底反射层氧化对模块式高温气冷堆进气事故的影响分析

摘要

进气事故是模块式高温气冷堆(HTR-PM)事故分析中重点考虑的一种事故类型.核级石墨在高温气冷堆中被广泛用作反射层材料、结构材料和慢化材料等.在进气事故中,燃料元件基体石墨发生氧化反应增加了燃料颗粒裸露和放射性释放的风险,底反射层发生氧化反应降低了石墨材料的机械性能,可能破坏堆芯底部结构的完整性.本文利用高温气冷堆专用系统分析程序TINTE,分别选取两种不同氧化速率的石墨材料作为底反射层材料,以热气导管双端断裂的进气事故为例,分析不同材料对进气事故的影响.在保证底反射层完整性的前提下,底反射层采用高氧化速率的材料时,能明显降低燃料颗粒裸露和放射性释放的风险.%Air ingress accident plays an important role in the safety analyses of the high temperature gas-cooled reactor pebble bed module (HTR-PM).The nuclear grade graphite has a broaden use in HTR-PM and it is usually used as the reflector material,structure material and the moderating material.In the air ingress accident,the oxidation of the matrix graphite increases the risk of the exposure of the fuel particles and the release of radioactivity.Besides,the oxidation of the bottom reflectors may damage the integrity of the reactor bottom structure.The influence of two kinds of nuclear grade graphites on the double-ended guillotine break (DEGB) of the horizontal coaxial gas duct accident was analyzed by using TINTE code.In the premise of ensuring the integrity of the bottom reflector,the nuclear grade graphite with high oxidation rate can obviously decrease the risk of the exposure of the fuel particles and radioactivity release.