不同轴向富集度布置下的超临界水堆物理热工耦合稳态特性

Coupling Characteristics of Supercritical Water-cooled Reactor With Different Enrichment Layouts

借助Dragon编制超临界水堆(supercritical water-cooled reactor,SCWR)中子截面数据库,并结合双群中子扩散方程建立物理计算模块,同时引入热工计算模块,建立超临界水堆物理热工耦合计算模型。选用2种不同的轴向富集度布置,进行物理热工耦合条件下的超临界水堆稳态特性分析。利用堆芯内部冷却剂温度、慢化剂温度和包壳温度的变化,对比分析了2种不同轴向富集度布置方式下的稳态特性差异,并且通过改变主冷却剂流量进行超临界水堆设计优化。结果表明,不论是轴向富集度单一布置为5%,还是分区布置为4%+5%,耦合条件下轴向功率分布因子均明显偏离余弦分布曲线,且堆芯出口冷却剂温度和最高包壳温度均低于日本东京大学Oka教授得到的计算结果。选用轴向富集度分区布置时,可以改善单一布置时的功率峰值严重偏移和部分轴向节点包壳温度升高现象,但是在功率峰值不变且平均富集度较小的条件下,堆芯出口冷却剂温度仍然低于额定值。降低主冷却剂设计流量,可以提高堆芯冷却剂出口温度,从而满足汽轮机入口蒸汽品质的要求。设计优化结果为,当采用轴向富集度单一布置5%时,主冷却剂设计流量值由1 418 kg/s降为1 219 kg/s;当采用轴向富集度分区布置为4%+5%时,主冷却剂设计流量值降至更低为1 035 kg/s。

On the basis of a neutron cross section library generated with the Dragon tool and a neutronics calculation module established with double-group neutron diffusion equations, together with a thermal calculation module introduced, a neutronics and thermo-hydraulics coupling model of supercritical water-cooled reactor （SCWR） was developed. The steady-state characteristics of SCWR under the condition of neutronics and thermo-hydraulies coupling were analyzed for two different enrichment layouts （single arrangement by 5% and division arrangement by 4%＋5% for fuel pellets） selected. The differences of steady-state characteristics of the two layouts were compared and analyzed according to the changes in coolant temperature, moderator temperature and cladding temperature along axial direction. The design of SCWR was optimized by means of changing the designed flow of coolant. The results show that, for whichever layout, the axial power distribution factors generated by the coupling method exhibit a clear deviation from cosine curve, and both the coolant temperature at core outlet and the maximum cladding temperature are lower than that calculated by Oka. If division arrangement by 4%＋5% is chosen, the phenomena of power peak position deviation and cladding temperature increase at partial nodes can be improved,but the coolant temperature at core outlet is still lower than the rated value if the power peak remains unchanged and the average enrichment is small. Dropping the designed flow rate of coolant can increase the coolant temperature at core outlet, so as to satisfy the quality requirement for steam at turbine inlet. The optimization results are as follows： for single arrangement by 5%, the designed flow rate of coolant is decreased from 1 418 kg/s to 1 219 kg/s; and for division arrangement by 4%＋5%, the figure is decreased even lower to 1 035 kg/s.