Alpha-autoradiography technique (by using a total of 48 plastic samples, 28 of CR-39 and 20 of LR-115 nuclear track detectors) was applied for the estimation of the concentration of uranium, thorium, and alpha-emitting members of their series in four types of ores (cassetrite, chromite, galena, and pyrite) from different locations of the Eastern Desert in Egypt. Effective radium contents and radon emanation coefficients for two of these rocks (galena and pyrite) were also determined. Also the calculation of gamma ray exposure dose rates from these four ores arising from226Ra and its daughters were calculated for four different locations.
The natural radiation levels in Niigata area were studied from aspect of the gamma-ray dose rate in Kaetsu district in the northern part of the prefecture around Niigata City, and in Sado Island. The quantity of radionuclides and their contribution to the gamma-ray dose rate were obtained by an in situ measurement method and the total dose rate with a scintillation survey meter. The identified radioactivities from collecting soil samples were converted to the dose rate at a point 1 m above ground using the γ-spectrometry. In Kaetsu district, the dose rates of the northern area of Niigata City were higher than those of the south parts, probably reflecting the geological situation of the northern area, which consists of granitic base rock belonging to the highly radioactive rock. The most of the measuring points showed radionuclide contribution in the order of40K>Th-series>U-series and the dose rate was significantly dependent on the different composition of radionuclides in the soils weathered from the original base rocks. Some radioactivity concentration were also analyzed in coastal sands. The sand collected from the northern district of Niigata City showed high concentration of both232Th and40K. The black and high radioactive sands from the coast in the central area of Niigata City were considered to be attributable to the active erosion effects of wave action after deposition from Shinano River. Annual dose equivalent due to natural radiation from ground was calculated based on average dose rate.
Bone mineral density (BMD) mass survey has been carrying out in many area in Japan and the number of the client will increase from now on. Recent reports indicate the decline of BMD in young age bracket and plead special needs to promote BMD of the youth. As BMD examination is thought to spread in young people, absorbed dose of these clients will become a serious problem. Absorbed dose of BMD examination with several different dual energy X-ray absorptiometry (DEXA) apparatus was measured and compared using a same measuring method. Measuring method employed in this study is easy and useful to measure absorbed dose of BMD examination using DEXA.