Performance of a Buried Radioactive High Level Waste Glass After 24 Years Page: 3 of 39
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PERFORMANCE OF A BURIED RADIOACTIVE HIGH LEVEL
WASTE (HLW) GLASS AFTER 24 YEARS
Carol M. Jantzen*, Daniel I. Kaplan, Ned E. Bibler, David K. Peeler,
and M. John Plodinec
Savannah River National Laboratory
Aiken, SC 29808
Abstract
A radioactive high level waste glass was made in 1980 with Savannah River Site (SRS)
Tank 15 waste. This glass was buried in the SRS burial ground for 24 years but lysimeter
data was only available for the first 8 years. The glass was exhumed and analyzed in 2004.
The glass was predicted to be very durable and laboratory tests confirmed the durability
response. The laboratory results indicated that the glass was very durable as did analysis of
the lysimeter data. Scanning electron microscopy of the glass burial surface showed no
significant glass alteration consistent with the results of the laboratory and field tests. No
detectable Pu, Am, Cm, Np, or Ru leached from the glass into the surrounding sediment.
Leaching of 0/8 from 90Sr and 137Cs in the glass was diffusion controlled. Less than 0.5%
of the Cs and Sr in the glass leached into the surrounding sediment, with >99% of the
leached radionuclides remaining within 8 centimeters of the glass pellet.
1. Introduction
The most important requirement for high-level waste (HLW) glass acceptance for
disposal in a geological repository is the chemical durability. During the early stages of
glass dissolution in a geological repository, near static conditions are expected to dominate.
Under these conditions, a gel layer resembling a membrane forms on the glass surface
through which ions exchange between the glass and the contacting groundwater. The
hydrated gel layer exhibits acid/base properties which are manifested as the pH dependence
of the thickness and nature of the gel layer. The gel layer has been determined to age into
either clay mineral assemblages or zeolite mineral assemblages [1]. The formation of one
phase preferentially over the other has been experimentally related to changes in the pH of
the contacting solution and related to the relative amounts of Al+3 and Fe 3 in a waste glass.
During laboratory studies the formation of clay mineral assemblages on the leached glass
surface layers (lower pH environments and/or Fe+3 rich waste glasses) causes the
dissolution rate to slow to a long term "steady state" rate.[1] The formation of zeolite
mineral assemblages of the analcime type (higher pH environments and/or Al+3 rich
glasses) on leached glass surface layers causes the dissolution rate to increase and return to
the initial high forward rate [1,2,3].
* Corresponding author. Tel: 803-725-2374; fax: 803-725-4704.
E-mail address: caroljantzen@srnl.doe.gov2 of 38
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Jantzen, Carol M.; Kaplan, Daniel J.; Bibler, Ned E.; Peeler, David K. & Plodinec, M. J. Performance of a Buried Radioactive High Level Waste Glass After 24 Years, article, May 5, 2008; [Aiken, South Carolina]. (https://digital.library.unt.edu/ark:/67531/metadc898741/m1/3/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.