球床式高温气冷堆进气事故机理研究及关键特性分析

项目名称： 球床式高温气冷堆进气事故机理研究及关键特性分析

项目编号： No.51306100

项目类型： 青年科学基金项目

立项/批准年度： 2014

项目学科： 能源与动力工程

项目作者： 郑艳华

作者单位： 清华大学

项目金额： 25万元

中文摘要： 高温气冷堆进气事故可导致石墨腐蚀、堆体结构强度减弱、燃料元件完整性破坏，从而影响反应堆的安全，是高温气冷堆研究中重点关注的超设计基准事故。项目以球床式高温气冷堆热气导管发生双端断裂、堆内外压力平衡后，舱室内空气-氦气混合物在密度梯度驱动分层流和分子扩散的作用下进入堆芯的过程为研究对象。一定量的空气进入堆芯后，由于堆内外存在较大的温度差，将会建立起稳定的自然对流，从而开始持续、大量的进空气，并造成较严重后果。通过对分层流现象和扩散现象进行理论研究，明确其物理机制和主要影响因素；研究不同结构和物理条件下两种现象对气体流动的支配作用；利用流体力学计算工具对反应堆进行整体建模分析，确定建立稳定自然对流的时间，评价反应堆内不同结构的进气时间尺度；通过敏感性分析，掌握球床式高温气冷堆进气事故的特性及关键影响参数，研究并验证能有效抑制空气进入堆芯的缓解措施，从而为论证高温气冷堆的安全特性提供可靠依据。

中文关键词： 高温气冷堆；进气事故；自然对流；分层流；扩散

英文摘要： Air-ingress accident of the high temperature gas-cooled reactor (HTGR), which will result in graphite corrosion, weakening of the structural strength and failure of the fuel element integrity so as to influence the safety of the reactor, is one of the beyond design basis accident (BDBA) being highly concerned about in HTGR research. This project focuses on the phenomenon that, in case of the double-ended guillotine of the hot-gas duct of the pebble-bed HTGR and after the pressures between the reactor and the cavity reach equilibrium, the air/helium mixture in the cavity will flow into the reactor because of the molecular diffusion, as well as the stratified flow driven by the density gradient. With a certain amount of air in the core, the natural convection will come into being due to the large temperature difference between the inside and outside of the core, so as to result in the continous and stable air ingress and more serious consequence. Based on the theoretical study on the phenomenon of stratified flow and molecular diffusion, the physical mechanism and main influencing factors of them would be analyzed, so as to find out the dominant role for gas flow under different structures and different physical conditions. With the suitable CFD software, the computational model of the whole reactor will be built

英文关键词： high temperature gas-cooled reactor；air ingress accident；natural convection；stratified flow；diffusion