核临界安全.反应堆外部钚铀混合燃料的临界值

[中文适用范围]： 本国际标准规定了基于代码间比较计算出的临界值的通用参考临界值（有效中子倍增因子 keff 等于 1），适用于水慢化钚 - 铀氧化物均匀混合物。它适用于核反应堆外未辐照混合铀 - 钚氧化物（MOX）燃料的操作。由于缺乏 MOX 燃料的临界实验，对这些系统的经典验证方法很困难。通过不同的计算代码和核数据库组合（即不同的计算方案，见附录 B）评估了各种参考系统，涉及同位素组成、水反射层厚度和氧化物密度。本国际标准中定义的临界值是这些计算方案中计算出的最低值，并被认为可信。本国际标准中的值是参考值，而非绝对临界值。 [外文原描述]： ISO 11311:2011 specifies common reference critical values (of which the effective neutron multiplication factor, k eff , is equal to 1) for homogeneous water-moderated plutonium-uranium oxide mixtures based on an inter-code comparison of calculated critical values. It is applicable to operations with unirradiated mixed uranium-plutonium oxide (MOX) outside nuclear reactors. A classical validation approach for these systems is difficult because of the paucity of critical experiments for MOX fuel. Various reference systems, in terms of isotopic compositions, thicknesses of water reflection, and densities of oxide are evaluated by different combinations of calculation codes and nuclear data libraries (i.e. different calculation schemes). The critical values defined in ISO 11311:2011 are the lowest of those calculated by each of these calculation schemes and accepted as credible. The values in ISO 11311:2011 are reference values and not absolute critical values.