Mar, 2026
Conference Paper
Publications
Showing 43 results for Author: Chris W. Chapman
Jul, 2025
Journal
Porosity in nuclear graphite and its impact on nuclear reactor science and criticality safety applications
Porosity in nuclear-grade graphite significantly influences its low-energy neutron scattering, yet its effect on underlying phonon properties remains debated. This work integrates inelastic and small-angle neutron scattering (INS/SANS) experiments, advanced atomistic simulations with a novel machine-learned potential (DeepMD), total cross-section measurements, and neutroni…
Feb, 2025
Conference Paper
Bayesian optimization of generalized data
Direct application of Bayes' theorem to generalized data yields a posterior probability distribution function (PDF) that is a product of a prior PDF of generalized data and a likelihood function, where generalized data consists of model parameters, measured data, and model defect data. The prior PDF of generalized data is defined by prior expectation values and a prior cov…
Dec, 2023
Conference Paper
140,142Ce Neutron Cross Section Resolved Resonance Region Evaluation
A resolved resonance region evaluation of 140,142Ce was conducted by Oak Ridge National Laboratory. Requested by the US Nuclear Criticality Safety Program, this evaluation is based on recent high-resolution transmission and capture high-resolution measurements of natCe and 142Ce conducted at JRC-Geel at the Geel Linear Accelerator facility. It is also based on recently mea…
Dec, 2023
Conference Paper
PROGRESS ON 140,142CE NEUTRON CROSS SECTION RESOLVED RESONANCE REGION EVALUATIONS
Oak Ridge National Laboratory is working on completing the resonance parameter evaluation of 140,142Ce in the neutron energy range up to 200 keV. Performed with the support of the US Nuclear Criticality Safety Program, this evaluation aims to generate high-fidelity cerium cross-section and covariance data. A point-wise representation of the cross sections derived from the…
Dec, 2023
Conference Paper
Thermal Neutron Scattering Measurements of YHx for the Transformational Challenge Reactor
Dec, 2023
Journal
Methodology for Generating Covariance Data of Thermal Neutron Scattering Cross Sections
This paper details and implements a framework for evaluating thermal neutron scattering cross sections that provide S(α,β) data and covariance data for hydrogen in light water. This methodology involves perturbing model parameters of molecular dynamics potentials and fitting the simulation results to experimental data. The framework is general and can be applied to any mat…