Nov. 5 (Bloomberg) -- Kansai Electric Power Co., Japan’s second-largest utility, is seeking to extend the lifespan of a 39 year-old nuclear reactor instead of replacing the unit.

The Osaka-based company filed a request today to Japan’s Nuclear and Industrial Safety Agency for an extension beyond next November for the 340-megawatt No. 1 Mihama reactor, it said in a statement released in Tokyo. The unit, built in November 1970, is the second-oldest of Japan’s 54 atomic plants.

Japanese utilities are considering measures including uprating reactors to improve output and running older units longer as the country seeks to rely more on nuclear energy and less on fossil fuels. Tokyo Electric Power Co., Asia’s biggest utility, is seeking to extend the life of a 38 year-old reactor to 60 years, Managing Director Sakae Muto said last month.

Japan aims to get 40 percent of its power from nuclear energy by 2030, the trade ministry said, up from 25 percent in 2008, according to the International Atomic Energy Agency.

Nuclear operators need permission every 10 years from the nuclear safety agency to operate reactors that are more than 30 years old. Kansai Electric hasn’t said how long it would run the reactor if it gets permission for an extension.

To contact the reporter on this story: Megumi Yamanaka in Tokyo at myamanaka@bloomberg.net.

Last Updated: November 5, 2009 00:33 EST