Title

Evaluation of Standard Durability Tests Towards the Qualification Process for the Glass-Zeolite Ceramic Waste Form

Abstract

Glass-bonded zeolite is being developed as a potential ceramic waste form for the disposition of radionuclides associated with the waste management system of spent nuclear fuels. In this connection, the utility of several standard durability tests namely: materials characterization center test #1 (MCC-1); product consistency test-B (PCT-B), and vapor hydration test (VHT), is evaluated towards the qualification process of the material. The effects of pH, leachant composition and sample surface-area-to-leachant-volume ratios on the durability tests are discussed to investigate the release mechanisms, and other physical and chemical parameters in the establishment of appropriate test methodologies required for product consistency measurements. Results from PCT-Bs conducted with 4 (im diameter salt-loaded zeolite powder indicate that a good correlation exists between release rate and ionic size and/or charge for the release behavior of the simulated fission products in deionized water (DIW), EJ-13 groundwater, and brine solutions. Simulated divalent and trivalent fission products [Sr, Ba, and rare earth (RE) ions] were preferentially retained in the zeolite (relative to the singly ionized cations) after tests with the salt-loaded zeolite in DIW. In general, the preferential cation release order for salt-loaded zeolite A in DIW is Li > Na > K > Cs > Al > Si > RE > Sr > Ba. Results from PCT-Bs with the salt-loaded zeolite A immersed in high-ionic-strength brines at 90°C indicate a significant increase, relative to DIW tests, in the release rates of the Sr, Ba, and RE ions despite a decrease in the release of the Si and Al ions that make up the framework matrix of the zeolite. An increase in the Mg and Ca concentrations in the reacted zeolites. An increase in the Mg and Ca concentrations in the reacted zeolites suggests that an ion exchange process may be responsible for this increase. Vapor hydration and MCC-1 tests were performed with ceramic waste form monoliths of glass-bonded zeolite. The VHTs (temperatures at 120,150, and 200°C) provided useful information about the effect of glass composition on corrosion rates and alteration phase formation, and about the overall toughness and structural integrity of the ceramic waste form. The MCC-1 test was investigated as an alternative to the PCT for acceptance criteria measurements. The MCC-1 results indicate that corrosion testing with both DIW and high-ionic-strength leachants (that specifically affect the ion exchange behavior of the fission products) are required to fully assess the durability of the ceramic waste form. These preliminary results establish the utility of the MCC-1 test for providing possible acceptance criteria measurements, including elemental release comparisons between the environmental assessment benchmark and the ceramic waste form.

Meeting Name

1996 MRS Fall Meeting (1996: Dec. 2-6, Boston, MA)

Department(s)

Geosciences and Geological and Petroleum Engineering

Keywords and Phrases

Ceramic Materials; Composition Effects; PH Effects; Radioisotopes; Spent Fuels; Zeolites; Ceramic Waste Forms; Durability Tests; Radioactive Waste Management; Radioactive Wastes

International Standard Serial Number (ISSN)

2729172

Document Type

Article - Conference proceedings

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 1997 Materials Research Society (MRS), All rights reserved.

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