Japan’s second largest utility Kansai Electric Power Co. said it plans to extend the lifespan of a 39 year-old nuclear reactor.

The Osaka-based company filed a request to Japan’s Nuclear and Industrial Safety Agency for an extension beyond next November for the 340MW No. 1 Mihama reactor.

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, writes Bloomberg.

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 announced last month.