COBRA-Ⅳ对8×8棒束计算的不确定性分析

Uncertainty Analysis on COBRA-Ⅳ Calculation of 8×8 Bundle Experiment

摘要: 综合现有不确定性分析方法的原理及特点，采用Wilks公式确定需要计算的最小次数，研究针对子通道程序不确定性的分析方法，并编写程序。运用该程序对8×8棒束的出口空泡份额实验的子通道计算进行了不确定性分析与研究，得到了每个子通道出口空泡份额的计算预测值，以及满足容忍限的不确定性上、下限。计算结果表明：边角子通道的计算不确定性较小，约为±5.5%；而水棒周围不规则形状的子通道的不确定性较大，约为±9%。堆芯热工水力问题中最关注的高空泡子通道的出口空泡份额，其不确定性为-5.5%～6%。

Abstract: For the uncertainty analysis, the Wilks’ formula was employed to identify the minimum runs and the upper and lower limits of the calculation. An uncertainty analysis method and program for sub-channel code were developed based on the existing uncertainty analysis method. The void fraction predicted by the sub-channel code was compared with the uncertainty limit. The results show that the uncertainty of the side and the corner sub-channel is smaller, which is about ±5.5%; the uncertainty of the sub-channel around the water rod inside the bundle is bigger, which is about ±9%. The uncertainty of high void fraction sub-channels which are the most important sub-channels is about -5.5%-6%.