Primary coolant system of reactor

Purpose: To facilitate the maintenance for components by greatly decreasing the level of radioactivity in the primary coolant circuit. Constitution: A clean-up loop comprising a trap, a pump, a heater, partition valves and a tank (auxiliary equipments) is provided to the primary coolant circuit of a nuclear reactor for decreasing the level of radioactivity. The cleaning procedures for the coolant circuit are carried out by draining the coolant at first, opening maintenance partitions valves, recycling a solvent from the tank to the coolant circuit by the operation of the pump while actuating the heater, dissolving radioactive materials in the solvent, precipitating the dissolved radioactive materials in the trap disposed behind a cooler and, thereafter, draining the solvent in the tank. Thus, the radioactive materials remaining in the coolant circuit are transferred to the auxiliary equipments to decrease the level of radioactivity in the circuit. (Horiuchi, T.)