Tohoku Electric Power TSE:9506 restarted the 825-megawatt (MW) No.2 reactor at its Onagawa nuclear power station in northern Japan on May 18 following scheduled maintenance and refuelling, a company spokesperson said on Tuesday.
The unit had been offline since January. It was restarted on May 11, but shut again on May 16 after a small amount of radioactive steam was found coming from a drain pit in the turbine building, prompting an inspection of a connected valve.
The utility found a thin piece of metal stuck inside the valve, preventing it from sealing properly. The valve returned to normal after the metal piece was removed, the company said.
Separately, Kansai Electric Power TSE:9503 shut the 826-MW No.3 reactor at its Mihama nuclear power station in western Japan on May 8 due to a technical problem, a company spokesperson said.
After an alarm went off, an operator saw steam leaking near the turbine via surveillance cameras inside the turbine building, prompting a manual shutdown. It is unclear when the unit will restart, the spokesperson said.
As of Tuesday, Japan has 10 nuclear reactors in operation, with a combined capacity of 10,087 MW.
Many utilities are undergoing re-licensing to meet stricter safety standards implemented after the 2011 Fukushima disaster. Prior to the disaster, Japan operated a total of 54 reactors.
The table below shows the status of Japan's nuclear power plants.
The regional utilities are: Chubu Electric Power TSE:9502, Chugoku Electric Power TSE:9504, Hokkaido Electric Power TSE:9509, Hokuriku Electric Power TSE:9505, Kansai Electric Power TSE:9503, Kyushu Electric Power TSE:9508, Shikoku Electric Power TSE:9507, Tohoku Electric Power TSE:9506 and Tokyo Electric Power (Tepco) TSE:9501.
In the table, the companies are referred to by their regional names.
Japan Atomic Power Company (Japco), a nuclear energy company, owns two reactors.
Company
Plant
Unit
MW
Status
Hokkaido
Tomari
1
579
Shutdown 22/4/11
Hokkaido
Tomari
2
579
Shutdown 26/8/11
Hokkaido
Tomari
3
912
Shutdown 5/5/12
Tohoku
Onagawa
2
825
Online 18/5/26
Tohoku
Onagawa
3
825
Shutdown 11/3/11
Tohoku
Higashidori
1
1,100
Shutdown 6/2/11
Tepco
Kashiwazaki-Kariwa
1
1,100
Shutdown 6/8/11
Tepco
Kashiwazaki-Kariwa
2
1,100
Shutdown 16/7/07
Tepco
Kashiwazaki-Kariwa
3
1,100
Shutdown 16/7/07
Tepco
Kashiwazaki-Kariwa
4
1,100
Shutdown 16/7/07
Tepco
Kashiwazaki-Kariwa
5
1,100
Shutdown 25/1/12
Tepco
Kashiwazaki-Kariwa
6
1,356
Online 9/2/26
Tepco
Kashiwazaki-Kariwa
7
1,356
Shutdown 23/8/11
Chubu
Hamaoka
3
1,100
Shutdown 29/11/10
Chubu
Hamaoka
4
1,137
Shutdown 13/5/11
Chubu
Hamaoka
5
1,380
Shutdown 14/5/11
Hokuriku
Shika
1
540
Shutdown 1/3/11
Hokuriku
Shika
2
1,206
Shutdown 11/3/11
Kansai
Mihama
3
826
Shutdown 8/5/26
Kansai
Takahama
1
826
Online 30/11/25
Kansai
Takahama
2
826
Shutdown 23/1/26
Kansai
Takahama
3
870
Shutdown 7/4/26
Kansai
Takahama
4
870
Online 16/10/25
Kansai
Ohi
3
1,180
Online 14/8/25
Kansai
Ohi
4
1,180
Shutdown 4/3/26
Chugoku
Shimane
2
820
Shutdown 9/2/26
Shikoku
Ikata
3
890
Online 25/12/25
Kyushu
Genkai
3
1,180
Online 13/6/25
Kyushu
Genkai
4
1,180
Online 17/10/25
Kyushu
Sendai
1
890
Online 21/12/25
Kyushu
Sendai
2
890
Online 28/3/26
Japco
Tokai Daini
1
1,100
Shutdown 11/3/11
Japco
Tsuruga
2
1,160
Shutdown 7/5/11
Total
33,083