核电软件NESTOR堆芯功率分布计算不确定性研究

堆芯功率分布作为堆芯核设计的关键指标,其计算精度对于评价核电厂的安全性和经济性尤为重要。作为国内首套自主核电软件包,NESTOR软件的计算精度和适用性是其应用的基础。本文基于随机取样统计方法和误差传递理论,通过分析程序物理模型引入的不确定性和堆芯状态参数不确定性引入的不确定性,将两者联合起来得到最终功率分布计算的不确定性。结果表明:随机取样统计方法在核设计软件计算不确定性研究中是可行的,将堆芯功率分布拆分为组件内功率分布计算不确定性和组件功率计算不确定性分别分析,再由误差传递理论联合得到在95%置信度和95%概率下由程序物理模型引入的径向功率峰因子计算不确定性为±3.653%,由参数不确定性引入的径向功率峰因子计算不确定性为±0.964%。从而得出最终径向功率峰因子的计算不确定性为:±3.778%。与国外成熟工程核设计软件包的计算精度相当,为NESTOR核设计软件包的应用和验证奠定了基础。 

Uncertainty Study of Core Power Distribution for Software NESTOR

As the key indicator of the nuclear design, the computational accuracy of the core power distribution is very important for the evaluation of the economy and safety of nuclear power plants. As the first nuclear power software developed on self-reliance in China, the computational accuracy and applicability of NESTOR is the foundation for its application. Based on the random sampling statistical analysis (RSSA) method and deviation transmission idea, the uncertainty of core power distribution was obtained by combining two independent uncertainties resulting from the analysis of the uncertainty of physical model and the uncertainty of the change of parameters. The results indicate that the RSSA is feasible in the uncertainty analysis of nuclear design. In addition, in the analysis of the uncertainty of physical model, the core power distribution was decomposed into 2 parts, including the uncertainty of detailed power distribution in an assembly and the uncertainty of assembly power. As a result, the uncertainty of radial power distribution caused by physical model was ±3.653%, the uncertainty of radial power distribution caused by the change of parameters was ±0.964%, and the final uncertainty of radial power distribution was ±3.778% under the condition of 95% confidence coefficient and 95% probability that computed through the deviation transmission idea. The computational accuracy is as high as the engineering design software, and it lays foundation for the application and verification of NESTOR.