Japanese nuclear operators on Monday applied to restart reactors under new rules drawn up following the Fukushima disaster, but early approval is unlikely as a more independent regulator strives to show a sceptical public it is serious about safety.
The ruling Liberal Democratic Party of Japan and the utilities are keen to get reactors running again to cut soaring fuel costs that have pushed the country into a record trade deficit.
But the Nuclear Regulation Authority has said it would take at least six months to review nuclear units, as it battles to build credibility with a public whose faith in nuclear power was decimated after meltdowns at Tokyo Electric Power Co's Fukushima Daiichi station.
All but two of Japan's 50 reactors have been closed in the wake of the disaster in March 2011, which forced 160,000 people from their homes, many of whom are unlikely to be able return for decades.
Nuclear power accounted for about a third of Japan's electricity supply before the Fukushima catastrophe, the worst nuclear crisis since Chernobyl in 1986.
The disaster, caused by an earthquake and tsunami that knocked out power and cooling functions at the Fukushima plant, highlighted lax oversight at the powerful electricity companies.
Polls show a majority of Japan's population want to end reliance on atomic power and are opposed to restarts, but the ruling party argues the country needs nuclear energy to cut fuel costs and help return loss-making utilities to profit.
Hokkaido Electric Power Co, Kansai Electric Power, Shikoku Electric Power and Kyushu Electric Power applied to get 10 reactors restarted, the NRA said.
Shunichi Tanaka, the chairman of the NRA, said on Thursday that elevating safety culture to international standards would "take a long time".
The regulator has said that reviewing each plant would likely take six months and that its review of Japan's nuclear fleet may take more than three years in total.
Once the authority signs off on safety, operators need to get the consent of local communities.
The difficulty they may face in getting that approval was highlighted as Tokyo Electric held back from applying to get units started at its Kashiwazaki Kariwa after local authorities rebuffed the company's plans.
The NRA will simultaneously review similar model units at the same plants. About 80 staff at the regulator have been divided into three groups for the safety checks, with another group overseeing earthquake resistance.
Japan is set to be free of nuclear power again in September for the first time since June 2012 as its only active reactors, Kansai Electric's Ohi No.3 and No.4 units, are due to enter planned maintenance shutdowns.
Industry sources believe that Shikoku Electric Power's Ikata plant maybe the first facility to come back online due to a lack of big hurdles, like the presence of active faultlines or concerns about tsunami.
The following is a list of reactors that are to be examined for safety review by the regulator. Capacity is in megawatts. PWR stands for pressurised water reactor.
Utilities Plant Reactors MW Type
Hokkaido Electric Tomari No.1 579 PWR
Hokkaido Electric Tomari No.2 579 PWR
Hokkaido Electric Tomari No.3 912 PWR
Kansai Electric Takahama No.3 870 PWR
Kansai Electric Takahama No.4 870 PWR
Kansai Electric Ohi No.3 1180 PWR
Kansai Electric Ohi No.4 1180 PWR
Shikoku Electric Ikata No.3 890 PWR
Kyushu Electric Sendai No.1 890 PWR
Kyushu Electric Sendai No.2 890 PWR