摘要
核电站发生堆芯熔化并熔穿压力容器的严重事故时,熔融物落入堆腔中会与混凝土相互作用(Molten Core-Concrete Interactions,MCCI),可能会威胁安全壳的完整性。本文基于MELCOR搭建AP1000核电站的计算模型,设置大破口事故叠加换料水箱重力注射失效情况,研究压力容器被熔穿后的事故现象及熔融物堆外冷却过程,分析了MC⁃CI现象对安全壳完整性的威胁,即超压风险,燃爆风险和直接熔穿风险。研究结果表明,熔融物落入堆腔后,安全壳内会经历初期快速降压,随后达到水蒸发和冷凝的动态平衡,壳内压力稳定维持在0.2 MPa。MCCI过程中会产生可燃气体,积累至爆炸极限并触发点火装置工作。混凝土底板相比于侧壁更易被消融,在事故时间105 s内被熔穿约1 m。安全壳内部空间在达到热工水力平衡后,熔融物衰变热不断被导出安全壳外,事故最终得到缓解。
When nuclear power plant has a serious accident which the core melts and penetrates the pressure vessel,molten material falls into the stack and interacts with the concrete(Molten core-concrete interactions,MCCI),threatening the integrity of the containment.Based on MELCOR's calculation model of AP1000 nuclear power plant,the failure of gravity injection in the refueling tank superposed by a large breach accident was set up in this paper to study the accident phenomenon after the pressure vessel was melted through and the cooling process of the molten material outside the reactor,and it analyzes the threat of MCCI to the integrity of the containment vessel,that is,the risk of overpressure,the risk of explosion and the risk of direct melting.The results show that after the molten material falls into the reactor cavity,the pressure inside the containment vessel will undergo initial rapid depressurization,and then reach the dynamic equilibrium of water evaporation and condensation,and the pressure inside the containment vessel will remain stable at 0.2 MPa.Combustible gas will be generated during MCCI process,which will accumulate to the explosion limit and trigger the ignition device to work.Compared with the side wall,the concrete bottom plate is more easily melted,and it is melted through about 1 m at 105 s.After the safety shell space reaches the thermal hydraulic balance,the decay heat of the molten material is continuously exported outside the safety shell,and the accident is alleviated.
作者
王钦
毕金生
丁铭
Wang Qin;Bi Jinsheng;Ding Ming(Harbin Engineering University,National Defense Key Discipline Laboratory of Nuclear Security and Simulation Technology,Harbin 150001,China;Nuclear and Radiation Safety Center,MEE,Beijing 100082,China)
出处
《核安全》
2019年第6期37-43,共7页
Nuclear Safety
关键词
熔融物与混凝土相互作用
熔融物堆外冷却
MELCOR
the interaction between molten material and concrete
external cooling of molten material
MELCOR
