Cr2O3掺杂UO2-锆合金包壳燃料稳态服役性能研究

Investigation of Steady-State Operating Performance of Cr?O?-Doped UO?-Zircaloy Nuclear Fuel

摘要:

Cr?O?掺杂UO?芯块可促进晶粒长大，并具有提高裂变气体滞留能力和缓解芯块-包壳相互作用（pellet-cladding interaction，PCI）的潜力。针对燃料棒尺度与晶粒尺度裂变气体行为难以统一描述的问题，本文在燃料性能分析程序BEEs中耦合裂变气体行为程序SCIANTIX：BEEs向积分点处的晶粒尺度模型传递局部温度、燃耗、裂变率和晶粒尺寸，SCIANTIX返回裂变气体释放（fission gas release，FGR）、气体肿胀等状态量并参与燃料棒内压与自由体积计算。采用BR-3反应堆36i8燃料棒终点数据进行验证，耦合模型预测FGR为28.49%，较实验值33.80%低15.7%；预测空腔体积为5.890×10-7 m³，较实验值8.046×10-7 m³低26.8%。由于仅有单棒终点实验值，该结果用于检验量级与变化趋势，尚不足以证明模型具有普遍预测精度。进一步的10～50 μm晶粒尺寸敏感性计算表明，在其余模型和边界条件不变时，晶粒增大可延缓晶内气体向晶界迁移并降低连通释放贡献，但会增加滞留气体肿胀。

Abstract:

Cr?O?-doped UO? pellets can promote grain growth and may improve fission-gas retention. This study coupled the fuel-performance code BEEs with the grain-scale fission-gas code SCIANTIX. BEEs transfers local temperature, burnup, fission rate, and grain size to SCIANTIX, while fission gas release (FGR) and gas swelling are returned to the rod-scale calculation. For the BR-3 36i8 rod, the coupled model predicted an end-of-life FGR of 28.49%, 15.7% below the measured value of 33.80%, and a void volume of 5.890×10?? m³, 26.8% below the measured value of 8.046×10?? m³. Because only one rod and endpoint measurements were available, this comparison establishes neither statistical significance nor general predictive accuracy. Deterministic sensitivity calculations for grain sizes of 10–50 μm showed lower FGR and gap pressure but higher retained-gas swelling at larger grain sizes under the adopted model settings.