利用燃耗计算程序MCORGS模拟反应堆燃耗与乏燃料中Pu同位素含量之间的关系,通过对轴向上分为20段的重复栅元模型和组件模型进行的燃耗计算,得到压水堆中乏燃料中轴向不同位置燃耗的分布和Pu-239同位素含量的变化,模拟发现Pu-239同位素含量随着燃料棒在堆芯中的位置不同变化很大。同时,对VVER1000组件和压水堆17×17组件也进行了燃耗计算,计算发现组件径向不同位置的燃耗有一定差别。轴向上和径向上不同位置的燃耗差别会导致同一批卸载的乏燃料中含有很多低燃耗的燃料区间,这种乏燃料给国际核不扩散带来了巨大的风险,应该加强监管。

In the field of nuclear arms control, non-proliferation is an significant area, particularly the proliferation of weapon usable nuclear materials, which is concerned by many countries. We used burnup calculating code MCORGS to simulate the relation between the burnup of spent fuel in PWR and Pu isotopic composition. We built the model of pin-cell with 20 average axial zones, calculated its axial burnup distribution, and got the axial burnup and Pu-239 isotopic mass concentration distribution in different axial positions in PWR. Based on burnup calculation we found that Pu-239 isotopic concentrations in different axial position varied greatly. Further more, we simulated VVER1000 and PWR’s 17×17 assembly. The simulation shows that the radial burnups in an assembly were also different. There are much different burnups in different positions of nuclear reactor, which result in many low burnup zones in spent fuel. This kind of spent fuel of LWR might brings serious nuclear proliferation to international community, and should be supervised more strictly.