Endo A, Oki Y, Kanda Y, Oishi T, Kondo K
Department of Health Physics, Japan Atomic Energy Research Institute, Tokai, Ibaraki 319-1195, Japan.
Radiat Prot Dosimetry. 2001;93(3):223-30. doi: 10.1093/oxfordjournals.rpd.a006433.
Air has been irradiated with high energy protons at the 12 GeV proton synchrotron to obtain the following parameters essential for the internal dose evaluation from airborne 11C produced through nuclear spallation reactions: the abundance of gaseous and particulate 11C, chemical forms, and particle size distribution. It was found that more than 98% of 11C is present as gas and the rest is aerosol. The gaseous components were only 11CO and 11CO2, and their proportions were approximately 80% and 20%, respectively. The particulate 11C was found to be sulphate and/or nitrate aerosols having a log-normal size distribution; the measurement using a diffusion battery showed a geometric mean radius of 0.035 micron and a geometric standard deviation of 1.8 at a beam intensity of 6.8 x 10(11) proton.pulse-1 and an irradiation time of 9.6 min. By taking the chemical composition and particle size into account, effective doses both from internal and from external exposures per unit concentration of 11C were calculated for various room sizes. The values can be used to evaluate the effective dose from the airborne 11C produced in the accelerator tunnels.
已在12 GeV质子同步加速器中用高能质子对空气进行辐照，以获取对通过核散裂反应产生的空气中的11C进行内照射剂量评估所需的以下参数：气态和颗粒态11C的丰度、化学形态以及粒径分布。结果发现，超过98%的11C以气体形式存在，其余为气溶胶。气态成分仅为11CO和11CO2，其比例分别约为80%和20%。发现颗粒态11C为具有对数正态粒径分布的硫酸盐和/或硝酸盐气溶胶；在束流强度为6.8×10(11)质子·脉冲-1且辐照时间为9.6分钟的条件下，使用扩散电池进行的测量显示几何平均半径为0.035微米，几何标准偏差为1.8。考虑到化学成分和粒径，针对不同房间大小计算了每单位浓度11C的内照射和外照射有效剂量。这些值可用于评估加速器隧道中产生的空气中11C的有效剂量。
