Validation of Thermal Scattering Laws for Light Water at Elevated Temperatures With Diffusion Experiments

Holmes, Jesse; Zerkle, Michael; Hawari, Ayman I.

doi:10.1051/epjconf/202124709016

Cited by 4 publications

(4 citation statements)

References 43 publications

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“…In absence of better experimental data, diffusion parameters have recently resurfaced [42] as a possible benchmark for temperature dependence. We compared measured data with computed values, and the new evaluation preserves the good behaviour shown by the CAB Model used in ENDF/B-VIII.0 (Fig.…”

Section: Improved Evaluation For Hydrogen Bound In Light Watermentioning

confidence: 99%

Nuclear data development at the European Spallation Source

Damián

DiJulio

Muhrer

2021

JNR

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Transport calculations for neutronic design require accurate nuclear data and validated computational tools. In the Spallation Physics Group, at the European Spallation Source, we perform shielding and neutron beam calculations to help the deployment of the instrument suite for the current high brilliance (top) moderator, as well for the design of the high intensity bottom moderator, currently under study for the facility. This work includes providing the best available nuclear data in addition to improving models and tools when necessary. In this paper we present the status of these activities, which include a set of thermal scattering kernels for moderator, reflector, and structural materials, the development of new kernels for beryllium considering crystallite size effects, nanodiamonds, liquid hydrogen and deuterium based on path integral molecular dynamics, and the use of the software package NCrystal to assist the development of nuclear data in the framework of the new HighNESS project.

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Section: Improved Evaluation For Hydrogen Bound In Light Watermentioning

confidence: 99%

Nuclear data development at the European Spallation Source

Damián

DiJulio

Muhrer

2021

JNR

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“…Several recent efforts have been made to validate thermal neutron scattering libraries (e.g., [1]). Although this work is certainly important, efforts must be made to ensure accurate modeling of double differential scattering cross sections (DDXSs) so they can be used in the evaluation procedure.…”

Section: Introductionmentioning

confidence: 99%

Advanced Modeling and Simulation Methods for Evaluation of Thermal Neutron Scattering Materials

et al. 2023

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With the rise of interest in thermal neutron scattering data for advanced reactor, criticality safety, and shielding applications, new experimental data are required for evaluation of new materials or for re-evaluation (or validations) of previously evaluated materials. New experimental data are evaluated in a three-step process: (1) computing the phonon characteristics, (2) computing the dynamic structure factor (DSF) from the data, and (3) using the experimental setup to simulate the experimental data. All three steps have challenges, ranging from the need for a suffciently general material simulation code—a processing code that can compute the corresponding DSF—to having a detailed layout of the instrument/beamline/facility where the data were measured. Whereas phonon characteristics of materials can be computed using various methods (molecular dynamics, density functional theory, etc.), a high-fidelity computation of the DSF and the simulation of the experiment based on the DSF is vital to the accuracy of the evaluation. The latter two steps can be achieved by using the two corresponding code systems developed by instrument scientists at the Spallation Neutron Source (SNS) at Oak Ridge National Laboratory: (1) OCLIMAX, a program that calculates the dynamic structure factor from DFT and MD simulation results, and (2) MCViNE, a Monte Carlo neutron ray-tracing program designed to simulate neutron scattering experiments. Recently, polyethylene and yttrium hydride were measured at the Wide Angular-Range Chopper (ARCS) and SEQUOIA instrument stations of the SNS. These experiments are simulated using the density functional theory code, the Cambridge Serial Total Energy Package (CASTEP), to compute its phonon characteristics (eigenvalues/vectors and PDOS), which is then processed using OCLIMAX to yield the DSF, and finally the data at each instrument station are simulated by the MCViNE for comparison to the measured data for evaluation. For comparison to conventional evaluation methods, the scattering data processed from OCLIMAX are compared against those processed from the LEAPR module of NJOY, and the results from MCViNE simulations are compared against previously used simplified beamline models implemented in the Monte Carlo N-Particle (MCNP) code.

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“…Pulsed-Neutron Die-Away (PNDA) experiments provide valuable performance data to validate TSLs and offer advantages over criticality experiments [2,3]. PNDA experiments have shown a greater sensitivity to TSL data than is commonly encountered in criticality experiments [4].…”

Section: Introductionmentioning

confidence: 99%

Pulsed-Neutron Die-Away Experiments for Plastics and Neutron Thermal Scattering Laws

et al. 2023

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Pulsed-neutron die-away (PNDA) experiments can be useful benchmarks to validate neutron thermal scattering laws (TSLs). The experiment uses a neutron generator to impinge a short (∼10−4 s), mono-energetic neutron pulse on a target sample. After the pulse, the neutron population within the sample moderates and reaches thermal equilibrium with a fundamental spatial mode and characteristic decay-time eigenvalue. The eigenvalue can be extracted from the experimental measurements of the neutron flux and used as an integral parameter in validation. For certain materials and geometric configurations, the eigenvalue is heavily influenced by thermal neutron scattering of only the target material. For that reason, a PNDA experiment can have a higher sensitivity to TSLs than is commonly available in critical experiments. Herein, we present results for a series of new PNDA experiments conducted at Lawrence Livermore National Laboratory with plastic materials, e.g. high-density polyethylene and Lucite. We compare the experimental integral parameters to simulated results and report trends in the biases. We evaluate the bias with different Monte Carlo transport codes (MCNP6.2 and Mercury) and show no significant differences between the results of the two codes.

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Validation of Thermal Scattering Laws for Light Water at Elevated Temperatures With Diffusion Experiments

Cited by 4 publications

References 43 publications

Nuclear data development at the European Spallation Source

Nuclear data development at the European Spallation Source

Advanced Modeling and Simulation Methods for Evaluation of Thermal Neutron Scattering Materials

Pulsed-Neutron Die-Away Experiments for Plastics and Neutron Thermal Scattering Laws

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