Dickson E D, Hamby D M
United States Nuclear Regulatory Commission, Rockville, DC 20555-0001, USA.
J Radiol Prot. 2016 Sep;36(3):579-615. doi: 10.1088/0952-4746/36/3/579. Epub 2016 Jul 27.
We describe a simplified method for calculating both building protection- and shielding-factors for generic one- and two-story housing-unit models that are source-term dependent. Typically, radionuclide-independent factors are applied generically to external dose coefficients to account for the radiation shielding effects of indoor residences. In reality, the shielding effectiveness of each housing-unit would change over time as the radionuclide mixture and gamma-ray energy spectrum change due to physical effects such as deposition, radioactive decay, weathering effects, and decontamination efforts. Thus, it is necessary to develop factors designed for multiple photon energy spectrums to generate a more realistic estimate of the shielding effectiveness of a particular building. It is impractical to develop factors specific to a spectrum of photons emitted by each radionuclide of interest. Therefore, Monte Carlo simulations have been performed for sixteen monoenergetic photon energies from 0.10 to 3.0 MeV to characterize the 3D radiation fluence through each housing-unit produced by two idealized, yet realistic, environmental exposure scenarios. Results of these simulations were then used to develop fitted logarithmic functions (extrapolated to 0.0 MeV) to correlate an estimated factor to any monoenergetic photon energy up to 3.0 MeV. To verify these functions, another series of Monte Carlo simulations were performed for a select set of radionuclides to develop radionuclide-specific building protection- and shielding-factors. Good agreement is achieved between factors estimated using the presented functions and those calculated directly using Monte Carlo methods. Factors predicted by these functions are found to be in general agreement with other study results reported on similar structures which applied various computational methods and source-terms. This study only focuses on generic one- and two-story homes to provide a practical application that can contribute to improve the preparedness for and the response to a nuclear or radiological emergency.
我们描述了一种简化方法，用于计算与源项相关的通用单层和两层住房单元模型的建筑物防护因子和屏蔽因子。通常，与放射性核素无关的因子被普遍应用于外部剂量系数，以考虑室内住宅的辐射屏蔽效应。实际上，随着放射性核素混合物和伽马射线能谱因沉积、放射性衰变、风化效应和去污努力等物理效应而发生变化，每个住房单元的屏蔽效果会随时间改变。因此，有必要开发针对多种光子能谱的因子，以便更实际地估计特定建筑物的屏蔽效果。针对感兴趣的每种放射性核素发射的光子能谱开发特定因子是不切实际的。因此，已针对从0.10至3.0 MeV的16种单能光子能量进行了蒙特卡罗模拟，以表征由两种理想化但实际的环境暴露场景产生的穿过每个住房单元的三维辐射注量。然后，利用这些模拟结果开发拟合对数函数（外推至0.0 MeV），以将估计因子与高达3.0 MeV的任何单能光子能量相关联。为了验证这些函数，针对一组选定的放射性核素进行了另一系列蒙特卡罗模拟，以开发特定于放射性核素的建筑物防护因子和屏蔽因子。使用所提出的函数估计的因子与直接使用蒙特卡罗方法计算的因子之间达成了良好的一致性。发现这些函数预测的因子与采用各种计算方法和源项的关于类似结构的其他研究结果总体一致。本研究仅关注通用的单层和两层房屋，以提供一种实际应用，有助于提高对核或放射性紧急情况的准备和应对能力。
