Download WIPP Repository: Geology, Hydrology, and Radionuclide Transport and more Study notes Chemistry in PDF only on Docsity!
SANDIA REPORT
SAND92-0700/2 l UC-
Unlimited Release
Printed December 1992
Preliminary Performance Assessment for the
Waste Isolation Pilot Plant, December 1992
Volume 2: Technical Basis
WIPP Performance Assessment Department
Prepared by Sandia National Laboratories Albuquerque, New Mexico 87185 and Livermore, California 94550 for the United States Department of Energy under Contract DE-AC04-76DPOO
SANDIA NATIONAL
LABORATORIES
TECHNICAL LIBRARY
SF29000(8-81)
Issued by Sandia National Laboratories, operated for the United States Denartment of Energy by Sandia Corporation. NOTICE: This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Govern- ment nor any agency thereof, nor any of their employees, nor any of their contractors, subcontractors, or their employees, makes any warranty, express or imnlied. or assumes anv leeal liabilitv or resnonsibilitv for the accuracv. compietenkss, or usefulness ;f any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government, any agency thereof or any of their contractors or subcontractors. The views and opinions expressed herein do not necessarily state or reflect those of the United States Government, any agency thereof or any of their contractors.
Printed in the United States of America. This report has been reproduced directly from the best available copy.
Available to DOE and DOE contractors from Office of Scientific and Technical Information PO Box 62 Oak Ridge, TN 37831 Prices available from (615) 5768401, FTS 626-
Available to the public from National Technical Information Service US Department of Commerce 5285 Port Royal Rd Springfield, VA 22161 NTIS price codes Printed copy: Al Microfiche copy: A
This volume of the report should be referenced as:
WIPP PA (Performance Assessment) Department. 1002. Preliminary Performance Assesment for the Waste Isolation Pilot Plant. December 1992 - Volume 2: Technical basis. SAND92-0700/2. Albuquerque, NM: Sandia National Laboratories.
ACKNOWLEDGMENTS
The Waste Isolation Pilot Plant (WIPP) Performance Assessment (PA) Dep‘artment is comprised of both Sandia National Laboratories (SNL) and contractor employees working as a team to produce preliminary
comparison with Environmental Protection Agency (EPA) regulations, assessments of overall long-term safety of
the repository, and interim IechnicaI guidance to the program. The on-site team, affiliations, and contributions to the l!H2 performance assessmentare listed in alphabetical order:
Assessment DenartmeM
Name R. Anderson B. B‘akcr J. Bean J. Berglund
S. Bertram-I-Iowery
W. Bcyeler
K. Brinster R. Blaine
T. Blaine
K. Byle J. Chapman D. Duncan K Economy D. Gallegos
D. Galsoll
J. Garner A. Gilkcy L. Gomcz M. Gmehel
R. Guzowski J. I-lehon
s. HOI-a l-l. Iuzzolino
R. Klert I’. Knupp M. LaVenue C. Leigh M. Marietta G. de Marsily R. McCurley B. Napier A. Pcccrson
Affil.’ SNL TEC UNM
SNL
SAI
SAI EC
GC
UNM TRI MAC EC SNL
GS
API UNM SNL TRl
SAI ASU
Ill-II- GC
SNL EC INr SNL SNL 1JP UNM I’NL SNL
Primary Author of Major Code
CUI’I‘INGS
PANEL. GARFIELD
PANEL
CCDFI’ERM
CCDFCAI,C, CCDI-I’ERM
SIXOTP GRASP-INV GENII-S
GENII
Area of Responsibility Department Manager SEC02D, Hydrology, Office Manager BRAGFLO, 2-Phase Flow Task Ldr., Cuttings/Cavings/SpaIlings, Engr. Mcch. PA Liaison with DOE, Criteria Document, Test Phase Plan Gcostatistics, Analytical Models, CAMCON Systems Codes C*ohydrology, Conceptual Models SEC02D, SECOTP, & CAMCON Systems COdCS Drilling Technology, Exposure Pathways Data Software and Analysis QA Documentation V. Data QA SEC02D, SECOTP, Hydrology & Transport Task Ldr., Hydrology, Geostatistics, NEA, PSAG NEA Working Groups, PSAG, PAAG, I-lum,an Intrusion Source Term, Sens. Anal. CAMCON Systems Codes Task Ldr., Safety Assessments EPA Regulations, Documentation V. 1, Editor v.l Geology, Scenario Construction Task I.dr., Uncert./Sens. Anal., Probability Models, Editor V. Expert Elicitation, Probability Models Ll-IS, CAMCON System Codes, Probability Models EPA Regulations Comp. Fluid Dyn. I-Iydrology/Geostatistics Exposure Pathways Dep. Dept. Manager, Tech. Coord. Geostatistics Expert Group Chair CAMCON System Codes S‘afcty Assessments Task Ldr., Inventory
.. 111
Acknowledgments
W. Wawersik SNL Fracturing S. Webb SNL^ 2-Phase Flow Sensitivity Analysis & Benchmarking
API = Applied Physics incorporated ASU = Arizona State LJnivcrsity BEC = Benchmark Environmenhl Colp. CON = Consultant DE = Drez Environmental ECO = Ecodynamics Resemch Assoeiatcs GC = Gcm-CentersIncorporated GRA = GRAM, hlC. GS = Galson Sciences INT = Inters MAC = MACTIX PNL = Pacific Northwest bbomtory
(^3) er Re view
Internal/S andia L. Gomez D. Schafer
ManagementlSandia w. Weart
PA Peer Review Panel R. I-lcath, Chair R. Budnitz T. Colton J. Mann T. Pigford F. Schwartz
Department of Energy R. Bcckcr
t ).^ nels
Futures M. Baram W. Bell G. Benforcl D. Chapman B. Cohen V. Fcrkiss T. Glickman T. Gordon C..Kirkworxl H. O[w:ly
RcS = RCSP SAI = Scientific Applications Intcmalional Corporation SNL = Sandia National Laboratories TEC = Technadync Engineering (hlsulklnts -I-RI = Tech Reps, Inc. UHH = University of Hawaii at Hilo UNM = University of Ncw Mexico/New Mexico Engineering Research Institute UP =^ University of Paris WEC =^ Westinghouse Electric Corporation
University of Washington Future Rcsourccs Associates, Inc. JK Research Associates, Inc. [Jnivcrsity of Illinois LJnivcrsityof California, Berkeley ohio Sta[e Univcrsily
Boston LJnivcrsity Yale LJnivcrsity University of California, Irvine The World Bank, Cornell University University of Pittsburgh Georgetown University Resources for the Future Futures Group Arizona State University Joint Rcse,arch Center (Ispra), Los Alamos National Laboratory
v
Acknowledgments
M. Pasqualetti D. Reichcr N. Rosenberg M. Singer T. Taylor M. Vinovskis
Markers D. Ast V. Baker M. Brill
F. Drake B. I:inney D. Givens W. Goodcnough M. Kaplan J. Lomberg L. Narens F. Newmeyer W. Sullivan W. Williams
Source Term C. Bruton I-Ming Chou D. Hobar[ F. Millcro
Retardation R. Dosch C. Novak M. Siegel
Gemtdtlst .’.. .ics Exo ert^ CrrouD
G. de Marsily, Chair R. Bras J. Carrera G. Dagan A. Galli S. Gorlick P. Grindrod A. Gu[jahr D. McLaughlin S. Neuman C. Ravennc Y. Ruhin
Arizona Sta~eUnivcrsily Natural Resources Defense Council Resources for the Future The Potomac Organization Consultant University of Michigm
Comcll University University of Arizona Buffalo Organization for Social and Technological Innovation Univcrsily of California at Santa Cruz University of 1Iawaii at Manoa Amcncan Anthropological Association University of Pennsylvania Eastern Research Group Consultant University of California at Irvine lJniversity of Washington University of Washington CasseWestcm Reserve University
Lawrence Livermorc National Laboratory U.S. Geological Survey Los Akunos National Laboratory LJniversity of Mi,ami
Sandia National Laboratories Sandia National Lahoralories Sandia Nalional Laboratories
(.J.of Paris Massachusetts Inst. of Tech. U. Polil&mica dc CalaMa Tcl Aviv U. Ecolc (lcs Mines de P,aris Stanford U. Intcra Sciences New Mexico Tech Massachusetts Inst. of Tech. U. of Arizona Inslilut Frnn;ais du PLtrole U. of California, Berkeley
vi
CONTENTS
Culebra Dolomite Mclnbcr .........................................................................2.l
Contents
6.1.7 Catcgorics of Distibu[iorls ........................................................................6. 6.1.7.1 Continuous Distributions ...................................................................& 6.1.7.2 Discrete Distributions ........................................................................ti 6.1.7.3 Constructed Distributions (Data) ..........................................................W 6.1.7.4 Construckxl Distributions (SubjccLivc) ..................................................W 6.1.7.5 Misccllanet~usC:lteg(Jrics...................................................................6- 6,2 Selection of ParamelcrDistributions ...................................................................... 6.2.1 Rcqucs[s for Data from S:lrldia Investigators and An:llysLs................................6- 6.2.2 Constructio no fDiskibutions ....................................................................6- 6.2.3 Some Limilalions on Distributions ............................................................. 6-
- ConsequcnceModcling ..............................................................................................7.l 7.1 Radioactive Decay ...............................................................................................7.l 7.2 Multiphase Flow Through Porous Media ................................................................7.l 7.2.1 Fe:itures:lndC:lpabili[iesofBWG~O ....................................................... 7- 7.2.2 Interaction of Important Rcposimry Processes ................................................7. 7.2.3 Gcncral Assumptions Usedin 1992PATwo-Pl]ase l;l(Jw M(tieling ...................7- 7.3 Wa$tc-lTillcdI<wlInI.)cfomalioll ...........................................................................7- 7.4 Was[c M{~hiliz.:lti(~ 11 .............................................................................................7. 7.4.1 Assulnpli(~ns...........................................................................................7- 7.4.2 Shnplitlcd Ma~cIn:][ic:ll Model ..................................................................7- 7.5 GroundwaterTransmissivityFickls ........................................................................7- 7.5.1 Unconditional Simulation ................... ......................................................7- 7.5.2 Conditional Simulation ............................................................................. 7- 7.5.3 Automated Calibraticm ..............................................................................7.ll 7.6 GroundwaterFlow andTransport ..........................................................................7- 7.6.1 GroundwatcrFlow in lhcCulcbra ................................................................ 7- 7.6.1.1 B()uIlda~C()l~diti(~tls......................................................................... 7- 7.6.1.2 Effects of Clima[e Cl~atlge..................................................................7.l 7.6.2 Solu[e Transport in Culebra .......................................................................7- 7.6.2.1 ModclingJ-IydrodynamicDispersion .....................................................7- 7.6.2.2 Mtdeli
gCl~emi~ll St[ioI] iI] Fracture Flows .....................................7- 7.7 Direc[Rcln{~val ~~fWas[e ..................................................................................... 7- 7.7.1 Cul[ings .................................................................................................7- 7.7.2 Cavings. .................................................................................................7. 7.7.2.1 Laminar Flow ..................................................................................7. 7.7.2.2 Turbulc[lt Flow ................................................................................ 7- 7.7.3 Spa]lings ................................................................................................ 7- - Refcn.mees: ...............................................................................................................8.l
AppcndixA: BllAGITl.O .wd P~EL ............................................................................ A-
AppendixB: SANCII() ...............................................................................................B.l
AppcndixC: SECO Flow and Transpor[ Model................................. ............................... C-
AppcndixD: (^) Culcbra Transmissivily Field Silnulations ....................................................D.l
Figures
1-1 (^) 19920rganization ofProgram sin(~AMCON ...........................................................1- 2-1 (^) Gtmcralizedgcology ofthc Dclawarc Basin, sl~(>wingti]el(xnti(>nofdwCapitan Rccfarld ticcrosi(>t~,ti limitsof ti]e basinal forln:lti(~lls.............................................. 2-2 (^) Geologic [imcscalc .................. .........................................................................2. 2-3 (^) Swaligrapl]y (JI’li]cl>l:lwarc BasilI ..........................................................................2- 24 Schematic cast-west cross scc[ion (hrough the northern Ddaw,arc Basin .......................... 2-
xi
Contents
2-2oa
Schematic north-south cross section through the northern IXlaware Basin 2-
Sources ofge(~logic inf()matiol~ ahuttie Culcbra Dolomite .......................................2-l
Isopachovcrburden forthe Culebra Dolomite Mclnkr .................................................2.2O
Potellti:~lscetl,viosf(~r tile WI1)Pdis~~sal sys[cln .......................................................4.
Idealiz.cdcollapsed WIPPpaIlel itla PANE1. mticl .....................................................7. Summary of Computer ModelslJsedinthc 1992 WIPPPerformanc cAsscssmen t............3-l
- Introduction 1-
- 1.1 Pu~secJf Vf)lutne 2 1-
- 1.2 Organiza(ionofVt}lwnc 2 1-
- 1.3 Ctie LinMgcand Dam~ow ................................................................................1- - 1.3.1 hmBa%s .............................................................................................. - 1.3.2 Program Linkageand Model Applications .....................................................
- 2.1 Introduction 2- 2. Conceptual Basis for Consequence Mdeling ..................................................................2.l - 2.1.1 Concepura lModels., ................................................................................2- - 2.1.2 ChaptcrOrg.wimtitJtl ................................................................................2-
- 2.2 Natural Barrier System .........................................................................................2. - 2.2.1 Regional Geology ....................................................................................2- - 2.2.2 Stratigraphy 2- - 2.2.2.1 Bell Canyon Formatio n....................................................................2- - 2.2.2.2 Cnpitan Limcstonc ............................................................................2.l - 2.2.2.4 .%lado Formation 2- 2.2.2.3 Castilc Forlnation .............................................................................2.ll - 2.2.2.5 Rustler-Sala(Jo Contact Zone ...............................................................2.l - 2.2.2.6 Rus[ler Formation 2- - The UnnamcdLowcrMcmber 2- - Culebra Dolomite Mclnbcr .........................................................................2.l - “~amariskMemlxx ....................................................................................2- - Magcnkl Dolomi[c Mc~nbcr .......................................................................2. - Forty -nincr Melnber 2- - 2.2.2.7 Supra-Rustler Rocks .........................................................................2. - 2.2.3 l.Iydrology ...............................................................................................2. - 2.2.3.1 Present Climate ................................................................................2. - 2.2.3.2 Paleoclimatcs and Climatic Variability 2- - 2.2.3.3 Surface Water ...................................................................................2. - 2.2.3.4 The WaterTahlc ...............................................................................2- - 2.2.3.5 Regiona lWalerBal,anc e.................................................................... 2- - 2.2.3.6 Groundwa[erFlow Above the Salado Formation .....................................2- - Polcnliomctic Surfaces .............................................................................2- - ReclmrgeandDi.sch,argc. ..............................................................2- Groundwater Gc()cllcrnistry .........................................................................2.M - 2.2.4 Radiolluclidc’~]nlls~)rl in tllc Culcbra ~lolnite ............................................2. - 2.2.4.1 Experl Judgment Elicitation for Kds ....................................................2. - Transport in tie Culebra ....................................................................2- 2.2.4.2 Planned and Ongoing Experimental Work Related to Radionuclide
- 2.3 Engineered Barrier Syslcm ....................................................................................2- - 2.3.1 llc Salado Fonnationat the Repository I[orizon ...........................................2- - 2.3.2 Repository and Seal Design ........................................................................2. - 2.3.2.1 Waslc Cl]aracterization .......................................................................2. - 2.3.2.2 Se:lls ..............................................................................................2- - 2.3.2.3 B:lckfill ...........................................................................................2. - 2,3.3 Mdiot~uclidc lnvcl]tory.............................................................................. 2- 2.3.2.4 Engineered Altcrl~atives ......................................................................2.SO - 2,3.4 Radionuclidc Solubilily and the Source Tcnn for Transport Calculations 2- - 2.3.4.1 ExpcrI .ludgmeat E1icit:l[i(Jll................................................................ 2- - 2.3.4.2 I~xpcrimcntidWork ...........................................................................2- - 2.3.5 Creep Closure, Fluid I:low, and Room/Waste Interactions 2- - 3.1 Conccptutiizalioll of Risk f(Jrtie WIPPPerfomance Assessment ...............................3- 3. Performance Assessment MWmdology .........................................................................3.l - 3.1.1 Calculation of l?isk .................................................................................3- - 3.1.2 Characlerizitio no fUnccWaintyinRisk ........................................................ - 3.1.3 Risk and the EPA Limits 3-
- 3.2 Selection ofScellmios 3- - 3.2.1 Conceptual BzsisforScentio Development ..................................................3- - 3.2.2 WIPPPcrfommce-Asscssment Appr~ch to SceI]wit) Development ..................3-l
- 3.3 Determination ofScen<ario Probabilities 3-
- 3.4 Calculatio nofScenarioConsequcnces ....................................................................3-
- 3.5 Monte Carlo Analysis Techniques ..........................................................................3.l - 3.5.1 Selection ofVariablesan(lTheirRanges and Distributions 3- - 3.5.3 Propagation ofthe Sample through the Analysis ............................................3- 3.5.2 Generation of the Sample ...........................................................................3.2l - 3.5.4 Unccrlainty Analysis 3- - 3.5.5 Sensitivity Anflysis 3-
- SccnarioConstruc[io n..............................................................................................4-
- 4.1 Evaluation ofEvcn[s and Processes ........................................................................4- - 4.1.1 Identifying Evet~ts~ld Pr~eses .................................................................4- - 4.1.2 Classifying Events and Processes 4- - 4.1.3 Screening Events and Pr(~cesses...................................................................4. - 4.1.4 Summary of Scrccned Events and Recesses ...................................................
- 4.2 Sum~Scenuios 4- - 4.2.1 Development of Summary Scenmios ............................................................ - 4.2.2 Screening ofSummary Scenarios 4- - 4.2.3.1 U1ldisturbd Su~n~Sccn~~(.$B) 4- 4.2.3 Retained Summary Scenarios ......................................................................4.lO - B.me.C~w Destiption ...............................................................................4- Guidance from40CFR 191 4-1o - 4.2.3.2 I-Iulnal~-I[~[rusioll Summary Scetl.wios ...................................................4.l - Guidmcefrom40CFR 191 .......................................................................4- - Brine in the Castilc Formation (Summary Sccnario El) ...........................4-l Intrusion Borehole through a Room or Drift into Pressurized - Intrusion Borchole into a Room or Drift (Summary Scenario E2) ......................4- - into the Same Panel (Summary Sccnario ElE2) .....................................4- BrineintheCastile Formationand Anofher IntrusionBorehole - 4.2.4 Compu[atitJnal Approximations of Sccntios El, E2, and ElE2 ........................4-l
- Drilling Intrusion Probabilities ...................................................................................5-
- 5.1 Introduction ......................................................................................................5-
- 5.2 Probability Cmnputations ..................................................................................5-
- 5.3 LmWFut]ctiO1lG eI]eratiO1~....” ............................................................................5- - 5.3.1 The Expert Judgment Process 5- - 5.3.2 Algoritlun forGcneraling Lambda Functions 5- - 5.3.3 lJscoflhe Lambda Functicms .....................................................................5-
- 6.1 Conventions ......................................................................................................6- 6. Data and CDFs .........................................................................................................&l - 6.1.1 Probability Distribution Functions 6- - 6.1.2 Empirical Distribution Functions ................................................................6- - 6.1.3 ~~ge 6- - 6.1.4 Mean and Sample Mean .............................................................................6. - 6.1.5 Mcdi,anand Sample Median ........................................................................6- - 6.1.6 Variance and Coefficient ofVariation ...........................................................6-
- 2-
- 2- 2-1o
- 2-
- 2-
- 2-
- 2-
- 2-
- 2-
- 2-
- 2-
- 2- 2-20b
- 2-
- 3-
- 3-
- 3-
- 3-
- 3-
- 3-
- 3-
- 3-
- 4-
- 4-
- 4-
- 5-
- 7-
- 7-
- 7-
- 7-
- 7-
- 7-
- 2-
- 3-
- 4-
- 4- - Schematic north-south cross section through the northern IXlaware Basin 2- - Boundary”), the study area of Brinstcr, and the location of observation wells 2- Map of the WIPP vicini[y showing the land-withdrawal area (labeled “WIPP - NeRed Be&s...................................................................................................2.l East-west cross section showing stratigraphy of the Rustler Formation and the Dewey - Rustler Foma[i(Jn halitcmt)undtllc WIPP ................................................................2.l - Log hydraulic conductivities of the Culcbra Dolomite Member of the Rustler Formation 2- - Sources ofge(~logic inf()matiol~ ahuttie Culcbra Dolomite .......................................2-l - Percentage of natural fractures in the Culcbra Dolomite Member filled with gypsum 2- Inte~rcted extent t)f Sdadodiss()lution .....................................................................2.2l - Log hydraulic conductivities of Ihc Magenta Dolomi(e Member of the Rustler Formation.. 2- - mdHoloccne 2- EstimaKxl mean annual precipitation at the WIPP during the Lute I’lcistocene - Adjusted polenliomelric surface of the Rusllcr-Salado Conklct zone in the WIPP vicinity 2- - Formation in the WIPP vicillity ............................................................................2. Adjusted potcntiomelric surface 01 the Culebra Dolomite Member of the Rustler - Formation in the WIPP vici[]i[y 2- Adjusted potcntiomctric surface of the Magenta Dolomite Member of the Rustler - Hydrochcmical Iacics in [he Culcbra Dolomite Member O! the Rustter Formation 2- - Rcfcrence lwtis~:I[igrapl~ yIle:~rrcpsitory ...............................................................2. - Plan view of waste-disposal horizon showing shaf~ drift, and panel seal locations 2- Stratigraphy at (he repository l)()riz()n.......................................................................2.U - Rcprcsentativc shaftamlplugscals 2- - ~tim:lted CCD17for consequence resul[cS ..............................................................3. - Example distribution of CCDFS oh[tincd by sampling imprecisely known variables 3- - Example summary curves derived from an estima[cd distribution of CCDFS 3- - Construction of a CCDF for comparison with the EPA release limils ............................3- Decom~sitionof thesamplc spaceSintohigh-level subseK .......................................3-lO - Models userlin 1992WIPP perfonnar~ce xssessmcnt ...................................................3.l - Distribution function for an imprecisely known analysis variable ..................................3- - Example of box plf~ts............................................................................................ 3- - Potellti:~lscetl,viosf(~r tile WI1)Pdis
sal sys[cln .......................................................4. - Conceptual model used in simulating undisturbed pcrfonnancc 4- - Conceptual model for scen,ario El ............................................................................4.l - Conceptual model for scen,ario E2 ............................................................................4.l - Conceptual ln(tiel forscentio l?lE2 ........................................................................4.l - drilling in[cnsity as functions of lime.. 5- A realization of cffeclive drilling in[ensity k(t) and i[s associated integrated effective - Interaction of some important repository processes ..................................................... - ofgasprNuced andti~nc M[ersctiillg 7- Surface giving porosity of waste-filled disposal room as a function of Iolal volume - Idealiz.cdcollapsed WIPPpaIlel itla PANE1. mticl .....................................................7. - Conceptual hydrologic model of the Culcbra Dolomite Member ....................................7- - calculatiotls 7- Example of regional and local grids used for disturbed Iluid flow and transport - R()tiilli[~g .....................................................................................................7. - Properties of the Rustler Forma(ion UniL$and Rustler-Salado Contact Zone 2- Tables - Summary of Computer ModelslJsedinthc 1992 WIPPPerformanc cAsscssmen t............3-l - P()tetlli:llly l>isruptivc Evcllts wld I>r(Ncsscs..............................................................4. - Summary of Screened Events and l]rocesses ...............................................................4.
Chapter 1. Introduction
1 2 3 4 5 6 7 8 9
10 11 12 13 14 15 16
17 18 19
20
21
22
23 24 25 26 27 28
29 30 31 32
33 34 35 36
PA, presents an ou[linc of the Momc Carlo technique that is used for uncertainly and scmsitivily analyses, and discusses the ccmstruclion of complemcnlruy cumulative distribution func[ions (CCDFS). This chapter is a detailed expansion of Chapter 4 of Volume 1, and is generally unchanged from the 1991 PA.
l Chapter 4 (Scenario Construction) exarnincs the fiist element (scenarios) of the conceptual model for risk. This chapter discusses the application of the methodology for scenario construction-identifying, screening, and classifying events and processes; developing scenarios using a logic diagram; and screening of sccrmrios —for the W IPP. Retained scenarios that are analyzed in the 1992 PA arc dcscribcd. ‘1’hismaterial is genemlly unchanged from the 1991 PA and therefore refercoccs previous documents extensively. Scenarios included in the Monte Carlo analysis in 1991 are included tigain in 1992.
l Chapter 5 (Drilling lnlrusion Probabilities) examines the second clement (probabilities or frequencies of sccn,arios) of the conceptual model for risk. The probability model that is used for the 1992 analysis was presented in the 1991 documcnmtion. so this chapter is a much briefer description that references previous documentation. The significant difference in the application of this model is that time-varying drilling intensities were used in 1992, whereas in 1991 only constant, but imprecisely known, drilling intensities were used. A brief discussion of how these ncw drilling intensity functions were derived from expert panel mrlput that rcfcrcnces malerial in Volume 3 is included.
l Chapter 6 (Data and cdfs) begins the dcscripticm of the tliffcrent steps of the Monte Carlo technique: selection of imprecisely known par,amctcrs, construc~ion of ranges and distributions for these parameters, generation of the s:unplc, propagation of uncertainly through the sys[em model, uncertainty analysis, and sensitivity analysis. This chnpler briefly describes the first steps: selection of imprecisely known parameters and construction of their ranges and distributions. “~he cnlirc^ Ma^ base, especially^ model parameters, is the subject of Volume 3.
l Chapter 7 (Consequence Modeling) describes the modeling system that is USC(Ito calcula[c consequences of scenarios. The 1.atin hypercubc s:unpling technique that is USC(Ito generate the sample for Monte Carlo anal ysis is dcscribcd elsewhere (1-lelton ct al., 1991) and is not repeated. ~lis chapter focuses on the 1992 modeling sysmn [hrough which umcr(ain[y is propagated for the uncer[.ain[yad sensitivity analysis. Each major module of Ibis sys[em is described in terms of governing equations ,and modeling assumptions. More detailed CO(ICdescriptions arc conktincd in the four appendices M follows:
Appendix A. A repository and shaft seal mmluh! is used that simulates two-phase (gas and brine) flow through the repository, sh,aftseals, and surrounding environs (BRAGFLO) with an equilibrium- mixing cell for calculating radionuclide concentrations in the brine phase (PANEL). These codes were used in the 1991 PA.
Appendix B. A module (SANCHO) for simulating quasislatic, large-deformation, inelastic response of the halilc is used to provide waste porosily as a function of time. These calculations incorporate the effect of creep closure and of halite response to waste-genernlecl gas into the PA; they arc Performed ou[sidc UNMomc Carlo analysis. Only [he waste porosity functions are used during
1-
Organization of Volume 2
1 consequence calculations. This is the first year lhal the cffecls of halite creep have been 2 incluckxfin PA calculations.
3 4 5 6 7 8 9
10 11
Appendix C. Groundwatcr flow and fransport models (SECO-2D1-I and SECO-TP) are usc(f to calculate suhsurlacc transport through the Culcbra Ilolomitc Member of the Rustler Formation to fhc Lmd-widldrawal bound,ary. Fkst, the groundwatcr flow is calculated for a single-porosity, matrix-only, porous mcxlium (dolomite). lle flow calculation is performed first on a regional scale and second on a local scale with boundary conditions derived from the regional-scale distribution. Clima[c variability enters through time-varying boundary conditions fha[ <arc bused oa a simple prccipi[a[ion/recharge concept ualization. Spalial variability enters by drawing one IIcld Irom a set of mul[iplc, plausible frausmissivily fields that are gcncratcd outsiclc Ihc Monte C:U1Oanalysis (CJRASP-INV). SECO-2DH was used in the 1991 PA.
12 Second, the flow field is USC(Jfor a r~dif)l~uclide-ral~s~~rtsimulation. The fransport simulalor 13 SECO-TP was used for [he first time in 1992. It models singie- or Uual-porosily transport 14 through an idcalizuf, frticturcd medium. Rctar(lation in pore volume of fhc dolomilc matrix 15 and/or the fmcturc-lining clay can be included simultaneously or sepamtely. SECO-TP is a 16 furlhcr improvement over previous capability in that it is more accurate and numerically 17 cff’icicnl,allowing Iligller-resoluliotl, higher-accuracy simulations in the sarnc time.
18 19 20 21 22 23 24 25
26
Appendix D. A module (GRASP-lNV) for gcnma[ing multiple, plausible mansmissivi[y fields m be used by SEC02-DH is uscxffor the firsl time in 1992. ‘1’hismodule is an improvement over previous qxhili(y in lh:i[ it produces Wmsmissivily fickts lha[ reproduce [k measured vafucs of transmissivity at well locations and that ,arccalibra[cd, i.e., flow calculations with these fields rcproducc ([o within a prc-selected criterion) sfcady-state and fransicnt pressure data at the well locations. lhcrcforc, each field is a plausible rcali?.ation of the true but unknown transmissivity field. One en[ire field is drawn and used for a single consequence calculation during the Monle (klo anafysis.
1.3 Code Linkage and Data Flow
27 The complexity of’ [lw compliance-assessment modeling systcm for [hc WIPP requires that calculations be 28 confrollcd by an cxccutivc program (Rcchard, 1989; Rcchard et al., 1989;^ Rechard,^ 1992).^ CAMCON 29 (Compliance Assessmcnl Mcfhodology Controller) con[rols CO(IClinkage and data flow during lengthy and 30 itemtivc consequence analyses, minimizes analyst inkrvcnfion during dam transfer, and automatically handles 31 quality assurance during [he calculations. CAMCON currently consis[s of about 75 codes and FORTRAN object 32 Iibrarics; i[ includes approximatc]y 293,000 Iincs of FORTRAN sotlware written specifically for the WIPP 33 Project and another 175,000 lines of’sotlwarc adapwf from other applicat ions.
34 The con[rollcr allows easy cx:unination of intcnnediatc diagnostics and final results. Computer modules 35 within the cxccu[ivc progr:un can bc easily rcplaccxf for model comparisons. CAMCON moduku’izcs tasks so
36 computer programs for n particular module arc intcrchangtzrble. CAMCON is Iully dcscribcd in Rechard (1992).
1-
Code Linkage and Data Flow Program Linkage and Model Applications
~etiiitotii ~
Shaft ~ Modeling l , :
General Task Description A
CAMCON Modules*
Ground water Cuttings Model and Flow and Modeling^ Parameter Transport SelectIon Culebra : Modeling l *****
I I^ .%lecl Sconan09 Sk.)^1
I
Mo~l COnc@uahzat,On (Dsposal System and f%.gmnal CharactenzatlOn and Scenano oev.~ment (S$)) I
I
(Conceptual Model Uncertatmy) (^) I
Data Base^ +
.... t. Meshk Getwratlon t
I
I I I I ph. I”SDBFIk I
AwgnOata(r+) ard
II
I
Parameters with ALGEBRA (^) I (^1) Ill
Q
setMakmal Propertms wth P1oporly MATSET,^ BCSET,^ ICSET I %1 Matertal I
GenerateWaste Porosfly Funti,on
wth SANCHO Y
A!trlbules wrlh GRIDGEOS
Compute Cede Parameters wkh ALGEBRA
I I Gmerate Comhonally !3mulated and CalbratOc Transmtsswny FBlds .smg GRASP II
I
Evaluate Gas Germratmn : Evaluate %gtonal and %na and Gas Fbw and L@al Culebra wflh BRAGFLO Flwd Flow wth SECO 2D
l Cedes from lhn SUKXMI and UtIIIty Mcdubs Are Used throqhou! Calculations Ground^ I Water Flow
I
Repositoryt i
t Transport i
CompharceI
I t SIalfitlcal i
.+ Ahfmugh Twcal Cedes Sfwwn, C+fwr Co&s from CAMCON Modubs May Se Used, Furthermore, Translators Necessary for several Codes COns&nceModalmg Have Been Ommod F,(q( k))
1 I :1 ReIme Calcubtlon^ I
Y
Evaluate Removal of Cbmgs With CUITINGS
}- Gwwrate DrIlhmJ (^) Evaluate ScOnar!o Prcb. Intensny (^) ab,lflms Wldl CCOFCALC
. I
P,obabMy^4 Mo&ahw P(S+(XJ) T Regulatory^4 Compllame Assessment t Smsrwwy^4 Analysts
t m TRI.6342.56.
Figure 1-1. 1992 Organim[ion of Programs in CAMCON (after Rechard,^ 1992).
1-
2 2.1 Introduction
3 2.1.1 Conceptual Models
4 This chapter describes the conceptual basis for modeling the performance of the WIPP repository, the waste it (^5) contains, and the surrounding geology and hydrology, and summarizes the available knowledge of the site and the 6 physicat processes that operate there. This knowledge forms the framework for the preferred conccphral model (^7) used in WIPP PA (i.e., the model bclicvcd by the WIPP PA Department to be the most realistic representation for 8 the behavior of the disposal system), and for allcmative conceptual models. Conceptual model and alternative 9 conceptual models are defined M follows (Gtillcgos et al., 1992; NEA, 1992):
10 l Conceptual model: A set of qualitative assumptions u.scd to describe a system or subsystem for a given
11 purpose. At a minimum, these assumptions concern the geometry and dimensionality of the system,
12 initial and boundary^ conditions,^ time dependence, and the nature of the relevant physical and chemical
13 processes.^ The assumptions^ should be consistent with one another and with existing information^ within
14 the context of the given purpose.
15 l Alternative conceptual models: Alternative sets of assumptions that describe the same system for the same
16 purpose, where each set of assumptions is consistent with the existing information.
17 Each alternative conceptual model identifies the processes that the mathematical models must characterize and
18 provides the comext within which the mathematical models must opera(e.
19
20
21
22
23
24
25
26
27
28
29
30
31
32
As an cx:unple of the role alternative conceptual models play in performance assessmcnti Volume 1 of the 1992 WIPP PA documents the usc of three al[cmativc conceptual models for the subsurface transport of radionuclidcs in the Culcbra Dolomite Member of the Rustler Formation. (See Section 2.2 for an explanation of the regional geohydrology, Scclion 4.2 for an cxplana[ion of the transport pathway, and Section 7.6 for a discussion of the transpor( model. Sce Section 5.1 of Volume 1 of this report for a comparison of disposal- system performance estimated using each of the three conceptual models. Scc Volume 4 of this report for additional analysis of’ these and olher alternative conceptual models.) In the first conceptual model, transport occurs only in clay-lined fraclures in a single-porosity medium, and chemical retardation does not occur. In the second conceptual model, transport occurs in a dual-porosity medium (clay-lined fractures and matrix); radionuclidcs may diffuse into the pore volume of both the clay linings and the rock matrix. Chemical retardation does not occur. In the third conceptual model, believed by the WIPP PA Department to be the most realistic representation for the behavior of the system, traasport occurs in a dual-porosity medium, as in the second conceptual model, except that chemical retardation does occur as a result of sorption of radionuclidcs in both clay linings and rock matrix.
