I N '. -

A

; 1, . 1,,j - ! r, -" -

K' ~~~/1/

APPENDIX B

Preliminary Geologic Description for the GeochemicalSensitivity Analysis of a Bedded-Salt Site

86091eo80 800A -1 6MRS EXISANL

A-i 756 PDR

k~fAei44 ~WM -15

WM Project /0 /v/6Docket No. . _ _ _

PDR VI D- I

Returi t ioo62S _ _ E,

(Re t urn to M, .623.SS) _ ______

Bedded-Salt Site

The geologic and hyrologic setting used for this study arebased on the portion of the Palo Duro Basin in Deaf SmithCounty. Texas (Figure B-1). J. Friemel #1 is the drill holeclosest to the proposed repository location. As a result, thestratigraphic data and information in this drill hole areassumed to be the same as those at the site.

Stratiaraphy

In J. Friemel No. 1. the units range in age from Pennsylvanianthrough Tertiary (Figure B-2). The rock of Pennsylvanian ageare primarily limestone and granite wash with lesser amounts ofsilty shale. Changes in the depositional environment areevident in the lower Permian sequence in that granite wash isabsent and dolomite is present. Otherwise, this portion of thestratigraphy is dominated by fine clastics and limestone.Higher in the Permian sequence, salt and anhydrite units becomecommon to abundant, and limestone is absent. At the top of thePermian sequence, the units composed of evaporite mineralsbecome progressively less abundant, and these types of unitsare absent in the rocks of Triassic age. Sandstone layers arecommon in the Triassic sequence and are predominant toexclusive in Tertiary time.

Regional Ground-Water Flow

Based on potentiometric maps for the Ogallala Fm and theWolfcamp Series (DOE, 1984). the direction of ground-water flowis different for units at different depths. In the OgallalaFm, flow across the reference site is from northwest tosoutheast (Figure B-3). For the much deeper Wolfcamp Series,flow across the site is from southwest to northeast (FigureB-4). Based on the approximate hydraulic-head data at thereference site in Figures B-3 and B-4. the vertical flowgradient is downward.

Geologic Setting

The Palo Duro Basin is located primarily in northern Texas andis separated from adjacent basins by Oldham Nose, Matador Arch,Milnesand Dome, and the Amarillo Uplift (Figure B-5). Althoughfaults that cut the Precambrian basement and those of Cenozoicage are present in the Palo Duro Basin, no earthquakeepicenters were recorded within the basin itself between 1907and 1971 (Northrop and Sanford, 1972). DOE (1984) states thatmany earthquakes in the Texas Panhandle seem to be associatedwith the Amarillo Uplift and Anadarko Basin. Faults of recentorigin probably' are the result of collapse caused by saltdissolution.

a £ Is 301Kiometwfs

0 3 5 Is mit

Figure B-1. Bedded-salt reference repository location(after DOE, 1984).

t

ERA SYSTEM SERIES GROUP FORMATION

O OUATERNARY _RECENT FLUVIAL AND LACUSTRINE DEPOSITS

N TERTIARY -OGALLALA0 DAKOTA.Z, . _ _ _ _ . _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

o CRETACEOUS FREDRICKSBURG

TRINITY

_ URASSIC -. MORRISONO JURASSIC EEE

_ _ _ _ _ _ _ _ _ _ _ _ _ _ EXETER0 _ _ _ _ _ _ _ _ _ _ _ _ _ _

S TRUJILLO:ETRIASSIC____ OOCKUM TECOVAS

OCHOA DEWEY LAKEOC4OA ALIBATES

SALADO -TANSILL

ARTESIA/ YATESGUADALUPE WHITEHORSE SEVEN RIVERS

QUEEN/GRAYOURG

____________ PEASE RIVER SAN ANDRES/BLAINEPERMIAN _ ______ _ _ GLORIETA

UPPER CLEAR FORK

CLEAR FORK TUBSo ~~~~LEONARD

_ LOWER CLEAR FORK0O RED CAVE

0A WICHITA

a WOLFCAMP

VIRGIL CISCO

MISSOURI CANYON

PENNSYLVANIAN DES MOINES STRAWN

ATOK SENDMORROW

CHESTER

MISSISSIPPIAN MERAMECOSAGE

ORDOVICIAN ELLENBURGER

CAMBRIAN UNNAMED SANDSTONE

PRECAMBRIAN

Explanation:

Unconformable Boundary

Boundary in Dispute

Figure B-2. Stratigraphic units of Palo Duro and DalhartBasins (after DOE, 1984).

Explanation:0 25 Contour Interval 100 Feet (30 Meters)

Scale - Miles

Scale Kilometers

Figure B-3. Ogallala potentiometric-surface map for1981 (after DOE, 1984).

( (

he2.l let.O 104.4 104.0 t 02.2 102.0 6 ~ tee.8 le. Sols oS Sol. Ie 99. f

99.p

5.3

CK~~~~~~~~~0~~~~~~~~~~~~~~~

x~~~~~~~~~~~~~~~~~

Explanation:

* DST Well

Contour Interval: 200 Feet (61 Meters) ° 25 50s-o__.Scale- Miles

O 25 50

Scale- Kilometers

Figure B-4. Wolfcamp potentiometric-surface map (after DOE, 1984).

o 30 So mioe 40eOm=

0 40 80 kin

DS - Deaf Smith County

Figure B-5. Major structural elements of the TexasPanhandle (after Dutton and others, 1979).

Salt dissolution is an ongoing process in the Palo Duro Basin.Figure B-6 illustrates areas of active dissolution andpaleodissolution. Whereas salt units within the Seven RiversFm are being dissolved in Deaf Smith County (Figure B-2), theseunits are at least 900 feet stratigraphically above theproposed host unit.

No volcanic activity has occurred in the Palo Duro Basin sincePrecambrian time.

Drilling exploration for oil and gas has occurred throughoutthe Palo Duro Basin. This activity is likely to continue atleast into the short-term future. Whereas Deaf Smith Countyhas had a very low level of exploration in the past, non- andlow productivity areas tend the be reexamined when energyprices rise.

Drill holes from resource exploration or from site evaluationfor the repository could be particularly troublesome. Thegenerally abundant water supply of the Ogalla aquifer and thehigh downward hydraulic gradient could result in substantialsalt dissolution if a drill hole connects the Ogallala aquiferwith a deeper aquifer.

Proposed Host Unit for Repository

The candidate unit for the repository is Lower San Andres Unit4 (Figure B-2). For this study, the canisters placed in therepository are assumed to be 10 feet long, and the top of thecanisters are at the midpoint of the salt unit.

Flow Paths

Because of the substantially higher downward hydraulic gradient(approximately two orders of magnitude) relative to thehorizontal gradient at the site and the relatively lowhydraulic conductivity of the units. radionuclides releasedfrom a repository in a host salt unit would migrate downwarduntil a unit with substantially higher horizontal conductivitywas encountered. Upon reaching such a unit, significanthorizontal migration could occur.

The DOE pathway (DOE. 1984) consists of downward flow from therepository to the dolomite unit at the top of the WolfcampSeries (Figure B-7). Horizontal flow in the dolomite is to theaccessible environment. The sparsity of conductivity data forother units at and near the site leaves open the possibilitythat other units stratigraphically higher than the Wolfcampdolomite could provide the horizontal pathway to the accessible

I. I. i 1Ei !

*_ _ _ M~~~~i, ' i , t 1 < l7W, -

5 - .--- - - - -- - - --

i ~ ~ ~~~ v Lcscc\ 0

J LFYpU gLO~SAM ~

i Ix j I1^ ! I , P i, \'0 '

( \t5/ 0 Y;I¢J1pboi@M4 UQ I..-.E.-.-i -.- S-L - - -

~~~~~~~~~~~~~~~~~~~~~~

OWES~~~~- FLOYDI~~so~1

Ue MexcoJf VafrGutavso andothrs 190)

ImeacA ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~~ ~~~k. BOC oz

___ j~VOKL IEt I Imfcf ' T! CU.

Figure B-6. Salt dissolution zones, Texas Panhandle and easternNew Mexico (after Gustavson and others, 1980).

Depth(ft)

2368

256(

2822

301U

3645

Salt and Lower SanAnhydrite Andres Unit 5

Lower SanSalt [Repository Andres Unit 4

_______________________. ._________________________

-- Dolomite Alt. 3

Salt, Dolomite Lower Sanand Anhydrite Andres Units 3&2

_______________________. ._________________________

Siltstone Alt. 2 Glorieta_______________________. ._________________________

Siltstone &Salt

Salt. Siltstone Upper Clear& Anhydrite Fork

Sandstone_______________________

Siltstone

~-Alt. 1

Tubb

4B22.4

Salt &Anhydrite

Lower ClearFork

4702

5253

5582

Shale & Red CaveSiltstone

Dolomite & WichitaShale

Dolomite > DOE…--------------------------------------------- Wolfcamp

Limestone &Shale (not drawn to scale)

Figure B-7. Schematic diagram of DOE and alternative flow paths atbedded-salt site.

environment. In this study, three alternative horizontal flowpath legs are proposed (Figure B-7):

1. The sandstone at the top of the Tubb Fm. Although nodata exist for this unit, the sandstone should have thehighest hydraulic conductivity of the clastic units inthe Permian sequence. This alternative path alsoeliminates the ground-water flow through thesubstantial thickness of shale in the Red Cave Fm asrequired in the DOE path.

2. The first substantial (>20 m thick) siltstone, which isin the Glorieta FM. beneath the repository (FigureB-7). As with the sandstone, no site-specifichydrologic data are available for this unit. In asequence containing numerous evaporite beds. siltstonewould be a relatively high permeability rock type basedon generic data. A siltstone layer exists higher inthe sequence than the unit chosen, but the layer isless than 3.5 m thick and as a result is likely topinch out before reaching the accessible environment.The difference in vertical distance between thesesiltstones is approximately 13 meters in J. Friemel#1. An advantage of this pathway over alternative 1above is that substantially fewer low conductivityevaporite units must be crossed in the vertical flowleg.

3. The first dolomite beneath the host salt unit.Although this dolomite has a much lower conductivitythan the dolomite chosen by DOE in the Wolfcamp Series(DOE, 1984, Table 3-19). the conductivity issubstantially higher than at least the lower end of therange of values for generic salt.

Because of the numerous stratigraphic units at the RRL, theunits have been consolidated into a more manageable number,hopefully without significantly altering ground-water flow orthe effects of retardation on radionuclide migration. TablesB-1 and B-2 list the data for the DOE and the three alternativeflow schemes. Appendix C explains the rationale used insimplifying the stratigraphy for the various flow paths.

Mineralogy of Rock Types

Table B-3 lists the mineral content of the major rock typesencountered along the flow paths from the repository to theaccessible environment. The sources of data are Fukui (1983,1984). Modal analyses of thin sections were made for samplesfrom drill holes G. Friemel #1. Grabbe #1. Rex White #1, andDetton #1. The rock names used by Fukui (1983, 1984) were not

Table 8-1. Date and sj-.nlliod htraLigraphy foe Dotflow path( idad-salt slt.. (

BualkI I ~~~~I Le Leftgth I HYdeandic conductivity 9 CompositionA

9J..LpLos J f t)- jaradientl Ref.b I porosity I. t~. I..!tL *ef. IMM/ .... It. .iDint. I.A5L1.J.. -I- ..A !A~ ft !

Li Repsitory 10 0.4 1 3 132-4-If-2 LA I j 3.3K-$-S.AR-31 4 LOI dI I(salt)

ILI Isalt anid 9 31 I0.41 3 I33-4-11-2 91.2 I K d~ 13.313-8-5.43t-3 4,2 ILK 4 1.?? .239 Anhyrita e

9L3 Dolomite 9 138 90.421 3 191-2-93-2 93 ILK Id 931-5-93-3 3Ia LEI I 1

9 MA9 AILt . 0.42 I3 I31-4-11-2 91 ILII I 4 3.3it-8-5.41-3 6 EA UI

1 LSI 107 I .1II I 1.q12-2ASK-1 1 a I N I a1-4-2ta S Ls

Ishl

IIIIIIIIIIIIIIIIIIIIIIII

i -- ----- iI [A I Salt II I IIL~1I aIslkaafte I

iIIIIIIIIIIIIII

LA

Lo

L10

Lit

LII

LII

L14

L14

LI?

LI

IL19

salt

Siltst"Oa

salt uid

anhydrite

Uiltatone

Aob drith

I Sanstone

Isiltstone

I Salt WAd

I sohydrite

I Dolomite

- -- i - I--- … … … -- -i - i - i - F - j j I78 9 0.42 9 3 936-4-19-2 I LK 9 13.33..8-5.41.-3 9 4 1Aj

214 10.42 1 3 91 9 - -. 1 l LK d 131-4-310 9 5 9 La200 9 0.42 I 3 931-4-11-2 9 1 9 LA I 93 3 - -.4 - LN

143 9 0.42 9 3 9 1 1- 2. 3 i 9 4 9 LIN d 933-A-390 I 5 Lo

130 9 0.42 (311-4-11-2 9 1,29 LK 9 d 13.31-8-5.42-31 6,29 LU

IS I I 1 98 2I I- A LA I I A-W I I L

35 9 0.42 I 3 II 9 -- I 5 1 LLKA 4 131-4-3W0 I95 I LKI I I 2 31 9 [ 9 939 93 t 9 E

152 9 .42 9 3 133-4-11-2 I 2 LU I 3.31-8-5.41-31I 2 [AL

3 10.42 I 3 971-2-22 .5.43 1 1 5 IA I 4 I 933-4-320 5 IL KA

184 0.42 I 3 1 31.9-2- 2.51 - 19 [A L 9 131-4-310 5 9 LA283 I 0.42 I 3 I 312-2-9 -2 I I LU 9 3.3t1--98-3. 3- 9 3 LA

529 9 1 0.0029 3 9312-2-91-i 943 1LII d 138-S-99-34 Is LK

4

4

4

I

(.72 .28

4

4

4

4

4

4

4

4

4

I

491

I,4 I1

I

I

I

.30.10

I

I

I

a. baeaM on unit thickneases in stallJ1. PrIamal no. I (mOe. 1904)

b. References1. Tian and others, 19332. Oenhydrite properties sassuiad

to be sam as salt3. O0M, 1904l assumed ne . nt/24. twhertwood. 1981S. Freeze end Cherry, 19794. aentalea, 1933

c. distribution of datat LU . lognormal

d. permeability data for thoea units plotted in DO3 (1934) has a lognorma1distribution. Assumed permeability data for all units have lognormaldistribution. blecause permeability and porosity are closely ralated,porosity data assumed to be lognormal.

a. proportional compesition of each log based on available data.S - salt A * anhydrite St . sandstoneo * dolomite St a eiltstonte oh . shale

(

i ( (-

Table B-2. Data and simplified stratigraphy for alternative flow path* for bedded-raItsite. (same reference and note designations as Table B-1).

| L Length I I Hydraulic Conductivity|L0(s) Rock Tvte I (ft) | Ovadlent | Ref. Porosity lRef I Dist. |Ref _ _| R f| I Dle | ef.

Alternative 1 - Horizontal flow In sandutone at top of Tubb Fm | | | |

|L1-112 | ea I values as lese for I IDOW pathway j I I Table B-1 | I I II I I I I I I I I . 1 1 1L L13 | Sandstone I 1.64R4 0.0045 | 3 | 71-2-1.41-1 5 ILN [-d 1 31-5-3M-1 | S I LN I d I

* ~ ~ ~ ~~ ~~~~~~~~~~I I I IIAlternative 2 - Horizontal flow In first "significant" silttone in Clorieta Fm |

IL1-LA I e a values as less for | IDOR Pathwa I I I I Table 8-1 I I IIIIII I I I I I I I IIILS I Siltotone | 1.64 U | 0.0045 I 3 11.91-2-2.58-1 1 4 I LN I d 1 31-4-310 | 5 I LN I d |

Alternative 3 - Horizontal flow In dolomite beneath host unit In Lower San Andres Pa | | I I

IL1 I *ame | values as l leg for | I DOE Pathway I I | | Table B-1 I I I I1L2 I Salt and 8a s 0.42 I 3 1 3-4-1E-2 1 1,2 LN I d 13.3R-8-5.41-3 I 7 I LN I d II I anhydrite I I I I I I I I I I I II I I d I | 1 I I a 1 I I d11.3 I Dolomite I 1.64R4 10.0045 3 11-2-99-2 13 I LN I d 131-5-91-3 1 3 I LNI d

Table B-3. Composition of rock types used for simplified conceptual model ofbedded-salt site (data from Fukui. 1983. 1984).

Halite (1 3 2 )aMinpral/Comnonent

Siltsone (3)Mineral/Comnonentvol. t vol. t

HaliteAnhydrite*ClayCarbonateQuartz

\- PolyhaliteOther

67.3-99.70-27.00-27.00-2.70-10-3.30-1.3

Quartz*Clay matrixSedimentary RockFragments

Dolomite CementHalite Cement*MuscoviteAdditionalDetrital Components

Halite Pore FillingAnhydriteHematite/Geothite

45-6118-28

3-145-95-71-2

Tr-10-10-10-1

Anhydrite (4) Dolomite (2)

HalitePolyhaliteAnhydriteCarbonate*Goethite*Clay

\- Pore SpacePyrite

0-340-Tr65-99Tr0-Tr0-10-10-Tr

AllochemsCalcite CementPore SpaceBariteAnydritePyritePhosphatic FossilFragments

Micrite MatrixVein PhasesHaliteQuartz

23-5230-350-130-TrTr0-Tr

Tr0-420-30-Tr0-Tr

Shale (1) Sandstone (o)b

Halite*ClayAnhydriteQuartzGypsumOther

46817821

Quartz 100

ab*

number of thin sections sampledno samples analyzed; assumed compositionimportant sorbing mineral

the same as those used in the lithologic-log description by DOE(1984) for J. Friemel #1. Tentative correlation of mineralcontents and rock types was made by comparison of samplelocations in a formation from Fukui (1983. 1984) with relativeposition in the same formation in J. Friemel #1 (DOE, 1984).Most units along the pathways do not have a correspondingmineral analysis. For these units, analyses of rock of thesame general rock type elsewhere in the stratigraphic sectionwere assumed to be applicable to the units along the flowpath. No data were available for a rock type that correspondsthe the sandstone unit at the top of the Tuff Fm.

References

Department of Energy, 1984, Draft environmental assessment.Deaf Smith County site, Texas: U.S. Dept. of Energy, Rept.DOE/RW-0014. variously paginated.

DOE. 1984 - see Department of Energy

Dutton, S. P.. Finley, R. J., Galloway, W. E., Gustavson. T. C..Handford. C.R.. and Presley, M. W.. 1979, Geology andhydrology of the Palo Duro Basin. Texas Panhandle, a reporton the progress of nuclear waste isolation feasibilitystudies (1978): Texas Bureau of Economic Geology, Geol.Circ. 79-1. 99 p.

Freeze. R. A.. and Cherry. J. A.. 1979. Groundwater: EngelwoodCliffs. N.J.. Prentice-Hall. 604 p.

Fukui, L. M., 1983, Petrographic report on clay-rich samplesfrom Permian Unit 4 salt, G. Friemel *1 well, Palo DuroBasin. Deaf Smith County. Texas: Unanalyzed data: BatelleMemorial Institute. Rept. BMI/ONWI-5001. 34 p.

Fukui. L. M.. 1984. Summary of petrologic and chemical data forPalo Duro Basin samples examined by Bendix FieldEngineering Corporation. Grand Junction. Colorado. as ofApril 29, 1983: Battelle Memorial Institute. Rept.BMI/ONWI-540. 100 p.

Gonzalez, D. D., 1983. Hydrochemical parameters of fluid-bearingzones in the Rustler and Bell Canyon Formations: WasteIsolation Pilot Plant (WIPP). southeast New Mexico (SENM):Sandia National Laboratories. Rept. SAND83-0210. 34 p.

Gustavson, T. C.. Finley, R. J.. and McGillis. K. A.. 1980,Regional dissolution of Permian salt in the Anadarko.Dalhart, and Palo Duro Basins of the Texas Panhandle:Texas Bureau of Economic Geology. Rept. of Invest. No. 106.40 p.

Isherwood, D.. 1981. Geoscience data base handbook formodeling a nuclear waste repository: U.S. NuclearRegulatory Commission. Rept. NUREG/CR-0912, vol. 2(UCRL-52719, vol. 2). 331 p.

Northrop. S. A., and Sanford, A. S., 1972. Earthquakes ofNew Mexico and the Texas Panhandle: New Mexico GeologicalSociety Guidebook 23, p. 148 - 160.

Tien. Pei-Lin. Nimick. F. B.. Muller, A. B., Davis. P. A..Guzowski. R. V., Duda. L. E., and Hunter. R. L., 1983,Repository site data and information in bedded salt: PaloDuro Basin, Texas: U.S. Nuclear Regulatory Commission,Rept. NUREG/CR-3129 (SAND82-2223) 486 p.

COMMENTS ON ISSUES PERTINENT TO SORPTION MODELSAND EXPERIMENTS IN SUPPORT OF PERFORMANCE ASSESSMENT STUDIES

NRC/ORNL WORKSHOPSilver Spring, MarylandMay 13-15, 1986

Malcolm SiegelWaste Management SystemsSandia National Labs.Albuquerque, NM.

INTRODUCTION

Geochemical interactions between radionuclides and rocksare but one of several barriers to the transport of radioactivewaste from proposed HLW repositories. Performance assessmentcalculations consider the roles of the waste package,engineered facility and hydrogeochemistry of the repositorysite in limiting potential releases of radioactivity. Theoverall objective of geochemical sensitivity analysis is toassess the relative contribution of the uncertainty ingeochemical data and models to the overall uncertainty in thepredicted performance of candidate HLW repositories.

In the past, performance assessment calculations have usedsimple models to represent complex geochemical processes. Inparticular. solute-water-rock interactions have beenrepresented by retardation factors calculated from empiricalsorption ratios (Kd. Rd. or Rs) obtained under conditions whichsimulate the range of environments predicted to prevail atspecific repository sites. Figure 1 illustrates the generalstructure of calculations carried out at Sandia NationalLaboratories to assess compliance of hypothetical HLW siteswith the EPA Standard 40 CFR Part 191. In these calculations.the discharge of radionuclides at the accessible enviroament iscalculated over a ten thousand year period. The use of simplealgorithms to represent geochemical processes has beenjustified in part by the complexity of the calculation ofintegrated discharge for solutes which are affected byradioactive decay and production. Statistical sampling ofmodel input parameters and a large number of calculations arerequired to represent the uncertainties in possiblehydrogeologic and geochemical conditions at the candidate ELWsites.

I,*CALCULATE R FOR EACH RADIONU'CUDE< v J S IN MATRIX (AND FRACTURE)

CALCULATE RADIONUCLIDE .TRANSP69T PARTICLESVELOCITY PROFILE - THROUGH FRACTURE

AND DIFFUSE' INTO MATRIX

INTEGRATE DISCHARGE CALCULATE RADIONUCLIDE DISCHARGEOVER 10.000 AT ACCESSIBLE ENVIRONMENT FOR

YEARS EACHMTIME STEP

Figure 1. Simplified Outline of Performance AssessmentCalculations. Shaded areas indicate steps in whichgeochemical processes are considered.

r I '

The adequacy of the use of simple retardation factors andsorption ratios in calculations of radionuclide discharge hasbeen questioned by a number of researchers. In general, thespeciations of the radioelements in the sorption experimentsare not known and sorption behavior cannot be confidentlypredicted for conditions that differ from those of theexperiments. Radionuclides are not introduced into theexperimental solutions in the forms that would be released fromthe nuclear waste, and the relatively short duration of theexperiments may preclude detection of any slow speciationreactions that could change sorption behavior and lead toincreased radionuclide discharge. -

Coupled reaction-transport models that explicitly modelgeochemical reactions have been proposed as an alternative tocurrently available performance assessment models. Thesemodels are clearly useful in providing basic mechanisticinsights and identifying key chemical parameters inradionuclide transport; however, the routine use of such codesin performance assessment is impractical. The use of coupledreaction-transport models is hampered in part by the lack offundamental thermochemical data describing surface complexationreactions. In addition, it is difficult to extrapolatetheoretical models of the sorption of trace metals by simpleoxides and aluminosilicates to the behavior of naturalmaterials. Finally, the high computing costs associated withrealistic calculations of radionuclide discharge over a 10 kmdistance and 10.000 year period, at present, preclude the useof coupled reaction-transport models in repository performanceassessment.

a

SOME GENERAL QUESTIONS RELATED TO SORPTION MODELS AND EXPERIMENTS IN HIGH LEVELWASTE PERFORMANCE ASSESSMENT

Can a range of (non-zero) sorption ratios or isotherm parameters be used to:1. obtain an upper bound to integrated radionuclide discharge?2. be used to bound maximum radionuclide concentrations?3. adequately bound the uncertainty due to sorption in performance assessment

calculations?

Is it possible to obtain upper bounds to discharge or concentration andbracket the geochemical uncertainty without understanding the detailedmechanisms of radionuclide/water/rock interactions?

Is it useful to obtain fundamental data and a detailed understanding ofgeochemical processes in laboratory studies even if site characterizationwill not provide similar data at the repository and 'average' parametervalues will be used in performance assessment calculations?

SOME SUGGESTIONS TO RESOLVE SOME ISSUES RELATED TO SORPTION

Table 1 lists some of the data requirements and modeling capabilities that arerequired in assessments of compliance of candidate repositories with the EPAStandard. The abilities of two codes being used at SNLA in HLW studies torepresent these processes are compared in the Table. The issues and questionsraised above should be addressed in a multi-dentate program involvingshort-term, medium-term and long-term activities. The approach described belowattempts to satisfy both technical and regulatory needs. It is designed tocontinuously decrease the level of uncertainty pertaining to geochemical dataand models used by the DOE and NRC in support of licensing activities.

Short-term Activities (1-3 years).

Site-specific physicochemical conditions under which the use of isotherms orretardation factors will significantly underestimate radionuclide dischargeand peak concentration must be identified. This effort should examine thegeochemical assumptions in current performance assessment modelsand assess the sensitivity of calculated integrated discharge and peakconcentration to the relaxation of these assumptions.

Computer codes such as NWFT/DVM and SWIFT can be used in conjunction withsampling techniques such as LHS to examine the importance of geochemicaluncertainty relative to uncertainties in other types of processes (eg.hydrology) for realistic conceptual sites.

Previous derivations of criteria for the local equilibrium assumption andfirst-order physical nonequilibrium transport models should be extended toexamine the effects of channeling, fracture geometry, non-linear sorption

TABLE 1. SOME REQUIRED AND CURRENT CHARACTERISTICS OF TRANSPORT CODES

FEATURE

Max. concentration

sPrecipitation/dissolution

Sorption

Number of sorbingspecies/run

TRANDL

yes

no

yesbut needs work

2

SWIFT/NWFT

yes/no

no

NRC

yes

?

KdFreundlich

no limit, but oneper nuclide

>8

-----------------------------------------------------------------------

Number of substrates/run

Number of 6W/run

Kinetics

\~Brines (chemical)

Brines (physical)

Dimension

Dispersion

Sat/unsat

Porous media

Radiodecay

>1

>1

no

no

1,2

TL

yes

yes

simple

no limit

no limit

no

no

yes

1,2,3

T, L

sat/unsat?

yes

yes

3-15

1-5

7

yes

1-3

TL

yes

yes

yes

Coupled heat/flow

Fractured mediawith matrix diffusion

Radioactiveproduction

Integrateddischarge

Efficient formultiple runs

no

maybe

no

under dev.

yes

yes

yes, 10member chains

yes

yes

yes

yes

yes

no yes yes

and hydrodynamic effects. Previous parametric studies of the effects of slowchemical reactions on integrated radionuclide sorption should be extended toother time-dependent phenomena such as changes in sorption capacities of therocks along flow paths or ground water evolution.

Available thermodynamic data, theoretical models and codes should be usedto gain insight onto potential variations in sorption behavior due to thepresence of competing cations and complexing ligands produced by dissolutionof non-radioactive components of the repository system (eg. canister,concreteand other sealing materials). This assessment should be made within thecontext of the behavior of the whole repository system and consider thebehavior of all system components. The required level of precision ofthermochemical data should be assessed by sensitivity analyses in geochemicalcalculations.

The results of these sensitivity studies should be used to obtain criteriafor future DOE and NRC experiments. Experimental efforts should be initiatedto examine mineral surfaces present in batch and column sorption experimentsto determine if sample preparation techniques and water-rock equilibrationtechniques produce substrates that are relevant to natural conditions or atleast produce conservative sorption data.

Mid-term activities: (3-7 years)

At the present time there are no robust theoretical models nor fundamental datathat can be used to predict the sorption of radionuclides onto rocks such astuff or basalt. In the mid-term, experimental efforts should be focused tounderstand a single well-defined nuclide/rock system under site-specifichydrochemical conditions. The data and model obtained from this investigationcan be used in sensitivity calculations. For example, the Integrated dischargecalculated with the data in a coupled speciation/transport code could becompared to that calculated with a retardation factor in a code such asNWFT/DVM or SWIFT. Such a comparison could give insight into the degree ofgeochemical complexity that must be represented in performance assessmentcalculations. Measurement of geometric factors for diffusion equations infractured or porous rock could be carried out at this stage. Such data could beused in support of calculations of matrix diffusion and in comparisons ofretardation factors obtained in column and batch tests.

Long-term studies (7-25 years):

Comprehensive studies of radionuclide sorption onto natural materials should becarried out. These projects should provide a theoretical basis for descriptionof nuclide/rock interactions in both dilute and saline waters. Identificationof sorbing species and elucidation of mechanisms of nuclide/rock reactionsshould be attempted. Fully-coupled speciation/transport codes that canrepresent all important processes (including radioactive production and decav)and that can be run efficiently in sensitivity studies should be written.

!

APPENDIX B

Preliminary Geologic Description for the GeochemicalSensitivity Analysis of a Basalt Site

Basalt Site

The geology and hydrology of the basalt site are based on thoseof the Pasco Basin in the Columbia Plateau (Figure B-1).Stratigraphic data for the site are based on lithologic logsfrom drill holes primarily within the Hanford Reservation(HR). Hydrologic data are from several test wells throughoutthe HR and primarily those at and near the reference repositorylocation (RRL). Potentiometric maps have been generated byseveral modeling efforts. As a result of the assumptions madeabout the flow system for the models and the uncertainties inthe data, none of the generated flow patterns has received aconsensus of acceptance. The flow pattern used in this studyis the result of regional and local models of the sitedeveloped by SNLA (Bonano and others, in preparation). Data onrock properties are either from the literature or assumedvalues.

StratigraPhy

Basaltic lava flows in the Pasco Basin are of Tertiary age(Figure B-2). Overlying the basaltic flows are Pliocene andPleistocene sedimentary units. When the time interval betweensubsequent lava flows was sufficiently long, sediments weredeposited on one flow and eventually overlain by a later flow.As a result, sedimentary interbeds occasionally occur in thesequence of basaltic lava flows (Figure B-2).

In addition to providing time for sediments to be deposited.the time intervals between lava flows can allow for varyingamounts of erosion. The extrusion of a liquid lava onto anerosion surface can result in considerable variation inthickness of the flow upon cooling.

As the liquid lava cools, a crust of solidified lava formswherever the lava is in contact with cooler material, eitherair or underlying rock. If movement of the flow occurs duringcooling, the crust that forms on the flow surface can break upto form a flow-top breccia. This breccia can range from acouple to tens of feet thick.

Once the lava solidifies, continued cooling results in theformation of extension fractures. These fractures typicallyare vertical and intersect to define generally irregularlyshaped, polygonal columns. The fracture density generallyvaries with different zones in the flow. In addition, thefracture pattern may be fan-shaped. Horizontal coolingfractures also occur in addition to the vertical fractures.

a - a

Figure B-1. Location of Columbia Plateau, Pasco Basin,and Reference Repository Location (DOE, 1982).

NINERR SEQUENCE

*EOLOOICMAPPINGSYMBOL / SIIDIMEN?

BThAIOATPNRIIOR BASALT FLOWS ''I

�r44

. I

V

41K

C

I

AUFlCOA; NITTS

ad

G6. GMf

old

ace

ILOKSS

SAND DUNMES

ALLUVIUM AND ALLUVIAL 1*A4S

IANDOSLIOES

TALUS

COLLUVIUM

IOUCHET BEDS' 011111,101

I

TICT*.

MIDDLE RIN0GiLD~LOWER RINGOLD FANGLOME RATE

RAA INGOLD

F-leg

c

c-,04

CLC,

0,

ai

Iia

xIDU

aV

I

I

IL5

10.1

tZ.0

135a

ELf EHAtMOUNTAINMEMBER

Tolw 1M-2

ICE NARBORMEMBER

t.I

POMONAMEMBER

VP Ta2I To,

ESOUATZELMEMItEt To. *{ Tm1

UPPER GABLE MOUNTAIN FLOW

CABLE MOUNTAIN INTERBED

LOWER GABLE MOUNTAIN FLOW

a

1I

I.1

TIN

*ib

COLO CRtEEK INTERNEDALSOTW MEMBER to HUNtTZING11 LLow

WILBUR CREEK MEMBER T" WA LLUKE fLOW

t~~~l^TIU z~ ~~ Tu. SILLUSI FLOWUMATILLA To U rAowMEMBER UMTLAFO

MABTON INTERBED

PRIEST RAPIOS t JP., LOLO FLOWMEMBER Tp,, ROSALIA FLOWS

OUINCT WITERBED

j 2 UrPIR R07A FLCWROZA MEMBER t,

T. LOA41 ROZA FLOW

SOU W CREER INTEREISD

RENI4MAN h T TOO AP"RIC FLOWS

VANI AGE INTERhED

UNDiOf ERENTIATfED fLOtW

ROCK V COULEE FLOW

UbhMEDFL*OWSENTINEL BLUFFS Elb CO.ASSfT1 FLOWSEOLENCE

UNDIFFERENTIATEO FLOWS

McCOY CANYON FLOW

INthTERME DIATE I My f LOW

z

2a1IIK

0a

K

LEVEY INTERBED

UPPER CELEPNANT MOUNTAIN FLOW

LOWER ELEPH4ANT MOUNTAIN FLOW

RAtTLISNAKE RIDGE INTERBEO

UPPER POMONA FLOW I

LOWER POMONA FLOW ISELAH ISTERiBEC

GOOSE ISLAND FLOW

MARTINDALE FLOWBSIN CITY FLOW

i

I, &C"WANASEOUENCE

LOW Mg FLOW ABOVE UM7ANUM

UMITANUM FLOW

HIGH Mg FLOWS BELOW UITANUM

VERY HOtG"t Mg FLOW

1s

Is I 4 T LEAST 30 LOW Mg FLOWSRCPBIOB IG

*Proposed host unit for repositoryFigure B-2. Stratigraphic units present in Pasco Basin and

proposed host unit for repository (after DOE,1984).

Regional Ground-Water Flow

The ground-water flow pattern used in this study was determinedfrom the modeling portion of the SNLA basalt methodologydevelopment project. Whereas the DOE model has lateral flowfrom the area of the RRL toward the southeast (DOE. 1984). thepreliminary run of the SNLA model has flow from the RRL towardthe northwest where Grande Ronde basalt outcrops are exposedalong the Columbia River. The horizontal segments of the flowpaths for both the DOE and SNLA models are greater than 5km,which is considered to be the distance to the accessibleenvironment.

Based on the boundary conditions and hydrologic properties ofthe units in-sthe SNLA model, the vertical hydraulic gradient atthe RRL was determined to be upward. Well data at and near theRRL in general agree with the upward gradient, although onedrill hole (RRL-14) has a downward gradient in the Grande Rondebasalt and another (DC-16A) has no gradient in the Grande Ronde(DOE, 1984. Table 6-5). A summary of the gradients in otherdrill holes is presented in Guzowski and others (1982).

Although the flow pattern determined by the SNLA model ispreliminary and the model was not calibrated, futurerefinements of rock properties are not expected tosubstantially change the overall pattern. The inclusion oflarge-scale structural features in the model may result indifferent flow patterns. Because the results are preliminary,potentiometric maps are not available for distribution orcitation at this time.

Geologic Setting and Relationship to Release Scenarios

The basalt site is located in a structural basin within theColumbia Plateau. This plateau is the result of anaccumulation of flood basalts erupted from earlier than 16.5 myago until approximately 8.5 my ago (Myers and others, 1979).Low heat flow and the isolation of the plateau fromcontemporary igneous provinces suggest that renewed volcanismin the Pasco Basin is unlikely.

Regional compression deformed the plateau into a series ofanticlines and synclines (Figure B-3). Most of this activityoccurred from the Miocene and into the late Cenozoic (DOE.1984). Whereas the Pasco Basin presently is undergoingnonuniform compression, the amount is extremely small (Savageand others. 1981).

"-

Figure B-3. Large-scale folds in the Pasco Basin (DOE, 1984).

Natural gas was produced from an interbed in the basaltsequence at the Rattlesnake Hills during the 1920's and early1930's. Shell Oil Company has drilled or planned to drillalong anticlines to determine the energy potential of thesediments beneath the basalts (McCaslin. 1981). Futuredrilling will depend on the costs of various energy resourcesand the results of exploration.

The Pasco Basin was not glaciated in Pleistocene time.Predictions as to the possibility of renewed glacial climateand the extent of future glaciers are complicated by theincrease of carbon dioxide in the atmosphere and the resultant"greenhouse effect" caused by the burning of hydrocarbons.During the Pleistocene, the Pasco Basin was subjected toflooding because of the melting of glaciers. Renewedglaciation of similar extent to the previous glaciationprobably would subject the basin to renewed flooding. One ofthe effects of this flooding could be rerouting of the ColumbiaRiver.

A preliminary set of release scenarios was developed for arepository site in the Columbia Plateau by Hunter (1983).

Host Unit

In this study, the repository is assumed to be in the denseinterior of the Cohassett basalt. The initial run of the SNLAmodel had the flow interior divided into two layers with theradionuclide release point in the upper layer. For thisreason, the top of the canisters are assumed to be at themidpoint of this upper layer.

Flow Path

The flow paths generated by both the SNLA and DOE (1984)modeling efforts result in radionuclide releases from therepository traveling upward to the flow-top breccia of the hostunit. After reaching the breccia, flow is lateral within thisbreccia to the accessible environment. Whereas the DOE flowmodel has lateral transport from the area of the RRL toward thesoutheast, the preliminary results of the SNLA model haslateral flow to the northwest. The upward hydraulic gradientat the RRL requires that releases from the canisters passthrough the backfill in the mined facility. To simplify theflow path, the backfill is not included in the calculations forthis report.

Figure B-4 illustrates the flow path used in this study, andTable B-1 contains the appropriate data.

Oeptj- ( ft)PcO Ck T

(

(

Rock �

unitW.-Z

r

L3

C ohast

L2

Dense Basalt

(

Li

cohassett

3250*

F ig u r e 3- 4 . 4 S c h e m a ~t i c r e p r e s e n t a t i o O f S JLA - d e t e r m i e d f l o w , a i o a a t S t

( ( I O' ,

4

Table B-1. Data for DOE and SNLA Plow Paths, Basalt Site.

Leg Length Gradient Porosity Nydraulic ConductivityIe* Rock T I (ft)Y e if.____ __tb Dit.-I Ref. |.. DIl Ref. I Dist. I Ref.I

I I I I ~I I I I I I I I I I I I I| Li | Repository g 1 1 0 jc | d | NA | 73-3-13-2 I 1 I U | (13-7-l1-211 e I W I f I1 33-8-38-O0l e I LU I f II I(Basalt)I I I I (0.18)31 1 1 1 1 1 1 1 1 1 I

|L2 |Dense e 85-124 | 2 | U |73-3-13-2 1 | U I mlE-7-19-611 h I LU | 3 13R-8-3-61 3 | LU |llI |lBasalt | (21.8) | | | (0.18) | | | (13-3) 1 I ' | (1.1r-6) | I I II I I . I I I I I I I I I I I I I I| L3 IBreeclated 1.6434 | J I NA 1IE-4-13-3 1 I U |INh-4-18-211 h I W I f 13R-3-30 lbh | LU | 1II | Basalt I I I 1 (1.49-3)1 1 |(13-3) | | | I(5.2) 1 1 1

_ _ _ _ _ _ _ .1 _ _ _ _ _ _ _ _ . ... ... . .. . I _ _ _ _ _ I _ _ _ _ _ _ _ _ I ... ... ... .I _ _ _ _ _ _ I _ _ _ _ _ _ _ _ I. ... ... ..I _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

a. ReFerences1. DOE, 19842. Cross, 19833. DOE, 1982

b. Distribution of DataNA - not applicableU - uniformLt - log normalLU - log uniform

c. 11 - assumed values, seeRef. column for explanation

4. assumed length of canisters

a. repository Is hypothetical,assumed properties are fullrange of dense and brecciated basalt

f. type of distribution is not known,can be varied In sensitivity analysis

J. equivalent to 5 kmdistance to accessibleenvironment

g. () - Input into or results frompreliminary run of SELAbasalt methodology

h. These values estimated fromthe relationship betweenporosity (Leonhart and others,1982) and conductivity (DOE, 1982)for the McCoy Canyon flow top

I. distribution assumed same asfor porosity because of closerelationship between porosityand conductivity (see Note h).

(

I

Mineralogy of Rock Types

Table B-2 lists the modal mineralogy of nine samples ofCohassett flow interior from drill hole RRL-2 (Figure B-5).Whereas the samples are differentiated with respect to beingfrom the colonnade or from the entablature portion of the flow,this distinction is not practical at this point in the siteanalysis. Table B-3 lists the relative percent of minerals infractures for samples of Cohasset flow interior from RRL-2.Table B-4 lists the estimated volume percent of the minerals infractures for samples from RRL-2. This estimated volumepercent is based on the volume percent of the minerals infractures, the mean width of the fractures, and the estimatednumber of fractures per unit volume of the Cohassett basalt.

No data are available for the-mineralogy of the flow-topbreccia. Because the breccia was exposed to weathering at thesurface after deposition and because the relatively highporosity has allowed large volumes of ground water to flowthrough the pores since burial, the breccia should be morehighly altered than the flow interior. Use of the samemineralogy as the flow interior will underestimate the amountsof minerals that can cause retardation of radionuclides.

Table B-2. Modal mineralogy of Cohassett basalt basedon nine samples from drill hole RRL-2 (datafrom Long, 1983).

Mineral/Component

Plagioclase

Pyroxene

Hesostasis

Fe-Ti Oxide

Apatite

AlterationProducts a

Others

Sulfide Blebs

I Col

138.38 -

123.50 -

120.37 -

1 2.38 -

1 0.45 -

II 1.80 -I 0.63 -

I Tr -

onrnade

45.38

28.28

29.03

3.50

1.13

7.401.93

0.13

.Total| Entablature | RangeI I

129.38 - 36.77 1 29.38 - 45.38I I113.10 - 19.50 I 13.10 - 28.28

136.03 - 50.20 I 20.37 - 50.20

1 2.28 - 3.13 1 2.28 - 3.50

| Trb _ 0.05 | Tr - 1.13

4.73 - 11.53 I 1.80 - 11.53Tr - 0.08 | Tr - 1.93

| Tr - 0.03 | Tr - 0.13I I

a. alteration product is clay, except for trace amounts of

a. alteration product is clay, except for trace amounts ofzeolite and silicon

b. Tr - Trace amount

ANFORD SITE r '*

.r-'""L. O ./, k

BOUDAR Ls OKA '

0055 4 REOIT

1, -e.UE'4Sq A4CI4'1 "

I @9812 ,. wEEENER

* DCC12 K 7ISO

!1 -- * - \

04 . 5 'u' *U ut..rrrr * D-1ItSH-l0 5*> i>- :IATTLE5NKEHILLS

LEGEND ,x, . t .,5 .... aja

* GAS WELL OD-

* REfERENCE REPOSITORY LOCATION BOREHOLES

=7 GENERALIZED OUTCAOP OF EASALT OUl..JWltHIN THE HANfORD SITE v

C=~~~~~~~~~~~~~~~~~~~C1

e s l Kt" | \SAW sum DRN9 4 L

.'~~~~ ~~~~~~~~~ . D __- %

Figure B-5. Location of key drill holes, Basalt WasteIsolation Project (DOE, 1982).

Table B-3. Relative percent infilling materialin fractures for samples of Cohassetbasalt from RRL-2 (after Long, 1983)

Volume %

Mean Fracture| Rock Type I Clay I Zeolite I Silica I Pyrite I Width (mm)

Entablature | 97 | 3.3 | 0.03 | 0.01 | 0.151 1 I I I I II Colonnade 88 o 10 I 1.8 I 0.4 1 0.12

I Overall l 89 I 9.3 1 1.2 I 0.2 I 0.13 I.1 1__ _ _ _ _ __ _ _ _ _ _ 1 1__ __ _ _ 1 1__ _ _ __ _ _ _ 1 _ _ _ _ _ __ _ _ _ _ _ _

Table B-4. Estimated volume percent of core comprisedof fractures and infilling material. Cohassetbasalt, drill hole RRL-2 (after Long, 1983)

Volume %

| Rock Type I Clay I Zeolitel Silica I Pyrite I Total

| Entablature | 0.21 I 0.007 1 0.0001 1 0.000021 0.22 II I I I 1 1 II Colonnade I 0.088 I 0.01 I 0.0018 I 0.0004 I 0.10 I

I Overall 1 0.12 I 0.012 1 0.0016 1 0.000031 0.13 1I _ _ _ _ _ I _ _ _ , _ _ _ _ _ _ _ _ _

References

Bonano. E. J.. Brinster. K. F., Updegraff. C. D.. Beyeler.W. E.. Davis, P. A.. Shepherd. E. R., Tilton, L. M.. andShipers. L. R.. in preparation. Performance assessmentmethodology for a high-level waste repository in basalt:Sandia National Laboratories.

Cross. R. W., 1983. Deep borehole stratigraphic correlationcharts and structure cross sections: Rockwell HanfordOperations. Rept. SD-BWI-DP-035. 142 p.

Department of Energy, 1982. Site characterization report forthe Basalt Waste Isolation Project. Volume 1: U.S. Dept.of Energy. Rept. DOE/RL-82-3 vol. 1. variously paginated.

Department of Energy. 1964. Draft environmental assessment:Reference repository location. Hanford Site, Washington:U.S. Dept. of Energy, Rept. DOE/RW-0017. variously paginated.

DOE, 1982 - See Department of Energy. 1982

DOE. 1984 - See Department of Energy, 1984

Guzowski. R. V., Nimick. F. B.. and Muller. A. B.. 1982.Repository site definition in basalt: Pasco Basin.Washington: U.S. Nuclear Regulatory Commission. Rept.NUREG/CR-2352 (SAND81-2088), variously paginated.

Hunter, R. L., 1983. Preliminary scenarios for the release ofradioactive waste from a hypothetical repository in basaltof the Columbia Plateau: Sandia National Laboratories.Rept. SANDB3-1342 (NUREG/CR-3353). 75 p.

Leonhart. L. S.. Jackson. R. L., Graham. D. L.. Thompson, G. M..and Gelhar, L. W.. 1982. Groundwater flow and transportcharacteristics of flood basalts as determined from tracerexperiments: Rockwell Hanford Operations, Rept.RHO-BW-SA-220 P. 13 p.

Long, P. E.. 1983. Repository horizon identification report.Draft. Volume 1: Rockwell Hanford Operations. Rept.5D-BWI-TY-OO1. variously paginated.

Loo, W. W., Arnett. R. C., Leonhart. L. S., Luttrell, S. P.,Wang. I-S. and McSpadden, W. R.. 1984, Effective porositiesof basalt: A technical basis for values and probabilitydistributions used in preliminary performance assessments:Rockwell Hanford Operations. Rept. SD-BWI-TI-254. 67 p.

McCaslin. J. C.. 1981. Shell slates three wildcats inWashington: Oil and Gas Jour.. v. 79, no. 24, p. 177-178.

Myers. C. W. and others. 1979. Geologic studies of the ColumbiaPlateau: A status report: Rockwell Hanford Operations.Rept. RHO-BWI-ST-4, 502 p.

Savage. J. C.. Lisowski. M.. and Prescott. W. H., 1981, Geodeticstrain measurements in Washington: Jour. Geophys. Research.v. 86. no. B6, p. 4929-4940.