失水事故后燃料厂房空气自然循环及氢气分布实验研究

针对乏燃料水池失水、乏燃料裸露的事故情景，通过实验研究了燃料厂房内空气自然循环及氢气分布的基本规律，得到了空间气体温度场及浓度分布实验数据。结果表明，由于空气自然循环的热量输运作用，各区域升温速率随温度的升高而降低；与外界自然对流通风的简单方式可显著减缓温度上升，实验24 h后加热元件温度低于490 ℃；喷淋则可迅速降低所覆盖区域温度，空间气体平均温度在喷淋后5 min内下降了100 ℃。氢气在空气环境中将形成浓度分层，喷淋搅混可在2 min内破坏该分层；对于氢气/蒸汽混合气体，随着蒸汽凝结及外界空气涌入逐渐具有可燃性，喷淋对此无积极作用。基于上述研究结果，提出了能动和非能动的事故缓解措施建议。

Experimental Research of Air Natural Circulation and Hydrogen Distribution in Fuel Building after Loss of Coolant Accident

Experiments regarding air natural circulation and hydrogen distribution inside the fuel building under loss of coolant accidents of the spent fuel pool and spent fuel uncovered were conducted, and the test data of gas temperature field and concentration distribution were acquired. It is found that heating rate will slow down while temperature rising because of heat removal effect of air circulation. Natural cross ventilation between the building and environment evidently delays heating process, and after 24 h the temperature of heaters is below 490 ℃. Inside the spray zone air temperature decreases rapidly, and average air temperature decreases by 100 ℃ within 5 min. Hydrogen stratifies in air, and the stratification is broken down by spray within 2 min. Regarding the hydrogen/steam atmosphere, as steam condensing and air inflowing the mixed gas becomes combustible, however spray makes no positive effect. On the basis of this work, both active and passive mitigation strategies are proposed.