Neutron noise simulator based on the boundary element method (BEM)

Abstract

The purpose of the present study is to develop the neutron diffusion solver and neutron noise simulator based on the Boundary Element Method (BEM). The 2-D, 2-G neutron/adjoint diffusion equation and corresponding neutron/adjoint noise equation were solved using the mentioned method. The developed neutron static and noise simulator based on the finite element method gives accurate results when the more number of the elements is used. The motivation of the present research is to use the boundary element method to reduce the computational cost. The boundary element method attempts to use the givenboundary conditionsto fit boundary values into the integral equation, rather than values throughout the space defined by a partial differential equation.The results of static calculation were then benchmarked against the valid data for BIBLIS-2D and IAEA-2D benchmark problems. The neutron noise calculation due to the absorber of variable strength neutron noise source was performed using BEM and the Green's function technique. The adjoint of noise equation was also solved using the same method applied to the forward calculation. Comparison of the calculated neutron noise at zero frequency with the results of static calculation, utilizing the result of adjoint noise calculation and qualitative comparison with similar reported results are three different procedures to validate the neutron noise calculation.The analysis of the results obtained from the BEM shows that the boundary element method alone, or coupled with the finite element method, is ideally suited for the static and neutron noise calculation from both the accuracy and efficiency viewpoints.