包覆燃料颗粒尺寸及其标准偏差对失效概率的影响

三结构同向性型(Tristructural isotropic,TRISO)包覆燃料颗粒是目前高温气冷堆和固态燃料熔盐堆采用的燃料元件。TRISO包覆燃料颗粒破损会导致裂变产物不可接受的释放,由此影响反应堆的安全运行。基于TRISO包覆燃料颗粒压力壳式破损模型,分析了TRISO包覆燃料颗粒核芯和各包覆层的尺寸对失效概率的影响,研究了TRISO包覆燃料颗粒核芯半径、疏松热解碳(Buffer)层厚度和碳化硅(Si C)层厚度的合理设计范围。同时,利用随机抽样统计的方法分析了TRISO包覆燃料颗粒核芯半径分布和各包覆层厚度分布对颗粒失效概率的影响。研究发现,降低Buffer层厚度分布的标准差至16μm可以使TRISO包覆燃料颗粒的失效概率降低一个数量级。

Influence of particle size and its standard deviation on failure probability of coated fuel particles

Background: Tristructural isotropic (TRISO) coated fuel particles are used as fuel carrier for high-temperature gas-cooled reactors and solid-fuel-molten-salt reactors. The failure of the TRISO coated fuel particles can result in unacceptable release of fission products.Purpose: The distribution of the kernel radius and coating layer thickness could impact the failure probability of the TRISO particles.Methods: The influence of the distribution of the kernel radius and coating layer thickness on the failure probability was also analyzed by random sampling.Results: The design of the kernel radius, Buffer PyC layer thickness as well as the SiC thickness affect the TRISO coated fuel particles failure probability much heavier.Conclusion: It is found that the failure probability of the TRISO coated fuel particles can be reduced by one order of magnitude when the standard deviation of the distribution of the Buffer PyC layer thickness is reduced to 16mm.