| Pan Yongxiang,Li Mingsheng,Guo Zhaohui,et al.Calculation of induced radioactivity of heavy concrete shielding wall in proton therapy room[J].Chinese Journal of Radiological Medicine and Protection,2020,40(4):321-325 |
| Calculation of induced radioactivity of heavy concrete shielding wall in proton therapy room |
| Received:December 10, 2019 |
| DOI：10.3760/cma.j.issn.0254-5098.2020.04.013 |
| KeyWords:Proton therapy Heavy concrete Induced radioactivity Ambient dose equivalent rate |
| FundProject: |
| Author Name | Affiliation | E-mail | | Pan Yongxiang | Key Laboratory of Radiological Protection and Nuclear Emergency, China CDC, National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention, Beijing 100088, China | | | Li Mingsheng | Key Laboratory of Radiological Protection and Nuclear Emergency, China CDC, National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention, Beijing 100088, China | | | Guo Zhaohui | Key Laboratory of Radiological Protection and Nuclear Emergency, China CDC, National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention, Beijing 100088, China | | | Cheng Jinsheng | Key Laboratory of Radiological Protection and Nuclear Emergency, China CDC, National Institute for Radiological Protection, Chinese Center for Disease Control and Prevention, Beijing 100088, China | chengjs3393@163.com |
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| Abstract:: |
| Objective To estimate the induced radioactive 56Mn and its level of iron in heavy concrete shielding wall due to neutron activation during tumor proton therapy. Methods A Geant4 program was adopted to build the model of a heavy concrete shielding wall in a proton therapy room, simulate secondary neutrons generated by 245 MeV proton beam irradiating water phantom. The statistical distribution of radionuclide 56Mn in shielding wall was calculated. The shielding wall was layered every 10 cm thickness, the dose equivalent rate of radionuclide 56Mn in the first three shielding walls was calculated. Results Under the maximum beam irradiation conditions (1.872×1010), the number of radionuclide 56Mn in the first three layers of shielding walls are 3.10×108, 1.60×108, 9.33×107. The ambient dose equivalent rate at a distance of 1 m from the treatment room are 2.13×10-3, 8.82×10-4, 9.10×10-4 μSv/h, and the total ambient dose equivalent rate for the first three layers was 3.92×10-3 μSv/h. Conclusions During proton therapy, the shielded walls near the central axis of the beam produce more induced radioactivity. The induced radioactivity produced by the neutron-activated iron element at the ahead of the shielding wall is the strongest, and decreases exponentially as the thickness of the shield wall increases.The induced radioactivity in front of the shielding wall of proton therapy room should be concerned. |
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