First-Collided Source Treatment for Discrete-Ordinate Radiation Transport Solutions in Rattlesnake
Abstract
Deterministic neutron transport plays a fundamental role in reactor core modeling and simulation.
With the growth of computing, higher fidelity simulation is desired and the most common
neutron transport scheme that produces these enhanced solutions is that of the method of discrete
ordinates. However, the discrete ordinates approximation suffers from large angular discretization
errors in problems with localized, small sources embedded in regions of low density or with low
scattering materials. It has long been recognized that a semi-analytical treatment of the uncollided
flux using ray-tracing techniques, coupled with a standard discrete ordinate treatment of the collided
flux, can be a remedy for ray effects. However, current ray-tracing techniques do not support
non block geometries, let alone FEM grids, and are not developed to be scalable. In this thesis, a
ray-tracing approach for obtaining the uncollided flux is considered that (1) can perform in arbitrary
grids, (2) supports arbitrary sources, and (3) is scalable. An implementation is then provided
for the use of this uncollided flux solution as a first-collision scattering source for the purpose
of ray effect treatment in the deterministic transport code Rattlesnake, a MOOSE (Multiphysics
Object Oriented Simulation Environment) application.
Subject
Uncollided fluxray effects
ray tracing
discrete ordinates
first-collided
treatment
radiation transport
Citation
Harbour, Logan Hunter (2018). First-Collided Source Treatment for Discrete-Ordinate Radiation Transport Solutions in Rattlesnake. Master's thesis, Texas A & M University. Available electronically from https : / /hdl .handle .net /1969 .1 /174588.