Abstract During the start-up or operation of pool type lead cooled fast reactor, it is probable that loss of flow transient appears from forced circulation or mass flow rate less than that during forced circulation, due to any flow blockage, station blackout or pump malfunction. In this type of scenario temperature distribution and movement of thermal stratification layer will be different from that during loss of flow transient from forced circulation. Computational fluid dynamics (CFD) transient analysis of three-dimensional model of CLEAR-S was performed in this research with the use of commercial code FLUENT to analyze the influence of initial coolant mass flow rate on flow and coolant temperature profile in different constituents of engineering validation facility (CLEAR-S) during loss of flow transient. Firstly, steady state was simulated at mass flow rate equal to 100%, 50% and 25% of the rated mass flow rate respectively. Than loss of flow transient was simulated after started from the steady state of 100%, 50% and 25% of the rated mass flow rate as t = 0sec respectively to understand the movement and temperature distribution of thermal stratification within the pools of CLEAR-S. Results showed that after loss of flow transient from 100%, 50% and 25% mass flow rate, LBE in the hot pool was distributed into five to six layers of different temperatures and temperature of LBE on both sides of stratification layer increased with the decrease of initial mass flow rate. As time progressed hot pool stratification layer proceeded upward and width of top most layer of LBE with high temperature reduced which ultimately vanished after giving birth to a new layer at hot pool bottom. Stratification initiated from DHR outlet in the cold pool after loss of flow transient from 100% mass flow rate. Thermal stratification was observed to be started at heat exchanger (HX) outlet during loss of flow transient initiated form 50% and 25% of mass flow rate. Temperature of LBE on both sides of stratification layer increased with the decrease of initial cold pool mass flow rate of CLEAR-S. With the proceeding of time Stratification layer raised upward and top most layer vanished.

中文翻译：

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CLEAR-S 池中 LOFA 期间热分层依赖于冷却剂质量流量的数值分析

摘要 池式铅冷快堆在启动或运行过程中，由于流量阻塞、站台停电或泵故障，很可能出现强制循环或质量流量小于强制循环时的流量瞬变损失。 . 在这种情况下，热分层层的温度分布和运动将不同于强制循环造成的流动瞬态损失期间的温度分布和运动。本研究使用商业代码 FLUENT 对 CLEAR-S 的三维模型进行计算流体动力学 (CFD) 瞬态分析，以分析初始冷却剂质量流量对不同工程组成部分的流量和冷却剂温度分布的影响流动瞬态损失期间的验证设施 (CLEAR-S)。首先，在质量流量分别等于额定质量流量的 100%、50% 和 25% 时模拟稳态。在t = 0sec时分别从额定质量流量的100%、50%和25%的稳态启动后模拟流动瞬态损失，以了解CLEAR-S水池内热分层的运动和温度分布. 结果表明，从100%、50%和25%质量流量失去流动瞬态后，热池中的LBE分布到5～6层不同温度的层中，分层层两侧LBE的温度随着降低而升高。初始质量流量。随着时间的推移，热池分层向上进行，高温LBE最顶层的宽度减小，最终在热池底部产生新层后消失。在从 100% 质量流速失去流动瞬态后，从冷池中的 DHR 出口开始分层。观察到在从 50% 和 25% 的质量流量开始的流动损失瞬态过程中，在热交换器 (HX) 出口处开始了热分层。随着CLEAR-S初始冷池质量流量的降低，分层层两侧的LBE温度升高。随着时间的推移，分层向上抬升，最上层消失。观察到在从 50% 和 25% 的质量流量开始的流动损失瞬态过程中，在热交换器 (HX) 出口处开始了热分层。随着CLEAR-S初始冷池质量流量的降低，分层层两侧的LBE温度升高。随着时间的推移，地层向上抬升，最上层消失。观察到在从 50% 和 25% 的质量流量开始的流动损失瞬态过程中，在热交换器 (HX) 出口处开始了热分层。随着CLEAR-S初始冷池质量流量的降低，分层层两侧的LBE温度升高。随着时间的推移，分层向上抬升，最上层消失。