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Dissertation/Thesis Abstract

Characterization of Sodalite Based Waste Forms for Immobilization of 129I
by Chong, Saehwa, Ph.D., Washington State University, 2017, 243; 10638078
Abstract (Summary)

Sodalite was investigated for application in waste forms for immobilization 129I. The goal of this research is to develop a chemically durable glass-bonded sodalite waste form for immobilization of 129I. The study is focused on 1) the synthesis and characterization of iodine-containing sodalite mineral, 2) the synthesis and characterization of glass-bonded iodosodalite waste form, and 3) understanding the formation of sodalite with different anions.

Sodalite is a microporous mineral that can incorporate alkali halides within the β-cage. The chemical formula of natural sodalite and iodosodalite are Na8(AlSiO4)6Cl2 and Na 8(AlSiO4)6I2 respectively. For 1), the optimal condition for the hydrothermal synthesis of iodosodalite was determined by studying the effects of different process variables including pH, temperature, precursor concentration, Al/Si ratio, aging time, and precursors.

For 2), the glass-bonded iodosodalite waste form was synthesized and investigated. The hydrothermally grown iodosodalite powder was mixed with 10 or 20 mass% of the borosilicate glass binders, pressed into pellets, and heat-treated at 650, 750, and 850 °C. The iodine quantification and chemical durability test in addition to the standard characterizations were performed to understand the efficiency of the final product as the waste form.

For 3), the selectivity of anions for the β-cage was investigated by comparing the experimental and computational results. For the experimental study, the sodalites with mixed anions, including I, Cl, and OH, were synthesized hydrothermally, and the selectivity constant was calculated using the lattice parameter. For the computational study, density functional theory was used to understand the formation of the sodalite with different anions.

In addition to this experimental study, background is provided for sodalite, the capture and immobilization of iodine, and the glass ceramic waste form. The appendix section provides general information on the classification of radioactive waste, illustration of various sodalites, and parameters for Rietveld analysis.

Indexing (document details)
Advisor: McCloy, John
Commitee: Norton, Grant, Song, Min Kyu
School: Washington State University
Department: Materials Science
School Location: United States -- Washington
Source: DAI-B 79/08(E), Dissertation Abstracts International
Subjects: Engineering, Materials science
Keywords: Glass-bonded waste form, Hydrothermal, Iodine-129, Iodosodalite, Radioactive waste form, Sodalite
Publication Number: 10638078
ISBN: 978-0-355-79200-3
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