Plutonium Behavior During Flush-out Operation of a Reprocessing Process

Determination of the time required for the plutonium flush-out by uranium remains an important issue for a commercial reprocessing plant in view of the nuclear material accountancy. Using a computer simulation code DYNAC, we computed the decrease in plutonium inventory during the flush-out operation of an extraction cycle consisting five pulsed columns. Plutonium inventory in the cycle decreased almost exponentially, which resulted more than 90% of plutonium being driven out from the process at least ten hours after the beginning of flush-out. We also confirmed that a simplified calculation model of a complete mixing vessel cannot evaluate the plutonium flush-out behavior.