The mixed oxide (MOX)-fueled core for liquid metal-cooled fast reactors has such high core performance and favorable neutron economy as to achieve an average fuel burnup of over 90 GWD/t with high power density. However, traditional MOX-fueled cores which are the ones without specific design measures to reduce the positive void reactivity worth has the potential to exceed prompt criticality during hypothetical core disruptive accidents (CDAs). Should the prompt criticality be exceeded, the core materials would heat up until their temperatures would exceed their boiling points. As a result, a release of significant mechanical energy cannot be ruled out, imposing serious damage on the reactor vessel. The released mechanical energy, termed “energetics,” is dominated by a rapid insertion of positive reactivity due to a fuel–coolant interaction (FCI) during the initiating phase of an unprotected loss-of-flow (ULOF) event. Considering the mechanism of energetics generation, a simple model was developed to estimate the design limit of positive component of core void reactivity against a ULOF event for traditional MOX-fueled cores. This simple model is constructed to evaluate the design limit based on the relation between the allowable positive reactivity insertion rate defined by the core characteristics and that assumed by the effect of FCI phenomena. The validity of the model is discussed by comparison with SAS4A which is the CDA analysis code devoted to calculate the initiating phase.

用于液态金属冷却快堆的混合氧化物（MOX）燃料堆芯具有如此高的堆芯性能和良好的中子经济性，可在高功率密度下实现平均燃耗超过90 GWD / t。但是，传统的以MOX为燃料的堆芯（没有采取专门的设计措施来降低正空反应性的价值）有可能在假设的堆芯破坏性事故（CDA）期间超过即时临界。如果超过了紧急临界值，则芯材将加热直至其温度超过其沸点。结果，不能排除大量机械能的释放，对反应堆容器造成严重损害。释放的机械能称为“能量学” 在无保护的流量损失（ULOF）事件的启动阶段，由于燃料与冷却剂的相互作用（FCI），迅速插入正反应性占主导地位。考虑到高能生成的机理，开发了一个简单的模型来估计传统MOX燃料芯对ULOF事件的芯空隙反应性正分量的设计极限。构建此简单模型以根据核心特征定义的允许正反应性插入率与FCI现象的影响所假定的正反应性插入率之间的关系来评估设计极限。通过与专用于计算启动阶段的CDA分析代码SAS4A进行比较，讨论了模型的有效性。考虑到高能生成的机理，开发了一个简单的模型来估计传统MOX燃料芯对ULOF事件的芯空隙反应性正分量的设计极限。构建此简单模型以根据核心特征定义的允许正反应性插入率与FCI现象的影响所假定的正反应性插入率之间的关系来评估设计极限。通过与专用于计算启动阶段的CDA分析代码SAS4A进行比较，讨论了模型的有效性。考虑到高能生成的机理，开发了一个简单的模型来估计传统MOX燃料芯对ULOF事件的芯空隙反应性正分量的设计极限。构建此简单模型以根据核心特征定义的允许正反应性插入率与FCI现象的影响所假定的正反应性插入率之间的关系来评估设计极限。通过与专用于计算启动阶段的CDA分析代码SAS4A进行比较，讨论了模型的有效性。构建此简单模型以根据核心特征定义的允许正反应性插入率与FCI现象的影响所假定的正反应性插入率之间的关系来评估设计极限。通过与专用于计算启动阶段的CDA分析代码SAS4A进行比较，讨论了模型的有效性。构建此简单模型以根据核心特征定义的允许正反应性插入率与FCI现象的影响所假定的正反应性插入率之间的关系来评估设计极限。通过与专用于计算启动阶段的CDA分析代码SAS4A进行比较，讨论了模型的有效性。