Fuel assemblies have a decisive impact on the performance and safety of nuclear reactors.Helical fuel has huge potential for application in small module reactors(SMRs)due to its advantages in volume power density and ...Fuel assemblies have a decisive impact on the performance and safety of nuclear reactors.Helical fuel has huge potential for application in small module reactors(SMRs)due to its advantages in volume power density and safety.Typical helical fuel elements are usually trilobal or cruciform in cross-section.The fuel rods are helically twisted in the axial direction,eliminating the need for spacer grids as the fuel rods are self-supporting.In this paper,a refined subchannel division approach is proposed based on the crossflow mechanism of helical fuel assemblies.Then,a refined helical fuel mixing model framework,including the helical fuel distributed resistance method and directed crossflow method,is developed and implemented in a helical fuel rod bundle to investigate the mixing characteristics.Validation is provided by a 5×5 helical fuel bundle mixing experiment.The refined model predicts about 92.7%of the data with the±10%error range.Compared with existing helical fuel mixing models,the refined mixing model has higher axial accuracy and radial spatial resolution,and can accurately predict the twist angledependent crossflow rate and entry effect.Meanwhile,the refined helical fuel mixing model framework is universal and can be effectively used for the mixing prediction of arbitrary geometric helical fuel after the calibration of coefficients.展开更多
文摘铅铋冷却快堆(Lead-Bismuth Cooled Fast Reactor)蒸汽发生器传热管发生破口(Steam Generator Tube Rupture,SGTR)事故时,高压水蒸汽进入一次侧高温液态金属。根据破口位置和尺寸不同,破口泄漏行为可能涉及破前泄漏(Leak-Before-Break,LBB)、单相临界流或两相临界流,不同形态的水在高温液态金属作用下发生不同形式的热质传输行为,对铅铋冷却快堆的安全运行具有重要影响。针对SGTR不同阶段,开展了系列研究,重点关注管内干涸阶段SGTR,传热管微裂纹低流量单相蒸汽渗入螺旋管束间液态铅铋合金(Lead-Bismuth Alloy,LBE)下降流场中汽泡动力学行为。基于VOF(Volume of Fluid)模型建立蒸汽-LBE两相流动及相界面捕捉数值模拟模型,研究高温LBE向下运动的流场中的单根传热管和3×3管束表面蒸汽泡生长与脱离行为。研究结果表明:汽泡在下降流场中的动力学行为与静止或向上流动的液体中的行为存在较大区别,蒸汽泡受LBE下降流场和浮力的作用脱离裂纹处后可能会沿着传热管表面滑动,在部分工况下蒸汽泡可能形成覆盖传热管表面的蒸汽膜或在管束区域内大量堆积,给LBE流动稳定性和蒸汽发生器换热带来不利影响。
基金supported by the National Natural Science Foundation of China (Grant Nos.12135008,12075150,and 12275174)the Shanghai Rising-Star Program (Grant No.22QA1404500)the Jingying Project of China National Nuclear Corporation。
文摘Fuel assemblies have a decisive impact on the performance and safety of nuclear reactors.Helical fuel has huge potential for application in small module reactors(SMRs)due to its advantages in volume power density and safety.Typical helical fuel elements are usually trilobal or cruciform in cross-section.The fuel rods are helically twisted in the axial direction,eliminating the need for spacer grids as the fuel rods are self-supporting.In this paper,a refined subchannel division approach is proposed based on the crossflow mechanism of helical fuel assemblies.Then,a refined helical fuel mixing model framework,including the helical fuel distributed resistance method and directed crossflow method,is developed and implemented in a helical fuel rod bundle to investigate the mixing characteristics.Validation is provided by a 5×5 helical fuel bundle mixing experiment.The refined model predicts about 92.7%of the data with the±10%error range.Compared with existing helical fuel mixing models,the refined mixing model has higher axial accuracy and radial spatial resolution,and can accurately predict the twist angledependent crossflow rate and entry effect.Meanwhile,the refined helical fuel mixing model framework is universal and can be effectively used for the mixing prediction of arbitrary geometric helical fuel after the calibration of coefficients.
