Glass Composition Constraint Recommendations for Use in Life-Cycle Mission Modeling

Abstract

Recent analyses of glass mass estimates from Hanford high-level waste (HLW) performed by the Washington River Protections Solutions (LLC) have shown a strong dependency on the allowable concentrations of Aluminum, Sulfur, Phosphorous, and Bismuth plus the constraint to avoid the precipitation of nepheline from glass. A review was made on the limits for these constraints and it was found that some of them may be overly conservative. Recommendations were made to relax some of the constraints to better estimate the amount of glass likely to be produced from Hanford HLW without significantly increasing the risk of overestimating waste loadings. These changes were made for the Sulfur, Phosphorous, and Bismuth concentration limits along with their basis. In addition, a new nepheline constraint based on glass optical basicity was recommended to help obtain higher alumina concentrations in glass without the formation of nepheline, which generally reduces glasses chemical durability. These recommendations enable continued Hanford live cycle waste treatment modeling until sufficient glass property data and models are generated. The generation of these glass data and models is an on-going, long-term technical need.

Formulation and Characterization of Waste Glasses with Varying Processing Temperature

“…The first of these advances include the use of crystal-tolerant glasses for HLW where sparingly insoluble components such as chromium are allowed to crystallize in the melter but are passed out of the melter before accumulating in a sludge layer (Matyas et al 2010). Another advancement is the development of glasses with significantly higher aluminum content than what would be allowed by the current nepheline precipitation constraints, as well as a corresponding revision to those constraints (McCloy and Vienna 2010). Yet another advancement is the development of very-low silica glasses for ultra-high waste loadings (Marra et al 2010;Matlack et al 2010).…”

“…The HTWOS 2009 baseline constraints are summarized in Belsher and Meinert (2009) derived from Vienna et al (2009) and the models used for the HTWOS are given in Vienna et al (2009). Selected constraints for the HTWOS were revised and described in McCloy and Vienna (2010). There are two groups of constraints, based on glass properties and concentrations, that are used when formulating glasses: acceptability constraints and processing constraints.…”

“…2.2) were calculated. Whenever possible the glass formulation was performed to satisfy the nepheline constraint, but this constraint was not used to limit the waste loading as this constraint is known to be conservative (McCloy and Vienna 2010).…”

Towards Increased Waste Loading in High Level Waste Glasses: Developing a Better Understanding of Crystallization Behavior

“…These models include modules that sequence the various wastes and predict glass quantities using existing glass composition property models and relationships to specify waste loading in the glass (Vienna et al 2009 andMcCloy et al 2010). There are also the baseline Waste Treatment and Immobilization Plant (WTP) glass property models and constraints that were developed for initial operation of WTP (Vienna and Kim 2008).…”

The Impact of Kinetics on Nepheline Formation in Nuclear Waste Glasses

“…[2][3][4][6][7][8] In general, these studies have suggested that particular oxides (B 2 O 3 and CaO) suppress nepheline crystallization; however, persuasive data to constitute modification of the current ND has not been forthcoming. McCloy et al 9 has proposed that an additional constraint, optical basicity (OB), be used to complement the ND. That OB model uses a modified electronegativity approach to rank constituent oxides according to their propensity to disassociate and has b een u sed to describe the effects of B 2 O 3 a nd CaO on nepheline crystallization in HLW glasses.…”