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.

Influence of Carbonate on Uranium Solubility in the WIPP

2012 ◽  
Vol 1444 ◽  
Author(s):  
Jean-Francois Lucchini ◽  
Sally Ballard ◽  
Hnin Khaing
Keyword(s):  
Performance Assessment ◽  
Pilot Plant ◽  
Solubility Limit ◽  
Experimental Results ◽  
Waste Isolation Pilot Plant ◽  
Long Term Experiments ◽  
Order Of Magnitude ◽  
Carbonate Complexation ◽  
Borate Complexation

ABSTRACTIn the performance assessment (PA) for the Waste Isolation Pilot Plant (WIPP), the solubility of uranium (VI) was conservatively set at 10-3 M for all expected WIPP conditions, including the potential and likely effects of carbonate complexation [1]. Under WIPP-relevant conditions, long-term experiments were performed to establish the uranium (VI) solubility limits in WIPP-simulated brine over a broad range of pCH+ values [7.5-12.5] and to evaluate the contribution of carbonate complexation and hydrolysis to uranium (VI) speciation. Data obtained in carbonate-free ERDA-6 brine, a simulated WIPP brine, were reported earlier [2]. In the absence of carbonate, uranium solubility approached 10-7 M at the expected pCH+ in the WIPP (~ 9.5). In the presence of a significant amount of carbonate (millimole levels), recent experimental results showed that uranium (VI) concentrations will not exceed 10-4M. This measured solubility limit is an order of magnitude lower than the uranium solubility value currently used in the WIPP PA [3]. A small effect of borate complexation was found in the pCH+ range [7.5-10]. At pCH+ ≥ 10, hydrolysis overwhelmed carbonate effects, and no amphoteric effect was observed.

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.

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.

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