[Background] Flow rate distribution design is one of the main contents of the thermal hydraulics study of molten salt reactor, because the flow rate distribution among all salt channels directly determines the location and peak value of local hotspots, which seriously affects the safety and reliability of the reactor operation. [Purpose] This study aims to improve the uniformity of mass flow rate distribution among salt channels of 373 MW molten salt reactor named TMSR-LF2 (Thorium Based Molten Salt Reactor - Liquid Fuel). [Method] First of all, the computational fluid dynamics program Fluent 15.0 was employ to is numerically simulate core flow field. Then the uniformity of structure optimization of upper plenum and lower plenum from several thermal-hydraulics characteristics were concluded according to the simulation output. Finally, several step-by-step improvement schemes were proposed. [Result] The schemes of inserting the cylindrical baffle plate can effectively suppress the eddy within the lower plenum and eliminate the radial inhomogeneity of the flow rate. Increasing the height of the upper plenum can balance the pressure drop of inner and outer channels on the radial direction to improve the flow rate uniformity. Reducing the radius of the inner channels on the metal support plate will bring about a platform area of flow rate among inner salt channels and the overall trend will be more gentle. [Conclusion] The modification results showed that the improvement methods mentioned above has important reference value for the further optimization design of MSR-LF.%流量分配设计是熔盐堆热工水力学研究的重点内容之一,流量分布直接决定了堆芯局部热点值和位置,制约着反应堆运行的安全性可靠性.以热功率373 MW钍基熔盐堆液态燃料(Thorium Based Molten Salt Reactor-Liquid Fuel,TMSR-LF)为研究对象,使用计算流体力学通用程序Fluent 15.0对堆芯流场进行了数值模拟.基于相应热工水力参数的分析结果,对原堆上下腔室的结构提出了若干分步式改进方案:下腔室设置折流板、增加上腔室高度、调整下腔室流量支撑板的孔径.优化结果表明:下腔室设置圆柱折流板能有效解决由局部涡流遮蔽部分通道引起的质量流量不均匀的问题;增加上腔室高度可以平衡径向方向内外侧通道出入口的压降,改善流量的均匀性;减小流量较高的内侧通道对应的金属支撑板孔道的半径可有效降低该处流量,使总体分布趋势更加平缓.最终确定的优化方案为在下腔室中央位置设置半径240 cm圆柱型折流板,半椭球型上腔室高度调整至45 cm,下腔室流量支撑板2~3排孔径由2.3 cm减至2.1 cm,4~5排由2.3 cm减至2.2 cm.以上结果对TMSR-LF2堆芯上下腔室的工程优化设计具有重要的参考价值.
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