Depletion calculations based on perturbations. Application to the study of a REP-like assembly at beginning of cycle with TRIPOLI-4®

Monte-Carlo burnup calculations are nowadays the reference method to obtain fuel inventories in reactor configurations. Their main drawback is the very long computing time associated with the calculation. A method is presented here which attempts to speed up the calculation by replacing full simulations by perturbation calculations based on correlated sampling. The method is tested in a PWR assembly configuration and numerical results are given for the figure of merit. These results show that a speed-up of up to a factor of 5 can be achieved.