TOKYO, March 31 (Xinhua) -- Japan began a test run of a nuclear fuel reprocessing plant on Friday, which would turn spent nuclear fuel into plutonium for making nuclear power plant fuel.

    The Rokkasho plant, located in northern Japan, is designed to reprocess some 800 tons of spent nuclear fuel annually into more than 4 tons of plutonium when fully operated in August 2007, Kyodo News said. The plutonium will be used as uranium-and-plutonium mixed fuel at Japan's nuclear power plants.

    "This is a very important step forward for the ministry, and the entire energy industry," Economy, Trade and Industry Minister Toshihiro Nikai said earlier on Friday. The Federation of Electric Power Companies of Japan plans to use such mixed fuel at 16 to 18 reactors across the country by March 2011.

    During the test run, about 430 tons of spent nuclear fuel will be melted to extract plutonium and uranium.

    Japan Nuclear Fuel, the operator of the plant, began to build the reprocessing plant in 1993. The construction costs of the plant, located 580 kilometers northeast of Tokyo, swelled to 2,193 billion yen (18.66 billion U.S. dollars) following a series of troubles such as a water leakage in the fuel pool and a design error in the cooling devices.

    Nuclear power is an essential part of Japan's energy portfolio, supplying more than one third of its energy. Enditem