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Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC., a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525.
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Fluid-RockProcessesDrivingIsolationofCrustalFluidsinCrystallineBasementSystems
DavidC.Sassani,PatrickV.Brady,KristopherL.Kuhlman,CarlosF.Jove-Colon,andCarlosM.Lopez
SandiaNationalLaboratoriesAugust,2016;SAND2017-8489C
PresentationOverview§ DeepBoreholeFieldTest(DBFT)Background
§ TheDeepBoreholeDisposal(DBD)Concept§ Feasibilityisbeingevaluated
§ DBFTOverview– ScienceandDatatoEvaluateDBDConcept§ CurrentProjectisBeingWrappedUp
§ GeoscienceGuidelinesforDBFTSite§ ConsideredCharacteristics§ CrystallineBasementCharacteristics/ConceptualProfiles
§ EvaluationofFluid-RockReactionsinCrystallineBasement§ Fluid-RockReactionConceptsandGeochemicalDescription§ GeneralObservationsandResults
§ SummaryandConclusions
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Sassani,SNL.Goldschmidt2017August14,2017
DeepBoreholeDisposal(DBD)Concept§ Deepboreholedisposalofhigh-levelradioactivewastehas
beenconsideredintheU.S.andelsewheresincethe1950sandhasbeenperiodicallystudiedsincethe1970s
§ CurrentDBDconceptconsistsofdrillingaborehole(orarrayofboreholes)intocrystallinebasementrock§ Totaldepthabout5,000mdepth§ Lower3000mincrystallinebasement§ Wastecanisterswouldbeemplacedinthelower2,000meters§ Uppercrystallinebasementportionwouldbesealedwithcompacted
bentoniteclay,cementplugs,andcementedbackfill§ Atleast1000m
§ Upperboreholefilled/sealed
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Sassani,SNL.Goldschmidt2017August14,2017
WhyConsiderDeepBoreholeDisposal?§ PotentialforRobustIsolation§ GivesDOEtheFlexibilitytoConsiderOptionsforDisposalof
SmallerWasteFormsinDeepBoreholes§ Potentiallyearlierdisposalofsomewastesthanmightbepossibleina
minedrepository§ Possiblereducedcostsassociatedwithprojectedtreatmentsofsome
wastes
§ SeveralDOE-managedSmallWasteFormsarePotentialCandidatesforDeepBoreholeDisposal(SNL2014),e.g.,§ 1,936cesiumandstrontiumcapsulesstoredattheHanfordSite§ UntreatedcalcineHLWcurrentlystoredatINLinsetsofstainlesssteel
binswithinconcretevaults
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Sassani,SNL.Goldschmidt2017August14,2017
DeepBoreholeDisposalConcept–SafetyandFeasibilityConsiderations
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Long-Term Waste Isolation (hydrogeochemical characteristics)
Waste emplacement is deep in crystalline basement• At least 1,000 m of crystalline rock
(seal zone) overlying the waste disposal zone
• Crystalline basement within 2,000 m of the surface is common in many stable continental regions
Deep groundwater in the crystalline basement:• Can have very long residence times – isolated from shallow groundwater• Can be highly saline and geochemically reducing – enhances the sorption and limits
solubility of many radionuclides• Can have density stratification (saline groundwater underlying fresh groundwater) –
opposes thermally-induced upward groundwater convection
Crystalline basement can have very low permeability• limits flow and transport
Sassani,SNL.Goldschmidt2017August14,2017
DeepBoreholeFieldTest(DBFT)Overview§ AssessDBDFeasibilityViaFieldStudyofSiteandHandling
§ NOTE:ProjectisBeingClosed-outthisFiscalYear
§ ConstructTwo5-kmBoreholes§ CharacterizationBorehole(CB): 21.6cm[8.5”]@TotalDepth§ FieldTestBorehole(FTB): 43.2cm[17”]@TotalDepth
§ EvaluateourAbilityto:§ Drilldeep,wide,straightincrystallinerocks(CB+FTB)§ Characterizebedrockviageophysics(CB)§ Conducttestsinbasement≤150oC&50MPa(CB)§ Collectgeochemicalprofiles(CB)§ Emplace/retrievesurrogatewastepackages(FTB)
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Sassani,SNL.Goldschmidt2017August14,2017
GeoscienceGuidelinesConsiderations
§ CrystallineBasement§ Depth§ RockFabric&StressState§ RegionalStructure(s)§ HydrologyandGeochemistry
§ HeatFlow§ RecentSeismicity/Volcanism§ Resources§ AnthropogenicContamination
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Sassani,SNL.Goldschmidt2017August14,2017
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DepthtoBasement– NationalScale
Distribution of crystalline basement at a depth of less than 2 km (tan shading) and granitic outcrop (red) in the contiguous US (from Figure 3-2 in Perry et al., 2015)
Sassani,SNL.Goldschmidt2017August14,2017
DeepBoreholeConceptualProfiles
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Sassani,SNL.Goldschmidt2017August14,2017
ObservedProfiles
10DeMaioandBates(2013)
SalinityIncreaseswithDepth
Stober andBucher(2007)
BulkPermeabilityDecreaseswithDepth
HowMuchofaRoleDoesFluid-RockReactionPlayinDriving
IncreasedSalinity?
Sassani,SNL.Goldschmidt2017August14,2017
Fluid-RockReactionEvaluations§ Analysesforgenericfluid-rockreactionsystemsincrystalline
basement§ Evaluatemechanismsinthecrystallinebasementtoformdeep,
isolatedbrines§ Reactionpathmodelsforgranitemineralreactionswithseawater
– Alterationmineralogy– hydrousphases(H2Osinks)– Evolvedbrinecompositions(majorelements,Cl,Br)
§ Fluidinclusioncontributions(solublesalts)considered§ CalculatingleachatecompositionsfromBlackForestcrystallinebasementrocks
§ ConditionsComparableto~5kmdepth§ GenericGraniteComposition(s)§ SeawaterStartingBrineComposition§ ~100– 150oC,Psat§ PHREEQCReactionPathCalculations
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Sassani,SNL.Goldschmidt2017August14,2017
HypotheticalGranite
§ 20%Quartz;40%K-feldspar;15%Plagioclase(Albite);9%Muscovite;8%Biotite;and8%Hornblende(volume%)
§ Representedasa10kg(3.8L)blockhavingamolarmixtureof§ 33.3molesQuartz:14.4molesK-feldspar:5.7molesAlbite:2.2moles
Muscovite:1.8molesBiotite:0.9molesHornblende
§ Graniteis“reacted”with0.1literofseawaterat100oC.§ Thisisa38:1rock:fluid ratiobyvolume,equivalenttoarockwitha
fluid-filledporosityof~3%
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Sassani,SNL.Goldschmidt2017August14,2017
GeneralObservations§ CalculatedGenericGraniteHydrologicAlterationResults
§ ReactioncreatesAlbite+K-feldspar+Chlorite+Laumontite +Brine§ Minoramounts(<0.02moles)ofepidote,calcite,andgypsumform§ AlbiteandK-feldsparmassesincreasesubstantially§ Almostallofthequartzisdissolved.
§ ProducesaresidualCa-Na-ClbrineatpHof6.8§ NetLossofwatercausestheionicstrengthofthesolutiontoincrease
– Fromaninitialionicstrengthof0.6upwardsto>5molal– TheCa/Nacalculatedforbrineis1.55– LowMgconcentration
§ End-memberCanadianShieldbrinesfromFrapeetal.(1984)withhighestsaltcontentsof~240– 325g/L§ Haveionicstrengthsof4.5- 6.2§ 0.7<Ca/Na<3§ LowMgconcentration
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Sassani,SNL.Goldschmidt2017August14,2017
SolutionandMineralogicEvolution
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Sassani,SNL.Goldschmidt2017August14,2017
0
1
2
3
4
5
6
0.0
0.1
1.0
0.0 0.1 0.2 0.3 0.4 0.5 0.6
Moles/L Biotite, Hornblende Reacted
Mol
es/L
Hyd
rous
Alte
ratio
n M
iner
als
Ionic Strength
Ca/Na
Laumontite
Chlorite
Ioni
c St
reng
th (m
olal
), or
Ca/
Na
SummaryandConclusions§ PlannedDBFTProjectisEndingthisFiscalYear§ ManySiteswithinU.S.withFunctionalGeology
§ MultifacetedObjectivesofDBFTProvideOpportunitiesforSuccess§ ChoosingAnySitewouldbebasedonUncertainGeologicInformation
§ GenerallyRegionsLackingExploration§ EachSitewillhaveitsownGeologicChallenges
§ WouldProvideSubstantialDirectDataandUnderstanding– Characterizationmethods– Feasibilityofimplementation
§ GeochemicalProcessesinGenericCrystallineBasementAppeartobeAbletoAffect/ControlFluidSystemIsolation§ Stilltoevaluate
§ SensitivityofthePHREEQCcalculationstoinputwaterchemistry§ Morethoroughcomparisonofpredicted/observedalteration§ Moredetailedconsiderationofactivitycoefficienteffects
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Sassani,SNL.Goldschmidt2017August14,2017
BackupMaterials
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Sassani,SNL.Goldschmidt2017August14,2017
DeepGeologicDisposalRemainsanEssentialElementofNuclearWasteManagement
“Theconclusionthatdisposalisneededandthatdeepgeologicdisposalisthescientificallypreferredapproachhasbeenreachedbyeveryexpertpanelthathaslookedattheissueandbyeveryothercountrythatispursuinganuclearwastemanagementprogram.”
BlueRibbonCommissiononAmerica’sNuclearFuture,2012
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Sassani,SNL.Goldschmidt2017August14,2017
DeepBoreholeFieldTestObjectives§ TheRD&Dobjectivesfordeepboreholedisposalarebeingmetwith
aboreholefieldtestthatisconductedtoadepthof5kminasuitablelocation(withoutemplacementofradioactivewastes)
§ TheDBFTincludesthefollowingmajoractivities:§ Obtainasuitabletestsite§ Design,drillandconstructtheCharacterizationBorehole(8.5”diameter)
torequirements§ CollectdataintheCharacterizationBoreholetocharacterizecrystalline
basementconditionsandevaluateexpectedhydrogeochemical conditions
§ AccommodateasubsequentFieldTestBorehole(17”diameter)§ Design,drillandconstructtheFieldTestboreholetorequirements§ Designanddevelopsurfacehandlingandemplacementequipment
systemsandoperationalmethodsforsafecanister/wastepackagehandlingandemplacement
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Sassani,SNL.Goldschmidt2017August14,2017
PreferredGeologicConditions§ Geohydrological Considerations
§ Nolarge-scaleconnectedpathwaysfromdepthtoaquifersystems§ Nothroughgoingfracture/fault/shearzonesthatprovidefastpaths§ Nostructuralfeaturesthatprovidepotentialconnectivepathways
§ Lowpermeabilityofcrystallinebasementatdepth§ Urach3:(Stober andBucher,2000;2004)
– ~10-19 m2 (intactrock);~10-14 to10-17 m2 (bulk:paralleltooracrossshears)– DecreasingwithDepth
§ Evidenceofancient,isolatednatureofgroundwater§ Salinitygradientincreasingdownwardtobrineatdepth(Parketal.,2009)
– Limitedrecharge/connectivitywithsurfacewaters/aquifers– Providesdensityresistancetoupwardflow
§ Majorelementandisotopicindicationofcompositionalequilibrationwithrock– Crystallinebasementreactingwithwater(Stober andBucher,2004)– Ancient/isolatedgroundwater
» Ages– isotopes,paleoseawater (Stober andBucher,2000)» Radiogenicisotopesfromatmospherelacking:81Kr,129I,36Cl» Radiogenicisotopes/ratiosfromrock:81Kr,87Sr/86Sr;238U/234U» Noblegases(4He,Ne)&stableisotopes(2H,18O)compositionsfromdeep
water:(e.g.,GascoyneandKamineni,1993)
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Sassani,SNL.Goldschmidt2017August14,2017
PreferredGeologicConditions(Continued)§ GeochemicalConsiderations
§ Reduced,orreducing,conditionsinthegeosphere(rockandwatersystem)§ Crystallinebasementmineralogical(andmaterial)controls§ Magnetite-hematitebufferlowoxygenpotential
– Oxidesequilibria=>T-lowƒO2 paths(e.g.,SassaniandPasteris,1988;Sassani,1992)§ BiotitecommonFe+2 phase(BucherandStober,2000)
– Rock-reactedfluidcompositions– watersink(Stober andBucher,2004)– Morerockdominatedatdepth(GascoyneandKamineni,1993)
§ Stratificationofsalinity– increasingtobrinedeepincrystallinebasement§ CanadianShieldsalinityincreaseswithdepthto~350g/LTDS;(GascoyneandKamineni,
1993;Parketal.,2009)– MoreCa-richbrineswithfurtherreactionwithdeeperrock
§ Urach3,Germany,~70- g/LTDSNaCl brine(Stober andBucher,1999;2004)§ Subsetofwasteformsandradionuclidesareredoxsensitive
§ Lowerdegradationrates§ Lowersolubility-limitedconcentrations§ Increasedsorptioncoefficients
§ Highersalinity§ Densitygradientopposesupwardflow§ Reduces/eliminatescolloidaltransport
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Sassani,SNL.Goldschmidt2017August14,2017
ReferencesAAPG, 1978, Basement map of North America: Am. Assoc. Petroleum Geologists, scale: 1:5,000,000
Blackwell, D.D., P. Negraru, and M. Richards, 2007. Assessment of the enhanced geothermal system resource base of the United States, Natural Resources Research, DOI 10:1007/s11053-007-9028-7.
Bucher K, and Stober I (2000) Hydrochemistry of water in the crystalline basement. In: Hydrogeology of Crystalline Rocks (eds Stober I, Bucher K), pp. 141-75. Kluwer Academic Publishers, Dordrecht.
Bucher, K. and Stober, I. (2002) Water-rock reaction experiments with Black Forest gneiss and granite, Water-Rock Interaction. Springer, pp. 61-95.
Bucher, K. and Stober, I. (2010) Fluids in the upper continental crust. Geofluids 10, 241-253.
DeMaio, W., and Bates, E. (2013). Salinity and Density in Deep Boreholes. Massachusetts Institute of Technology. UROP REPORT: October 29, 2013. 14 p.
Frape, S., Fritz, P. and McNutt, R.t. (1984) Water-rock interaction and chemistry of groundwaters from the Canadian Shield. Geochimica et Cosmochimica Acta 48, 1617-1627.
Gascoyne, M. and Kamineni, D. C. (1993) The hydrogeochemistry of fractured plutonic rocks in the canadian shield. In: Hydrogeology of Hard Rocks, 440- 449. Banks, S. B. and Banks, D. (editors) Geol. Survey of Norway: Trondheim.
Park, Y.-J., E.A. Sudicky, and J.F. Sykes (2009), Effects of shield brine on the safe disposal of waste in deep geologic environments, Advances in Water Resources 32: 1352-1358.
Perry, F., Kelley, R., Houseworth, J., and Dobson, P., 2015. A GIS Database to Support the Application of Technical Siting Guidelines to a Deep Borehole Field Test. FCRD-UFD-2015-000603. LA-UR-15-22397. Los Alamos , NM: US Department of Energy Used Fuel Disposition Campaign.
Sassani, D.C., 1992. Petrologic and Thermodynamic Investigation of the Aqueous Transport of Platinum-Group Elements During Alteration of Mafic Intrusive Rocks, Ph.D. Dissertation, Washington University, St. Louis, University Microfilms.
Sassani, D.C., and Pasteris, J.D., 1988. Preliminary investigation of alteration in a basal section of the southern Duluth Complex, Minnesota, and the effects on the sulfide and oxide mineralization, in G. Kisvarzanyi and S.K. Grant, eds., North American Conference on Tectonic Control of Ore Deposits and the Vertical and Horizontal Extent of Ore Systems, Proceedings Volume, University of Missouri-Rolla, 280-291.
SNL (Sandia National Laboratories), 2014. Evaluation of Options for Permanent Geologic Disposal of Spent Nuclear Fuel and High-Level Radioactive Waste in Support of a Comprehensive National Nuclear Fuel Cycle Strategy (2 Volumes). FCRD-UFD-2013-000371. Albuquerque, NM: US Department of Energy Used Fuel Disposition Campaign.
Stober I, and Bucher K.,1999, Origin of salinity of deep groundwater in crystalline rocks, Terra Nova, 11, p. 181-189.
Stober I, and Bucher K (2000) Hydraulic Properties of the upper Continental Crust: data from the Urach 3 geothermal well. In: Hydrogeology of Crystalline Rocks (edsStober I, Bucher K), pp. 53-78. Kluwer Academic Publishers, Dordrecht.
Stober I and Bucher K (2004) Fluid sinks within the earth’s crust. Geofluids 4(2): 143–151.
Stober, I. & K. Bucher, 2007. Hydraulic properties of the crystalline basement. Hydrogeology Journal, 15:213 224.
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