Monte Carlo perturbation method for optimum surface geometry due to sloshing motion

Abstract

For the nuclear criticality safety of a fuel solution, it is important to identify the maximum positive reactivity induced by the upper surface sloshing motion. Deterministic methods for obtaining optimum surface geometry have been previously developed. This study proposes a Monte Carlo perturbation method for this purpose. Surface importance (SI) is defined as a small reactivity added by an upward lifting of a point on the upper surface. The reactivity is obtained using the correlated sampling method. The optimum geometry is attained by iteratively changing the surface geometry such that the SI distribution is eventually flattened throughout the upper surface. Examples of optimum surface geometries are presented for the bare and water-reflected fuel solutions.