TOKYO (Reuters) - Nearly half of Japan's 54 commercial nuclear power reactors had problems that needed to be addressed during operations last financial year but none required operations to be suspended, a report said on Monday.

The Nuclear and Industrial Safety Agency report said 21 reactors had "significant issues" over occurrences or safety, two needed more inspections and 29 had little or no problem.

"The report is to identify problems that need to be addressed so we can prioritise inspections and use our limited resources effectively," said an official at the agency, an affiliate of the Economy, Trade and Industry Ministry.

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"The rating doesn't affect current operations. There are no nuclear reactors that need to halt operations."

The agency rated reactors on malfunctions and operational status for the year to March 31.

One case deemed to have "significant issues" involved radioactive materials being discharged into the sea by mistake through a drainage pipe.

The agency did not evaluate the No.1 and 2 reactors at Chugoku Electric Power Co's Shimane nuclear plant in southern Japan, which have been shut for inspections after it was discovered that equipment had not been properly checked.

Japan's nuclear power generators for commercial use have a capacity of 48,847 megawatts, the world's third-biggest nuclear generation capacity after the United States and France.

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Japan is stepping up its efforts to raise nuclear run rates so as to accelerate a shift towards cleaner energy sources.

(Reporting by Chikako Mogi)