Startup Thermal Analysis of a High-Temperature Supercritical-Pressure Light Water Reactor

The startup systems of a high-temperature supercritical-pressure light-water-cooled thermal reactor (SCLWR-H), in which the core outlet temperature is 500°C and downward-flowing water rods are used as moderators, are studied by thermal-hydraulic analysis. The thermal analyses are carried out for various startup phases and detailed procedures for these phases are investigated. In constant pressure startup system, the reactor starts at supercritical pressure. A flash tank and pressure-reducing valves are necessary. The flash tank is designed so that the moisture content in the steam is less than 0.1%. In sliding pressure startup system, the reactor starts at subcritical pressure. A steam-water separator and a drain tank are required. The separator is designed by referring to those of supercritical fossil-fired power plants (FPPs). The maximum cladding surface temperature is restricted not to exceed the rated value of 620°C. The minimum flow rate is 25% for constant pressure startup and 35% for sliding pressure startup. Both constant pressure and sliding pressure startup systems are found feasible from thermal analysis. Because of lower flow rate than SCFR, of which the core outlet temperature is about 430°C, the component weight required is reduced in SCLWR-H. The sliding pressure startup system should be used to reduce the component weight and to simplify the plant system.     

A Linear Stability Analysis of Supercritical Water Reactors, (I)

This paper summarizes the analysis results of the thermal-hydraulic stability of a high-temperature reactor cooled and moderated by supercritical-pressure light water (SCLWR-H). A linear stability analysis code in the frequency domain was developed to study the thermal-hydraulic stability of SCLWR-H at constant supercritical pressure. The analysis method is based on linearization by perturbation of numerically-discretized one-dimensional single-channel single-phase conservation equations. The effect of water rods on stability is considered. The thermal-hydraulic stability of SCLWR-H for full-power and partial-power normal operations was investigated by frequency domain method. Our analysis reveals that though SCLWR-H has low coolant flow rate and large density change in the core, the thermal-hydraulic stability can be maintained both at normal operation and during power raising phase of constant pressure startup by applying an orifice pressure drop coefficient at the inlet of the fuel assemblies. A parametric study was also carried out to determine the parameters affecting the stability.     

超临界水堆滑压启堆工况下堆芯热工水力动态模拟

对ATHLET-SC系统程序进行改进,实现了两流体模型下的跨临界瞬态计算。以该程序为基础,采用超临界轻水堆型(SCLWR-H)的滑压启堆方案,针对混合谱堆型的堆芯部分进行启堆工况下的热工水力动态模拟。模拟结果表明,整个启堆过程中燃料棒包壳表面温度均未超过限值(650℃),跨临界瞬态下水的物性突变不会对堆芯燃料棒包壳传热造成不良影响。     

超临界压力水冷包层方案第一壁的热与应力分析

针对超临界水冷包层中第一壁的运行工况,利用数值计算软件ANSYS中CFX和Workbench两个模块对第一壁结构中的固体域和流体域进行数值分析研究。对比矩形管道和圆形管道内传热及热应力分布发现,矩形管道四个角域强化了壁面流体和主流流体的动量和热量的交换,使传热性能优于圆形管道,而四个角域的存在也造成了该处的应力集中,使结构材料的最大应力明显高于圆形管道。进一步研究冷却剂流向和冷却管道几何结构参数对第一壁结构温度场和应力场的影响发现,在ITER运行工况下,冷却剂流向影响很小,增大冷却管道直径和减小冷却管道最小壁厚均能改善第一壁结构材料中的最高温度,而这两个几何结构参数对第一壁应力的影响较为复杂。