Fission gas diffusion and release for Cr2O3-doped UO2: From the atomic to the engineering scale
Fission gas diffusion and release for Cr2O3-doped UO2: From the atomic to the engineering scale
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DOI：
10.1016/j.jnucmat.2020.152590
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发表时间：
2021-01-12
影响因子：
3.1
通讯作者：
Andersson, David A.
中科院分区：
文献类型：
--
作者：
Cooper, Michael W. D.;Pastore, Giovanni;Andersson, David A.
在cr2o3掺杂的UO2球团中，大颗粒的预期好处包括改善机械和裂变气体保留性能。为了支持对掺杂球团裂变气体释放（FGR）的评估，必须了解在反应堆条件下掺杂对裂变气体扩散率的影响。在这项工作中，我们通过在BISON燃料性能代码中使用原子尺度上开发的材料模型来告知裂变气体模型来解决这个问题。采用簇动力学模型对cr2o3掺杂UO2中颗粒内裂变气体扩散率进行了研究，该模型考虑了UO2的热化学性质，能够描述Xe在未掺杂UO2中辐照下的扩散。热力学分析表明，在加入Cr2O3的化学计量UO2中，氧势由Cr-Cr2O3两相平衡决定。利用簇动力学模型，与未掺杂的UO2相比，掺杂UO2中的Xe扩散率在本禀和辐照增强两种情况下都显著增加，这分别是由于更高浓度的铀和氧空位。这是由于在高温下有更多的氧化条件，而在低温下有更多的还原条件，这是掺杂的结果。阿伦尼乌斯函数被拟合到簇动力学结果中，使新的扩散系数能够在BISON裂变气体行为模型中实现。BISON模拟结果表明，增大颗粒和新的裂变气体扩散率模型分别抑制和促进了裂变气体的释放。新的物理信息模型在正常运行下通过反应堆内实验测量进行了验证。此外，还对功率斜坡条件进行了基准测试。预测的裂变气体释放与实验数据吻合得很好，比标准UO2模型有了明显的改进。Elsevier B.V.出版
The anticipated benefits of large grains in Cr2O3-doped UO2 pellets include improved mechanical and fission gas retention properties. To support the assessment of fission gas release (FGR) from doped pellets, the impact of doping on fission gas diffusivity for in-reactor conditions must be understood. In this work, we tackle this issue by informing the fission gas model within the BISON fuel performance code using material models developed at the atomic scale. The investigation of intra-granular fission gas diffusivity in Cr2O3-doped UO2 is carried out by adapting a cluster dynamics model that, accounting for UO2 thermochemistry, is capable of describing Xe diffusion under irradiation in undoped UO2 as the starting point. Using a thermodynamic analysis, it is shown that in stoichiometric UO2 with additions of Cr2O3, the oxygen potential is defined by the Cr-Cr2O3 two-phase equilibrium. Using the cluster dynamics model, the predicted Xe diffusivity in doped UO2 was significantly increased in both the intrinsic and irradiation-enhanced regimes compared to undoped UO2, as a result of higher concentrations of uranium and oxygen vacancies, respectively. This is a consequence of the more oxidizing conditions at high temperature, and more reducing conditions at low temperature, as a result of doping. Arrhenius functions have been fitted to the cluster dynamics results to enable implementation of the new diffusivities in the BISON fission gas behavior model. BISON simulations were carried out, showing the competing effects of the enlarged grains and the new fission gas diffusivity model, which act to suppress and enhance fission gas release, respectively. The new physics-informed model was validated against in-reactor experimental measurements under normal operation. Additionally, benchmarking was carried out for power ramp conditions. The predicted fission gas release agreed well with the experimental data, showing noticeable improvements over the standard UO2 model. Published by Elsevier B.V.