某核电厂碘源溶液安全管控优化改进

Improvement and practice of safety management and control forNa ^(131) I solution in a nuclear power plant

某核电厂通风系统碘吸附器效率试验采用放射性甲基碘法,试验需要用到放射性碘源(Na^(131)I)溶液,由于碘具有易挥发性,在碘源溶液的配制和存储过程中发生过微量^(131)I挥发排向通风系统,最终在烟囱中取样检测到^(131)I(远小于豁免水平)的情况。基于核电厂安全第一和防患于未然的管理原则,为了防止在碘源溶液配制和存储过程中^(131)I挥发并经通风系统向外排放,对^(131)I挥发的原因进行了分析研究。研究结果表明:^(131)I挥发的主要原是因为在手套箱中进行碘源配制操作过程中使用注射器抽取碘源溶液,注射器内壁和针头表面粘附的少量碘源溶液挥发到碘源间内,最终通过排风系统排向环境;此外,存储在碘源柜中的碘源溶液密封性较差也是造成^(131)I向外挥发的原因之一。针对碘吸附器效率试验用碘源溶液配制和存储过程中微量^(131)I挥发问题,制定了改进优化方案,多次现场实践验证表明,改进优化方案实施效果显著。

A radioactive methyl iodine method is adopted to carry out the efficiency test of iodine adsorbers of ventilation systems for a nuclear power plant.Radioactive iodine source(Na ^(131) I)solution is used in the tests.During the operation and storage of the iodine source solution,an event that a small amount of ^(131) I released into the ventilation system occurred and ^(131) I was detected in periodic sampling of the exhaust stack.In order to prevent the problem before their occurring and to ensure safety,the cause analysis of this event was carried out and the results show that the main reason is the volatilization of ^(131) I into the iodine source room when a small amount of Na ^(131) I solution attached to the inner wall of the syringe and the surface of the needle during the preparation of Na ^(131) I solution using a syringe in a glove box.The poor sealing of the bottle of Na ^(131) I solution stored in the iodine source cabinet is also a main reason for the volatilization of ^(131) I.Therefore,some improvement measures are implemented with a good results in this nuclear power plant.