An attempt was made to apply Mn-impregnated acrylic fiber to the collection of small amounts of Raisotopes in natural waters. The Mn compound incorporated in this material was estimated to be KMn8O16⋅xH2O, which occurred naturally in Japan as cryptomelane. Collection by the Mn-impregnated acrylic fiber was effective in the pH region higher than 4 and the collecting efficiency was dependent on the temperature of water. Radium concentrations observed at the upper stream of Tamagawa River tended to increase after rainfalls. The observed rises in Ra concentrations suggested that the rainfalls forced the stored water in the subsurface layer of the ground to discharge into the river water system.
This study was performed in order to make a safety guideline for veterinary nuclear medicine in Japan. Well often used radionuclides (18F and99mTc) were employed for evaluating the external radiation exposures of veterinarians, animal owners, and the public. The human external radiation exposure from radiation sources in phantom likened to animal was considered by comparing the results of computer simulation and the actually measured exposure. The computer simulation was performed by using macro program of Microsoft VBA. In this simulation calculation process, radiation absorption and buildup were taken into consideration with the gamma ray emitted from radioactive materials in the body of the animal. Both corresponded well though the simulation result tended to be overvalued from the actual measurement value. Therefore, it is thought that this system can be applied to the estimation of human's external exposure. When the calculation was done on the condition that the radioactive substance exists only in internal organs (heart, liver, kidneys, and bladder), the unequal distribution of the dose rate was found near the animal body. External radiation exposure estimation to the veterinarian, the animal owner, and the public was performed under consideration of the actual working condition, the distance from the source, and the time of exposure. In the calculation, the radiation dose of the animal owner and the public did not exceed the dose limit (5 mSv/yr for the animal owner, and 1 mSv/yr for the general public : ICRP 1990) in the release after 24 hours of the radiopharmaceutical administering. The calculation condition used in this study was actually more excessive. So the authors consider these exposures would cause no significant issue by starting the veterinary nuclear medicine in Japan. Moreover, since injected radiopharmaceutical is excreted out of the body actually, the exposure of the animal owner and the general public will actually be much lower than the estimation. The safety guideline for the veterinary nuclear medicine in Japan will be established by further application of this type of research.
Recently we developed an analyzer capable of measuring hydrogen concentrations of less than 5 cm3/1000 cm3. The analyzer is characterized by the fact that it uses a carrier gas purifier, a thermal conductivity detector, high- and low-temperature separation columns, and an “after-cut method”to remove impurities from sample and carrier gases. In the after-cut method, nitrogen gas is removed by switching gas lines. In the analyzer, a trace reduction detector is also used to detect extremely small amounts of hydrogen based on the reduction reaction of mercuric oxide with hydrogen. This is another distinctive characteristic of this analyzer. In the present study, we evaluated the performance of the analyzer in measuring deuterium concentrations. We measured spectra for five sample gases with different concentrations and examined the peaks and retention times of the spectra. The peaks and retention times were stable within a relative standard deviation of less than 10%, and a definite linear relationship between the peaks and deuterium concentrations was also observed. Based on these results, we have considered how to develop an analyzer capable of directly measuring the deuterium existing in natural air.