Thermal Processing Optimization for Simulated Hanford Waste Glass (AZ 101)

Abstract

This paper presents the results of a Time-Temperature-Transformation (TTT) study of the effect of different heat treatments on the final form and durability of the wasteform produced by the vitrification of Hanford High Level Waste (HLW). A borosilicate glass formulation containing 60 weight % of a Hanford Tank AZ 101 simulant approximated the radioactive waste glass. The TTT diagram was generated by analyzing thirty-six wasteforms produced by melting the frit-waste mixture at 1450°C, and then heat-treating the melts at specified temperatures for a predetermined length of time. The temperatures studied ranged from 500°C to 1200°C, and the length of the heat treatments ranged from 0.75 hour to 768 hours (32 days). The wasteforms produced were analyzed by Toxicity Characteristic Leaching Procedure (TCLP), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM) - Energy Dispersive Spectrometry (EDS). Rietveld analysis was performed on some of the XRD results. Crystalline forms detected include transition metal (predominantly Fe) spinel, zircon, zirconia, and iron oxide. These crystalline forms are characteristic to specific heat treatment conditions. The types or concentrations of crystals have little to no impact on the Product Consistency Test (PCT) performance of the wasteform. The results show a strong relationship between heat treatment conditions (time and temperature) and TCLP test response for cadmium only. Samples heat-treated at higher temperatures or longer periods of time show a considerably higher cadmium response (by TCLP) than samples heat-treated at lower temperatures or for shorter times.

Meeting Name

Science and Technology in Addressing Environmental Issues in the Ceramic Industry and Ceramic Science and Technology for the Nuclear Industry Symposia at the 105th American Ceramic Society Annual Meeting and Exposition: (2003: Apr. 27-30, Nashville, TN)

Department(s)

Materials Science and Engineering

Second Department

Chemistry

Keywords and Phrases

Glass wasteforms; Melter temperature; Time temperature transformation (TTT); Toxicity characteristic leaching procedure (TCLP), Energy dispersive spectroscopy; Glass manufacture; Heat treatment; Leaching; Optimization; Radioactive waste vitrification; Scanning electron microscopy; X ray diffraction, Radioactive wastes

International Standard Book Number (ISBN)

978-1-57498209-1

International Standard Serial Number (ISSN)

1042-1122

Document Type

Article - Conference proceedings

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2004 American Ceramic Society, All rights reserved.

Publication Date

01 Apr 2004

Link to Full Text

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