EFFECT OF CALCINING TEMPERATURE ON VOLATILIZATION OF RUTHENIUM IN BATCH CALCINATION OF SIMULATED HIGH-LEVEL LIQUID WASTE

The effect of calcining temperature on ruthenium volatilization in batch calcination of simulated high-level liquid waste (HLLW) was studied together with the effects of nitric acid concentration and glass additives. More than 80% of the total ruthenium volatilized between room temperature and 500-degrees-C was volatilized between 200 and 300-degrees-C. A small amount of ruthenium volatilized above 300-degrees-C and below 135-degrees-C. The low volatility above 300-degrees-C was attributed to the thermal decomposition of the volatile ruthenium species into solid oxides such as RuO2. The overall volatilization increased with the nitric acid concentration of the simulated HLLW, but the presence of glass additives suppressed this effect of nitric acid. The volatile ruthenium in the off-gas from the calcination was identified to be nitrosylruthenium complex.