By Mari Saito and Kentaro Hamada
TOKYO (Reuters) - The fight over restarting Japan's nuclear industry is moving to the courts, where power companies face the risk of further delays in firing up idled reactors if judges side with local residents worried about nuclear safety.
Four reactors owned by two utilities cleared regulatory safety checks in recent months, potentially soon ending more than a year without atomic power in Japan, the first such spell in the four decades the nation has been using nuclear energy.
And while ruling politicians and Japan's bureaucracy are pushing the restarts, the judiciary - which typically sided with power companies before the 2011 Fukushima nuclear disaster - may be shifting its attitude.
Judges are now considering injunctions that could halt the restarts and indefinitely extend the countrywide shutdown of Japan's 48 reactors that followed Fukushima, posing a threat to power companies already surviving on government support.
"Japan's courts have always been hesitant to properly check the state and its legislative process," but the shift in public opinion against nuclear power may have turned some judges in favor of residents, said Hiroshi Segi, a former judge turned critic of Japan's judicial system.
The court decisions, which might come this month - four years after the earthquake and tsunami that knocked out the Fukushima reactors - could mean months, even years of delays and hundreds of millions of dollars in losses for Kansai Electric Power and Kyushu Electric Power.
Japanese were shocked when Tokyo Electric Power repeatedly mishandled and misreported the Fukushima meltdowns and explosions that have forced a decontamination and decommissioning that will take up to 30 years and cost billions of dollars. National opposition to restarts remains about two-to-one over support, polls have consistently shown.
"Now that we are drawing closer to restarts, there is no other entity but the judiciary to realistically stop it," said Yuichi Kaido, a lawyer involved in the cases to stop the restarts of nuclear plants at Sendai and Takahama and who has been battling utilities in court for three decades.
The plaintiffs contend the utilities are underestimating the earthquake risks at Sendai and Takahama and not meeting tougher post-Fukushima standards. Residents also say the government has not set credible evacuation plans in case of a nuclear accident.
Kaido's team of anti-nuclear lawyers are planning to seek injunctions on every plant that wins regulatory approval.
"Judges must know that their decision could stop the next nuclear accident," Kaido said.
Ten utilities have so far submitted reactors at 13 nuclear facilities nationwide for restart. Electric Power Development Co, or J-Power, is also seeking approval for its Ohma plant now under construction.
The costs of halting the restarts are high. Every day the Sendai reactors sit idle costs Kyushu Electric more than $4.6 million, the operator estimates.
Kansai and Kyushu Electric, the utilities most-reliant on nuclear power before Fukushima, have amassed more than $10 billion combined in losses in the past four years.
Both are also on track for their fourth straight year of losses, Kyushu Electric even after receiving a government bailout in 2014. Kansai said last year that its corporate survival was at risk.
Halting restarts would also further complicate Prime Minister Shinzo Abe's plan to reduce imports of more expensive thermal fuels by reinstating nuclear power, which previously supplied nearly a third of Japan's energy.
Abe's government wants the first restarts, of Kyushu Electric's Sendai reactors in southern Japan, by around June, people familiar with the matter said last month. The industry had initially hoped the first reactors would be back online by last summer.
With judges appearing more sympathetic to anti nuclear activists, though, the utilities face tougher prospects before the judiciary.
The lead judge in the Takahama case, Hideaki Higuchi, ruled against restarting Kansai Electric's Ohi plant in May last year, a rare victory for activists.
"I think residents could win the (Takahama) shutdown in Fukui District Court," said Akihiro Sawa, a former official with the Ministry of Economy Trade and Industry, which oversees electric power companies.
Sawa, now a research director at the 21st Century Public Policy Institute, affiliated with Japan's biggest business lobby, said he has been warning utility executives to take the lawsuits seriously.
A Kansai Electric representative said the company will continue telling the court its plant is safe. Still, "Kansai Electric believes there is a significant possibility that they will lose," said a person familiar with the utility's thinking.
Kyushu Electric has asked the court to dismiss the injunction request against its restart at Sendai, saying it has taken additional safety precautions after Fukushima and that there is no danger of an accident that would release large amounts of radiation.
In the Ohi decision last May, the Fukui court judge said protecting residents' health from a potential nuclear accident was more important than any financial gains the country may get from restarting stalled plants.
"I am hopeful that the Sendai judge will feel the same," Kaido said.
(Editing by William Mallard and Tom Hogue)