基于ASTEC程序的反应堆严重事故下压力容器下封头传热分析  

Analysis of heat transfer of the RPV lower head under severe accidents with ASTEC

作　　者：左嘉旭 宋维 安婕铷 庄少欣 石兴伟 ZUO Jiaxu;SONG Wei;AN Jieru;ZHUANG Shaoxin;SHI Xingwei(Nuclear and Radiation Safety Center,Beijing 100082,China;State Environmental Protection Key Laboratory of Nuclear and Radiation Safety Regulatory Simulation and Validation,Beijing 100082,China)

机构地区：[1]生态环境部核与辐射安全中心,北京100082 [2]国家环境保护核与辐射安全审评模拟分析与验证重点实验室,北京100082

出　　处：《核技术》2023年第1期100-105,共6页Nuclear Techniques

基　　金：国家重点研发计划(No.2019YFB1900701)资助。

摘　　要：反应堆压力容器内熔融物滞留是先进反应堆设计严重事故缓解措施中的重要选项之一,在维持反应堆压力容器的完整性,包容堆芯熔融物方面具有重要作用。确保熔融物滞留有效性的关键是保证下封头内壁热负荷不超过下封头外壁面换热能力,而且在整个过程中不发生结构失效,即下封头剩余壁厚能够实现熔融物的承载。应用ASTEC程序,基于大型先进压水堆的设计,针对反应堆压力容器内熔融物滞留系统运行过程中冷却剂热工参数、下封头外壁面临界热流密度和最终下封头厚度进行计算分析,通过研究熔池对下封头的熔蚀和剩余厚度,判断下封头残留厚度对于熔融物的包容,评估系统的有效性。结果表明:在下封头较上部位置的部分区域内,换热较为剧烈,其中热流密度最大值出现在熔融物分两层的交界处,事故过程中下封头内壁将被熔融物金属层熔化,剩余厚度满足包容要求,但是最终剩余厚度十分有限。[Background]Among the mitigating strategies for severe accidents,the in-vessel retention(IVR)is one of the useful remission measurements.The key point to evaluating IVR is to analyze that the final steady-state thermal load of the melt does not exceed the critical heat flux(CHF),which occurs during boiling heat transfer on the outer wall of the lower head,and the remaining wall thickness of the lower head can carry the melt to prevent the structural failure.[Purpose]This study aims to analyze heat transfer of the reactor pressure vessel(RPV)lower head under severe accidents by using ASTEC code.[Methods]First of all,the composition and mass of the molten substance were assumed to be UO2,92353.29 kg;Fe,43000 kg;Zr,23133.9 kg;Zr oxidation,41.8%,for a large advanced pressurized water reactor(LAPWR).With the heavy metal oxide layer and metal layer of stable molten pool in the lower RPV of this LAPWR,the average value of core decay power and the physical properties of molten materials in RPV were input as the condition boundaries for ASTEC,the middle break accident sequence was selected for the calculation of the thermal parameters of the coolant,the outer wall CHF and the final thickness of the lower head.Then,the CHAWLA-CHAN heat transfer relationship was used to calculate the heat transfer coefficient between the melt and the inner wall of the lower head.The key safety related issues such as the heat transfer parameters of the outer wall of the lower head,the heat transfer through the lower head,and the wall thickness of the lower head were analyzed.Finally,the IVR effectiveness was estimated by the thermal properties and the structure of the lower head.[Results]When the decay power is 21 MW and the core molten pool is divided into two layers,the average thickness of the oxide layer is 1.6 m,and the metal layer is 0.8 m.The results show that the heat exchange is more intense in the upper part of the lower head,and the maximum value of the heat flux occurs at the junction of the two melt layers,which the correspondin

关 键 词：严重事故 ASTEC 反应堆压力容器内熔融物滞留 临界热流密度 

分 类 号：TL99[核科学技术—核技术及应用]