A NEW ESTIMATION METHOD FOR NUCLIDE NUMBER DENSITIES IN EQUILIBRIUM CYCLE

A new method is proposed for estimating nuclide number densities of LW R equilibrium cycle by multi-recycling calculation. Conventionally, it is necessary to spend a large computation time for attaining the ulti mate equilibrium state. Hence, the cycle in nearly constant fuel compo sition has been considered as an equilibrium state which can be achiev ed by a few of recycling calculations on a simulated cycle operation u nder a specific fuel core design. The present method uses steady state fuel nuclide number densities as the initial guess for multi-recyclin g burnup calculation obtained by a continuously fuel supplied core mod el. The number densities are modified to be the initial number densiti es for nuclides of a batch supplied fuel. It was found that the calcul ated number densities could attain to more precise equilibrium state t han that of a conventional multi-recycling calculation with a small nu mber of recyclings. In particular, the present method could give the u ltimate equilibrium number densities of the nuclides with the higher m ass number than Cm-245 and Pu-244 which were not able to attain to the ultimate equilibrium state within a reasonable number of iterations u sing a conventional method.