By Linda Sieg

TOKYO, May 25 (Reuters) - Japan is leaning toward a policy of halving nuclear power's share of electricity supply from pre-Fukushima levels to about 15 percent by 2030, but will likely stop short of pledging the long-term exit strategy that many voters favour, experts said.

That would be a victory of sorts for a nuclear industry that has been under fire since a huge earthquake and tsunami devasted the Fukushima atomic plant in March 2011, triggering meltdowns in the world's worst radiation accident in a quarter century.

With discussions on shaping future energy policy extending over months, the government has already pledged to reduce the role of nuclear power and in principle to decommission reactors after they have been running for 40 years. That formula would yield a share of around 15 percent by 2030 if strictly followed.

"It is government policy to set the limit on nuclear reactors' operation at 40 years," Goshi Hosono, the minister in charge of the nuclear crisis, told reporters on Friday.

"Fifteen percent (by 2030) would be in line with that," Kyodo news agency quoted him as saying after a meeting of expert advisers to the government the night before.

Nuclear power provided about 30 percent of Japan's electricity needs before the Fukushima disaster, while a 2010 energy policy, ditched after the crisis, had set a target of more than 50 percent for 2030.

Some experts and lawmakers also want to set a target to exit nuclear power by 2050, if not earlier, but are meeting fierce resistance from those who want to throw the industry a lifeline.

"It is highly likely that the cabinet will make a final decision not to make it (a 2050 target) clear," said Hiroshi Takahashi, a fellow at the Fujitsu Reseach Institute and a member of the expert panel advising on energy mix policy.

"In my view, that is a mediocre option, but it may be good for both sides. Those in favour of a phase out will say 'We're trying' and those in favour of nuclear power will say 'Let's see, there might be radical innovations in the next 20-30 years.'"

A draft proposal of five energy mix options, with nuclear's share ranging from zero to 35 percent, was presented at the panel's meeting on Thursday. But the draft dropped a variation that would have set a 15 percent target for nuclear power by 2030 while having that share fall to zero two decades later.

"They (the secretariat) did not want to make it clear that this is an option because they don't want to phase out the nuclear industry," Takahashi said.


SUMMER SHOWDOWN

The panel's secretariat is run by the government's Agency for Natural Resources and Energy, under the jurisdiction of the trade and industry ministry -- long a promoter of nuclear power.

"If you look at major economies, their nuclear policies have changed drastically in the past 20 years and there are so many uncertain factors to look at by 2050," said a former industry ministry official with deep knowledge of the debate. "I'm very cautious about that (setting a 2050 target)."

Prime Minister Yoshihiko Noda, his ratings already below 30 percent as he battles a divided parliament and fractious ruling party, is being buffetted by conflicting pressures from voters worried about safety and business groups arguing higher power rates will increase pressure to move their production offshore.

Japan's biggest business lobby, Keidanren, has voiced worries that a rise in electricity costs due to a phase out of nuclear power could prompt companies to relocate overseas, costing jobs and growth.

A Reuters survey, however, showed that nearly three-quarters of Japanese companies support abandoning nuclear power after the Fukushima disaster, although a majority set the condition that alternative energy resources must be secured.

The survey suggests big companies are less wedded to nuclear power than Keidanren's position suggests.

Key cabinet ministers are expected to make a decision on Japan's energy mix in August after a period of public comment.

What happens during Japan's hot summer months, however, is likely to have an impact.

All 50 nuclear reactors have been taken off line for maintenance in the months since the Fukushima accident and none has been restarted due to public worries about safety.

The government has therefore asked businesses and consumers in western Japan, where forecasts of power gaps are most acute, to cut summer usage by 15 percent from 2010 levels.

If businesses and consumers manage without major glitches, support for an early exit from nuclear power will likely grow.

"This summer will be the showdown for both pro- and anti-nuclear camps," said Shoichi Kondo, a ruling Democratic Party lawmaker and founding member of a non-partisan group advocating an exit from nuclear power. (Editing by Ron Popeski)

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