Approach to assess the occurrence probability of a long-term evolution scenario of a long-lived nuclear waste repository

2010 ◽  
Vol 224 (3) ◽  
pp. 217-224 ◽  
Author(s):  
H Chraibi ◽  
S Pierlot
Keyword(s):  
Nuclear Waste ◽  
Long Term Evolution ◽  
Nuclear Waste Repository ◽  
Occurrence Probability ◽  
Term Evolution ◽  
Waste Repository

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.

Characterization and Assessment of the Groundwater Pathway for the Low Level Waste Repository, UK

2011 ◽  
Author(s):  
Lee J. Hartley ◽  
Martin James ◽  
Peter Jackson ◽  
Matt Couch ◽  
John Shevelan
Keyword(s):  
Radioactive Waste ◽  
Groundwater Flow ◽  
Environmental Safety ◽  
Long Term Evolution ◽  
Low Level ◽  
Term Evolution ◽  
Groundwater Flow Modelling ◽  
Safety Case ◽  
Waste Repository

The Low Level Waste Repository (LLWR) is the UK’s principal facility for the disposal of solid low-level radioactive waste and is operated by LLW Repository Limited. Presently, LLWR Ltd is establishing the long-term environmental safety of disposals of solid radioactive waste at the LLWR, through the submission of the 2011 Environmental Safety Case for the LLWR. This Environmental Safety Case addresses the Environment Agency Guidance on Requirements for Authorisation. Aspects of the submission consider improved vault design, closure design, and quantitative assessments. Each of these issues requires an understanding of the movement of water through the facility and the surrounding geology during operations and following facility closure. Groundwater flow modelling has been used extensively in support of the interpretation of field investigations, the development of the engineering design, and an assessment of the groundwater pathway as one of the major pathways by which contaminants may reach the environment. This paper describes these important aspects of the Environmental Safety Case. The geological environment in the region of the LLWR consists of Quaternary age deposits overlying older bedrock. The facility involves shallow excavations into the Quaternary deposits, originally for trenches, with disposals to a vault system beginning in 1988. In the post-closure phase these disposals are covered by a cap and surrounded by a cut-off wall to minimise the water flow around or through the waste. An innovative modelling methodology has been developed to represent the range of scales that have to be considered from the regional groundwater flow patterns over several kilometres, the scale of tens of metres around the immediate site area, and down to about 1 metre for details of flows within the repository itself in three dimensions. Detailed finite-element models of the flow through geological media and the engineered features are used to interpret site data and assess a credible set of post-closure situations and model cases. In the radiological assessment, a more simplified compartment model is used to assess uncertainties in hydrogeological properties and the long-term evolution of the engineered barriers. Together the approach provides flexible tools for understanding and assessing a comprehensive range of aspects including details of flows within the repository, dilution and migration in the external geology, the long-term evolution of the hydrogeological system, the implications of spatial variability and alternative geological models, and effects of uncertainties.

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.

Hydrogeological simulation of sedimentary basin evolution during a glacial cycle

2021 ◽  
Author(s):  
Christian Silbermann
Keyword(s):  
Boundary Conditions ◽  
Large Scale ◽  
Sedimentary Basin ◽  
Long Term Evolution ◽  
Nuclear Waste Repository ◽  
Glacial Cycle ◽  
Thermal Problem ◽  
Term Evolution ◽  
The Impact

<p><strong>Co-authors: Francesco Parisio, Thomas Nagel</strong></p><p>Glaciation cycles affect the long-term evolution of geosystems by crustal deformation, ground freezing and thawing, as well as large-scale hydrogeological changes. In order to properly understand the present and future conditions of potential nuclear waste repository sites, we need to simulate the past history. <br>For this, a sedimentary basin is considered here as a large-scale hydrogeological benchmark study. The long-term evolution during one glacial cycle is simulated using the open-source multi-field finite element code <em>OpenGeoSys</em>. The impact of the glacial loading (weight and induced shear) is taken into account using appropriate time-dependent stress boundary conditions. As a preliminary study, the hydro-mechanically coupled problem and the thermal problem are considered separately. For comparison with a previously published study by Bense et al. (2008), the entire displacement field is prescribed and the groundwater evolution (hydraulic problem) is regarded. Then, the displacement is only prescribed by means of boundary conditions. The impact of different constitutive assumptions on the deformation and hydraulic behavior is analyzed. The thermal problem is used to simulate the evolution of frost bodies in the subsurface beneath and ahead of the glacier.</p><p>V. F. Bense and M. A. Person. Transient hydrodynamics within intercratonic sedimentary basins during glacial cycles. Journal of Geophysical Research,<br>113(F4):F04005, 10 2008.</p>

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