Feed process studies: Research-Scale Melter

Abstract

In support of a two-phase approach to privatizing the processing of hazardous and radioactive waste at Hanford, research-scale melter (RSM) experiments were conducted to determine feed processing characteristics of two potential privatization Phase 1 high-level waste glass formulations and to determine if increased Ag, Te, and noble metal amounts would have bad effects. Effects of feed compositions and process conditions were examined for processing rate, cold cap behavior, off-gas, and glass properties. The 2 glass formulations used were: NOM-2 with adjusted waste loading (all components except silica and soda) of 25 wt%, and NOM-3 (max waste loaded glass) with adjusted waste loading of 30 wt%. The 25 wt% figure is the minimum required in the privatization Request for Proposal. RSM operated for 19 days (5 runs). 1010 kg feed was processed, producing 362 kg glass. Parts of runs 2 and 3 were run at 10 to 30 degrees above the nominal temperature 1150 C, with the most significant processing rate increase in run 3. Processing observations led to the choice of NOM-3 for noble metal testing in runs 4 and 5. During noble metal testing, processing rates fell 50% from baseline. Destructive analysis showed that a layer of noble metals and noble metal oxides settled on the floor of the melter, leading to current ``channeling`` which allowed the top section to cool, reducing production rates.