核燃料溶解器临界计算对截面的要求

REQUIREMENTS FOR THE CROSS SCTION IN CRITICALITY CALCULATION OF FUEL DISSOLVER

用群截面对燃料溶解过程中出现的栅格、燃料双重不均匀和溶液３种系统作临界计算时，需要考虑中子的共振自屏效应。标准自屏公式或经过丹可夫因子修正的自屏公式不适用于燃料双重不均匀系统。ＯＥＣＤ／ＮＥＡ临界工作小组的结果表明，必须用碰撞概率（ＰＩＣ）方法，子群方法或精细慢化方法修正才能得到共振自屏效应的准确结果。用点截面作临界计算时，不会观察到自屏效应，可以准确进行包括燃料双重不均匀系统在内的临界计算。

The criticality calculation of three systems of lattice,solution,and double heterogeneity in-volved in fuel dissolving should be performed for evaluation of criticality safety of fuel dissolver.The resonance selfshielding effects should be considered in criticality calculation using group crosssection, The standard formula of self shiclding or the self shielding fownula corrected by DanCofffactor should not be applied to the system of double heterogeneity. The results of OECD/NEAcriti cality working group showed that PIC method and sup-group method and hyperfine slowingdown treatment could be used for the systeIn of double heterogeneity in order to obtain a realisticevaluation of the effective cross secton. The resonance self shielding effect would not be observedin criticality calculation using point cross section. The criticality calculation using point cross sec-tion could be perforn1ed in fuel dissolving.