It is important to measure external and internal exposure dose in the case of accident. The external exposure can be measured by various dosimeters, but the internal exposure is usually calculated from estimated amounts of intake radioactivity because of difficulty of direct measurement. Detection efficiency of human counter used in direct measurement is necessary, but there is no effective method to determine it for non-uniform distribution. The γ-ray sum peak method is tried for the cascade γ-ray emitter under the consideration of small diffusion such as just after intake. After disintegration rates of sources of46Sc and60Co were determined by 4πβ-γ coincidence method, γ-ray spectra were measured at various positions. Calculated disintegration rates by sum peak method agreed with those by coincidence method within 10%. The similar results were obtained for distributed plural sources in restricted condition. It is also investigated as application for the case that the other nuclide is contained in it. Using peak-to-total ratios measured in advance, the disintegration rates were determined only from the peak intensities. In this case the results had systematic uncertainty of about 20%.
Instability of peak 4 in LiF: Mg, Ti (TLD-600/700) was experimentally examined by comparing the glow curves obtained for137Cs γ-rays and Fe-ion beam. After post-annealing at 100°C×30min, thermoluminescence (TL) intensity around peak 4 notably decreased only for γ-ray irradiation. In Fe-ion irradiated samples, post-annealing effects were scarcely observed in the TL intensities in the peak-4 region. These results suggest that the peak-4 luminescent centers are unstable and more vulnerable than other peaks to highly-dense ionization.
The characteristics of an anion exchange paper membrane and an activated carbon loaded paper membrane to remove125I from radioactive experimental waste in filtration system have been studied with various solutions which were filtrated. These paper membranes have the large solution fluxes in comparison with the column loaded with the anion exchange resin or the activated charcoal though the former totally bound less iodide ion than the latter. These feature suggest that the paper membranes might be utilized to treat a large quantity of radioactive waste, in which125I concentration slightly exceeded the dose limit. Notably, the anion exchange paper membrane possesses the three outstanding characteristics; 1) the rapid binding to the125I ion, 2) less influence of the substances, e.g. cell fragments, coexisted in the solutions on the125I adsorption than the activated carbon loaded paper membrane, and 3) higher selective adsorption to iodide ion than to the bromide and chloride ions. The results suggested that an anion exchange membrane might be appropriate for the filtration remov-ing system.
A simple device for evaporating the sample solutions in 48 well-microplates (MP) was developed in order to facilitate the application of MP-radioluminography (RLG) . The proposed device makes it possible to dry-up six MPs containing 0.2ml water in each well within 1.5 h at one time. The MPs were placed overnight in a desiccator. The cross radioactive contamination accompanied with the evaporation process was not detected. A slight increase in the background photo-stimulated luminescense (PSL) value that was observed in the wells adjacent a radiation well could be attributed to a flare caused during analysis by a bio-imaging anayzer system (BAS) . The detection limit of the MP-RLG was 0.05 Bq 14C, when the evaporated MP was brought into contact with an imaging plate for 72h and analyzed by a BAS.