Year
2000
Abstract
In-process inventory verification is an essential element in the safeguards approach for the Rokkasho Reprocessing Plant (RRP). In particular, it is necessary to establish an accurate method for estimating the plutonium(Pu) inventories in the thermo-siphon type Pu evaporator. Both solution volume and concentration, under boiling conditions must be determined in order to estimate the Pu inventory in the evaporator, but, it will be impossible to draw the whole solution from the evaporator to measure Pu content because it will be continuously in operation . This paper describes a practical method of determining solution volume and Pu concentration in the RRP evaporator using dip-tube pressure and solution temperature measurements. Extensive experiments focussing on volume and concentration under various conditions have been 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 uranyl nitrate solution. It is demonstrated that U concentration, under boiling conditions can be derived from determinations of the solution density and the boiling point only.