STUDY ON INVENTORY ESTIMATION METHOD OF PLUTONIUM EVAPORATOR

摘要

In-process inventory verification is an essential element in the safeguards approach for theRokkasho Reprocessing Plant (RRP). In particular, it is necessary to establish an accuratemethod for estimating the plutonium(Pu) inventories in the thermo-siphon type Pu evaporator.Both solution volume and concentration, under boiling conditions must be determined inorder to estimate the Pu inventory in the evaporator, but, it will be impossible to draw thewhole solution from the evaporator to measure Pu content because it will be continuously inoperation . This paper describes a practical method of determining solution volume and Puconcentration in the RRP evaporator using dip-tube pressure and solution temperaturemeasurements.Extensive experiments focussing on volume and concentration under various conditions havebeen carried out in a scaled down(1/5) experimental evaporator to correlate liquid level,density and boiling point with solution volume and uranium(U) concentration using a uranylnitrate solution. It is demonstrated that U concentration, under boiling conditions can bederived from determinations of the solution density and the boiling point only.