Effect of Sulfate Sequestration by Ba-Sn Composite Material on Re Retention in Low-Activity Waste Glass

Journal Article · Mon Apr 15 00:00:00 EDT 2019 · Journal of Non-crystalline Solids

DOI:https://doi.org/10.1016/j.jnoncrysol.2018.12.029· OSTI ID:1515842

George, Jaime L.  ^[1]; Cholsaipant, Pornsinee ^[1]; Kim, Dong-Sang  ^[1]; Levitskaia, Tatiana G.  ^[1]; Fujimoto, Meghan S. ^[1]; Johnson, Isaac  ^[1]; Kruger, Albert A. ^[2]

---

1. BATTELLE (PACIFIC NW LAB)
2. OFFICE RIVER PROTECTION

Difficulty incorporating radioactive Tc-99 into glass during vitrification of low-activity waste (LAW) at the Hanford Site is a technical challenge. Previous studies suggested that the presence of sulfate salts in the melt hinder the incorporation of Re, a non-radioactive surrogate for Tc-99, into nuclear waste glass. In this study, we assessed the capability of a Ba-Sn composite to sequester sulfate during vitrification of AN-102 LAW feed and the resulting effects on Re retention in the glass. We also investigated a feed where the initial soluble sulfate source in the simulated LAW (Na2SO4) was replaced with insoluble BaSO4. The Ba-Sn composite-treated feed and BaSO4-substitute feed were compared to a control, AN-102 baseline. The feeds were prepared and then heated to temperatures from 400-1000 °C at 5 °C/min and air-quenched to room temperature. The heated samples and dried feeds were leached in deionized water. The solutions from the leach test were analyzed by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) to determine the amount of soluble sulfate as a function of temperature and the resulting solids were analyzed for Re retention. Although the Ba-Sn composite material successfully sequestered sulfate in the as-prepared LAW feed, heating to 400 °C resulted in most of the sulfate partitioning to a soluble salt phase. By 700°C, sulfate partitioning in the composite-treated feed was identical to the baseline feed. Throughout the entire temperature range the BaSO4-substitute feed behaved similarly to the composite-treated feed. The results of the study show that sequestering sulfate into a BaSO4 phase is ineffective for rhenium retention as the sulfate salt behavior was identical in the three feeds at =700 °C. The fraction of rhenium retained in the glass at 1000°C varied from 39.4-46.6% for the three feeds, which is shown to be an insignificant difference.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1515842
• Report Number(s): PNNL-SA-138950
• Journal Information: Journal of Non-crystalline Solids, Vol. 510
• Country of Publication: United States
• Language: English