High-Level Nuclear-Waste Borosilicate Glass: A Compendium of Characteristics

Abstract

With the imminent startup, in the United States, of facilities for vitrification of high-level nuclear waste, a document has been prepared that compiles the scientific basis for understanding the alteration of the waste glass products under the range of service conditions to which they may be exposed during storage, transportation, and eventual geologic disposal. A summary of selected parts of the content of this document is provided.Waste glass alterations in a geologic repository may include corrosion of the glass network due to groundwater and/or water vapor contact. Experimental testing results are described and interpreted in terms of the underlying chemical reactions and physical processes involved. The status of mechanistic modeling, which can be used for long-term predictions, is described and the remaining uncertainties associated with long-term simulations are summarized. INTRODUCTION AND BACKGROUND

Glass optimization for vitrification of Hanford Site low-level tank waste

“…This order of durability improvement was consistent with the current understanding of glass chemistry (Feng 1989(Feng ,1994Ellison 1994).…”

“…However, a three-stage corrosion mechanism of typical silicate glasses in aqueous media is generally accepted (Cunnane 1994). The initial stage under solutiondominated condition (dilute solution) is characterized by a forward-reaction rate; that is, the maximum rate achievable depends only on glass composition, temperature, and solution pH.…”

Characteristics of silicate glasses derived from vitrification of manganese crust tailings

“…Chemical resistance of waste glasses is directly related to the extent these glasses resist chemical reactions with water and associated chemicals. Waste glasses undergo a variety of complex changes in aqueous environments, which is referred to as glass corrosion or glass dissolution [29,30]. As industrial materials, glasses should have acceptable durability, which is often linked to high mechanical strength [31].…”

Status of ceramic waste form degradation and radionuclide release modeling.

“…This value was obtained from glass corrosion tests at 90°C. 7 Because no temperature dependence was available, the temperature dependence for the forward rate was assumed for in the TSPA-VA. No estimates of have been made for the CWF, however it is expected to be relatively unimportant for the current calculations (see Sect. IV-C).…”