Characteristics of plutonium oxide aerosols, 239PuO2, were investigated. Plutonium oxide aerosols were generated by nebulizing the Pu (OH)4 dispersed in HCl and passing the resultant droplets through a high temperature furnace to produce the PuO2. When a nebulizer solution containing plutonium of 3.21×105Bq/cm3 was used, aerosols with air concentration of 0.088Bq/cm3 were produced. Size distributions of these aerosols were determined with a cascade impactor to be 0.17μm AMAD (Activity Median Aerodynamic Diameter) and 2.1 geometric standard deviation. When a nebulizer solution with plutonium concentration of 3.95×106Bq/cm3 was used, 0.47μm AMAD was observed as expected roughly for the higher concentrated plutonium solutions. Observations of alpha trucks by autoradiograph and particle shape by scanning eletcron microscopy were also made for selected filter samples.
The combination neutron dosemeter based on track detection using allyl diglycol carbonate plastic was developed. As the fast neutron detector the conventional track detector was used. For the thermal neutron detection Al-3% Li alloy was applied as a charged particle radiator. For the intermediate neutron detection Al-3% Li alloy was also used as the radiator and the detection element was covered by a polyethylene plate including 25% boron of 1cm thickness which was applied for improving the dose-equivalent response over the wide neutron energy range. The response of the combination dosemeter was almost flat within the error of ±50% except the under response in the energy range of 3keV-30keV with the intermediate neutron detector and the over response in the energy range of 30keV-200keV with the fast neutron detector.
An improved type of HTO-in-air monitor was developed. The HTO contained in the air was condensed to liquid water using a cold trap. The tritium activity in the trapped water was measured using a flow cell filled with glass scintillator powder. This monitor made it possible to measure the airborne HTO concentration with a detection limit of 1.4×10-4Bq/cm3 under a representative atmospheric condition, 22°C in temperature and 55% in relative humidity. This system is now in use to observe the HTO level of the exhaust gas released from the reactor containment building of the research reactor of Kyoto University.
The formerly used X-ray contrast medium, Thorotrast—a colloidal thorium dioxide—causes a chronic exposure to α-particles. In this paper, a method for the colorimetric determination of thorium content in Thorotrast patient's organs is described. The sequential chemical separation of thorium has been studied on the basis of coprecipitation, ion exchange, and solvent extraction methods, followed by colonmetric analysis using Arsenazo III. The experimental values were compared with those obtained by radiation measurement or neutron activation analysis of patient's organs.