A Boundary Element-Response Matrix method for criticality diffusion problems in xyz geometry

The Boundary Element-Response Matrix (BERM) method shown in the paper aims to represent an alternative to the Finite Element method in order to solve 3D multigroup diffusion (criticality) problems in xyz geometry. The theory extends the previous work on the diffusion equations in two dimensions and new techniques for the evaluation of the integrals involved in the boundary integral equations, as well as new procedures for solving the resulting linear system, have greatly enhanced the performances of the method. Results show that BERM can achieve an excellent accuracy, still keeping a good computational efficiency.