Hybrid space–angle adaptivity for whole-core particle transport calculations

Highlights: • A hybrid space–angle refinement for whole-core transport calculations is developed. • Our method is implemented for response matrix and collision probability methods. • The adaptive method leads to substantial reduction of the response matrix dimensions. • A new approach for coupling surface angular flux is introduced. • The results show the ability of the algorithm to obtain a desired accuracy. - Abstract: Adaptive refinement is a powerful method for efficiently solving physical problems. In this paper we present a new coupled space–angle adaptive algorithm for neutron transport calculations. The scheme is specifically employed for the solution of the integral form of transport equation based on the collision probability–response matrix method. The adaptive algorithm is started by first applying angular adaptivity and then projecting the solution to the spatial mesh refinement. A posteriori error estimate is derived by utilizing the flux gradient approach based on the net current leakage of nodes. A new approach is used to apply continuity of flux in the interface between nodes by escalating the order of spherical harmonics expansions of entrance response matrix to the same order of spherical harmonics expansions of outgoing angular flux at the neighboring node. Using an integral transport method within the node and refined space and angle variables, a new method for whole-core transport calculations is introduced. The validity of the developed adaptive strategy is assessed by a series of numerical experiments. Comparisons indicate that the space–angle adaptivity framework is capable of resulting acceptable solution with less number of the degrees of freedom (DOFs)