Liquidus Temperature and Crystallization Behavior of US Waste Glasses Investigated at KRI
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Liquidus Temperature and Crystallization Behavior of US Waste Glasses Investigated at KRI Albert S. Aloy, Alexander V. Trofimenko, Valery Z. Belov, James C. Marra1, Kevin M. Fox1, David Peeler1, John D. Vienna2 and Dong-Sang Kim2 FSUE RPA «V.G. Khlopin Radium Institute» (KRI) 2–nd Murinsky Ave., 28, St. Petersburg, 194021, Russian Federation 1 Savannah River National Laboratory (SRNL) Savannah River Site, 999-W, Aiken, SC 29808, USA 2 Pacific Northwest National Laboratory (PNNL) P. O. Box 999, Richland, WA, 99352, USA ABSTRACT As a part of the optimization study for achieving the highest possible Hanford and Savannah River Site waste loading into acceptable borosilicate glasses, thirty glass compositions were selected for testing at KRI. These thirty test matrix glasses were designed to augment existing data within the compositional regions of interest with relatively high concentration of Al2O3 between 10 and 20 wt%. This paper reports experimental data on liquidus temperature (TL) and crystallization behavior of all synthesized glasses as well as durability of quenched and heat-treated glasses. The results of this study will be used to develop glass formulations for specific DOE waste streams to maintain or meet waste loading and/or waste throughput expectations while satisfying critical process and product performance related constraints. INTRODUCTION The U.S. Department of Energy (DOE) is currently processing (or planning to process) highlevel waste (HLW) through Joule-heated melters at the Savannah River Site (SRS) and Hanford [1]. The process combines the HLW sludge with a prefritted or mined mineral glass forming additives which are subsequently melted and poured into stainless steel canisters to create the final waste form. The product performance issue relates to the durability of the glass waste form. While it is well known that the addition of small amounts of Al2O3 to borosilicate glasses generally enhances the durability of the waste form (through creation of network-forming tetrahedral Na+-[AlO4/2]- pairs), nepheline (NaAlSiO4) formation, which depends in part on the Al2O3 concentration, can result in a severe deterioration of the chemical durability of the slowly cooled glass near the center of the canister through residual glass compositional changes [2]. The scientific and engineering challenges associated with the waste glasses in this case result from a high quantity of aluminum, iron, chromium, and other troublesome elements in the waste that either have a limited solubility in the glass or affect its durability due to crystallization. At the same time, the U.S. DOE sites focus on increasing productivity of the waste vitrification systems, and this productivity directly depends on the melt rate. The melt rate can be increased with increasing the alkali content in the feed, but a high alkali concentration could affect the glass quality. Therefore, a desire to increase a waste melt rate for processing waste
with a complex chemical composition appears to conflict with a requirement to assure an ac
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