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目的探讨基于“避免防护过度”和“辐射防护最优化”原则的屏蔽防护门2种设计方案下电子直线加速器机房中子辐射屏蔽估算方法,评价屏蔽效果。方法以25 Me V电子直线加速器机房为研究对象,依据美国辐射防护和测量委员会(NCRP)151号报告建议书(NCRP 151号报告)相关建议和要求,采用2种设计方案对屏蔽防护门进行辐射屏蔽,典型设计方案为在迷道入口处安装50 mm铅当量加12.00 cm的含硼聚乙烯(BPE)屏蔽防护门,优化设计方案为在迷道内增加10.00 cm的BPE屏蔽防护门和在迷道入口处安装8 mm铅当量屏蔽防护门,采用相应的公式和参数对2种设计方案的屏蔽效果进行估算和分析。结果采用典型设计方案和优化设计方案时,迷道入口M点处总的每周剂量当量分别为3 662.000和564.345μSv/周,屏蔽防护门外总的剂量当量率分别为1.820和0.391μSv/h,均小于2.500μSv/h。优化设计方案总的剂量当量率仅为典型设计方案的21.43%,无论从屏蔽效果还是从屏蔽用材方面均优于典型设计方案。结论采用优化设计方案在迷道入口内部安装BPE屏蔽防护门的屏蔽方案合理可行,可作为电子直线加速器机房中子辐射防护评价方法。
OBJECTIVE To explore the method of estimating the shielding effectiveness of neutron radiation shielding in electron linear accelerator room with two kinds of design schemes based on the principle of “avoid over-protection” and “radiation protection optimization”. Methods Based on the suggestions and requirements of the NCRP 151 report (NCRP 151), a 25 MeV linear accelerator room was used as the research object. Two kinds of design schemes were adopted to radiate the shielding door Shielding, Typical Design A 50 mm lead-free, boron-added polyethylene (BPE) screened protective door with a 50 mm lead equivalent plus 12.00 cm at the entrance to the maze is optimized to include a 10.00 cm BPE screened protective door in the maze, Entrance 8 mm lead-equivalent shield protective door installed, using the appropriate formula and parameters of the two designs of shielding effectiveness estimation and analysis. Results When using the typical design and optimized design, the total weekly dose equivalent at M point of the entrance was 3 662.000 and 564.345 μSv / week, respectively, and the total dose equivalent rates outside the barrier were 1.820 and 0.391 μSv / h, respectively , Both less than 2.500μSv / h. Optimized design The total dose equivalent rate of only 21.43% of the typical design, both from the shielding effect or shielding materials are better than the typical design. Conclusion The shield scheme of BPE shielding door installed inside the entrance of the trampoline with optimized design scheme is reasonable and feasible and can be used as a method to evaluate the neutron radiation protection of the electron linear accelerator room.