Introducing the Coarse-Scattering Multigroup Method and Fine-Tuning the Finite-Element with Discontiguous-Support Multigroup Method for Time-Dependent Neutron Transport
Abstract
The purpose of this research is to reduce the runtime and improve the accuracy of deterministic neutron transport simulations. Here, we introduce the coarse-scattering (CS) method, and prove its ability to reduce the computational time required to model scattering in multigroup (MG) simulations. We applied the CS method to a slab-geometry criticality simulation and showed that it was able to reduce the overall runtime of the simulation by almost a factor of four. Furthermore, we proved that the coarse-scattering method can conserve particle balance as long as the CS scattering spectrum and CS fission spectrum are recomputed in the last iteration.
In this study, we also showed that finite-element with discontiguous-support (FEDS) method and the multigroup (MG) method have certain advantages and disadvantages for simulating time-of-flight problems. FEDS is inherently able to model cross sections more accurately, while MG inherently is able to model neutron speeds more accurately. We compared a wide variety of FEDS energy discretizations, and determined their performance for a single-material and a multi-material time-of-flight simulation. We found that either using FEDS energy discretizations with large energy penalties or FEDS energy discretizations with a small number of elements per coarse group performed best for time-of-flight sim-ulations. The FEDS energy discretizations that used energy penalties were usually more accurate than the MG simulations for the single-material and the multi-material time-of-flight problems, for various detector distances and number of time bins. Also, the FEDS energy discretization that used exactly two FEDS elements in each coarse group was competitive with MG for the single-material time-of-flight problem and usually more accurate than MG for the multi-material time-of-flight problem.
Subject
Coarse-ScatteringMultigroup
Finite-Element
Discontiguous
Neutron
Transport
Energy
Penalty
Time-Of-Flight
Citation
Vaquer, Pablo A (2022). Introducing the Coarse-Scattering Multigroup Method and Fine-Tuning the Finite-Element with Discontiguous-Support Multigroup Method for Time-Dependent Neutron Transport. Doctoral dissertation, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /198810.