快堆局部事故时受损燃料组件的径向传热机理

Radial Heat Transfer Mechanisms of Faulted Fast Reactor Fuel Subassembly During Local Accidents

为了预测正常功率下快堆单个燃料组件入口完全堵流所导致的事故序列,根据SCARABEE系列堆内实验建立了模型,针对SCARABEE BE+1实验的计算结果与实测数据吻合,进一步使用该模型对实际快堆中的单组件完全堵流事故进行了预测。结果表明:1)对实际快堆中发生全堵的燃料组件而言,其外部的冷却条件与SCARABEE BE+系列实验非常相似;2)堵流组件向上和向下的传热可忽略不计,径向传热对事故有较强的延缓作用;3)随着时间推进,径向传热的主导机理依次为液态钠单相对流、钠蒸汽在组件盒内壁冷凝、体热源沸腾池散热。

To predict the accident scenario caused by the total instantaneous inlet blockage of single fuel subassembly at full power（TIB） in fast reactors, a model was developed according to the SCARABEE experiments. The calculation results for the SCAR- ABEE BE＋1 experiment agree well with the experimental observation. The model was then applied to an actual reactor to predict the consequences of TIE. In actual reactors, the cooling condition outside the hexcan-wall of blocked fuel subassembly is analogous to its counterparts in the SCARABEE BE＋ experiments. The upward and downward heat transfer could be neglected, while the radial heat transfer plays a key role in slowdown the accident scenario. As time goes on, the dominant radial heat transfer mechanism is liquidus sodium convection at first, and then gradually transforms into sodium condensation near the inner surface of the hexcan-wall, and finally becomes volume heated boiling pool convection.