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Title: Revisiting thermodynamics and kinetic diffusivities of uranium–niobium with Bayesian uncertainty analysis

In this paper, thermodynamic and kinetic diffusivities of uranium–niobium (U–Nb) are re-assessed by means of the CALPHAD (CALculation of PHAse Diagram) methodology. In order to improve the consistency and reliability of the assessments, first-principles calculations are coupled with CALPHAD. In particular, heats of formation of γ -U–Nb are estimated and verified using various density-functional theory (DFT) approaches. These thermochemistry data are then used as constraints to guide the thermodynamic optimization process in such a way that the mutual-consistency between first-principles calculations and CALPHAD assessment is satisfactory. In addition, long-term aging experiments are conducted in order to generate new phase equilibria data at the γ 2/α+γ 2 boundary. These data are meant to verify the thermodynamic model. Assessment results are generally in good agreement with experiments and previous calculations, without showing the artifacts that were observed in previous modeling. The mutual-consistent thermodynamic description is then used to evaluate atomic mobility and diffusivity of γ-U–Nb. Finally, Bayesian analysis is conducted to evaluate the uncertainty of the thermodynamic model and its impact on the system's phase stability.
Authors:
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Publication Date:
Report Number(s):
LLNL-JRNL-703367; LA-UR-16-22697
Journal ID: ISSN 0364-5916
Grant/Contract Number:
AC52-07NA27344; AC52-06NA25396; DMR-1410983; CMMI-1534534; AC02-05CH11231
Type:
Accepted Manuscript
Journal Name:
Calphad
Additional Journal Information:
Journal Volume: 55; Journal Issue: P2; Journal ID: ISSN 0364-5916
Publisher:
Elsevier
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States); Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC); USDOE National Nuclear Security Administration (NNSA); National Science Foundation (NSF)
Country of Publication:
United States
Language:
English
Subject:
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSICS; 36 MATERIALS SCIENCE; DFT; CALPHAD; Bayesian; uncertainty analysis; metallic fuels; U–Nb; thermodynamics; kinetic diffusivity; 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY
OSTI Identifier:
1368005
Alternate Identifier(s):
OSTI ID: 1334151; OSTI ID: 1411073; OSTI ID: 1440946