Japan nears zero nuclear again

Just one Japanese nuclear power reactor is left in operation following the shut down today of unit 3 of the Ohi plant for maintenance and inspections. Its sister unit, Ohi 4, is scheduled to begin an outage in two weeks.

Both Ohi units 3 and 4 will be offline by mid-September (Image: IAEA)

In response to the Fukushima nuclear accident in March 2011, 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 was to be carried out while the reactor is shut down for a scheduled outage and government approval is required to restart it.

Kansai Electric Power Company's (Kepco's) test results for Ohi 3 and 4 - two 1180 MWe pressurized water reactors - were the first to be submitted. These were reviewed by the Nuclear and Industrial Safety Agency and confirmed by the Nuclear Safety Commission. Approval for the units' restart was announced by then-prime minister Yoshihiko Noda in June 2012 to help meet power demand in the Kansai region. The units subsequently restarted the following month, ending a two-month period when all of Japan's reactors were offline.

In June this year, the Japanese Nuclear Regulatory Authority (NRA) concluded that there were no immediate safety issues at the two units under new regulatory standards that come into effect that month. The decision meant that the units could continue to operate until their next scheduled outage for maintenance.

In normal operations, Japan's nuclear power plants are taken offline for refuelling, maintenance and safety inspections every 13 months. Kepco has today taken Ohi 3 offline for its next scheduled inspections. Ohi 4 is set to enter an inspection outage on 15 September, which will leave Japan once again with no reactors in operation.

It is not yet known when Ohi 3 and 4 are likely to restart. The NRA earlier said that it will not conduct inspections of the units until an ongoing investigation is completed into seismic fault lines at the site.

Since the new safety requirements for power reactors were launched, four Japanese utilities - Kansai, Hokkaido, Shikoku and Kyushu - have applied for permission to restart twelve of the country's non-operating reactors. The NRA said it will begin safety inspections at four of these units: Hokkaido's Tomari unit 3, Shikoku's Ikata unit 3, and units 1 and 2 of Kyushu's Sendai plant.

The NRA expects to take around six months to process an application, meaning that some units could potentially come back online before the end of this year.

Researched and written
by World Nuclear News