15 MV高能电子直线加速器机房门屏蔽理论计算和防护效果验证对比研究

Comparative study on theoretical calculation and protection effect verification of door shielding for 15 MV high energy electron linear accelerator room

目的 :比较国内外高能电子直线加速器机房门屏蔽规范,寻求最优化的防护门屏蔽设计方法。方法 :采用国标GBZ/T 201.2—2011《放射治疗机房的辐射屏蔽规范第2部分:电子直线加速器放射治疗机房》、NCRP 151号报告和IAEA 47号报告3种规范对15 MV高能电子直线加速器机房门进行屏蔽理论计算,并与实际的迷路外入口辐射水平和机房门防护效果进行对比验证。结果:机房防护门中子屏蔽3种理论计算与验证检测基本一致,需含硼(0.5%)聚乙烯屏蔽厚度是101~109 mm。光子铅屏蔽厚度差别较大,依次是36、64、14 mm,验证检测只需12 mm。结论:3种理论计算结果都能满足屏蔽要求,但按照屏蔽设计防护最优化原则,IAEA 47号报告计算方法比较符合实际需要。

Objective To compare the specifications of door shielding for 15 MV high energy electron linear accelerator room in foreign countries and China to find the optimal design method of door shielding. Methods The theoretical calculation on the door shielding for 15 MV high energy electron linear accelerator room was executed according to national standard, NCRP151 report and IAEA 47 report, and the entrance radiation out of the maze and the door shielding effect were verified practically. Results Verification indicated the calculation results on neutron according to national standard GBZ/T 201.2—2011 Radiation shielding requirements for radiotherapy room—Part 2 ： Radiotherapy room of electron linear accelerators,NCRP 151 report and IAEA 47 report were gifted with high consistency, which had the thickness of boron polyethylene be from 101 to 109 mm. The results on photon lead thickness according to national standard, NCRP 151 report and IAEA 47 report had low consistency, which was 36, 64 and 14 mm respectively, while verification test proved the desired thickness was only 12 mm. Conclusion The theoretical calculation results according to national standard, NCRP 151 report and IAEA 47 report proves to meet the requirements for shielding, and the design based on IAEA 47 report is selected with considerations on the principle of optimization.