CERT试验台架传热特性比例分析失真评价

Assessment of heat transfer phenomenon scaling distortion in CERT

非能动安全壳冷却系统(Passive containment cooling system,PCS)是大型先进压水堆核电厂专设安全系统之一,壳外冷却水膜在事故发生后对壳内的降温降压过程有着重要的作用。为了分析LOCA(Loss of Coolant Accident)事故工况下PCS整体响应过程的主要传热现象,验证PCS设计水膜覆盖率的安全裕度,本文利用安全壳专用分析程序分别对PCS原型系统和模拟试验台架(Containment safety v Erification via integ Ral Test,CERT)进行建模,分析基准工况和恶劣工况下安全壳内的传热相关无量纲参数群((47)群)及其相似准则数((47)比)的变化,比较影响PCS降温降压能力的不同能量传递方式的重要程度,同时对其在试验台架上出现的失真度进行评价。结果表明,安全壳外冷却水膜建立后,壳内破口能量主要通过壳内壁面蒸汽冷凝和壳外壁面水膜蒸发载出,相应物理现象在台架模拟试验中应优先准确模拟;此阶段壳内热阱传热失真度较大,但由于其换热量很低可以忽略不计。通过传热特性失真评价认为,CERT试验台架可以有效模拟原型PCS在小水膜覆盖率时的传热现象。

[Background] The cooling liquid film is very important during the depressurization and cooling down process of the passive containment cooling system（PCS） which is part of the passive reactor safety design. [Purpose] This study aims to analyze the main heat transfer phenomenon in PCS overall response process during loss of coolant accident（LOCA） accident and to verify the design liquid film coverage safety margin. [Methods] The calculating model of integral test facility and PCS prototype were established respectively using passive containment safety analysis code. Based on scaling analysis, the（47）（similarity number） related to heat transfer in containment and the（47） ratio between test facility and prototype were obtained in both base and severe accident condition. The importance degrees of different heat transfer modes affecting the containment cooled down were compared, and the heat transfer distortion was assessed. [Results] After the cooling liquid film was established, the break energy was mainly carried out by steam condensation inner shell and the liquid evaporation outer shell. The condensation and evaporation phenomenon was simulated accurately in the containment integral test. [Conclusion] Since the energy absorbed by heat sinks is tiny, its relatively large heat transfer distortion could be neglected. The assessment of heat transfer phenomenon scaling distortion show that the integral test facility could simulate heat transfer process of PCS prototype in low liquid film coverage condition effectively.