Chen Wei-Lin, Sheu Rong-Jiun
Institute of Nuclear Engineering and Science, National Tsing-Hua University, 101, Sec. 2, Kuang-Fu Road, Hsinchu, Taiwan.
Department of Engineering and System Science, National Tsing-Hua University, 101, Sec. 2, Kuang-Fu Road, Hsinchu, Taiwan.
Radiat Prot Dosimetry. 2018 May 1;179(3):233-243. doi: 10.1093/rpd/ncx260.
This study thoroughly determined the flux and dose rate distributions of cosmic-ray muons and neutrons in a five-story concrete building by comparing measurements with Monte Carlo simulations of cosmic-ray showers. An angular-energy-dependent surface source comprising secondary muons and neutrons at a height of 200 m above ground level was established and verified, which was used to concatenate the shower development in the upper atmosphere with subsequent simulations of radiation transport down to ground level, including the effect of the terrain and studied building. A Berkeley Lab cosmic-ray detector and a highly sensitive Bonner cylinder were used to perform muon and neutron measurements on each building floor. After careful calibration and correction, the measured responses of the two detectors were discovered to be reasonably consistent with the theoretical predictions, thus confirming the validity of the two-step calculation model employed in this study. The annual effective doses from cosmic-ray muons and neutrons on the open roof of the building were estimated to be 115.2 and 35.2 μSv, respectively. Muons and neutrons were attenuated floor-by-floor with different attenuation factors of 0.97 and 0.78, and their resultant dose rates on the first floor of the building were 97.8 and 9.9 μSv, respectively.
本研究通过将测量结果与宇宙射线簇射的蒙特卡罗模拟进行比较，全面确定了一座五层混凝土建筑中宇宙射线μ子和中子的通量及剂量率分布。建立并验证了一个地面以上200米高度处由次级μ子和中子组成的角度 - 能量相关表面源，该表面源用于将高层大气中的簇射发展与随后直至地面的辐射传输模拟相衔接，包括地形和所研究建筑的影响。使用伯克利实验室宇宙射线探测器和高灵敏度邦纳球进行各楼层的μ子和中子测量。经过仔细校准和校正后，发现两个探测器的测量响应与理论预测合理一致，从而证实了本研究中采用的两步计算模型的有效性。该建筑露天屋顶上宇宙射线μ子和中子的年有效剂量估计分别为115.2和35.2 μSv。μ子和中子逐层衰减，衰减因子分别为0.97和0.78，它们在建筑一楼的剂量率分别为97.8和9.9 μSv。
