Fission Gas Behaviors and Relevant Phenomena in Different Nuclear Fuels: A Review of Models and Experiments

Jingyu Guo,Wenzhong Zhou,Jie Wei,Huansheng Lai

doi:10.3389/fenrg.2022.766865

Jingyu Guo, Wenzhong Zhou + Show 2 more

Open Access

https://doi.org/10.3389/fenrg.2022.766865

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Abstract

Reactor structural integrity and nuclear safety are seriously affected by the fission gas behaviors and relevant physical phenomena in nuclear fuels. In this review, the fission gas behavior and relevant phenomena in different fuels for both models and experiments have been comprehensively overviewed, including fission gas release, gap/plenum pressure, grain growth, swelling, fission gas diffusion coefficients, and fuel cladding mechanical and chemical interactions under irradiations. The fission gas behaviors can be classified into single fission gas behavior and combined fission gas behavior with more interacting physics together. In addition, fission gas behaviors are also profoundly influenced by fuel performance, which is different in different kinds of fuels. The data of different nuclear fuels are collected, for example, UO2, MOX, metallic, U3Si2, UN, UC, and TRISO fuels. The models and experiments on fission gas behaviors are summarized into figures and tables for better comparisons. The fission gas behaviors are mainly subjected to burnup, time, and temperature, which profoundly impact these behaviors. The burnup will motivate the fission gas release and other fission gas behaviors. With the fuel temperature increase, the extent of some fission gas behaviors will be more strengthened, including fission gas release, gap/plenum pressure, grain growth, swelling, and fuel cladding mechanical and chemical interactions. The predicted data are consistent with the measured data, and the modeling results generally agree well with the experimental data. In addition, the observation of enhanced gas release at high burnups is unexpected. However, the modeling approaches on fission gas release behaviors still have certain uncertainties. Therefore, it still has considerable space to be improved and is worth studying in future work.

Highlights

Nuclear fuels are the most critical materials in different types of reactors
The experiments indicated that the FGR is related to release mechanisms, observing three FGR stages at the range of 30–1,000°C: the first is the precipitation of fission gas products from the solid solution, coalescence into large pores, and final diffusion via the uncovered edges of the samples; the second is heating the system to cause the U-Mo fuel swelling greatly and fracking, which is the most critical FGR behavior; and the third is the final FGR behavior observed as the sample exceeding two-thirds of the alloy melting temperature
The results show that compared with the UO2–zircaloy system, the amount of fission gas release is reduced in this composite cladding, and the internal pressure of the fuel rod is dropped under the normal condition

Summary

INTRODUCTION

Nuclear fuels are the most critical materials in different types of reactors. UO2 fuels have been successfully and broadly used as primary fuels in commercial light-water reactors. The experiments indicated that the FGR is related to release mechanisms, observing three FGR stages at the range of 30–1,000°C: the first is the precipitation of fission gas products from the solid solution, coalescence into large pores, and final diffusion via the uncovered edges of the samples; the second is heating the system to cause the U-Mo fuel swelling greatly and fracking, which is the most critical FGR behavior; and the third is the final FGR behavior observed as the sample exceeding two-thirds of the alloy melting temperature. Sensitivity analysis indicates that the uncertainties of parameters exist in the model, such as the grain-boundary vacancy diffusion coefficient related to weak Pearson and sensitive coefficients exceeding the expected temperature range In this model, an operational multiscale modeling approach for fission gas behavior in U3Si2 was built; a promising potential modeling framework was provided for the calculation of FGR and swelling in the U3Si2 and engineering-scale fuel analysis in LWR, indicating that future research on the characterization of the parameters can be addressed by using a sensitivity analysis.

Findings

DISCUSSION

CONCLUSION