A nodal analytical discrete ordinates solver for pin-homogenized core calculation

Advanced reactor designs require highly accurate and efficient neutronics modeling capabilities for practical design needs. Many transport codes are designed for high-fidelity pin-resolved calculations, which are often computationally expensive, while low order solvers such as those based on diffusion theory or SP_N methods cannot accurately model transport effects and their solution is often prone to oscillations in regions with significant local heterogeneities. In this paper, we try to address such modeling challenges by developing a viable pin-wise whole-core transport solver based on a newly developed nodal analytical discrete ordinates (ANDO) method (Rocheleau and Wang, 2020, 2022). Here we extend the ANDO solution for fixed-source problems to k-eigenvalue problems, which are solved with the power iteration algorithm. In our implementation of the ANDO method, all the fission or part of it is combined with the scattering source and integrated analytically during each power iteration. Such a novel treatment can greatly improve computational accuracy and efficiency of the ANDO method for k-eigenvalue neutron transport calculations.