On the validity of the dilute gas assumption for gap conductance calculations in nuclear fuel performance codes

Aysenur Toptan; David J. Kropaczek; Maria N. Avramova

doi:10.1016/j.nucengdes.2019.04.042

On the validity of the dilute gas assumption for gap conductance calculations in nuclear fuel performance codes

Aysenur Toptan, David J. Kropaczek, Maria N. Avramova

Nuclear Energy and Fuel Cycle Division

Research output: Contribution to journal › Article › peer-review

10 Scopus citations

Abstract

Fill gas thermal conductivity's dependence on pressure is neglected in today's nuclear fuel performance codes. Current codes assume that gas behaves as a dilute gas, but the pressure effect is more pronounced at temperatures lower than ten times the critical temperature of each pure gas. The validity of this assumption for nuclear fuel performance is examined herein. Theories related to dilute and dense gas properties are presented, along with their validation against literature data at up to 30 MPa for selected inert gases. Underlying assumptions are clearly described for each model, and their possible impacts on gap conductance calculations are discussed. The dilute gas assumption is valid for helium because it behaves as a dilute gas. However, the assumption is not valid in most gap conductance calculations when the gap is mostly occupied with either lower conductivity gaseous fission products or an initial fill gas other than helium.

Original language	English
Pages (from-to)	1-8
Number of pages	8
Journal	Nuclear Engineering and Design
Volume	350
DOIs	https://doi.org/10.1016/j.nucengdes.2019.04.042
State	Published - Aug 15 2019

Funding

The authors would like to thank Kevin Clarno and Robert K. Salko of Oak Ridge National Laboratory for their suggestions and thoughtful reviews. Special thanks to Taylor S. Blyth and Nathan W. Porter for their reviews of this paper. This research is supported by and performed in conjunction with the Consortium for Advanced Simulation of Light Water Reactors ( http://www.casl.gov ), an Energy Innovation Hub ( http://www.energy.gov/hubs ) for Modeling and Simulation of Nuclear Reactors under US Department of Energy Contract No. DE-AC05-00OR22725. Any opinions, findings and conclusions or recommendations expressed in this material are those of the authors and do not necessarily reflect the views of the US Department of Energy.

Funders	Funder number
Consortium for Advanced Simulation of Light Water Reactors
Energy Innovation Hub
Modeling and Simulation of Nuclear Reactors
US Department of Energy

Keywords

Dense
Dilute
Doppler
Fill gas thermal conductivity
Fuel performance
Gap conductance
Mixture thermal conductivity
Rod internal pressure

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10.1016/j.nucengdes.2019.04.042

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abstract = "Fill gas thermal conductivity's dependence on pressure is neglected in today's nuclear fuel performance codes. Current codes assume that gas behaves as a dilute gas, but the pressure effect is more pronounced at temperatures lower than ten times the critical temperature of each pure gas. The validity of this assumption for nuclear fuel performance is examined herein. Theories related to dilute and dense gas properties are presented, along with their validation against literature data at up to 30 MPa for selected inert gases. Underlying assumptions are clearly described for each model, and their possible impacts on gap conductance calculations are discussed. The dilute gas assumption is valid for helium because it behaves as a dilute gas. However, the assumption is not valid in most gap conductance calculations when the gap is mostly occupied with either lower conductivity gaseous fission products or an initial fill gas other than helium.",

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On the validity of the dilute gas assumption for gap conductance calculations in nuclear fuel performance codes

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