15 reactors have now returned to service since 2011 Fukushima disaster
Tokyo Electric Power Company (Tepco) has restarted Unit 6 of its Kashiwazaki Kariwa nuclear power station in western Japan after a 24-hour delay caused an alarm malfunction, reports said.
Tepco brought the unit back online on 21 January at the seven-unit station in Niigata Prefecture after a last-minute control-rod alarm failure during a test forced it to delay the resumption initially set for Tuesday.
An alarm system for the control rods, which are used to suppress the nuclear fission reaction, failed to sound during a test operation held on Saturday, Tepco said.
Tepco was reported as saying on Wednesday that it was “proceeding with preparations” and aimed to restart operations at the plant at 19:00 local time (11:00 CET). The Japan Times said Tepco received approval from the Nuclear Regulation Authority to conduct trial operations at 14:00 local time on Wednesday.
Unit 6 is a 1,315-MW boiling water reactor unit that originally began commercial operation in 1996. Fuel loading at Unit 6 was completed in June.
The plant’s restart means Japan has now returned 15 units to service since the 2011 Fukushima disaster.
Kashiwazaki Kariwa is the world’s largest nuclear power station by capacity. According to the International Atomic Energy Agency, its seven boiling water reactor units have a combined net capacity of 7,965 MW.
The facility served as an important energy source to supply electricity to the Tokyo metropolitan area before the 2011 earthquake, tsunami and nuclear accident at Fukushima-Daiichi.
Tepco wants to bring the station back online and said in 2020 it was concentrating its resources on restarting the newer Units 6 and 7.
However, in September, Tepco said it was planning to remove fuel from Unit 7 due to delays in the reactor’s restart.
The Tokyo-based industry group Japan Atomic Industrial Forum (Jaif) reported at the time that Unit 7 would remain in a cold shutdown state because construction of special safety facilities required after the Fukushima disaster will not be completed by a 13 October 2025 deadline.
Units 6 and 7 at Kashiwazaki Kariwa have been offline since March 2012 and August 2011 respectively.
In July 2007 an earthquake shook the plant beyond design basis and initiated an extended shutdown for inspection. The station was completely shut down for 21 months.
Unit 7 was restarted after seismic upgrades in May 2009, followed by units 1, 5, and 6. Units 2, 3, and 4 were not restarted by the time of the March 2011 earthquake.
The four restarted and operating units were not affected by the 2011 earthquake and tsunami in Fukushima, but all units were shut down to carry out safety improvements.
Background: The 15 Units That Have Returned To Service
Japan has 33 commercially available units, 15 of which have resumed operation under stringent post-Fukushima rules. Restarts face high regulatory hurdles and need local government support.
The 14 that have restarted are: Kashiwazaki Kariwa-6 (Tepco), Onagawa-2 (Tohoku Electric Power), Shimane-2 (Chugoku Electric Power), Mihama-3, Takahama-1, -2, -3, -4, and Ohi-3, -4 (Kansai Electric Power), Ikata-3 (Shikoku Electric Power), Genkai-3, -4, and Sendai-1 -2 (Kyushu Electric Power).
Before the 2011 Fukushima disaster Japan’s fleet of 54 nuclear plants generated about 30% of the country’s electricity, but were all shut down for safety checks following the accident.
According to the International Atomic Energy Agency, the figure for 2023, was 5.5%, but the government want to see this climb to 20%.
Japan’s new prime minister Sanae Takaichi has said she will push for the accelerated revival of nuclear power with reactor restarts key to reducing costly fuel imports.
