含掉块缺陷燃料棒的热力性能模拟研究

Simulation Investigation of Thermal-Mechanical Behaviors of MPS Defect Fuel Rod

燃料棒制造过程中会不可避免地产生芯块掉块(MPS)缺陷,该缺陷有可能导致运行过程中燃料包壳局部应力超过受力限值,产生包壳失效。本研究借助ABAQUS软件,通过编写相应的用户自定义子程序,将燃料棒相关的辐照效应、热效应、间隙热传导模型等引入数值模拟计算,完成了对具有MPS缺陷燃料棒热力性能的分析。对比具有不同MPS缺陷尺寸燃料棒的热力学性能模拟结果,完成MPS缺陷尺寸对燃料棒热力性能的敏感性分析。模拟结果表明,MPS缺陷会造成燃料棒中心温度升高,并且在包壳内外表面上出现拉压应力交替的现象;MPS缺陷尺寸越大,该影响越显著。较大的掉块尺寸会对反应堆运行过程中燃料棒的结构完整性造成威胁,应引起注意。

Manufacturing defects such as missing pellet surface （MPS） defect are inevitable in the manufacturing of pellets, which may result in over local stress on the cladding and cause cladding failure. In this paper, under the calculation frame of ABAQUS software, the related irradiation effects and thermal effects of fuel rods were introduced into the simulation based on vairous kinds of user defined subroutines, and then the thermal -mechanical behaviors of nuclear fuel rods were simulated. The sensitivity analysis of MPS defect sizes effect on thermal -mechanical behaviors of fuel rods were completed. The simulation results found that MPS defect causes higher center temperature, and the tensile stress and comprehensive stress appears on the cladding surface coinstantaneous. These effects would be more obvious with the increasing of MPS size. The defects with relatively bigger sizes should be concerned because these defects may threat the integrity of nuclear fuel rods during the operation period.