包覆颗粒燃料分布随机性的影响研究

高温气冷堆采用弥散在石墨基体中的包覆颗粒燃料。包覆颗粒在燃料球内的离散分布及燃料球在堆芯内的离散分布共同导致了燃料分布的双重不均匀性，其分布还具有随机性，由此可能对反应堆的某些参数造成影响。建立适当燃料颗粒随机分布的几何模型，并用MCNP对模型进行相关计算，并与规则分布模型相比较，分析了分布的随机性对有效增殖因数的影响。结果显示，燃料颗粒随机分布会使全堆有效增殖因数较规则模型的稍大，两种模型偏差的主要原因在于两种颗粒排列方式在空间和角度分布的不同。

Effect of Random Distribution of Coated Particle Fuel

Coated fuel particles dispersed in graphite matrix were used in high-temperature gas-cooled reactor (HTR). Thousands of coated particles in a fuel pebble and thousands of pebbles in the core arouse the double heterogeneity effects in pebble bed HTR. Actually the distribution of particles and pebbles is random. The random distribution may affect some reactor parameters. Some models with random distribution of the particles were setup, evaluated by MCNP, and compared with regular distribution model, as a result, the effect of random distribution on effective multiplying factor were analyzed. The results show that effective multiplying factor of the random distribution model is a little larger than that of the regular distribution model, and the deviation between the two models is caused by the distribution of fuel particles in space and angle.