Glass/Water Reaction with and without Bentonite Present - Experiment and Model

1985 ◽  
Vol 50 ◽  
Author(s):  
B. Grambow ◽  
H. P. Hermansson ◽  
I. K. Björner ◽  
L. Werme
Keyword(s):  
Nuclear Waste ◽  
Water Permeability ◽  
Borosilicate Glass ◽  
Waste Form ◽  
Nuclear Waste Repository ◽  
Aqueous Environment ◽  
Long Term Stability ◽  
Chemical Effects ◽  
Waste Repository

In nuclear waste repository design bentonite has been included as part of the backfill for its sorbtive capacity and low water permeability. Nevertheless, it cannot keep the waste form dry once intrusion of groundwater has occured [1]. Leach experiments [2], [3] with the radioactive nuclear waste form borosilicate glass JSS-A have been performed with and without bentonite present to provide a database which allows the long term stability of the glass in aqueous environment to be forecasted and the chemical effects of bentonite to be studied.

Leached Nuclear Waste Glasses: Ultramicrotomy and AEM Characterization

1990 ◽  
Vol 48 (2) ◽  
pp. 444-445
Author(s):  
J.P. Bradley ◽  
J.K. Bates
Keyword(s):  
Nuclear Waste ◽  
Waste Form ◽  
Experimental Program ◽  
Nuclear Waste Repository ◽  
Aqueous Environment ◽  
Borosilicate Glasses ◽  
Secondary Phases ◽  
Thin Sections ◽  
The Stability

The long term performance of a nuclear waste repository depends ultimately on the stability of the waste form. Borosilicate glasses have been proposed as a waste form because they can incorporate radionuclides into their structures and they are relatively resistant to corrosion in an aqueous environment. Experimental and computer modeling programs are in progress to evaluate their long term stability in a geological repository. In the experimental program, glasses have been reacted in sealed vessels (for between 7 and 280 days) to simulate the effects of terrestrial aqueous alteration (leaching). During leaching, a layer of secondary phases (predominantly layer silicates) builds up on the glass surfaces (Pigs. 1-3). Determination of the mineralogy of the leached layer is critical for evaluation of glass performance, but the layers are typically ultra-thin (1-50 μm), poorly crystallized, friable coatings that have eluded detailed characterization. Using ultramicrotomy, we have successfully prepared electron transparent thin-sections of the glasses plus leached layers with minimal disturbance of their indigenous microstructures (Figs. 2-4).

scholarly journals Uranium (VI) Solubility in Carbonate-Free ERDA-6 Brine

2010 ◽  
Vol 1265 ◽  
Author(s):  
Jean-Francois Lucchini ◽  
Hnin Khaing ◽  
Donald T. Reed
Keyword(s):  
Nuclear Waste ◽  
Research Program ◽  
Pilot Plant ◽  
Nuclear Waste Repository ◽  
Ongoing Research ◽  
Waste Isolation Pilot Plant ◽  
Long Term Experiments ◽  
Carbonate Complexation ◽  
Waste Repository

AbstractWhen present, uranium is usually an element of importance in a nuclear waste repository. In the Waste Isolation Pilot Plant (WIPP), uranium is present in significant quantities, with about 647 metric tons to be placed in the repository [1]. Therefore, the chemistry of uranium, and especially its solubility, needs to be determined under WIPP-relevant conditions.Long-term experiments were performed to measure the solubility of uranium (VI) in carbonate-free ERDA-6 brine, a simulated WIPP brine, at pCH+ values between 8 and 12.5. These data, obtained from the over-saturation approach, were the first WIPP repository-relevant data for the VI actinide oxidation state. The solubility trends observed pointed towards low uranium solubility in WIPP brine and a lack of amphotericity. At the expected pCH+ in the WIPP (˜ 9.5), measured uranium solubility approached 10-7 M. The objective of these experiments was to establish a baseline solubility to further investigate the effects of carbonate complexation on uranium solubility in WIPP brines, during the ongoing research program in actinide solubility under WIPP-relevant conditions.

Natural Analogues: Their Application to the Prediction of the Long-Term Behavior of Nuclear Waste Forms

1986 ◽  
Vol 84 ◽  
Author(s):  
Rodney C. Ewing ◽  
Michael J. Jercinovic
Keyword(s):  
Nuclear Waste ◽  
Borosilicate Glass ◽  
Large Scale ◽  
Laboratory Data ◽  
Waste Form ◽  
Long Time ◽  
Natural Analogues ◽  
Long Term Behavior ◽  
Nuclear Waste Forms

AbstractOne of the unique and scientifically most difficult aspects of nuclear waste isolation is the extrapolation ofshot-term laboratory data (hours to years) to the long time periods (103-105 years) required by regulatory agencies for performance assessment. The direct verification of these extrapolations is not possible, but methods must be developed to demonstrate compliance with government regulations and to satisfy the lay public that there is a demonstrable and reasonable basis for accepting the long-term extrapolations. Natural analogues of both the repository environment (e.g. radionuclide migration at Oklo) and nuclear waste form behavior (e.g. alteration of basaltic glasses and radiation damage in minerals) have been used to demonstrate the long-term behavior of large scale geologic systems and, on a smaller scale, waste form durability. This paper reviews the use of natural analogues to predict the long-term behavior of nuclear waste form glasses. Particular emphasis is placed on the inherent limitations of any conclusions that are based on “proof” by analogy. An example -- corrosion of borosilicate glass -- is discussed in detail with specific attention to the proper and successful use of natural analogues (basaltic glass) in understanding the long-term corrosion behavior of borosilicate glass.

scholarly journals Simulating 10,000 Years of Erosion to Assess Nuclear Waste Repository Performance

Geosciences ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 120 ◽  
Author(s):  
Adam Atchley ◽  
Kay Birdsell ◽  
Kelly Crowell ◽  
Richard Middleton ◽  
Philip Stauffer
Keyword(s):  
Nuclear Waste ◽  
Parameter Uncertainty ◽  
National Laboratory ◽  
Model Development ◽  
Surrogate Data ◽  
Nuclear Waste Repository ◽  
Multiple Sources ◽  
Low Level ◽  
Waste Repository

Long-term environmental performance assessments of natural processes, including erosion, are critically important for waste repository site evaluation. However, assessing a site’s ability to continuously function is challenging due to parameter uncertainty and compounding nonlinear processes. In lieu of unavailable site data for model calibration, we present a workflow to include multiple sources of surrogate data and reduced-order models to validate parameters for a long-term erosion assessment of a low-level radioactive nuclear waste repository. We apply this new workflow to a low-level waste repository on mesas in Los Alamos National Laboratory in New Mexico. To account for parameter uncertainty, we simulate high-, moderate-, and low-erosion cases. The assessment extends to 10,000 years, which results in large erosion uncertainties, but is necessary given the nature of the interred waste. Our long-term erosion analysis shows that high-erosion scenarios produce rounded mesa tops and partially filled canyons, diverging from the moderate-erosion case that results in gullies and sharp mesa rims. Our novel model parameterization workflow and modeling exercise demonstrates the utility of long-term assessments, identifies sources of erosion forecast uncertainty, and demonstrates the utility of landscape evolution model development. We conclude with a discussion on methods to reduce assessment uncertainty and increase model confidence.

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