TIGHTNESS CHECK TECHNIQUE FOR CANS OF FUEL ELEMENTS BEFORE PLACING THEM IN DRY STORAGE Russian patent published in 2000 - IPC

FIELD: nuclear power engineering. SUBSTANCE: after spent nuclear fuel has been kept in water for long time, bag holding fuel bundles is placed in container pre- filled with demineralized water, and water is drained from refueling pool and from container. In the course of draining, water samples are taken in several steps. First sample is taken as soon as water drain is started. Then container is held for a day to allow decay of radioactivity. After that samples are taken during further emptying of container upon infusion for a day. Increment of specific radioactivity of Cs-134 and Cs-137 radionuclides is measured in water samples which is not to exceed 2,2•10^-7 Ci/l. After container is fully emptied, it is decayed and then evacuated; air discharged from container is conveyed to system that has air cooler, aerodynamic filter, and beta-activity gas sensors of noble gases Kr-85 and Xe-133. If increment of specific activity of Cs-134 and Cs-137 radionuclides in the last water sample does not exceed specified value and air evacuated is free from radioactive noble gases, cans are considered tight. EFFECT: facilitated procedure.