Shizuma Kiyoshi, Endo Satoru, Hoshi Masaharu, Takada Jun, Ishikawa Masayori, Iwatani Kazuo, Hasai Hiromi, Oka Takamitsu, Fujita Shoichiro, Watanabe Tadaaki, Yamashita Tomoaki, Imanaka Tetsuji
Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima 739-8527, Japan.
J Radiat Res. 2003 Jun;44(2):133-9. doi: 10.1269/jrr.44.133.
Residual 152Eu activities induced by neutrons from the Nagasaki atomic bomb were measured for nine mineral samples located up to 1,061 m in the slant range and one control sample at 2,850 m from the hypocenter. A chemical separation to prepare europium-enriched samples was performed for all samples, and gamma ray measurements were carried out with a low background well-type germanium detector. In this paper, the measured specific activities of 152Eu are compared with activation calculations based on the DS86 neutron fluence and the 93Rev one. The calculated-to-measured ratios are also compared with those of 60Co and 36Cl. The present results indicate that the measurements agree to the calculation within a factor of three as observed in the nuclear tests at Nevada. The activation level of environmental neutrons and the detection limit for 152Eu are also discussed.
