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Title: Diffusional exchange of isotopes in a metal hydride sphere.

Abstract

This report describes the Spherical Particle Exchange Model (SPEM), which simulates exchange of one hydrogen isotope by another hydrogen isotope in a spherical metal hydride particle. This is one of the fundamental physical processes during isotope exchange in a bed of spherical metal particles and is thus one of the key components in any comprehensive physics-based model of exchange. There are two important physical processes in the model. One is the entropy of mixing between the two isotopes; the entropy of mixing is increased by having both isotopes randomly placed at interstitial sites on the lattice and thus impedes the exchange process. The other physical process is the elastic interaction between isotope atoms on the lattice. The elastic interaction is the cause for {beta}-phase formation and is independent of the isotope species. In this report the coupled diffusion equations for two isotopes in the {beta}-phase hydride are solved. A key concept is that the diffusion of one isotope depends not only on its concentration gradient, but also on the concentration gradient of the other isotope. Diffusion rate constants and the chemical potentials for deuterium and hydrogen in the {beta}-phase hydride are reviewed because these quantities are essential for an accuratemore » model of the diffusion process. Finally, a summary of some of the predictions from the SPEM model are provided.« less

Authors:
; ;
Publication Date:
Research Org.:
Sandia National Laboratories (SNL), Albuquerque, NM, and Livermore, CA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1013224
Report Number(s):
SAND2011-2340
TRN: US201110%%621
DOE Contract Number:  
AC04-94AL85000
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
08 HYDROGEN; ATOMS; DEUTERIUM; DIFFUSION; DIFFUSION EQUATIONS; ENTROPY; HYDRIDES; HYDROGEN; HYDROGEN ISOTOPES; INTERSTITIALS; ISOTOPIC EXCHANGE; PERIPHERAL MODELS

Citation Formats

Wolfer, Wilhelm G, Hamilton, John C, and James, Scott Carlton. Diffusional exchange of isotopes in a metal hydride sphere.. United States: N. p., 2011. Web. doi:10.2172/1013224.
Wolfer, Wilhelm G, Hamilton, John C, & James, Scott Carlton. Diffusional exchange of isotopes in a metal hydride sphere.. United States. https://doi.org/10.2172/1013224
Wolfer, Wilhelm G, Hamilton, John C, and James, Scott Carlton. 2011. "Diffusional exchange of isotopes in a metal hydride sphere.". United States. https://doi.org/10.2172/1013224. https://www.osti.gov/servlets/purl/1013224.
@article{osti_1013224,
title = {Diffusional exchange of isotopes in a metal hydride sphere.},
author = {Wolfer, Wilhelm G and Hamilton, John C and James, Scott Carlton},
abstractNote = {This report describes the Spherical Particle Exchange Model (SPEM), which simulates exchange of one hydrogen isotope by another hydrogen isotope in a spherical metal hydride particle. This is one of the fundamental physical processes during isotope exchange in a bed of spherical metal particles and is thus one of the key components in any comprehensive physics-based model of exchange. There are two important physical processes in the model. One is the entropy of mixing between the two isotopes; the entropy of mixing is increased by having both isotopes randomly placed at interstitial sites on the lattice and thus impedes the exchange process. The other physical process is the elastic interaction between isotope atoms on the lattice. The elastic interaction is the cause for {beta}-phase formation and is independent of the isotope species. In this report the coupled diffusion equations for two isotopes in the {beta}-phase hydride are solved. A key concept is that the diffusion of one isotope depends not only on its concentration gradient, but also on the concentration gradient of the other isotope. Diffusion rate constants and the chemical potentials for deuterium and hydrogen in the {beta}-phase hydride are reviewed because these quantities are essential for an accurate model of the diffusion process. Finally, a summary of some of the predictions from the SPEM model are provided.},
doi = {10.2172/1013224},
url = {https://www.osti.gov/biblio/1013224}, journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri Apr 01 00:00:00 EDT 2011},
month = {Fri Apr 01 00:00:00 EDT 2011}
}