Unit 4 of Japan’s Ohi nuclear power plant is online again, the eighth reactor in the country to resume service after the Fukushima disaster in 2011.
Japan idled all 50 of its remaining nuclear units after the incident at the Fukushima Daiichi plant, which occurred when a 9.0-magnitude earthquake in March 2011 caused a massive tsunami that flooded the Fukushima facility in the northeastern part of the country. The resulting release of radiation was the largest since the Chernobyl meltdown in Ukraine in 1986.
There are 39 operable reactors in Japan, according to World Nuclear News (WNN); electric companies in recent years have said they will not seek to restart some units, mostly older reactors. The Japanese government after Fukushima said any units seeking to restart must meet new regulatory safety standards before resuming operation. Nuclear operators also have been seeking approval from local governments before beginning plans to restart reactors.
Kansai Electric Power this week said Ohi 4 began supplying electricity to the grid on May 11. Ohi Units 3 and 4 in August 2012 were among the first reactors in Japan to receive permission to restart after the Fukushima incident, although operation of the two 1,180-MWe pressurized water reactors was put on hold after the Nuclear Regulation Authority (NRA) ordered inspections in September 2013.
The NRA in May 2017 said the two units met the group’s new safety standards that were introduced in July 2013. After the agency approved Kansai’s plan for upgrades, the NRA conducted more inspections, and the governor of Fukui Prefecture approved the restart of Ohi 3 and 4 in November 2017. Ohi 3 began producing power again in March of this year.
Fuel loading at Unit 4 was completed in early April and the reactor was restarted May 9, reaching criticality the next day, and beginning power generation May 11, according to Kansai.
Kansai President and Director Shigeki Iwane in a statement said: “It is planned to increase the generator output in a stepwise manner while confirming the plant status at each power output. We will continuously give sincere and deliberate support to the subsequent inspections to be performed by the NRA.”
Kansai in December 2017 said it would permanently close and decommission units 1 and 2 at Ohi, two older reactors that began service in 1979. Each has a generation capacity of 1,175 MW. The two reactors will be the largest decommissioned in the country since Fukushima.
Along with Ohi 3 and 4, other nuclear units that have resumed operation are Kyushu Electric Power’s Sendai Units 1 and 2; Shikoku’s Ikata Unit 3; Kansai’s Takahama Units 3 and 4; and Kyushu’s Genkai Unit 3. There are 17 restart applications pending with the NRA, according to WNN.
Kyushu on May 14 said that it had withdrawn its application to the NRA for a test operation of Unit 4 at the Genkai plant, which it planned to restart this month. Kyushu had applied for a test permit on April 25, required to complete final inspections in advance of a restart. The company on Monday said it had “temporarily stopped the start-up process” to take a closer look at the seal on the unit’s primary coolant pump.
—Darrell Proctor is a POWER associate editor (@DarrellProctor1, @POWERmagazine)