Ohi reactors cleared for restart

Permission to restart the first two of Japan's idled fleet of nuclear power reactors has been given by the prime minister following approvals from local municipal and prefectural authorities. Units 3 and 4 of the Ohi plant are both expected to be back at full power by the end of next month.

Ohi units 3 and 4 (Image: IAEA)

After a meeting with trade and industry minister Yukio Edano and two other cabinet colleagues on 16 June, prime minister Yoshihiko Noda announced that the two units at Kansai Electric Power Company's (Kepco's) Ohi plant in Fukui prefecture have been given clearance to restart. The units have been off-line since entering a scheduled periodic inspection outage on 18 March 2011 and 22 July 2011, respectively.

In response to the Fukushima Daiichi 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. In normal operations, Japan's nuclear power plants are taken offline for safety inspections every 13-18 months. The final reactor to shut down for such inspections was Hokkaido Electric's Tomari 3, which began its outage on 5 May 2012. Since then, all units in the country's potential operating fleet of 44 have remained idle.

Regulatory reform

The approval to restart Ohi 3 and 4 came the day after Japan's lower house of parliament, the House of Representatives, passed a bill to establish a new national nuclear regulatory body. The current regulator, NISA, falls under the Ministry of Economy, Trade and Industry, which has previously promoted the use of nuclear energy.

Under the proposed arrangement, a new body called the Nuclear Regulatory Authority (NRA) will be created. This will be linked to the Ministry of Environment and will have its own independent staff of 500 and a budget of ¥50 billion (about $600 million) per year. Also coming under the remit of the Ministry of the Environment will be the Nuclear Safety Investigation Committee, which will review the effectiveness of the NRA and be responsible for the investigation of nuclear accidents.

The bill is expected to be approved by the upper house of parliament so that the new regulatory regime can be in place by September.

Under the first stage of stress tests utilities are required to examine the safety margin of important pieces of equipment in accordance with guidelines set by the country's Nuclear and Industrial Safety Agency (NISA) and Nuclear Safety Commission (NSC). Analyses for this at Ohi 3 and 4 were presented to NISA in October and November last year respectively. A review by NISA was completed by mid-February this year, confirmed by the NSC in March. The results of these tests were subsequently approved by ministers in April. Although the final decision to restart the units lay with Noda and the other three ministers, approval from municipal and prefectural authorities has since been sought. Last week, the mayor of Ohi town, Shinobu Tokioka, gave his approval for the restart of the units, closely followed by approval from the governor of Fukui prefecture, Issei Nishikawa.

Noda said: "Now that we have won the understanding of the municipality in which the nuclear power plant is located, the restart of unit 3 and 4 of the Ohi nuclear power station by the four ministers shall be the final judgement by the government." However, he added, "The administration is committed to further carry forward the approaches to restore the public's trust in nuclear power administration and the safety regulation."

Noda said that his decision to grant permission for the restart was made in order to protect the livelihood of the Japanese people. That decision, he said, had been based on a "comprehensive, all-embracing evaluation." There had been concerns that Kepco's distribution region - one of Japan's most dense in terms of industry and population - would suffer from power shortages during the forthcoming hot summer months if the units were not restarted.

Edano commented, "There is no such thing as a perfect score when it comes to disaster prevention steps. But, based on what we learned from the Fukushima accident, those measures that need to be taken urgently have been addressed, and the level of safety [at the Ohi plant] has been considerably enhanced."

Kepco announced that it has already begun work to restart the two 1180 MWe pressurized water reactors. It expects unit 3 to be restarted in early July, while unit 4 will return to operation in mid- to late-July.

Further reactor restart approvals could soon follow.

Without its nuclear plants, Japan is having to turn to other sources of power. According to figures from the Japanese Atomic Industry Forum, the country faces a 12% shortage of electricity in summer 2012. Meanwhile additional fossil fuel imports are costing it about $40 billion, or $333 per person, per year while its carbon emissions have risen some 14% above 1990 levels.

Researched and written
by World Nuclear News