IRIS反应堆严重事故下堆内自然循环及下封头失效分析

使用REALP5/SCDAP分析了IRIS堆汽轮机停机和部分失流事故导致的严重事故进程及缓解措施。分析结果表明IRIS堆内水装量大,使得堆芯较长时间处于淹没状态,事故发生后近7个小时堆芯开始裸露,10小时后堆芯开始损坏。对于不卸压不安注的情况,压力容器会完全干涸,堆芯和蒸汽发生器之间形成蒸汽自然循环流动,堆芯温度缓慢升高,低熔点的控制棒金属首先熔化落入下腔室并加热下封头,使得下封头底部区域发生蠕变断裂失效。在不卸压的情况下一个上充泵的安注流量就能够缓解事故。

Analysis of In-vessel Natural Circulation and Lower Head Rupture of IRIS under Severe Accidents

The progression and mitigation measures of the severe accident induced by turbine trip and partial loss of forced coolant flow of IRIS reactor were analyzed with RELAP5/SCDAP computer code. The analytic results show that with the large inventory of water in the vessel,the core will under submerged for a long time,nearly 7 hours later the core begin uncovered,and the core became damaged 10 hours later. For the case with no injection and no depression,the vessel will fully dry out,there will be nature circulation between the core and steam generator,the core temperature will rise slowly,the low melting point control rod metal firstly meltdown,and fall into the lower plenum. The molten control rod material will heat the lower head,under high temperature and high pressure difference,the lower head will suffer creep rupture at the lowest region. For the case with no depression,a charging pump inj ection will mitigate the severe accident.