A monolithic fuel design based on a U–Mo alloy has been selected as the fuel type for conversion of the United States High-Performance Research Reactors (HPRRs). An issue with U–Mo monolithic fuel is the large amount of swelling that takes place during operation. The accurate prediction of fuel evolution under irradiation requires implementation of correct thermodynamic properties into mesoscale and continuum level fuel performance modeling codes. However, the thermodynamic properties of the fission gas bubbles (such as the relationship among bubble size, equilibrium Xe concentration, and bubble pressure) are not well known. This work studies Xe bubbles in γU-Mo from a diameter of 3 nm up to 8.5 nm and from 400 K up to 700 K. The energetic relationship of Xe bubbles with regard to voids and Xe substitutional atoms is described. The transition is also determined for when a bubble becomes over-pressurized. Finally, an equation of state is fit to the pressure as a function of molar volume and temperature.

基于U-Mo合金的整体式燃料设计已被选作美国高性能研究堆（HPRR）转换的燃料类型。U-Mo整体式燃料的一个问题是在运行过程中会发生大量溶胀。辐射下燃料放出量的准确预测要求将正确的热力学特性实施到中尺度和连续水平的燃料性能建模代码中。但是，裂变气泡的热力学性质（例如气泡尺寸，平衡氙浓度和气泡压力之间的关系）尚不为人所知。这项工作研究了γU-Mo中从3 nm到8.5 nm的Xe气泡，从400 K到700 K的Xe气泡。描述了Xe气泡与空隙和Xe取代原子的能量关系。还确定气泡何时变得过压的过渡。最后，根据摩尔体积和温度，将状态方程拟合到压力。