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Title: Corrosion Behavior and Microstructure Influence of Glass-Ceramic Nuclear Waste Forms

Abstract

Glass ceramic waste forms present a potentially viable technology for the long term immobilization and disposal of liquid nuclear wastes. Through control of chemistry during fabrication, such waste forms can have designed secondary crystalline phases within a borosilicate glass matrix. In this work, a glass ceramic containing powellite and oxyapatite secondary phases was tested for its corrosion properties in dilute conditions using single pass flow through testing (SPFT). Three glass ceramic samples were prepared using different cooling rates to produce samples with varying microstructure sizes. In testing at 90 °C in buffered pH 7 and pH 9 solutions, it was found that increasing pH and decreasing microstructure size (resulting from rapid cooling during fabrication) both led to a reduction in overall corrosion rate. The phases of the glass ceramic were found, using a combination of solutions analysis, SEM and AFM, to corrode preferably in the order of powellite > bulk glass matrix > oxyapatite.

Authors:
 [1];  [1];  [1];  [1]
  1. Pacific Northwest National Laboratory, 902 Battelle Blvd, Richland, WA.
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
1398165
Report Number(s):
PNNL-SA-121385
Journal ID: ISSN 0010-9312; 49141; AF5805020
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Corrosion; Journal Volume: 73; Journal Issue: 11
Country of Publication:
United States
Language:
English
Subject:
Environmental Molecular Sciences Laboratory

Citation Formats

Matthew Asmussen, R., Neeway, James J., Kaspar, Tiffany C., and Crum, Jarrod V.. Corrosion Behavior and Microstructure Influence of Glass-Ceramic Nuclear Waste Forms. United States: N. p., 2017. Web. doi:10.5006/2449.
Matthew Asmussen, R., Neeway, James J., Kaspar, Tiffany C., & Crum, Jarrod V.. Corrosion Behavior and Microstructure Influence of Glass-Ceramic Nuclear Waste Forms. United States. doi:10.5006/2449.
Matthew Asmussen, R., Neeway, James J., Kaspar, Tiffany C., and Crum, Jarrod V.. 2017. "Corrosion Behavior and Microstructure Influence of Glass-Ceramic Nuclear Waste Forms". United States. doi:10.5006/2449.
@article{osti_1398165,
title = {Corrosion Behavior and Microstructure Influence of Glass-Ceramic Nuclear Waste Forms},
author = {Matthew Asmussen, R. and Neeway, James J. and Kaspar, Tiffany C. and Crum, Jarrod V.},
abstractNote = {Glass ceramic waste forms present a potentially viable technology for the long term immobilization and disposal of liquid nuclear wastes. Through control of chemistry during fabrication, such waste forms can have designed secondary crystalline phases within a borosilicate glass matrix. In this work, a glass ceramic containing powellite and oxyapatite secondary phases was tested for its corrosion properties in dilute conditions using single pass flow through testing (SPFT). Three glass ceramic samples were prepared using different cooling rates to produce samples with varying microstructure sizes. In testing at 90 °C in buffered pH 7 and pH 9 solutions, it was found that increasing pH and decreasing microstructure size (resulting from rapid cooling during fabrication) both led to a reduction in overall corrosion rate. The phases of the glass ceramic were found, using a combination of solutions analysis, SEM and AFM, to corrode preferably in the order of powellite > bulk glass matrix > oxyapatite.},
doi = {10.5006/2449},
journal = {Corrosion},
number = 11,
volume = 73,
place = {United States},
year = 2017,
month = 6
}
  • A process leading to titanate-based crystalline ceramic waste forms for commercial high-level nuclear waste is described. Precursor materials referred to as hydrous calcium titanates are prepared by sol-gel-related techniques. Radionuclides are retained on the precursors by ion-exchange/sorption reactions and the material is converted to a dense, ceramic form by hot-pressing. Transmission electron microscopy-electron microprobe characterization was used to determine the effects of compositional changes and process variations on microstructure.
  • Alteration of borosilicate glass, sintered ceramic, glass-ceramic, and supercalcine ceramic was studied under hydrothermal conditions of 100/degree/, 200/degree/, or 220/degree/C and 300/degree/C for 28 days under a confining pressure of 30 MPa. Results show that the chemical composition of the waste, in addition to its form, plays an important role in keeping the hazardous nuclides out of solution during waste-form alteration under hydrothermal conditions that may arise in a nuclear-waste repository. 18 refs.
  • Borosilicate glass-ceramics are being developed to immobilize high-level waste generated by aqueous reprocessing into a stable waste form. The corrosion behavior of this multiphase waste form is expected to be complicated by multiple phases and crystal-glass interfaces. A modified single-pass flow-through test was performed on polished monolithic coupons at a neutral pH (25 °C) and 90 °C for 33 d. The measured glass corrosion rates by micro analysis in the samples ranged from 0.019 to 0.29 g m -2 d -1 at a flow rate per surface area = 1.73 × 10 -6 m s -1. The crystal phases (oxyapatitemore » and Ca-rich powellite) corroded below quantifiable rates, by micro analysis. While, Ba-rich powellite corroded considerably in O10 sample. The corrosion rates of C1 and its replicate C20 were elevated an order of magnitude by mechanical stresses at crystal-glass interface caused by thermal expansion mismatch during cooling and unique morphology (oxyapatite clustering).« less
  • Borosilicate glass-ceramics are being developed to immobilize high-level waste generated by aqueous reprocessing into a stable waste form. The corrosion behavior of this multiphase waste form is expected to be complicated by multiple phases and crystal-glass interfaces. A modified single-pass flow-through test was performed on polished monolithic coupons at a neutral pH (25 °C) and 90 °C for 33 d. The measured glass corrosion rates by micro analysis in the samples ranged from 0.019 to 0.29 g m -2 d -1 at a flow rate per surface area = 1.73 × 10 -6 m s -1. The crystal phases (oxyapatitemore » and Ca-rich powellite) corroded below quantifiable rates, by micro analysis. While, Ba-rich powellite corroded considerably in O10 sample. The corrosion rates of C1 and its replicate C20 were elevated an order of magnitude by mechanical stresses at crystal-glass interface caused by thermal expansion mismatch during cooling and unique morphology (oxyapatite clustering).« less
  • Glass ceramic waste forms have been investigated as alternatives to borosilicate glasses for the immobilization of high-level radioactive waste at Pacific Northwest Laboratory (PNL). Three glass ceramic systems were investigated, including basalt, celsian, and fresnoite, each containing 20 wt % simulated high-level waste calcine. Static leach tests were performed on seven glass ceramic materials and one parent glass (before recrystallization). Samples were leached at 90/sup 0/C for 3 to 28 days in deionized water and silicate water. The results, expressed in normalized elemental mass loss, (g/m/sup 2/), show comparable releases from celsian and fresnoite glass ceramics. Basalt glass ceramics demonstratedmore » the lowest normalized elemental losses with a nominal release less than 2 g/m/sup 2/ when leached in polypropylene containers. The releases from basalt glass ceramics when leached in silicate water were nearly identical with those in deionized water. The overall leachability of celsian and fresnoite glass ceramics was improved when silicate water was used as the leachant.« less