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Regional Evaluations of Crystalline Rock for Disposal of DOE-Managed Waste
Frank Perry, Rick Kelley Los Alamos National Laboratory
UFD Working Group Meeting
June 9, 2016
Milestone: M4FT-16LA080504081, Preliminary regional site evaluations for disposal of DOE-managed HLW and SNF
Los Alamos Unlimited Release LA-UR-16-23845
2
Distribution of Surface or Near-Surface Crystalline Rocks in the US
June 2016
3
Aspects of the Regional Evaluation
Evaluation of the Superior Craton region of the north-central US as a potential region for siting a repository in crystalline rock • Ties to R&D from Canadian HLW programs • Potential ties to DBH field test site – granitic/gneissic
terrane of the Superior Craton Assessment and documentation of available geologic
and geophysical data Question of sedimentary overburden to enhance
repository isolation Question of similarity of fracture characteristics of
granites in US and the Forsmark site in Sweden June 2016
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Superior Craton and Potential Siting Factors
• Glaciation • Basement
tectonic zones • Seismic hazard • Topography • Heat flow • Ore deposits • Population
June 2016
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Cl versus Depth for Crystalline Rocks
June 2016
0
500
1000
1500
2000
2500
30001 10 100 1,000 10,000 100,000 1,000,000
Dept
h (m
)
Cl (mg/L)
All Canadian Shield
Whiteshell URL (Canada)
Finland
Sweden
Russia
Western Europe
UK
~freshwater
Seawater
~2 molal NaCl
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New Geologic Maps of Crystalline and Sedimentary Bedrock (Jirsa et al. 2011, 2013)
June 2016
Precambrian basement geology Basement rocks plus Mesozoic (green) and Paleozoic (blue) rocks
High-quality maps provide a framework for evaluating more detailed information on specific crystalline rock bodies, or other aspects of the regional geology
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Geophysical Data - Aeromagnetic Data for Identification of Structural and Lithologic Boundaries
June 2016
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Sedimentary overburden in the US
June 2016
200-300 meters overburden 100-400 meters overburden
Is sedimentary overburden needed for isolation of a granite repository? • Siting would be at margins of granitic terrraes, not within the
terrane
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Forsmark-like fracture systems in the US?
The granitic rocks at Forsmark are among the four or five most well-studied and documented in the world
The best documented granite fracture systems are the products of HLW programs – even these involve uncertainties in fracture characteristics such and size and connectivity
There are very few complete fracture data sets available in the US available for comparison
In the absence of data, determining similarity with Forsmark is based on granitic analogs that share similar emplacement, deformation and cooling histories, which may produce overall similarities in fracture characteristics
Best analogs identified so far are well-studied granites in Canada and, by extension, granites of the same age in the north-central US
June 2016
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The Canadian Shield in the North-Central US
June 2016
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Forsmark and Analogous Granites in the Superior Craton
Granite plutons and their properties are relatively well studied in this part of Canada, including the AECL URL in the Lac du Bonnet batholith (LDBB)
The LDBB has similarities to the granitic rocks at Forsmark in terms of compressional deformation, cooling history, glacial loading and unloading, and resultant geometry of fracture zones
LDBB is part of a regional episode of granitic plutonism that intruded older gneissic terranes of both Manitoba and Northern Minnesota at about 2.6 Ga
June 2016
United States
Canada
12
Forsmark vs. Lac du Bonnet Fracture/Deformation Zones
June 2016
Both rock masses characterized by regions of low fracture intensity bounded by more highly fractured shallow-dipping deformation zones (minor thrust faults) related to compressional tectonics
Forsmark Lac du Bonnet
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LDPP EDP
Fractures, Granite Volume and the Ductile-Brittle Transition during Cooling
June 2016
Longer cooling times under compressional stress allow more time in ductile deformation relative to brittle deformation
EDP 102 km3
LDPP 104 km3
Fractures/meter
“Comparison of fracture styles in two granite bodies of the Superior Province” Stone et al. 1989
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Analogous granites in North-Central US Granitic Terrane?
Not enough existing data for rigorous comparison of fracture properties
Forsmark fracture characteristics are not unusual for a sparsely fractured granite
Larger plutons have longer periods of cooling and ductile deformation, less time in brittle deformation
Analogs contain low-angle faulting or deformation zones that accommodate strain and leave intervening rock volumes relativity intact and sparsely fractured
June 2016
15
Summary
Technical site evaluations using capabilities and tools that include geology, geophysics, GIS and Geologic Framework Models are key components of evaluating future disposal options including disposal of DOE-managed waste and Deep Borehole Disposal
June 2016
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Backup
June 2016
17
Fracture Orientations at Forsmark (SKB R-12-04)
June 2016
Open All
PFL-f (flowing) PFL-f in
FFM01
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Summary of Fracture Sets at Forsmark
June 2016
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Climax Stock Fractures Sets
The number and specific orientations of fracture sets are unique to every occurrence of granite
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Summary of Tectonic History of the Forsmark Region (SKB R-10-04)
June 2016
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Fracture Density
June 2016
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DFN Components Important to System Performance (Posiva 2009-77)
Variability in fracture size (aperture and radius) Variability in fracture density Both of the above have large impact on fracture connectivity Less important are specific fracture orientations
June 2016
Prefer to site within sparsely fractured granite
repository
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The Western Margin of the Superior Craton in the US and Canada {{DELETE??}}
Tectonically stable craton New geologic mapping data from
Minnesota Geological Survey (Jirsa et al. 2013), an extension of the Canadian Shield into US
In proximity to the well-characterized Lac du Bonnet Batholith in Canada, host rock for the AECL-URL
Assert that it is a reasonable analog for granitic terrane in Sweden that hosts the Forsmark site • Similar emplacement mechanisms
during accretionary tectonic events • Similar gross fracture domains
generated during cooling and deformation
June 2016
United States
Canada
NC-6
NC-7
NC-10