Japanese nuclear operators have 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 following the disaster in March 2011, which forced 160,000 people from their homes, many of whom are unlikely to be able return for decades.
The ruling Liberal Democratic Party of Japan and the utilities are keen to get reactors running again, with Prime Minister Shizo Abe singling out reining in soaring fuel costs as a key part of his economic reform plans.
But the pro-nuclear LDP must tread carefully to avoid compromising the independence of the new regulator, which is battling to build credibility with a public whose faith in nuclear power was decimated after meltdowns at Tokyo Electric Power’s Fukushima Daiichi station.
The Nuclear Regulation Authority has said it would take at least six months to review nuclear units, following which the consent of communities hosting reactors is needed.
Nuclear power accounted for about a third of Japan's electricity supply before the Fukushima catastrophe, the worst nuclear crisis since Chernobyl in 1986, after which all but two of Japan's 50 reactors were closed.
The disaster, caused by an earthquake and tsunami that knocked out power and cooling functions at the Fukushima plant, highlighted lax oversight of 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 nuclear energy will cut fuel costs that have pushed the country into a record trade deficit and will help return loss-making utilities to profit.
Hokkaido Electric Power, Kansai Electric Power, Shikoku Electric Power and Kyushu Electric Power applied to get 10 reactors restarted yesterday, 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.
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 facility after local authorities rebuffed the company's plans.
Equipment upgrades that reactors need to comply with the new rules may cost the industry as much as $12bn, according to one estimate.
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.