Hashimoto T, Aoyagi Y, Takahashi T, Sotobayashi T
Radioisotopes. 1982 Oct;31(10):509-14.
Determination of the average uranium contents in several fossil bones was carried out using an improved fission track method. Four standard samples were prepared from silica-gel powder containing known amounts of natural uranium. The powdered fossil bones was fixed on a muscovite detector as well as the standard samples and followed by the neutron irradiation. After cooling, the muscovites were chemically etched with HF-solution to develop the fission tracks. By using standard samples, it was found that a reliable track counting is impossible through the transmission optical microscope in the region over track density of 5 X 10(5) cm-2 because of overlap of fission tracks in each other. In order to improve this situation bearing most of the present muscovites, the observation using the reflection microscope was applied after coating the muscovite surface with the vacuum-evaporated gold film and verified to be extremely efficient to the counting of high track density up to 5 X 10(7) cm-2, which could be no longer to distinguish intrinsic tracks through ordinary microscope. All of the fossil samples were subjected to the track counting through the reflection microscope and after correcting the estimated difference of track ranges between the standard and fossil bone samples the experimental uranium contents were evaluated. The uranium contents in the fossil bones were in the range of 30-460 ppm.
采用改进的裂变径迹法测定了几块化石骨骼中的平均铀含量。用含有已知量天然铀的硅胶粉末制备了四个标准样品。将粉末状化石骨骼与标准样品一起固定在白云母探测器上，然后进行中子辐照。冷却后，用氢氟酸溶液对白云母进行化学蚀刻以显示裂变径迹。通过使用标准样品发现，由于裂变径迹相互重叠，在径迹密度超过5×10⁵ cm⁻²的区域，通过透射光学显微镜无法进行可靠的径迹计数。为了改善目前大多数白云母存在的这种情况，在白云母表面镀上真空蒸发金膜后，采用反射显微镜进行观察，结果证明对于计数高达5×10⁷ cm⁻²的高径迹密度非常有效，而通过普通显微镜已无法区分这些径迹。所有化石样品都通过反射显微镜进行径迹计数，并在校正标准样品和化石骨骼样品之间径迹范围的估计差异后，评估了实验铀含量。化石骨骼中的铀含量在30 - 460 ppm范围内。
