Low corrosive chemical decontamination method using pH control,(II) Decomposition of reducing agent by using catalyst with hydrogen peroxide

In the development of a. new chemical decontamination method which provides a high decontamination effect, less corrosion of base metal, and less radioactive waste generation, we developed a decomposition method for oxalic acid coexisting with hydrazine to decrease the amount of radioactive waste. Using a catalyst of 0.5 wt% Ru supported by activated carbon grains, we decomposed oxalic acid and hydrazine, simultaneously and efficiently, with a stoichiometric concentration of H2O2. The decomposition ratios were decreased by the deposition of oxides. But even if the simulated reducing agent solution with high concentrations of coexisting Fe and K ions, which negatively effect decomposition ratio, was decomposed, the decomposition ratios of oxalic acid and hydrazine were kept high during decomposition of the amount of reducing agent used in actual chemical decontamination. Additionally, we examined the deposition ratios of metal ions on the catalyst as metal oxides. These results indicated about 2% of the radioactive species which were removed by the chemical decontamination were deposited on the catalyst column. Fe-59 and Cr-51 were estimated to be about 90%, of the total deposited amount of radioactive species and about 60% of the, dose equivalent in the model calculation. But this problem should be easily, dealt with by using shielding.