【摘要】 核电厂严重事故条件下,外部冷却对安全壳内混合气体行为的影响可能带来额外的氢气风险。本文对大空间内混合气体迁移行为及外部冷却的影响进行了试验研究。试验中采用氦气来替代氢气,试验开始阶段将一定体积份额的水蒸气和氦气混合物注入试验容器。混合气体在初始动量的作用下,向容器上部空间迁移,在空间内形成上部氦气体积浓度高、中下部氦气体积浓度低的分层现象。当混合喷放停止一段时间后开启外部冷却系统,由于外部冷却带走热量使得空间内蒸汽产生冷凝,随着系统温度和压力的下降,氦气体积浓度呈现快速上升的趋势。结果表明,外部冷却增强了对流换热,使得容器内温度更加均匀,但蒸汽冷凝引起氦气体积浓度大幅升高。更多还原

【Abstract】 Under severe accident conditions in nuclear power plants,the influence of external cooling on the behavior of mixed gas in the containment may bring additional hydrogen risks.This paper conducts an experimental study on the transport behavior of mixed gas in a large space and the influence of external cooling.In the test,helium is used to replace hydrogen,and a certain volume fraction of steam and helium mixture is injected into the test vessel at the beginning.Under the effect of the initial momentum,the mixed gas transports to the upper space of the large space,resulting in the stratification of high helium volume concentration in the upper part and low helium volume concentration in the middle and lower parts.When the mixed gas injection stops,the external cooling system is opened after standing for a period of time.With the heat removal by the external cooling system,the steam in the space is condensed.As the decrease of the system temperature and pressure,the helium volume concentration increases rapidly.The results show that the external cooling enhances convective heat transfer,makes the temperature in the space more uniform,but the helium concentration increases greatly due to steam condensation.更多还原