TEPCO stated it would proceed cautiously at each stage of the restart process, ensuring commercial operation resumptions only after meeting all regulatory conditions.