Attempts to reassure the Japanese public on nuclear power by ordering stress tests on reactors have backfired.
The mayor of Genkai responded furiously to the announcement of tests after previously being given safety assurances, and called off a planned restart of two reactors at a local plant run by Kyushu Electric Power .
This adds to uncertainty whether other utilities will be able to bring reactors back on line quickly after shutting them for mandatory safety checks, which could have all of Japan's reactors offline by next spring.
"We have confirmed the safety of (the Genkai) nuclear power plant in Saga Prefecture, but I cannot deny that there are still some people who have doubts and concerns about safety," said Chief Cabinet Secretary Yukio Edano.
"We want the stress tests to serve as a reference point for restarting nuclear reactors. This is so the public can feel more safe and secure."
Failure to restart reactors raises the prospect of further power supply disruptions that would be a blow to Japanese industry, which is already staggering production schedules due to power shortages in several parts of the country.
The government has been reviewing its energy policy to reduce the nation's reliance on nuclear energy but says restarting reactors is essential to meet peak energy demand, and hoped the tests would ease public mistrust of the nuclear industry.
The tests will use simulations to confirm how well each reactor could withstand a severe event such as the March earthquake and tsunami that hit northeast Japan and triggered a crisis at Tokyo Electric Power Co's Fukushima Daiichi plant.
It is unclear how long the stress tests will take, said Hirofumi Kawachi, senior analyst covering Japanese electric utilities at Mizuho Investors Securities.
EU stress tests that began in June require each nuclear plant operator to submit a progress report in August and a final report in October
These will become the basis for national reports to be subjected to peer review, which will be completed next April, and a final report will be filed by the EU Commission to the EU Council next June.
"If stress tests in Japan take a year like in the EU, reactor restarts will be impossible this winter, let alone this summer," Kawachi said.
"Considering that more plants will continue shutting down until then, depending on temperatures, the impact on our lives in winter may be even greater."
The prospects of prolonged shutdown, which would require electric utilities to depend more on costly fossil fuels for thermal power generation, drove down shares of Japanese power firms including Genkai plant operator Kyushu Electric Power Co, which fell 7.5 per cent, and Kansai Electric Power Co, which was down 8.4 per cent.
Safety fears after the March disaster knocked out cooling systems at the Fukushima Daiichi plant, 240 km north of Tokyo, triggering reactor meltdowns, have made local governments wary of agreeing to the restart of reactors shut for maintenance.
The government was relying on Genkai to set an example.
Only 19 out of Japan's 54 reactors are now in operation and the trade and industry ministry, which manages the nuclear industry, is keen to get idled ones back on line to avoid power blackouts during the summer, when electricity demand peaks.
This week's announcement that the government was planning stress tests for all nuclear facilities caught local authorities off-guard and came under fire in media as the latest policy flip-flop by unpopular Prime Minister Naoto Kan.
The mayor of Genkai, in Saga Prefecture, had given the green light for a restart that would have brought all four reactors at the 36-year-old plant on line, after assurances from the government that they were safe.
But the town has now reversed course.
"Prime Minister Kan made a statement suggesting that stress tests are necessary for reactor restarts," said Genkai Mayor Hideo Kishimoto.
"This made me feel my decision (consenting to a restart) was meaningless, and I feel furious about it."
Yasushi Furukawa, governor of Saga Prefecture, also slammed Kan for lacking a consistent policy on restarting reactors.
The consent of the governor, along with the mayors of Genkai and a neighboring town, is needed for the reactors to resume operation.