Tatsuo Izumida

LiNO3 Addition to Prevent Hydrogen Gas Generation from Cement-Solidified Aluminum Wastes

LiNO3 addition to the cement solidified miscellaneous wastes has been proposed for preventing hydrogen ges generation caused by the corrosion of aluminum materials contained in the wastes. To determine an additive among alkaline metal ions, galvanic current was measured in 0.1 M alkaline metal hydroxide solution between aluminum and platinum electrodes. The volume of hydrogen gas generated from an aluminum specimen was measured in a KOH solution with LiNO3, LiCl, LiBr, Li2CO3 or Li2SO4 to decide the best additive. Applicability of the chosen additive to cement was confirmed by hydrogen gas generation measurement from an aluminum specimen in cement paste. The prevention mechanism was analyzed by X-ray diffraction, SEM and SIMS. The current measured in LiOH solution decreased with time, then reached 0 μA/mm2, while the current was detected in other alkaline metal hydroxide solutions. The least volume of hydrogen gas generation was measured in a KOH solution with LiNO3. The volume of generated hydrogen gas i...

Compatibility of the ultraviolet light-ozone system for laundry waste water treatment in nuclear power plants

As an alternative treatment system for laundry waste water in nuclear power plants, a system was chosen in which such organic compounds as surfactant would be oxidized by ultraviolet (UV) light and ozone. The system compatibility, UV light source, and dissolved ozone concentration were examined through experiments. First, ozone gas was absorbed in the waste water. After the dissolved ozone concentration equilibrated at the desired value, the waste water was irradiated by a mercury lamp. Then, the time dependence of the concentrations of the organic compounds, the dissolved ozone, and the hydrogen peroxide were measured to estimate the treatment rate of the system. The mercury lamp with a 10{sup 5}-Pa vapor pressure achieved large UV radiation and a treatment rate increase, leading to a compatible system without secondary waste generation. The effect of the dissolved ozone concentration on the treatment rate was saturated when concentration was >3.3 {times} 10{sup {minus}4} mol/10{sup {minus}3} m{sup 3} at the time UV radiation was started. Numerical results indicated the saturation was due to hydrogen peroxide generation, which prevents hydroxyl radical generation.

Sorption Mechanism of Carbon-14 by Hardened Cement Paste

Carbon-14 sorption by cementitious materials should be enhanced to ensure the long term safety of radioactive waste repositories. The sorption mechanism of inorganic C- 14 (CO 3 2- was investigated using batch sorption experiments and zeta potential measurements. The results suggested that C-14 was adsorbed onto the cement surface by an electrostatic force, due to the reaction between SiO 2 and CaO contained in the cementitious composition. That is, SiO 2 was originally negatively charged (SiO - ) in cement, but became positively charged through the interaction of Ca 2+ . These positive sites on the SiO 2 surface adsorbed inorganic C-14. Ordinary Portland cement (OPC) did not contain enough SiO 2 compared with its CaO content to produce sufficient numbers of C-14 adsorption sites. The C-14 distribution coefficient (Kd) was increased from 2,000 to 7,000 mL/g by adding SiO 2 to OPC.

Stability of cement-glass packages containing sodium borate salt generated from pressurized water reactor power plants

A new solidification technique using cement-glass, which is a mixture of sodium silicate and cement, was studied for solidification of sodium borate salt of liquid waste generated from pressurized water reactor plants. When the sodium borate salt was solidified with the cement-glass, the resulting package contained eight times more sodium borate than was found in cement because it did not interact with sodium borate. The leaching ratio of cesium ion from the cement-glass package was one-tenth that of cement. Its low leaching ratio was due to the high cesium adsorption ability of cement-glass. The ratio could be theoretically evaluated by considering the cesium adsorption-desorption equilibrium.

Electrolytic Decontamination of Surface-Contaminated Metal by Alternating Electrolysis Using Square-Wave Current in a Neutral Salt Electrolyte

Alternating square-wave current electrolysis using a Na2SO4 electrolyte was studied as a removal method for radioactive contaminated oxidation film on metal surfaces. After the oxidation film was selectively removed using the Na2SO4 electrolyte, base metal was removed. Based on a diffusion model in which the removal rate of the surface oxidation film depends on the diffusion rates of OS and FeS ions in the film, the optimum cycle of the alternating square current was estimated to be 90 s (the square widths of the negative and positive currents were 60 and 30 s, respectively). The theoretical estimation was in good agreement with the experiment results. Using this decontamination method, decontamination factors of 10T to 10U were obtained for stainless steels of a boiling water reactor coolant system and radioactive simulated samples.

LiNO3 Addition to Cement Which Prevents Aluminum Corrosion

LiNO 3 addition to cement was examined to prevent hydrogen gas generation from metallic aluminum in dry active wastes during waste solidification and under circumstances of underground water penetration into the land disposal site. And its reaction mechanism was identified by some chemical analyses. The volume of the hydrogen gas generation with LiNO 3 addition was 10% as much as that without LiNO 3 , by formation of the insoluble Li-Al preservation film on aluminum. After the land disposal of waste forms, LiNO 3 would be expected to be effective to prevent aluminum corrosion as long as the cement forms keep their alkaline character, and when it became ineffective, the circumstances around the waste forms can be made less corrosive for aluminum. The aluminum corrosion at that time would be as much as 10% of that without LiNO 3 addition.