By Shinichi Saoshiro
TOKYO (Reuters) - U.N. nuclear experts Tuesday gave their backing to stress tests aimed at showing Japan's nuclear plants can withstand the sort of disasters that devastated the Fukushima plant last year, potentially bolstering a government campaign to restart idled reactors and avoid a summer power crunch.
But the government still faces an uphill battle to restore tattered public trust in the nation's power utilities after the March 11 earthquake and tsunami triggered the world's worst nuclear crisis in a quarter century.
The Vienna-based International Atomic Agency's (IAEA) team was in Japan at the request of the government to review stress tests conducted by its watchdog Nuclear and Industrial Safety Agency (NISA) on the country's halted nuclear reactors in a bid to verify their safety.
"We concluded that NISA's instructions to power plants an its review process for the comprehensive safety assessments are generally consistent with IAEA safety standards," James Lyons, the leader of the 10-member IAEA team, said in a statement.
Stress tests are computer simulations that evaluate a nuclear reactor's resilience to severe events, such as earthquakes and tsunamis.
NISA completed a review of the stress tests earlier in January and said they showed reactors at Fukui prefecture's Ohi plant, the first ones it assessed, were capable of withstanding a severe shock similar to the magnitude 9.0 earthquake and massive tsunami that wrecked the Fukushima plant.
Some experts, however, have questioned the validity of the stress tests, charging the IAEA's visit was just for show.
"It is obvious that a visit by an international organization advocating nuclear power is part of a political agenda that is built into a story already finished in advance," said University of Tokyo professor Hiromitsu Ino and former nuclear plant design engineer Masashi Goto in a joint statement last week.
Ino and Goto, who serve on a committee that advises on NISA's review of the stress tests, said the tests were insufficient as they only simulate one natural disaster at a time and do not take into account the possibility of the sort of equipment failure and human error seen at Fukushima.
ENERGY POLICY SHIFT
In another effort to restore public confidence in nuclear power, the cabinet Tuesday approved bills that would set up a new nuclear safety agency, separating regulation of the industry from the trade and industry ministry, which has promoted nuclear power and came under criticism for its cozy ties with utilities.
The Fukushima disaster has prompted a major shift in Japan's energy policy.
The resource-poor nation had aimed to increase the share of nuclear power to more than half of the electricity supply by 2030 before the disaster, but now looks to reduce its reliance on nuclear power and raise the role renewable sources such as wind and solar power.
Before the Fukushima meltdowns, nuclear power covered about a third of Japan's electricity needs, but now only three out of the country's 54 nuclear reactors are in operation after being damaged or taken off-line for checks and the rest likely to be halted by spring. The government hopes the stress tests will help persuade a wary public that it is safe to restart some of the reactors and avoid an economically crippling power crunch during the peak summer season.
Local governments hosting nuclear plants, however, have said the stress tests were not sufficient to allow them to give their approval, with some requesting that findings from the Fukushima disaster be considered in drafting new safety standards as well.
There is no legal requirement for local authorities to sign off on restarts but custom requires their approval, and riding roughshod over public opinion would be risky for a five-month old government which has seen its ratings slide over its tax hike plans and some ministers' blunders.
"A utility would not be violating any law if it went ahead and restarted a reactor after properly completing scheduled maintenance. But the Fukushima accident has heightened public concern over nuclear safety, making local consent an important part of the restart process," a trade ministry official said.
Japan had promoted nuclear power as safe, cheap and clean before the Fukushima crisis, but the accident destroyed that "safety myth."
"The myth that nuclear power was absolutely safe is a theme we will explore. We need to find out how such a mindset developed," Kiyoshi Kurokawa, the head of a parliamentary committee investigating the causes of the Fukushima accident, told reporters Monday.
(Additional reporting by Kiyoshi Takenaka; Editing by Linda Sieg and Tomasz Janowski)