Tso M Y, Ng C Y, Leung J K
Radioisotope Unit, University of Hong Kong.
Health Phys. 1994 Oct;67(4):378-84. doi: 10.1097/00004032-199410000-00008.
Indoor 222Rn in high-rise buildings originates inside the building materials, then diffuses gradually through the intergranular spaces of the material into the room atmosphere. Therefore, the radionuclide contents and the physical properties of the building materials are important for indoor 222Rn levels in Hong Kong. In this paper, the radionuclide contents of typical building materials used locally were determined by gamma spectrometry, and the results indicate that the average 226Ra, 232Th, and 40K contents in Hong Kong concrete are the highest known in the world. Physical properties, such as the emanation coefficients and 222Rn diffusion coefficients, were measured in these materials and they are not much different from those in other countries. The effect of surface coatings on 222Rn exhalation rate was studied and the observed reduction was from 2-68%. The 222Rn exhalation rate was found to increase steadily with temperature up to 50 degrees C; at 50 degrees C, the 222Rn exhalation rate can be as high as four times the rate at 20 degrees C.
高层建筑中的室内氡-222源自建筑材料内部，随后逐渐通过材料的晶隙扩散到室内空气中。因此，建筑材料的放射性核素含量和物理性质对香港室内氡-222水平至关重要。本文通过伽马能谱法测定了本地使用的典型建筑材料的放射性核素含量，结果表明，香港混凝土中镭-226、钍-232和钾-40的平均含量是世界上已知的最高值。对这些材料的物理性质，如发射系数和氡-222扩散系数进行了测量，其与其他国家的材料并无太大差异。研究了表面涂层对氡-222析出率的影响，观察到的降低幅度为2%至68%。发现氡-222析出率随温度升高至50摄氏度时稳步增加；在50摄氏度时，氡-222析出率可高达20摄氏度时的四倍。
