Sodium leakage countermeasures at prototype FBR Monju

In the light of lessons learnt from the sodium leakage accident at MONJU, several problems which ought to be improved have been studied from the viewpoint of early detection, damage limitation and mitigation of the damage consequent to the accident. An improvement program for the plant has been prepared. 1.To help the operators detect sodium leakage more quickly, an integral leakage monitoring system and cell-monitors will be installed. 2.To reduce the drain time, the drain system will be modified. 3.To limit the spread of aerosol outside the building and to suppress the combustion of sodium, the ventilation system will be improved. 4.To reduce water release from the structural concrete, thermal insulation will be fitted to the walls and ceilings. 5.To suppress combustion of sodium spilled and to prevent re-ignition, a nitrogen gas extinguisher system will be installed. (author)