Influence of contactor and evaporator holdups on detection sensitivity

A comparative investigation of statistical tests for material loss/diversion in the reference plant has been carried out, placing emphasis on obtaining, as far as possible, closed analytical expressions for detection probabilities and average run lengths. To this end, simplifying assumptions were made regarding the material balance area: a steady state or stationary process was assumed, i.e. input and in-process inventory constant in time; all process tanks with less than 1000 g Pu inventory were neglected; and the Pu holdups in the solvent extraction contactors and Pu evaporator were also neglected. In the present contribution these assumptions have been relaxed. In particular, the robustness of NTRMA methods with respect to inventory fluctuations in the hard-to-measure Pu evaporator and solvent extraction contactors is examined