Improvement of the Transcritical Heat Transfer Look-up Table by Including separate Effects

现行的反应堆安全规范是为了评估CANDU反应堆在正常和事故条件下的燃料热性能而设计的。这些安全规范可能已经被修改，以预测与超临界水冷堆（SCWR）有关的条件下的燃料热行为，但对于理想的几何形状。目前第二阶段研究计划的结果将提供一种改进的传热预测方法，用于反应堆安全规范，使其更适用于各种正常和事故SCWR条件，并适用于更现实的流动几何形状，即通过考虑(i)流动方向效应，（II）流动几何形状的影响（通过比较管状几何形状和束状几何形状的超临界传热（SCHT））。（iii）存在流动障碍，例如由燃料棒间隔片引入的流动障碍，以及（iv）具有随时间变化的压力、质量流量和/或热通量的瞬态流动条件。这将使反应堆安全分析人员能够更好地评估前面提到的在正常操作和事故条件下对护套温度行为的单独影响。

Current reactor safety codes are designed to assess the fuel thermal behaviour under normal and accident conditions of CANDU reactors. These safety codes may have been modified to predict fuel thermal behaviour at conditions relevant to supercritical water-cooled reactors (SCWR) but for an idealized geometry. The results of the present Phase II research proposal will provide an improved heat transfer prediction method to be used in reactor safety codes in order to make them more applicable to various normal and accident SCWR conditions and applicable for a more realistic flow geometry, i.e. by considering (i) the flow direction effect, (ii) the effect of flow geometry (by comparing the supercritical heat transfer (SCHT) in tubular geometries vs. bundle geometries), (iii) the presence of flow obstructions, e.g., introduced by fuel rod spacers, and (iv) transient flow conditions, with time dependent pressure, mass flow and/or heat flux. This will enable the reactor safety analysts to better assess the impact of the previously mentioned separate effects on the sheath temperature behaviour during normal operating and accident conditions.