燃料组件堵流工况下铅铋-氩气两相流的传热压降特性分析

Flow Blockage Phenomenon of LBE-argon Two Phase Flow in a Wire-wrapped Fuel Assembly

带绕丝燃料组件的堵流事故是铅冷快堆安全分析的重要工况之一。由于在铅铋自由液面处的气体夹带或在气体增强自然循环条件下存在铅铋-氩气的两相流情况,可能引起燃料组件堵流工况下的局部热工水力特性变化。本文通过计算流体力学软件Fluent,对带绕丝19棒束燃料组件进行建模,模拟分析了堵流工况下的铅铋-氩气两相流传热压降特性,并对两相流模型进行了对比验证,对入口雷诺数、堵块孔隙率、氩气气泡直径等因素进行参数敏感性分析。结果表明:在堵流条件下氩气气泡的流动行为包括逃逸、耗散和受限,在气相体积分率较高的区域会产生局部微正压及过热现象。研究结果可为铅冷快堆堵流事故的安全分析提供参考。

The flow blockage phenomenon is one of the most important safety issues for wire-wrapped fuel assemblies in lead-based reactors.The LBE-argon two phase flow can occur at bubble-carried free surfaces or in gas-enhanced natural circulations,which may in turn cause local thermal hydraulic change at blockage regions in the assembly.In this paper,numerical models for the 19-pins wire-wrapped fuel assembly are being built using Fluent software,heat transfer and pressure drops of LBE-argon two phase flow are studied under blockage conditions.And the numerical model for two phase flow is validated through comparisons.Parameter-sensitivity analysis are given including the inlet Reynold number,porosities for the blockage regions and bubble diameters.It is concluded that:the behaviors for gas bubbles including escape,dispersion and being sealed.Local pressure increases and overheating are discovered at regions with high volume fraction of gas phase.This work can be a reference of safety analysis for the flow blockage in LBE-cooled fuel assemblies.