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By Chisa Fujioka

TOKYO, Aug 10 (Reuters) - It could take months or even longer for an earthquake-damaged nuclear power plant in northwest Japan to restart operations, the United Nations' nuclear watchdog said on Friday.

The Kashiwazaki-Kariwa nuclear plant, the world's largest, suffered low-level leaks of radioactive material when a 6.8 magnitude quake struck on July 16, renewing safety concerns in Japan's scandal-hit nuclear sector.

Speaking after a four-day inspection of the plant, Philippe Jamet, director of the International Atomic Energy Agency's (IAEA) Nuclear Installation Safety division, said months would be needed to go through the process of checking the site.

"This is one of the tasks in the following months, year, I don't know, to be carried out if this plant is to be restarted," Jamet told reporters.

"That's not something you can do very fast."

Japan had initially told the IAEA that it did not need help but later said it would allow inspectors into the facility after pressure from local authorities who worried that talk of the plant's problems would hurt tourism and fisheries.

The plant, run by Tokyo Electric Power Co. (TEPCO) <9501.T>, lies above an active fault line and was shut down automatically after the quake. It is closed indefinitely for safety checks.

TEPCO has said the tremor, which killed 11, injured more than 1,000 and flattened hundreds of houses, was stronger than the quakes the plant had been designed to withstand.

Quake-proofing regulations for Japan's 17 nuclear power stations -- which supply about one-third of the country's electricity -- were tightened last year, but reassessing the risks could take more than two years.

LESSONS LEARNED

Jamet, who headed a six-member team, declined to disclose details on the group's findings, saying a report would be compiled shortly after his returning to Vienna and meeting IAEA Director Mohamed ElBaradei.

"From the agency point of view, it's a very positive fact that Japan is willing to share as much as possible the result from this earthquake with the international community," he said.

"There will be a lot of working groups, conferences, workshops where the lessons learned from this earthquake will be shared."

Officials in Niigata said they were hoping for an all-clear from the IAEA to help restore confidence in local safety. The quake in July also triggered a fire at the plant's electrical transformer, which workers took hours to put out.

Jamet said he was impressed with the professionalism and the dedication of the workers at the facility and said his team had no worries going into the site.

"We felt comfortable going everywhere, investigating everything and also living there," he said.

"Someone asked us whether we ate fish because apparently some people are worried that the fish might be a problem.

"We all ate sushi and we didn't feel that it was a problem to eat sushi."

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