Metallurgical Evaluation of an Inconel 690 Insert from a Radioactive Waste Glass Melter Pour Spout

A metallurgical evaluation was conducted to assess the performance of an Inconel 690 insert that was removed from the pour spout of a radioactive waste glass melter. The insert was in service for approximately three months during which time 64 canisters, 114,300 kg (252,000 lbs), of glass had been poured. The insert was exposed to molten borosilicate glass and corrosive vapors at temperatures in excess of 1000 degrees Celsius. The most severe degradation occurred in the upper portion of the insert in the glass contact region. Degradation was attributed to the synergistic effects of oxidation and molten glass corrosion. Oxidation was the primary degradation mechanism in the vapor space. Results of the metallurgical evaluation including degradation rates will be presented.