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Title: Modeling the influence of bubble pressure on grain boundary separation and fission gas release

Abstract

Grain boundary (GB) separation as a mechanism for fission gas release (FGR), complementary to gas bubble interlinkage, has been experimentally observed in irradiated light water reactor fuel. However there has been limited effort to develop physics-based models incorporating this mechanism for the analysis of FGR. In this work, a computational study is carried out to investigate GB separation in UO2 fuel under the effect of gas bubble pressure and hydrostatic stress. A non-dimensional stress intensity factor formula is obtained through 2D axisymmetric analyses considering lenticular bubbles and Mode-I crack growth. The obtained functional form can be used in higher length-scale models to estimate the contribution of GB separation to FGR.

Authors:
; ;
Publication Date:
Research Org.:
Idaho National Laboratory (INL)
Sponsoring Org.:
DOE - NE
OSTI Identifier:
1136318
Report Number(s):
INL/JOU-13-30956
Journal ID: ISSN 0022-3115
DOE Contract Number:
DE-AC07-05ID14517
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Nuclear Materials; Journal Volume: 452; Journal Issue: 1 - 3
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; 11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS; 97 MATHEMATICS AND COMPUTING; Fission Gas Bubble; Fission Gas Release; Fracture

Citation Formats

Pritam Chakraborty, Michael R. Tonks, and Giovanni Pastore. Modeling the influence of bubble pressure on grain boundary separation and fission gas release. United States: N. p., 2014. Web. doi:10.1016/j.jnucmat.2014.04.023.
Pritam Chakraborty, Michael R. Tonks, & Giovanni Pastore. Modeling the influence of bubble pressure on grain boundary separation and fission gas release. United States. doi:10.1016/j.jnucmat.2014.04.023.
Pritam Chakraborty, Michael R. Tonks, and Giovanni Pastore. Mon . "Modeling the influence of bubble pressure on grain boundary separation and fission gas release". United States. doi:10.1016/j.jnucmat.2014.04.023.
@article{osti_1136318,
title = {Modeling the influence of bubble pressure on grain boundary separation and fission gas release},
author = {Pritam Chakraborty and Michael R. Tonks and Giovanni Pastore},
abstractNote = {Grain boundary (GB) separation as a mechanism for fission gas release (FGR), complementary to gas bubble interlinkage, has been experimentally observed in irradiated light water reactor fuel. However there has been limited effort to develop physics-based models incorporating this mechanism for the analysis of FGR. In this work, a computational study is carried out to investigate GB separation in UO2 fuel under the effect of gas bubble pressure and hydrostatic stress. A non-dimensional stress intensity factor formula is obtained through 2D axisymmetric analyses considering lenticular bubbles and Mode-I crack growth. The obtained functional form can be used in higher length-scale models to estimate the contribution of GB separation to FGR.},
doi = {10.1016/j.jnucmat.2014.04.023},
journal = {Journal of Nuclear Materials},
number = 1 - 3,
volume = 452,
place = {United States},
year = {Mon Sep 01 00:00:00 EDT 2014},
month = {Mon Sep 01 00:00:00 EDT 2014}
}
  • This paper reports on a comprehensive fission gas release model developed by considering the behavior of multiple bubble sizes on the fuel grain boundary in terms of relevant physical parameters. This model takes into account bubble migration and coalescence; critical bubble size, which depends on the thermal gradient on the grain boundary; and the lenticular shape of the bubbles. Booth's classical diffusion theory is directly adopted in the modeling of intragranular fission gas behavior. To consider the bubble drift due to the thermal gradient, those bubbles that exceed the critical bubble size are assumed to be left on the grainmore » boundary and to migrate along the thermal gradient until they encounter free voidages. Use of this model in the KAFEPA code, which predicts the absolute magnitude and the trend of the gas release depending on power history, gives better agreement with the experimental data than the predictions of the model in the ELESIM code, which considers only a single bubble size at the grain boundary.« less
  • We present a new approach to fission gas release modeling in oxide fuels based on grain boundary network percolation. The method accounts for variability in the bubble growth and coalescence rates on individual grain boundaries, and the resulting effect on macroscopic fission gas release. Two-dimensional representa- tions of fuel pellet microstructures are considered, and the resulting gas release rates are compared with traditional two-stage Booth models, which do not account for long-range percolation on grain boundary net- works. The results show that the requirement of percolation of saturated grain boundaries can considerably reduce the total gas release rates, particularly whenmore » gas resolution is considered.« less
  • The percolation behavior of grain boundary networks is characterized in two- and three-dimensional lattices with circular macroscale cross-sections that correspond to nuclear fuel elements. The percolation of gas bubbles on grain boundaries, and the subsequent percolation of grain boundary networks is the primary mechanism of fission gas release from nuclear fuels. Both radial cracks and radial gradients in grain boundary property distributions are correlated with the fraction of grain boundaries vented to the free surfaces. Our results show that cracks surprisingly do not significantly increase the percolation of uniform grain boundary networks. However, for networks with radial gradients in boundarymore » properties, the cracks can considerably raise the vented grain boundary content.« less