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Title: Grass-SST analysis of intragranular fission gas release and discussion of related physical phenomena in fuel subjected to TMI-2 type transients

Authors:
;
Publication Date:
Research Org.:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
12036950
Report Number(s):
ANL/LWR/SAF-80-3
DOE Contract Number:
W-31109-ENG-38
Resource Type:
Technical Report
Country of Publication:
United States
Language:
English
Subject:
DC - 78 - Light Water Reactor Technology

Citation Formats

Rest, J., and Johnson, C. E. Grass-SST analysis of intragranular fission gas release and discussion of related physical phenomena in fuel subjected to TMI-2 type transients. United States: N. p., 1980. Web. doi:10.2172/12036950.
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Rest, J., & Johnson, C. E. Grass-SST analysis of intragranular fission gas release and discussion of related physical phenomena in fuel subjected to TMI-2 type transients. United States. doi:10.2172/12036950.
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Rest, J., and Johnson, C. E. Fri . "Grass-SST analysis of intragranular fission gas release and discussion of related physical phenomena in fuel subjected to TMI-2 type transients". United States. doi:10.2172/12036950. https://www.osti.gov/servlets/purl/12036950.
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@article{osti_12036950,
title = {Grass-SST analysis of intragranular fission gas release and discussion of related physical phenomena in fuel subjected to TMI-2 type transients},
author = {Rest, J. and Johnson, C. E.},
abstractNote = {},
doi = {10.2172/12036950},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Fri May 30 00:00:00 EDT 1980},
month = {Fri May 30 00:00:00 EDT 1980}
}
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Technical Report:
View Technical Report (1.27 MB)
DOI:  10.2172/12036950
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  • GRASS-SST is a comprehensive, mechanistic model for the prediction of fission-gas behavior in UO2-base fuels during steady-state and transient conditions. GRASS-SST treats fission-gas release and fuel swelling on an equal basis and simultaneously treats all major mechanisms that influence fission-gas behavior. Models are included for intra and inter-granular fission-gas bubble behavior as well as a mechanistic description of the role of grain-edge interlinked porosity on fission-gas release and swelling. GRASS-SST calculations include the effects of gas production from fissioning uranium atoms, bubble nucleation, a realistic equation of state for xenon, lattice bubble diffusivities based on experimental observations, bubble migration, bubblemore » coalescence, re-solution, temperature and temperature gradients, interlinked porosity, and fission-gas interaction with structural defects (dislocations and grain boundaries) on both the distribution of fission-gas within the fuel and on the amount of fission-gas within the fuel and on the amount of fission-gas released from the fuel. GRASS-SST includes the effects of the degree of nonequilibrium in the UO2 lattice on fission-gas bubble mobility and bubble coalescence and also accounts for the observed formation of grain-surface channels. GRASS-SST also includes mechanistic models for grain-growth/grain boundary sweeping and for the behavior of fission gas during liquefaction/dissolution and fuel melting conditions.« less

  • GRASS-SST is a comprehensive, mechanistic model for the prediction of fission-gas behavior in UO2-base fuels during steady-state and transient conditions. GRASS-SST treats fission-gas release and fuel swelling on an equal basis and simultaneously treats all major mechanisms that influence fission-gas behavior. Models are included for intra and inter-granular fission-gas bubble behavior as well as a mechanistic description of the role of grain-edge interlinked porosity on fission-gas release and swelling. GRASS-SST calculations include the effects of gas production from fissioning uranium atoms, bubble nucleation, a realistic equation of state for xenon, lattice bubble diffusivities based on experimental observations, bubble migration, bubblemore » coalescence, re-solution, temperature and temperature gradients, interlinked porosity, and fission-gas interaction with structural defects (dislocations and grain boundaries) on both the distribution of fission-gas within the fuel and on the amount of fission-gas within the fuel and on the amount of fission-gas released from the fuel. GRASS-SST includes the effects of the degree of nonequilibrium in the UO2 lattice on fission-gas bubble mobility and bubble coalescence and also accounts for the observed formation of grain-surface channels. GRASS-SST also includes mechanistic models for grain-growth/grain boundary sweeping and for the behavior of fission gas during liquefaction/dissolution and fuel melting conditions.« less

  • GRASS-SST is a comprehensive, mechanistic model for the prediction of fission-gas behavior in UO2-base fuels during steady-state and transient conditions. GRASS-SST treats fission-gas release and fuel swelling on an equal basis and simultaneously treats all major mechanisms that influence fission-gas behavior. Models are included for intra and inter-granular fission-gas bubble behavior as well as a mechanistic description of the role of grain-edge interlinked porosity on fission-gas release and swelling. GRASS-SST calculations include the effects of gas production from fissioning uranium atoms, bubble nucleation, a realistic equation of state for xenon, lattice bubble diffusivities based on experimental observations, bubble migration, bubblemore » coalescence, re-solution, temperature and temperature gradients, interlinked porosity, and fission-gas interaction with structural defects (dislocations and grain boundaries) on both the distribution of fission-gas within the fuel and on the amount of fission-gas within the fuel and on the amount of fission-gas released from the fuel. GRASS-SST includes the effects of the degree of nonequilibrium in the UO2 lattice on fission-gas bubble mobility and bubble coalescence and also accounts for the observed formation of grain-surface channels. GRASS-SST also includes mechanistic models for grain-growth/grain boundary sweeping and for the behavior of fission gas during liquefaction/dissolution and fuel melting conditions.« less

  • The steady-state and transient gas release and swelling subroutine (GRASS-SST) is a mechanistic computer code for predicting fission-gas behavior in UO/sub 2/-base fuels. GRASS-SST treats fission-gas release and fuel swelling on an equal basis and simultaneously treats all major mechanisms that influence fission-gas behavior. The GRASS-SST transient analysis has evolved through comparisons of code predictions with the fission-gas release and physical phenomena that occur during reactor operation and transient direct-electrical-heating (DEH) testing of irradiated light-water reactor fuel. The GRASS-SST steady-state analysis has undergone verification for end-of-life fission-gas release and intragranular bubble-size distributions. The results of GRASS-SST predictions for transient fission-gasmore » release during DEH tests are in good agreement with experimental data. Comparisons of GRASS-SST predictions of gas release and bubble-size distributions with the results of DEH transient tests indicate that (1) coalescing bubbles do not have sufficient time to grow to equilibrium size during most transient conditions, (2) mobilities of fission-gas bubbles in UO/sub 2/ are enhanced during nonequilibrium conditions if the excess pressure in the bubble is sufficient to generate an equivalent stress greater or equal to the yield stress of the surrounding matrix, and (3) channel formation on grain surfaces and coalescence of the channels with each other and with the tunnels of gas along the grain edges can contribute to grain-boundary separation and/or the rapid, long-range interconnection of porosity. The phenomena of grain-boundary separation and/or long-range interconnection of porosity provides an important release mechanism for fission gas that has moved out of the grains of irradiated fuel.« less

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