CaSO4: Tm thermoluminescence dosimeters and radiophotoluminescence dosimeters were used to carry out an investigation of indoor and outdoor environmental radiation in Akita Prefecture, Japan, during the period from April to October 1994. The results showed that the average absorbed-dose rate in air from outdoor terrestrial gamma-radiation was 38.8nGy h-1 with a range of 26.6-50.2nGy h-1. The indoor average absorbed-dose rate of wooden houses was 40.2nGy h-1 with a range of 29.5-50.4nGy h-1, and for concrete buildings it was 55.3nGy h-1 with a range of 41.7-66.9nGy h-1. The indoor weighted average absorbed-dose rate of concrete buildings was 42.9nGy h-1. Among different geological areas, the gamma-radiation absorbed-dose rate of andesite was the highest (50.2nGy h-1), and alluvium was the lowest (30.3nGy h-1). As for the results of measurement the two kinds of dosimeters were quite similar. Eighty-two percent of the results of measurement from twenty-eight monitoring sites where the two kinds of dosimeters were used coincided within ±5%, and there were only two sites where the difference was larger than 10%; deviations were +10% and +11%, respectively. These results indicated that the radiophotoluminescence dosimeter is also suitable for the measurement of environmental radiation.
Feasibility for the use of the collimated NaI (Tl) scintillation spectrosurvey meter SS-γ C3475 (Hamamatsu Photonics) in the estimation of thyroidal 131I burden in patients that received emergency exposure to radioiodine (131I) is demonstrated. When the NaI (Tl) crystal probe collimated well to a neck phantom simulating the human thyroid gland, the detection limit of 131I deposited in that organ was estimated at 0.58kBq, which was well below the generally adopted screening level of 30kBq. The detection system for thyroidal 131I presented in this report is remarkably inexpensive compared to the conventional whole-body counters, and is considered to provide a satisfactorily accurate evaluation of thyroidal 131I burden.
Concentrations of uranium were measured, by neutron activation analysis, in gypsum used in a plaster cast. The gypsum samples were powdered and mixed thoroughly using an agate mortar. Measurements of uranium were made by detecting γ-rays from 239U, since those from 239Np (a daughter nuclide of 239U) cannot be detected because of the high background of bremsstrahlungs due to β-rays from 32P produced by an (n, p) reaction of 32S in gypsum. The results of these measurements showed the concentration of uranium to be 0.0358±0.0030ppm, which was much lower than that in other samples such as CRT glass and concrete blocks measured previously. This lower concentration probably results from the fact that the gypsum used in the present study was manufactured as a by-product of phcsphatic fertilizer from phosphate rock.
This survey on daily food intake in the south-western part (Southern Tsugaru area) of Aomori Prefecture was a continuation of a previous survey conducted in the south-eastern part (Sanpachi-Kamikita area). The 50 families surveyed were composed of three different groups of primary occupations: fishery workers, farmers and “other occupations.” The average total daily food consumption of the whole survey group was about 2, 160g/d/p, and showed no significant seasonal variation. The consumption rates of marine and agricultural products were about 230 and 1, 180g/d/p respectively, being relatively constant year-round. Those of livestock products and other products were about 340 and 406g/d/p, with slight seasonal variations. The proportions of agricultural, livestock and marine products in the total food consumption among all families were on average about 55, 16 and 11%, respectively. The highest daily food consumption recorded of 2, 255g/d/p was observed in “other workers' families, ” followed by 2, 149 and 2, 046g/d/p in farming and fishery workers' families, respectively. Families of fishery workers showed the highest consumption of marine products, but the lowest consumption of livestock products. The consumption of agricultural products and other foods was remarkably high in “other workers' families.” Those representative foods with high consumption rates in the area were a) squid, salmon and cod in marine products, b) rice, apples, radishes, cucumbers, tomatoes and tofu (soybean curd) in agricultural products and c) milk, eggs and pork in livestock products. Some slight but statistically-significant differences were recognized in the consumption patterns of the area compared to its previous survey.
Exposure to cosmic rays in commercial airplanes was outlined. Although cosmic rays are a type of natural radiation, the magnitude of their dose is significant in airplanes. Therefore, there may be demands to regulate the dose of cosmic rays received by aircrews. In order to find reasonable countermeasures, the first prerequisite is to estimate the dose of cosmic rays precisely. In this paper, various problems in the measurement and calibration of cosmic rays as well as dose estimation and the method of control were outlined. Data of in situ measurements and those obtained by model calculations are presented, and factors which affect the level of the dose are discussed. In addition, potential dose ranges received during various flight routes are shown for various dose conversion parameter sets. Characteristics of domestic flights in Japan are also mentioned.