In this dissertation, we derive and implement a new transport-diffusion hybrid algorithm for solving thermal radiative transfer (TRT) problems. Using the method of nonlinear elimination (NLEM), the TRT system of equations can be written in terms of a transport equation with the absence of scattering and a diffusion equation. The...
This is the investigation into The generation of high-fidelity multigroup multiband cross sections from Monte Carlo neutron transport simulations. Previous methods for generating multigroup multiband (MGMB) cross sections, and multigroup cross sections, assume an approximate shape for the scalar flux. This approximate flux shape is the product of an energy-dependent...
In source-detector radiation transport simulations, pulse height distributions are a useful metric in assessing the effectiveness of nuclear instrumentation. In the area of spectroscopy, pulse height distributions are used to identify an unknown source. It is widely believed that pulse height distributions cannot be created using deterministic methods. This quantity...
Benchmark calculations are performed for neutron transport in a two material
(binary) stochastic multiplying medium. Spatial, angular, and energy dependence
are included. The problem considered is based on a fuel assembly of a common
pressurized water nuclear reactor. The mean chord length through the assembly is
determined and used as...
The Adams-Larsen-Pomraning coupled transport model has been used to describe neutral particle transport in binary stochastic mixtures. Here, the mixing statistics are considered to be homogeneous Markovian processes. While the model is robust, the convergence behavior and efficiency of this coupled model have not been addressed. Countless iterative methods could...
We present a deterministic spectral method to predict equilibrium temperature distributions, heat flux, and thermal conductivity in homogeneous and heterogeneous media. We solve the Boltzmann transport equation in a second order spatial, self-adjoint angular flux formulation. We implemented this method into the radiation transport code Rattlesnake, built using the MOOSE...
The high-order finite element S[subscript N] transport equations are solved on several test problems to investigate the behavior of the discretization method on meshes with curved edges in X-Y geometry. Simpler problems ensured the correct implementation of MFEM, the general fi nite element library employed. A convergence study using the...
A new method for accelerating the Upstream Corner Balance (UCB) discretization of the equation of transfer is introduced. The inconsistent acceleration equations for the UCB discretization are derived by applying the "Modified 4-Step" diffusion synthetic acceleration technique not to the UCB discretization, but instead to the simple corner balance (SCB)...
We spatially discretize the Sn transport equation using the high-order (HO) discontinuous finite element method (DFEM) on HO meshes. Previous work provided a proof-of-concept for this spatial discretization method in X-Y geometry. Included in the present work, we derive a spatial discretization for the Sn transport equation in both X-Y...
DSA (Diffusion Synthetic Acceleration) has been developed to accelerate the SN transport iteration. We have developed solution techniques for the diffusion equations of FLBLD (Fully Lumped Bilinear Discontinuous), SCB (Simple Corner Balance) and UCB (Upstream Corner Balance) modified 4-step DSA in x-y geometry. Our first multi-level method includes a block...
Characteristic methods are widely known to be very accurate approaches to the
solution of numerical transport problems. These methods are most often used for
neutron transport applications (i.e. lattice physics calculations) where spatial cells
are of intermediate optical thickness (O(1) - O(100) mean free paths, depending on
the energy group)...
In order to address the energy needs of developing countries and remote communities, Oregon State University has proposed the Multi-Application Small Light Water Reactor (MASLWR) design. In order to achieve five years of operation without refueling, use of 8% enriched fuel is necessary.
This dissertation is focused on core design...
Circulating fuel reactor (CFR) kinetics are characterized by delayed neutron precursor (DNP) drift in addition to the neutronic and thermal hydraulic phenomena typical of other reactor types. This environment can be computationally challenging to model, given that the multiphysics phenomena generally have non-linear interdependencies requiring the use of iterative solution...
The subject of this thesis is the development of a nodal discretization of the low-order quasi-diffusion (QDLO) equations for global reactor core calculations. The advantage of quasi-diffusion (QD) is that it is able to capture transport effects at the surface between unlike fuel assemblies better than the diffusion approximation. We...
The objective of this thesis was to investigate the use of the Jacobian Free Newton Krylov Method (JFNK) with physics based preconditioning for solving coupled radiative transport and material energy balance. Modeling of these physics is important in inertial confinement fusion and other high energy density systems. In this thesis,...
We present a method for deterministically solving the consistent temperature and frequency dependent phonon radiative transport problem. We use the single relaxation time (SRT) approximation in the Self-Adjoint Angular Flux (SAAF) form with discrete ordinates (S_N) angular discretization method and continuous finite element method (CFEM) for spatial discretization. Included are...
There exists a variety of methods to solve the radiation transport equation in stochastic materials, including the Levermore-Pomraning method and the atomic mix method, each of which is designed to replicate the results given by benchmarks with materials rearranged in a randomized fashion. While the atomic mix method is very...
Nuclear fuel management is an optimization problem on many levels. Finding “viable” solutions for the core reload design problem is difficult without expert knowledge and software automation. Small modular reactors with a shared used fuel pool demonstrate a novel opportunity for fuel cycle optimization.
A Python package was developed and...
This thesis presents methods for treating annihilation photon pairs in deterministic pulse height distribution (PHD) simulations. The methods are applied in PHD simulations for monoenergtic sources of 1.6 and 2.6 MeV photons incident on 5 and 10 cm 1-D slabs of germanium, sodium iodide, and lead and the results are...
In this dissertation, we attempt to overcome the "curse of dimensionality" inherent to radiation diffusion kinetics problems by employing a novel reduced order modeling technique known as proper generalized decomposition (PGD). After verifying a proposed PGD algorithm and associated solvers through various tests, we explore its performance for computing reduced-order...
Radiation therapy is a sophisticated complex process. Systematic methods are needed to quantitatively evaluate the quality of a complex process and hence radiation therapy treatments. An ideal result for a complex process must be established to determine if the complex process is completed acceptably. For radiation therapy, this can be...
During the past few decades, the U.S. Department of Energy (DOE) has made significant investments to improve nuclear data libraries, as the quality of this data impacts nearly all analyses of nuclear systems. Nuclear fission product yields are one component of these libraries, and are important for the analysis of...