标题：Measurement of Residual 152Eu Activity Induced by Atomic Bomb Neutrons in Nagasaki and the Contribution of Environmental Neutrons to This Activity
其他标题：Measurement of Residual 152Eu Activity Induced by Atomic Bomb Neutrons in Nagasaki and the Contribution of Environmental Neutrons to This Activity
摘要：Residual 152 Eu 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 152 Eu 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 60 Co and 36 Cl. 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 152 Eu are also discussed.
