Komura K, Kuwahara Y, Abe T, Tanaka K, Murata Y, Inoue M
Low Level Radioactivity Laboratory, Institute of Nature and Environmental Technology (K-INET), Kanazawa University, Wake, Tatsunokuchi, Ishikawa 923-1224, Japan.
J Environ Radioact. 2007;96(1-3):103-9. doi: 10.1016/j.jenvrad.2007.01.022. Epub 2007 Apr 10.
Cosmic-ray-produced (CP) nuclides with half-lives shorter than 21h were measured in rainwater by ultra-low-background gamma spectrometry at Ogoya Underground Laboratory. As levels of CP nuclides are extremely low and their half-lives are very short, quick sampling methods for a large volume of rainwater and rapid chemical separations by ion exchange method were developed. The nuclides measured were short-lived (24)Na, (28)Mg, (38)S, (38)Cl, (39)Cl, as well as nuclides with longer half-lives (7)Be and (22)Na. The number of atoms of CP nuclides in rainwater were evaluated to range from 30 to 1500L(-1) for (24)Na (n=16, mean; 520 [6.7mBqL(-1)]), 80 to 600L(-1) for (28)Mg (n=13, mean; 260 [2.4mBqL(-1)]), 400 to 1900L(-1) for (39)Cl (n=6, mean; 1200 [250mBqL(-1)]), 1x10(6) to 4x10(7)L(-1) for (7)Be (n=16, mean; 7x10(6) [1.05BqL(-1)]) and 2x10(3) to 1x10(5)L(-1) for (22)Na (n=9, mean; 2x10(4) [0.2mBqL(-1)]).
在小俣地下实验室，通过超低本底伽马能谱法测量了雨水中半衰期短于21小时的宇宙射线产生（CP）核素。由于CP核素的含量极低且半衰期很短，因此开发了大量雨水的快速采样方法以及通过离子交换法进行的快速化学分离方法。所测量的核素包括短寿命的（24）Na、（28）Mg、（38）S、（38）Cl、（39）Cl，以及半衰期较长的（7）Be和（22）Na。雨水中CP核素的原子数评估结果为：（24）Na为30至1500 L-1（n = 16，平均值；520 [6.7 mBq L-1]），（28）Mg为80至600 L-1（n = 13，平均值；260 [2.4 mBq L-1]），（39）Cl为400至1900 L-1（n = 6，平均值；1200 [250 mBq L-1]），（7）Be为1×106至4×10（7）L-1（n = 16，平均值；7×106 [1.05 Bq L-1]），（22）Na为2×103至1×105 L-1（n = 9，平均值；2×104 [0.2 mBq L-1]）。
