Plaintiffs made their closing arguments Wednesday in an appeal before the Nagoya High Court seeking the permanent shutdown of the Monju fast-breeder nuclear reactor prototype, which has stood idle since a massive sodium coolant leak in December 1995.

The plaintiffs, residents of Tsuruga, Fukui Prefecture, are requesting that the Kanazawa branch of the high court overturn a Fukui District Court decision that in March 2000 rejected their suit seeking to annul the government's permission to build the plant and a court order to scrap the project.

Construction of the plant began in October 1985 in the town on the Sea of Japan coast. The reactor was operating at 40 percent of capacity when the leak occurred and sparked a fire. The governmental operator of the plant tried to cover up the accident and submitted a falsified report.

The high court is expected to examine whether a risk assessment, conducted by the governmental Nuclear Safety Commission before the construction, was adequate, and it will assess the risks of future sodium leaks and heat-exchanger ruptures.