Abstract

The suppression pool is an important component in a boiling water reactor nuclear power plant. Under design-basis, loss-of-coolant accident conditions, pressure in the containment increases. Gas flows from the drywell to the wetwell after the normally submerged connecting vents between the drywell and the wetwell have been purged of water through a vent clearing process so that the suppression pool may prevent pressure in the containment from exceeding the designed pressure limit. To analyze such complicated thermal-hydraulic behavior of the suppression pool under a specific accident, an advanced reasonable model should be developed. The SPARC-90 model used in MELCOR calculates the mass and energy transfer between the bubbles of the injected gas and the suppression pool, which is affected by distance efficiency and subcooling efficiency. The dedicated vent flow model used in CONTAIN can well simulate the vent clearing time, that is, the time required for the liquid level on either side of the suppression pool to drop to the level at which the vent begins to clear. However, it is necessary and better to combine them into one integrated code. This paper presents a newly developed suppression pool model based on the self-developed severe accident analysis code Integrated Severe Accident Analysis (ISAA), which combines the advantages of the dedicated vent flow model and the SPARC-90 model to analyze the suppression pool’s thermal-hydraulic behavior. The simulation results of the developed suppression pool model shows reasonableness compared with the result in the CONTAIN 2.0 code manual. The good agreement between the simulation results and the analysis results from the COLUMBIA power station final safety analysis report demonstrates the rationality and effectiveness of the developed model, although future improvement is needed.

摘要

抑制池是沸水反应堆核电站的重要组成部分。在设计基准、冷却剂损失事故工况下，安全壳内的压力会增加。在干井和湿井之间通常浸没的连接通风口已经通过通风口清除过程清除水之后，气体从干井流向湿井，从而抑制池可以防止安全壳中的压力超过设计压力限制。为了分析特定事故下抑制池的这种复杂的热工水力行为，需要开发一个先进的合理模型。MELCOR 中使用的 SPARC-90 模型计算注入气体的气泡与抑制池之间的质量和能量传递，它受距离效率和过冷效率的影响。CONTAIN 中使用的专用排气流模型可以很好地模拟排气孔清除时间，即抑制池两侧的液位下降到排气孔开始清除的水平所需的时间。然而，将它们组合成一个集成代码是必要的，也是更好的。本文基于自主开发的严重事故分析程序综合严重事故分析（ISAA）提出了一种新开发的抑制池模型，该模型结合了专用排气流模型和SPARC-90模型的优点来分析抑制池的热-水力行为。开发的抑制池模型的仿真结果与 CONTAIN 2.0 代码手册中的结果相比显示出合理性。