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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。
When boron-containing polyethylene is used as a spent fuel storage tank outer shielding can neutron shielding material, due to its sensitivity to temperature, if the structural design is unreasonable, when the temperature of the environment is large or the temperature of the tank changes greatly due to an accident, So that the deformation of the boron-containing polyethylene outer shield is too large, affecting the structural stability and shielding effect, such as the generation of gaps and cracks, resulting in the ray through the gap or crack scattering into the environment, causing serious pollution to the surrounding environment. The neutron protection structure of the spent fuel storage tank is provided with a double-layer neutron shielding structure in the fuel storage tank, the inner layer is provided with expansion joints for the main shielding layer so as to adapt to the environment and accident conditions with large temperature difference and the outer layer is the supplementary protection Layer, which can effectively solve the problem of leakage at expansion joints. The upper end of the neutron shielding layer is open and designed to be filled with boron-containing polyethylene powder. The powder will melt and fill in in accident conditions to ensure the height of the shielding layer and prevent the exposure of the radiation.