The double-ended guillotine break (DEGB) of the horizontal coaxial gas duct of a high-temperature gas-cooled reactor is an extremely hypothetical accident, which could cause the air to enter into the primary circuit and react with graphite in the reactor core. The performance of the HTR-PM plant under this extremely hypothetical accident has been studied by the system code TINTE in this work. The results show that the maximum fuel temperature will not reach the temperature design limitation, and the graphite oxidation will not cause unacceptable consequences even under some conservative assumptions. Moreover, nitrogen and helium injected from the fuel charging tube were studied as the possible mitigation measures to further alleviate the consequences of this air ingress accident. The preliminary results show that only the flow rate of nitrogen injected reaches a certain value, which can effectively alleviate the consequences, while for helium injection, both high and small flow rate can prevent or cut off the natural circulation and alleviate the consequences. The reason is that helium is much lighter than nitrogen, and the density difference between the coolant channel and the reactor core is small when helium is injected. Considering the injection velocity, the total usage amount, and the start time of gas injection, helium injected with a small flow rate is suggested.

中文翻译：

---

HTR-PM进气事故的数值研究及可能的缓解措施

高温气冷反应堆的水平同轴燃气管道的双头断头台断裂（DEGB）是一个非常假想的事故，它可能导致空气进入一次回路并与反应堆堆芯中的石墨发生反应。在这项工作中，系统代码TINTE对HTR-PM工厂在这种极端假设事故下的性能进行了研究。结果表明，即使在某些保守的假设下，最高燃料温度也不会达到温度设计极限，并且石墨氧化也不会造成不可接受的后果。此外，还研究了从加油管注入的氮气和氦气作为可能的缓解措施，以进一步减轻这种进气事故的后果。初步结果表明，只有注入的氮气流量达到一定的数值​​，才能有效地减轻后果；而对于注入氦气，无论流量大小，都能阻止或切断自然循环，减轻后果。原因是氦气比氮气轻得多，注入氦气时冷却剂通道和反应堆堆芯之间的密度差很小。考虑到喷射速度，总用量和气体喷射的开始时间，建议以小流量喷射氦气。原因是氦气比氮气轻得多，注入氦气时冷却剂通道和反应堆堆芯之间的密度差很小。考虑到喷射速度，总用量和气体喷射的开始时间，建议以小流量喷射氦气。原因是氦气比氮气轻得多，注入氦气时冷却剂通道和反应堆堆芯之间的密度差很小。考虑到喷射速度，总用量和气体喷射的开始时间，建议以小流量喷射氦气。