PEPSICODE - A computer code for the dynamic simulation of SNM hold-up in mixer settlers

Hold-up of processing facilities is an insidious problem from both safety and safeguards point of view. Large inventory differences (IDs) are often proven to be caused by wrong estimates of hold-up, consequently, for a more efficient SNM accounting system, a new awareness about the problem of hold-up estimation has been created. In order to simulate the dynamic behaviour of mixer-settlers in an extraction solvent process, ENEA, in cooperation with the University of Rome, developed a Purex Extraction Process SImulation Code (PEPSICODE). PEPSICODE, due to a peculiar hydrodynamic modelling, describes time evolution of U, Pu and fission products concentrations both for transient and steady-state conditions. Simulation of an extraction campaign öf EUREX plant will be reported.