Seven power reactors in operation at sites in areas that were hit by series of quakes, but tsunami warnings now downgraded
No irregularities have been identified at nuclear power plants following a series of strong earthquakes that hit western Japan and warnings of possible tsunamis along the west coast, the country’s nuclear regulator said.
The quakes were felt along the west coast in areas that are home to seven nuclear power stations: Ohi, Takahama, Mihama, Tsuruga, Shika, Kashiwazaki Kariwa and the Fugen prototype plant, which was shut down in 2013 and is being decommissioned.
Seven reactors are in commercial operation at the seven sites: two at Ohi, four at Takahama and one at Mihama.
Kansai Electric Power has three nuclear stations – Ohi, Takahama and Mihama – in Fukui prefecture. All three appear not to have been affected by the earthquakes, the Nuclear Regulation Authority (NRA) added.
Ohi has two units in operation and Takahama has four. The stations are about 20 km from each other and both in the area affected by quakes.
The three-unit Mihama station, about 70 km to the northeast of Takahama, has one unit in operation.
Also in Fukui prefecture, no problems were reported with Japan Atomic Power’s Tsuruga nuclear power station and its two units, one of which is being decommissioned, while the other is undergoing inspections.
In Ishikawa prefecture, Hokuriku Electric Power’s Shika nuclear station saw its electricity system partially disabled following the quake, but no major abnormalities have been reported.
The two-unit Shika station, about 250 km north of Ohi and closest to the strongest quake’s epicentre, has been offline since the 2011 Fukushima disaster and saw no other impact from the quake, the NRA said.
The NRA reported that Shika plant workers heard what sounded like an explosion, and then smelled something burning near a transformer that received electricity for use in Unit 2. Staff checking the area discovered the fire extinguishing system had been activated.
No fire was detected but the plant’s electricity supply was partially disabled. Hokuriku officials believe pressure inside the transformer increased due to the tremor. This triggered a device to release the pressure, causing a loud noise and activation of the fire extinguishing system rather than an actual fire.
Electric power for equipment critical for the plant’s safety was secured through other systems, and cooling pools where spent nuclear fuel is stored continued to operate.
Hokuriku Electric officials said on Monday they were assessing the damage but that there was no change in the readings of the plant’s monitoring posts, and that no external radiation had been detected. However, of the 101 radiation monitoring posts in the plant's vicinity, 13 were no longer operational, the officials said.
‘No Risk Of Radioactivity,’ Says NRA
Tokyo Electric Power Company’s Kashiwazaki Kariwa nuclear station, which has seven shut-down units, was also unaffected, said the NRA. The station is in Niigata prefecture, to the north of Ishakawa prefecture
The NRA added there is “no risk of radioactivity leaking from nuclear power plants” in the areas affected by the earthquakes.
The International Atomic Energy Agency said it is in contact with the NRA, which had confirmed no abnormalities in nuclear power plants within the affected area. “The IAEA will continue to monitor the situation,” a statement said.
A succession of 21 earthquakes registering 4.0 magnitude or stronger struck central Japan in just over 90 minutes on Monday (1 January), the Japan Meteorological Agency said. The strongest tremor hit at 16:10 local time (08:10 Central European time), measuring 7.6.
People along the west coast were told to evacuate to high ground due to a tsunami risk. Tsunami warnings were issued for the three west coast prefectures of Ishikawa, Toyama and Niigata.
At least 48 people have died in the quakes. Press reports said all tsunami warnings have been downgraded, but there are warnings of possible further tremors.
Following a major earthquake in northeastern Japan in March 2011, a 15-metre tsunami disabled the power supply and cooling of three Fukushima-Daiichi reactors, causing a major nuclear accident.
All the country’s commercial reactors were shut down following the Fukushima-Daiichi accident and are not allowed to restart until they have passed stringent new safety checks.
Before Fukushima-Daiichi, Japan’s fleet of 54 nuclear plants generated about 30% of the country’s electricity. According to the International Atomic Energy Agency that figure was 7.2% in 2021.
Among the 33 operable nuclear reactors in Japan, 12 have now resumed operations after meeting post-Fukushima safety standards. The restarted plants are: Sendai-1 and -2, Genkai-3 and -4, Ikata-3, Mihama-3, Ohi-3 and -4 and Takahama-1, -2, -3 and -4.
Prime minister Fumio Kishida’s government wants nuclear power generation to play a greater role in efforts to cut carbon emissions and ensure stable sources of energy.
