Application of functional expansions Tally (FET) filter in a gas-cooled fast reactor design

Abstract

This paper discusses the application of Functional Expansions Tally (FET) filter in a modular gas-cooled fast reactor design. The modular GFR is a fast reactor design concept that proposes a longer operation time than a traditional nuclear reactor. However, the modular GFR design still needs in-depth analysis to understand the neutronics performance. The OpenMC is an open-source Monte Carlo code that offers the exact solution to solve the neutron transport equation in a full-scale model and three-dimensional (3D) geometry using Evaluated Nuclear Data File (ENDF/B-VII.b5) nuclear data and continuous energy. The physical parameter is the neutron flux distribution in the axial and radial directions. The objective is to understand the radial-axial flux distribution for modular GFR using OpenMC code. This study implemented the Legendre polynomial feature for the axial calculation, whereas the Zernike polynomial for the radial calculation. We evaluated flux distribution from traditional mesh and FET feature, which performed 350x350 mesh and the variation of FET order range 5, 10, 50 and 100. The results inform the integral of each Zernike polynomial flux time with the boundary condition in radial and axial directions. The main findings are that order 10 is the optimum value after implementing the radial-axial Zernike polynomial of orders 5, 10, 50, and 100 of flux distribution calculation. We concluded that using FET features for flux distribution in radial and axial directions gives a good understanding of the GFR core profile.