Veinot K G, Dewji S A, Hiller M M, Eckerman K F, Easterly C E
Easterly Scientific, 6412 Westminster Rd., Knoxville, TN, 37919, USA.
Y-12 National Security Complex, P.O. Box 2009, Oak Ridge, TN, 37831-8206, USA.
Radiat Environ Biophys. 2017 Nov;56(4):453-462. doi: 10.1007/s00411-017-0705-6. Epub 2017 Aug 24.
External dose coefficients for environmental exposure scenarios are often computed using assumption on infinite or semi-infinite radiation sources. For example, in the case of a person standing on contaminated ground, the source is assumed to be distributed at a given depth (or between various depths) and extending outwards to an essentially infinite distance. In the case of exposure to contaminated air, the person is modeled as standing within a cloud of infinite, or semi-infinite, source distribution. However, these scenarios do not mimic common workplace environments where scatter off walls and ceilings may significantly alter the energy spectrum and dose coefficients. In this paper, dose rate coefficients were calculated using the International Commission on Radiological Protection (ICRP) reference voxel phantoms positioned in rooms of three sizes representing an office, laboratory, and warehouse. For each room size calculations using the reference phantoms were performed for photons, electrons, and positrons as the source particles to derive mono-energetic dose rate coefficients. Since the voxel phantoms lack the resolution to perform dose calculations at the sensitive depth for the skin, a mathematical phantom was developed and calculations were performed in each room size with the three source particle types. Coefficients for the noble gas radionuclides of ICRP Publication 107 (e.g., Ne, Ar, Kr, Xe, and Rn) were generated by folding the corresponding photon, electron, and positron emissions over the mono-energetic dose rate coefficients. Results indicate that the smaller room sizes have a significant impact on the dose rate per unit air concentration compared to the semi-infinite cloud case. For example, for Kr-85 the warehouse dose rate coefficient is 7% higher than the office dose rate coefficient while it is 71% higher for Xe-133.
环境暴露情景的外照射剂量系数通常是基于无限或半无限辐射源的假设来计算的。例如，对于站在受污染地面上的人，假设源分布在给定深度（或不同深度之间）并向外延伸至基本无限远的距离。对于暴露于受污染空气中的情况，将人建模为站在无限或半无限源分布的云团中。然而，这些情景并不能模拟常见的工作场所环境，在这种环境中，来自墙壁和天花板的散射可能会显著改变能谱和剂量系数。在本文中，使用国际放射防护委员会（ICRP）的参考体素模型计算剂量率系数，这些模型放置在代表办公室、实验室和仓库的三种不同大小的房间中。对于每种房间大小，使用参考模型针对光子、电子和正电子作为源粒子进行计算，以得出单能剂量率系数。由于体素模型缺乏在皮肤敏感深度进行剂量计算的分辨率，因此开发了一个数学模型，并针对三种源粒子类型在每种房间大小中进行计算。通过将相应的光子、电子和正电子发射与单能剂量率系数相乘，得出ICRP第107号出版物中稀有气体放射性核素（例如氖、氩、氪、氙和氡）的系数。结果表明，与半无限云团情况相比，较小的房间大小对单位空气浓度的剂量率有显著影响。例如，对于氪 - 85，仓库的剂量率系数比办公室的剂量率系数高7%，而对于氙 - 133则高71%。
