低温供热堆选址阶段的环境影响评价与分析

根据低温供热堆选址阶段环境影响评价的要求,结合工程具体设计方案,对低温供热堆在正常运行和事故工况下可能造成的环境影响进行分析、预测与评价,以作为审管当局决策的重要依据。低温供热堆在正常运行状态时,放射性气载流出物在大气中迁移和扩散及对公众的辐射剂量估算采用的是IAEA安全系列19号报告中给出的筛选模式(稀释模式);事故工况下保守考虑全堆熔事故作为选址假想事故,采用USNRC RG1.4中给出的最大可信事故(30d)的大气扩散因子计算方法,估算假想事故各时段的大气扩散因子。正常运行工况下,在半径1km的环形区域内烟囱排放和蒸发池排放叠加的最大个人有效剂量为7.84×10^-6 Sv/a,小于本工程对公众的剂量约束值0.03mSv/a;事故工况下,两厂址所致公众个人(成人)在整个事故持续时间内厂址边界处(150m)最大个人有效剂量为5.66mSv,甲状腺当量剂量为7.43mSv,均小于《小型压水堆核动力厂安全审评原则(试行)》要求。低温供热堆在正常运行和事故工况下,对周围环境和公众的影响均满足参考的相关标准要求,是可以接受的。

Environmental impact Assessment and Analysis of Low Temperature Heating Reactor Site Selection Stage

According to the requirements of environmental impact assessment in the site selection stage of the low temperature heating reactor,combined with the specific design scheme of the project,this paper analyzed,predicted and evaluated the possible environmental impact of low temperature heating reactor under normal operation and accident conditions,so as to provide an important basis for the administrative authority to make decisions.Methods When the low temperature heating reactor was in normal operation,the radioactive airborne effluents migrated and diffused in the atmosphere,and the radiation dose to the public was estimated using the screening mode(dilution mode)given in IAEA Safety Series Report No.19;under accident conditions,the whole reactor melting accident was conservatively considered as a hypothetical site selection accident,and the atmospheric diffusion factor calculation method of the maximum credible accident(30d)given in USNRC RG1.4 was used to estimate the atmospheric diffusion factor of each period of the hypothetical accident.Result Under normal operation conditions,the maximum individual effective dose of stack emission and evaporation pool emission in the circular area with a radius of 1km is 7.84×10^-6 Sv/a,which is less than the dose constraint value of 0.03msv/a for the public in this project;under the accident condition,the maximum individual effective dose of the public(adults)caused by the two plant sites was 5.66msv at the boundary of the plant site(150m)in the whole duration of the accident.The thyroid equivalent dose was 7.43 mSv,both of which were less than the requirements of"safety evaluation principles for small PWR nuclear power plants(Trial)".Conclusion Under normal operation and accident conditions,the impact of low temperature heating reactor on the surrounding environment and the public can meet the requirements of relevant standards,which is acceptable.