超临界水冷堆环形燃料组件核热耦合分析

Coupled Neutronics and Thermal-hydraulics Analysis of Annular Fuel Assembly for SCWR

在超临界水冷堆预概念设计中,组件设计是十分重要的,将影响堆芯性能。超临界水冷堆中水密度变化剧烈的特性要求必须进行核热耦合分析。从中子学及热工性能角度,使用三维核热耦合程序对环形燃料组件进行了优化设计。应用中子学计算程序FENNEL-N对环形燃料组件进行三维扩散计算,可得到组件内单棒功率分布,应用热工计算程序SUBSC对组件进行子通道分析。在计算过程中,分析了燃料棒间距及燃料棒与组件壁盒之间的间隙对组件性能的影响。计算结果显示,增大棒间距和棒壁间隙能提高组件kinf,但会增大组件内功率峰因子;子通道受热不均匀性对组件热工性能影响较大,通过加入定位格架的方式能展平冷却剂出口温度,降低最大包壳温度。对环形燃料组件的安全分析表明,从中子学角度该组件是安全的。

During the pre-conceptual design of supercritical water-cooled reactor（SCWR）,assembly design is very important and affects core performance.Coupled neutronics and thermal-hydraulics analysis is required for dramatic changes of water density in SCWR.Annular fuel assembly was optimized from the point of view of neutronics and thermal-hydraulics performance using three-dimensional coupling code.Three-dimensional diffusion calculation for annular fuel assemblies was carried out using FENNEL-N and pin power distributions were obtained.With these pin power distributions,SUBSC was used to perform the sub-channel analysis.The effects of fuel rod distance and gapbetween fuel rods and assembly box on assembly performance were researched in the coupled analysis.Results show that increasing fuel rod distance and rod-to-box gap will increase kinfand assembly power peaking factor.It is also shown in the results that heating heterogeneity of sub-channels plays a big role in assembly thermal performance and adding grid will flatten coolant outlet temperature as well as decrease maximum cladding surface temperature.Safety analysis of annular fuel assembly shows that the assembly is safe from the point of view of neutronics.