JAPAN NUCLEAR FUEL LIMITED

April 11, 2001

Temporary Stoppage of Operation of Some Building-Ventilation Air-Blower/Exhaust Fans at the Rokkasho Reprocessing Plant's Spent Fuel Storage Facility

Japan Nuclear Fuel Limited

At 16:20 on April 11, 2001, power was cut off to System A, one of two power source systems at the Rokkasho Reprocessing Plant's Spent Fuel Storage Facility, because the changeover switch was mistaken during the power-source changeover after the completion of the start-up test for the No. 1 emergency diesel generator (A) in System A. The No. 1 emergency diesel generator (A) automatically started up immediately and restored power. At that time, two of the three building-ventilation air-blower/exhaust fans (Fans B and C) that had been operating stopped temporarily. Fan C stopped temporarily at 16:20, and Fan B at 16:22. Fan A, which was on standby, was started up at 16:27, and Fan B was also restarted. Normal operation was restored. The plant was not affected by this event. The radiation monitor registered no abnormality, indicating that the event did not affect the surrounding environment.