Laboratory scale experiments on the adsorption of radioactive elemental iodine (I2) gas onto atmospheric aerosol showed that the adsorption reached an equilibrium state in about twelve minutes at high initial I2 concentrations. The proportion of iodine which was adsorbed on the aerosol gradually decreased with increasing initial I2 concentration ranging over 10-13 to 10-9g/cm3 at a reaction time of 31min but was almost constant at a reaction time of 2min. A fraction of iodine desorbed from particulate iodine as mainly I2 gas. An adsorption isotherm of atmospheric aerosol for I2 gas was estimated from the experimental data of long reaction time and high I2 concentrations. Using this adsorption isotherm, a theoretical equation, which was similar to our previous equation, was derived to explain the experimental results. A geometric mean and standard deviation of sticking probability in the equation were estimated to be 1.2×10-2 and 2.7, respectively. Almost all experimental data were within ranges of calculated results considering the geometric standard deviation of sticking probability.
The bulk etching rate of polycarbonate during chemical and electrochemical etching was measured for two kinds of polycarbonate foils, Makrofol and Iupilon, at various etching temperatures from 20 to 40°C. The etching rate of polycarbonate could be determined by weight measurements with sufficient accuracy since no water was absorbed in polycarbonate. The chemical bulk etching rates obtained for Makrofol and Iupilon at 20°C were 1.78 and 1.69μm/h, respectively. The corresponding electrochemical bulk etching rates were 1.86 and 1.89μm/h, respectively. Fairly small difference in the bulk etching rates was found between chemical and electrochemical etching as well as between Makrofol and Iupilon. The activation energy evaluated from the present experiments was 0.55eV for polycarbonate, which was lower than that for allyl diglycol carbonate (CR-39).
Several kinds of incinerator that satisfy essential requirements in the safety guideline have been developed so as to burn radioactive organic liquid wastes, and they are on the market. But, in the case of organic wastes which contain much water, such as emulsive scintillator liquid, it is often difficult to incinerate them continuously owing to high viscosity and low fluidity. Concerning this problem, we have already proposed, in a few reports, the validity of a pre-treatment process using salt-out technique. In this study, the above method was applied to other wastes containing several nuclides and chemical forms, such as 3H, 14C, 32P, 35S, and 45Ca, even if they may be different from what were reported before. As result, it was defined that the pre-treatment process could be developed for incineration of those wastes. Recently, scintillator cocktails with higher boiling solvent have been developed for fire safety during storage. But these cocktails are much more costly than toluene, and they are more difficult to incinerate. Therefore, as a premise of collection and reuse of the costly solvent, we propose that the chemical pre-treatment process by salt-out technique before usual distillation will be promising in respect to cost and reliability.