“…The low-order moment equations are closed with the high-order RT equation by means of prolongation operators and exact closures. The iteration methods for solving RT equation based on the NPA are the quasidiffusion (QD) method (aka Eddington Variable Factor (VEF) method), nonlinear diffusion acceleration, coarse-mesh finite differencing (CMFD) method, partial currentbased CMFD, α-weighted methods [13,15,16,17,18,19,20]. The NPA has been applied to TRT and radiation hydrodynamics problems [21,22,23,24,25,26,27,28,29].…”