快堆MOX燃料氧与金属原子比控制原理

本文论述了快堆MOX燃料的氧势模型和氧与金属原子比（O/M比）控制原理。Blackburn模型和点缺陷模型是两种常用的核燃料氧势模型，而离子反应平衡常数、热力学数据及实验测量数据是影响氧势模型精确度的主要因素。当要求(U_0.75Pu_0.25)O_2-x燃料的O/M比为1.97时，若在1 750 ℃、0.1 MPa Ar-5%H₂气中烧结，采用Blackburn模型进行计算，则理论上要求将氧分压控制在1.07×10^-5 Pa，或将氧势控制在-386.15 kJ/mol；采用点缺陷模型进行计算，要求将氧分压控制在0.70×10^-5 Pa，或将氧势控制在-393.22 kJ/mol。当要求O/M比分别为1.95、1.96、1.97、1.98、1.99、1.995时，理论上应将气体中的水分含量分别控制在370.4、739.8、1 633.7、4 403.6、17 855.4、43 064.8 ppm，或将气体露点分别控制在-30.10、-23.27、-14.98、-3.77、13.83、26.16 ℃。

Control Theory of Atom Ratio of Oxygen and Metal for FBR MOX Fuel

In this paper, model of oxygen potential and control theory of atom ratio of oxygen and metal (O/M ratio) for FBR MOX fuel were discussed. Blackburn model and point defect model are usually used two types of oxygen potential model of nuclear fuel, whose precision is affected by ion reaction equilibrium constant, thermodynamic data and experimental measured data. If a designed O/M ratio of 1.97 is required for (U_0.75Pu_0.25)O_2-x fuel sintered at 1 750 ℃ in 0.1 MPa Ar-5%H₂ mixture gases, oxygen partial pressure will be limited to 1.07×10^-5 Pa or oxygen potential will be limited to -386.15 kJ/mol when calculated by Blackburn model; oxygen partial pressure will be limited to 0.70×10^-5 Pa and oxygen potential will be limited to -393.22 kJ/mol when calculated by point defect model. If a designed O/M ratio of 1.95, 1.96, 1.97, 1.98, 1.99 and 1.995 is required respectively, water content in gas will be limited to 370.4, 739.8, 1 633.7, 4 403.6, 17 855.4 and 43 064.8 ppm respectively, or gas dew point will be limited to -30.10, -23.27, -14.98, -3.77, 13.83 and 26.16 ℃ respectively.