Hasai H, Iwatani K, Shizuma K, Hoshi M, Yokoro K, Sawada S, Kosako T, Morishima H
Health Phys. 1987 Sep;53(3):227-39. doi: 10.1097/00004032-198709000-00002.
The 152Eu activity depth profile of a granite pillar of the Motoyasu bridge located 132 m from the Hiroshima atomic bomb hypocenter was assessed. The pillars each measured 82 cm in depth, 82 cm in width and 193 cm in height. One of the pillars was bored and 6.8-cm-diameter core samples were removed and cut into 2-cm-thick disks. Two gamma rays of 152Eu, 122 keV and 344 keV, in each disk were measured using a low background, gamma-ray spectrometer, and the activity distribution was determined as a function of depth in the granite. A concentration of stable Eu in the granite was determined by activation analysis. The specific radioactivity of 152Eu and 154Eu at the pillar surface was determined to have been 117 and 24 Bq per mg Eu, respectively, at the time of detonation. The value of 152Eu agrees within 20% of that calculated by Loewe. The depth profile of 152Eu in granite demonstrates a distinct difference from the estimates made only by thermal neutrons. Present data provide valuable information for the analysis of the neutron spectrum of the Hiroshima atomic bomb and its intensity.
对位于距广岛原子弹爆心132米处的元安桥花岗岩柱的152铕活度深度分布进行了评估。这些柱子深度均为82厘米，宽度为82厘米，高度为193厘米。其中一根柱子被钻孔，取出直径6.8厘米的岩芯样本并切成2厘米厚的圆盘。使用低本底伽马射线光谱仪测量每个圆盘中152铕的122千电子伏和344千电子伏的两条伽马射线，并确定花岗岩中活度分布随深度的函数关系。通过活化分析确定花岗岩中稳定铕的浓度。爆轰时，柱面处152铕和154铕的比活度分别确定为每毫克铕117贝可和24贝可。152铕的值与勒韦计算值的误差在20%以内。花岗岩中152铕的深度分布与仅由热中子得出的估计值有明显差异。目前的数据为分析广岛原子弹的中子能谱及其强度提供了有价值的信息。
