Ohi producing power again

Japan has generated its first nuclear electricity in two months after unit 3 of the Ohi plant began supplying power to the grid today. While unit 4 of the plant is expected to resume operation by the end of the month, it is not yet known when the country's other idled reactors will restart.

Japan has generated its first nuclear electricity in two months after unit 3 of the Ohi plant began supplying power to the grid today. While unit 4 of the plant is expected to resume operation by the end of the month, it is not yet known when the country's other idled reactors will restart.

Ohi 3 and 4 are the first Japanese units to restart (Image: Kepco)

Unit 3 at Kansai Electric Power Company's (Kepco's) Ohi plant in Fukui prefecture had been off-line since entering a scheduled periodic inspection outage on 18 March 2011, a week after the Fukushima Daiichi plant was struck by a massive earthquake and tsunami which lead to the nuclear accident there. Unit 4 at the Ohi plant entered its scheduled inspection outage in July 2011.

In response to the Fukushima nuclear accident, the Japanese government ordered all of the country's nuclear plants to undergo two-phase 'stress tests' to verify their ability to withstand extreme events. The first phase of these tests must be carried out while the reactor is shut down for a scheduled outage and government approval is required to restart it. Kepco's test results for Ohi 3 and 4 - two 1180 MWe pressurized water reactors - were the first to be submitted and subsequently reviewed by the Nuclear and Industrial Safety Agency (NISA) and confirmed by the Nuclear Safety Commission (NSC). Approval for the units' restart was announced by prime minister Yoshihiko Noda on 16 June.

Kepco restarted the reactor of unit 3 on 1 July and it attained criticality the following day. The utility announced that the unit began providing electricity to the grid at 7.00am this morning. The reactor was initially operating at 5% of capacity but output is being raised incrementally until the unit reaches 100% by 9-10 July.

Ohi unit 4 is scheduled to resume operations between 18-20 July and to start supplying electricity between 21-25 July. That unit is expected to reach full generating capacity by the end of the month. The restart of Ohi 3 and 4 will help the region meet electricity demand during the coming hot summer months.

Although permission for further reactors to restart is still awaited, unit 3 of Shikoku Electric Power Company's Ikata plant in Ehime prefecture appears likely to be the next unit to get such approval. Following Kepco, the utility was the second to submit results to the regulator for the first stage of the stress tests for a reactor. Of all such results that have so far been submitted, Ikata 3's is the only one that NISA has completed its review of and passed on to NSC for confirmation.

Researched and written
by World Nuclear News