Reactions during conversion of simplified low-activity waste glass feeds

Journal Article · Tue Dec 01 00:00:00 EST 2020 · Thermochimica Acta

DOI:https://doi.org/10.1016/j.tca.2020.178783· OSTI ID:1706672

Jin, Tongan  ^[1]; Mar, Derek ^[1]; Kim, Dong-Sang  ^[1]; Weese, Brigitte L. ^[2]; Kruger, Albert A. ^[3]

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1. BATTELLE (PACIFIC NW LAB)
2. DEPT OF ECOLOGY
3. OFFICE RIVER PROTECTION

The mechanisms that affect the incorporation of 99Tc, a volatile radioactive component of concern, into glass melt during vitrification of low-activity waste (LAW) are being investigated to develop the method to increase the retention of 99Tc in glass waste form. Previous studies with simulated LAW glass feeds (slurry mixture of liquid waste and chemical/mineral additives) demonstrated that the early stage feed-to-glass conversion reactions below 800°C are critical for the Re (used as a nonradioactive surrogate of 99Tc) retention in glass. To examine the effect of feed composition on the feed-to-glass conversion reactions, simplified systems containing major LAW components (NaNO3 and NaOH) and representative additive components (SiO2 and H3BO3) were designed and tested. The ratio of H3BO3 to NaNO3 was varied in three-component system without NaOH and that of NaOH to NaNO3 was varied in the four-component system at a fixed H3BO3 to NaNO3 ratio. As a first step of testing with simplified feeds, this study applied thermal analyses and phase characterization of the reacting feeds, which were performed without the addition of Re, to investigate the evolution of salt phases during slurry drying process and upon heating of dried feeds.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1706672
• Report Number(s): PNNL-SA-149641
• Journal Information: Thermochimica Acta, Vol. 694
• Country of Publication: United States
• Language: English