Development of a multiple perturbation Monte Carlo methods for criticality problems and implementation on parallel processors

Monte Carlo correlated sampling technique has been combined with the fission matrix method to calculate reactivity perturbations due to small changes in cross-sections. The actual Monte Carlo simulation is performed a reference system different from both the unperturbed and perturbed systems. This approach allows to correlated the unperturbed system and multiple perturbed systems to the reference system. Hence it is possible to determine multiple reactivities due to multiple cross-section perturbations from a single Monte Carlo simulation. This method has been tested for once energy group isotropic scattering problems. It was also implemented the fission matrix algorithm for eigenvalue calculation and the multiple reactivity calculation algorithm on the IBM-SP2 parallel processor. Speedup performances from IBM-SP2 parallel computer are presented and a theoretical model is used to predict the speedup curves. (author) 8 refs, 2 figs