This paper describes the development of a piled ionization chamber system consisting of 3 stacked thin box-type ionization chambers, which is used for measuring the radioactive concentration of three energetically grouped β-emitters. This system consists of a central ionization chamber in which the sample gas flows and two outer ionization chambers which detect medium and high energy β-rays penetrating through the walls of the central chamber. This radioactive concentration ofβ-emitters of each energy group is determined by the ionization current from the chambers. Performance tests were carried out for the central chamber filled with tritium and133Xe. It was experimentally found that the radioactive concentration can be measured for each energetically grouped β-emitter and the minimum detectable tritium concentration for this system is about 3.8×10-3Bq/cm3in He.
The most commonly available226Ra determination was too time-consuming to be suited to226Ra monitoring for the accidental release. The formula for determination of226Ra was derived by224Ra correction for WHO's equation. A rapid determination of226Ra in environmental materials was made possible by using this formula. The226Ra values of the soil and natural water at Ningyoh-Tohge obtained by the present method were in good agreement with those by the conventional WHO method. It was demonstrated that226Ra of more than about 37mBq (1 pCi) in the sample could be determined within 4 days by this method.
Changing cream pearls into bluish-grey by γ ray irradiation is a technique in coloring of pearls. Irradiated pearls are similar in color to cultured blue pearls. The pearl layers hardly change their color but the nuclei change into dark brown by irradiation. Visible light (500-700 nm) penetrating the pearl layer is absorbed by dark brown nucleus. The intensity of reflecting light between 400 and 500 nm at pearl surface, therefore, becomes stronger than that between 500 and 700 nm; therefore color of irradiated pearls look bluish-grey. The density of bluish-grey color increases with increasing absorbed doses, but their luster at surface diminishes owing to the deterioration of the pearl layer by prolonged irradiation; high doses irradiation should be avoided. Irradiated pearls show no substantial fading of their color in a year and the rate of the fading is found to be lower than that for cultured blue pearls.
The solvent extraction of tin (II) from hydrochloric acid solutions with tri-n-octyl phosphine oxide (TOPO) in carbon tetrachloride has been studied. The extraction of the metal increases with increase in the concentration of the acid and that of the extractant. The species extracted is shown to be SnCl2·2TOPO. The influence of the metal concentration, temperature and the diluent on the extraction of tin (II) have been investigated.
Industrial micro-robots are now being applied to hazardous jobs or tedious jobs. These in-house micro-robots (MELFA, RM-501, Mitsubishi Electric Inc.) were used to make a collection system of waste scintillator solution on the experimental basis. Newly developed were hands, vial holders and a system soft ware, and satisfactory results have been obtained.