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

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Distribution of Surface or Near-Surface Crystalline Rocks in the US

June 2016

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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

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500

1000

1500

2000

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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

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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

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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

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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

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