New Developments in Field Studies of Low Activity Waste Glass Corrosion and Contaminant Transport

Abstract

Performance assessment calculations for low-activity waste glass to be disposed at the Hanford site depend on simulations of long-term glass corrosion behavior and contaminant transport that are being performed via reactive chemical transport modeling. Confidence in the underlying physical and chemical processes that are being approximated by the computer model could be significantly enhanced through carefully-controlled field testing, which includes studies of buried ancient glasses. Field tests with simulated low-activity waste glasses have been initiated on the Hanford site and at the Ballidon site in the United Kingdom. In addition, a joint PNNL – SIA RADON research project has been initiated to analyze a unique data set collected over 12+ years during a Russian in-situ testing program with actual low-activity waste glass. The glasses buried at Hanford are scaled down cylinders (45 kg mass) and include a representative glass composition for Hanford low-activity waste and a glass designed to be highly reactive. Each glass was doped with chemical analog tracers (Re, Se, and Mo). Design of the lysimeter test facility and sampling locations were done with aid of predictive calculations performed with the STORM code. These same glasses were also buried at Ballidon but in the form of small glass coupons. The coupons will be retrieved over a period of several years for detailed analysis along with core samples of the surrounding limestone, which will be analyzed for contaminant transport profiles. Analysis of porewater from underneath the Russian burial site ha s been compared with modeling calculations. Good agreement between the model and the field data has been obtained so far using estimated parameters for the glass corrosion. Independent laboratory tests are in progress to parameterize the STORM model for quantitative comparisons.

Change of structure and properties of vitrified radioactive wastes during long-time storage in an experimental repository

“…The results of the investigations agree with the existing data on the meaning of embryos of the surface layer and the intermediate gel-like layer, which, possessing sorption properties, impede further leaching of the radionuclides out of the glass blocks [3,4,[6][7][8][9]17].…”

“…periodic sampling of the material being tested. In the case of vitrified high-level wastes, the interaction of the products of radiolysis of water with the surface of the glass has a large effect on the glass matrix, while this effect is negligible for vitrified medium-level wastes.The glasses were placed in an experimental repository in Canada, Sweden, France, USA, Belgium, and Great Britain [3,4]. Since 1987, glass samples containing operating wastes from nuclear power plants with RBMK and VVER nuclear reactors and obtained in a vitrification setup based on an electric tank furnace (Joule heating ceramic melter) [5,6] have been tested under natural conditions on a test site of the Moscow Scientific and Industrial Association Radon [3,4,7,8].…”

“…Since 1987, glass samples containing operating wastes from nuclear power plants with RBMK and VVER nuclear reactors and obtained in a vitrification setup based on an electric tank furnace (Joule heating ceramic melter) [5,6] have been tested under natural conditions on a test site of the Moscow Scientific and Industrial Association Radon [3,4,7,8]. The changes of the structure and the properties of the vitrified medium-level wastes from nuclear power plants after 17 years of storage are described in the present article.…”

“…In general, the structure of the glass is formed predominately by two-bond tetrehedra [ 4 ] tetrahedra. However, the effect of these groups is negligible.…”

A fractured roman glass block altered for 1800 years in seawater: Analogy with nuclear waste glass in a deep geological repository

“…In order to validate this kind of predictive models over long time scales, basaltic glass (Ewing, 1979(Ewing, , 2001Techer et al, 2000Techer et al, , 2001Crovisier et al, 2003) and archaeological glass Ford, 1989, 1993;Macquet and Thomassin, 1992;Libourel, 2001, 2006;Roemich et al, 2003;McGrail et al, 2003) have been extensively studied as analogs of nuclear glass. These studies are based on the high durability of natural glasses in different environments, and seek to demonstrate the analogy in the formation of alteration products (e.g.…”