乏燃料贮存罐体中子防护结构研究

Research on Spent Fuel Storage Tanks for Neutron Protection Structure

使用含硼聚乙烯作为乏燃料贮存罐体外层屏蔽罐中子屏蔽层材料时,由于其对温度比较敏感,若结构设计不合理,在环境温差大或出现事故致使罐体温度变化大时,会使罐体外含硼聚乙烯屏蔽层变形过大,影响结构稳定性和屏蔽效果,如产生间隙和裂纹等,致使射线经间隙或裂纹中散射到环境中,对周围环境造成严重污染。乏燃料贮存罐体中子防护结构采用在燃料贮存罐外加双层中子屏蔽结构,内层为主屏蔽层预留伸缩缝,以适应温差较大的环境和事故工况,外层为补充防护层,可有效解决伸缩缝处泄漏问题。中子屏蔽层上端为敞口设计,用含硼聚乙烯粉末填充,事故工况下粉末将熔融补充填充,保证屏蔽层高度,避免射线外露。

Boron-containing polyethylene could be selected as the neutron shielding of the spent fuel storage tank outer casing shield tank. Because of it's sensitive to temperature, if the structural design is unreasonable, the deformation of boron-containing polyethylene could be too large for the structure stability and shielding effect when the ambient temperature difference is large or the tank temperature changes greatly for accident. This may produce gaps and cracks, who scatter the ray to environment and cause pollution. Double layer structure is used for neutron shielding out of the spent fuel storage tank. The inner layer is the main shielding layer, for which expansion joints are reserved to meet large temperature difference of environment and the accident conditions. The outer layer is a supplementary protective layer, which can effectively solve the problem of leakage at the expansion joints. The top of the shielding structure is designed open, filled with boron-containing polyethylene powder. In accident conditions, the powder will melt to fill, and the height of shielding structure could be kept to avoid radiation exposure.