低流量工况下燃料组件优化设计研究

为了探索适用于模块式小堆（SMR）的燃料组件优化设计，本文针对截短型CF2燃料组件在SMR参数范围下的热工-水力性能开展分析研究，获得搅混格架的间距及布置形式对于燃料组件热工-水力性能的影响规律。研究结果表明:①低流量工况下，搅混格架间距过长或过短都将降低燃料组件的热工性能，设计上应合理考虑搅混格架间距；② 燃料组件加热段上游区域的搅混格架布置对于提升SMR燃料组件的热工性能不明显，设计上在此区域应简化布置；③ SMR在正常运行与事故工况下，燃料组件的中下游区域的状态点参数相对恶劣，在中下游区域合理地设计搅混格架的间距与布置可以显著地提升燃料组件的热工性能，提高热工安全裕量。本文研究结果可为SMR燃料组件的设计优化提供参考。 

Study on Optimization Design of Fuel Assembly under Low Flow Condition

In order to explore the optimization design of fuel assembly for modular small reactor (SMR), in this paper, the thermal-hydraulic performance of truncated CF2 fuel assembly under the range of SMR parameters is analyzed and studied, and the influence law of the spacing and layout of mixing grid on the thermal-hydraulic performance of fuel assembly is obtained. The results show that: ① Under low flow condition, too long or too short spacing of the mixing grid will reduce the thermal performance of the fuel assembly, and the spacing of the mixing grid shall be reasonably considered in the design. ② The arrangement of the mixing grid in the upstream region of the heating section of the fuel assembly is not obvious for improving the thermal performance of the SMR fuel assembly, so the layout shall be simplified in this region. ③ Under normal operation and accident conditions of SMR, the state point parameters of the middle and downstream regions of the fuel assembly are relatively bad. Reasonably designing the spacing and arrangement of the mixing grid in the middle and downstream regions can significantly improve the thermal performance of the fuel assembly and improve the thermal safety margin. The results of this paper can provide a reference for the design optimization of SMR fuel assembly.