Submixture model to predict nepheline precipitation in waste glasses

Journal Article · Wed May 11 04:00:00 EDT 2016 · International Journal of Applied Glass Science

DOI:https://doi.org/10.1111/ijag.12207· OSTI ID:1372992

Vienna, John D. ^[1]; Kroll, Jared O. ^[1]; Hrma, Pavel R. ^[1]; Lang, Jesse B. ^[1]; Crum, Jarrod V. ^[1]

---

1. Pacific Northwest National Laboratory, Richland Washington

High-alumina high-level waste (HLW) glasses are prone to nepheline (nominally NaAlSiO4) precipitation during canister-centerline cooling (CCC). If sufficient nepheline forms the chemical durability of the glass will be significantly impacted. Overly conservative constraints have been developed and used to avoid the deleterious effects of nepheline formation in U.S. HLW vitrification plants. The constraint used has been shown to significantly limit the loading of waste in glass at Hanford and therefore the cost and schedule of cleanup. A study was performed to develop an improved understanding of the impacts of glass composition on the formation of nepheline during CCC. Four experimental phases were conducted in which 90 independent glass compositions were fabricated, subjected to simulated CCC heat-treatments, and characterized for crystallinity – 38 of the 90 test glasses formed nepheline. These data were examined separately and combined with 657 glasses previously tested glasses found in literature. The trends showed that in addition to Na2O, Al2O3, and SiO2 components included in previous constraints B2O3, CaO, K2O, and Li2O also significant impacted the propensity for nepheline formation. A pseudo-ternary submixture approach was proposed to identify the glass composition region prone to nepheline precipitation. This pseudo-ternary with axis of SiO2 + 1.70B2O3, Na2O + 0.813Li2O + 0.439K2O + 0.223CaO, and Al2O3 was found to effectively divide typical U.S. HLW glasses that precipitate nepheline during CCC from those that do not. This approach results in a total misclassification rate of 13%, 7% of which are false negatives (those glasses predicted not to form nepheline that actually do for nepheline). When applied to the 90 glasses developed specifically for Hanford high-alumina HLWs, the misclassification rate is 19% (17/90) with 1/38 false negatives. Application of such a constraint is anticipated to increase the loading of Hanford high-alumina HLWs in glass by roughly one third.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1372992
• Report Number(s): PNNL-SA-114489; 830403000
• Journal Information: International Journal of Applied Glass Science, Journal Name: International Journal of Applied Glass Science Journal Issue: 2 Vol. 8; ISSN 2041-1286
• Publisher: American Ceramic Society
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
Canister Centerline Cooling
Crystallization
Glass
Nepheline
Nuclear Waste