Panel Discussion of Engineered Barriers

1. Panel Discussion of Engineered Barriers Ernest Hardin (Moderator) Sandia National Laboratories, Lead Laboratory Yucca Mountain Project SAND #: 2008-7211P

2. TOPICS • Compare EBS concepts developed for different settings • How to demonstrate EBS capability? • How to select the spent-fuel repository EBS design? Panelists • Chris White, U.S. Department of Energy • Peter Baumgartner, Atomic Energy of Canda, Ltd. • Neil Brown, Los Alamos National Laboratory • Ernest Hardin, Sandia National Laboratories (moderator)

3. EBS Panel Discussion • What is an Engineered Barrier System? • Canadian EBS design: 1) the sealing system, 2) the container system and 3) the spent fuel. • KBS-3 EBS design: 1) sealing system including backfill and buffer material, 2) waste container, and 3) spent fuel. • Yucca Mountain EBS design: 1) emplacement drift, 2) drip shield, 3) container system, and 4) waste forms. • What are the EBS functions? • 1) limit contact of groundwater with waste or waste containers (in conjunction with natural barriers), • 2) limit rates of radionuclide release from waste forms, and • 3) limit rates of release to the natural system (in conjunction with natural barriers).

4. Disposal Concept Examples Yucca Mountain and KBS-3 Repositories

5. EBS Design Principles - Hydrologic Environment Saturated • Liquid water as transport vector • Long-range hydraulics • Small hydraulic gradient (after equilibration) • Near-field as hydro-barrier (e.g., salt or bentonite) • Material interactions limited by transport through near-field barriers • Seals influence movement to/from waste containers Unsaturated • Liquid water as transport vector • Predominantly vertical flow • Fixed flow potential gradient • EBS drains freely; use repository “grade plan” • Material interactions are limited by patterns of vertical drainage • Sealing limited to backfilling

6. EBS Design Principles - Performance of EBS Features Saturated • Sealing System • Limit water contacting container • Stagnate water around containers • Seal important locations • Use sorptive materials • Container System • Limit water contacting waste form • Structural strength • Resist degradation (corrosion) • Feasible/flexible • Spent Fuel Waste Form • Rate limited degradation • Solubility limited release (redox) • Retarded diffusive release Unsaturated • Sealing System • Backfilling of shafts, boreholes, and access tunnels only • Container System • Limit water contacting waste form • Structural strength • Resist degradation (corrosion) • Feasible/flexible • Spent Fuel Waste Form • Rate limited degradation • Solubility limited release • Retarded diffusive release

7. EBS Design Principles - Thermal-Chemical Environment Saturated • Reducing environment • Buffer as micro-environment • Reducing minerals in host rock • Waste package environment • Controlled by buffer • Heat transfer • Conduction dominated • T < boiling preserves clays (or other water-sensitive EBS materials) • Radionuclide transport • Diffusive release into natural system • Naturally occurring materials Unsaturated • Oxidizing environment • Gas exchange with atmosphere • Oxidizing minerals • Waste package environment • Controlled by host rock • Heat transfer • Conduction dominated; radiative across air gaps • T > boiling possible • Radionuclide transport • Diffusive release into natural system • EBS degradation

8. Demonstrating EBS Capability • Underground laboratories are needed to demonstrate EBS capability • Aspö Hard Rock Laboratory • Underground Research Laboratory • Exploratory Studies Facility • International collaboration • Pilot-scale initial/confirmatory testing of spent-fuel disposal • Salt Vault (1965) • Spent Fuel Test - Climax (1982) • SKB’s SFR-1 project (planned) • U.S. DOE Performance Confirmation (planned)

9. Spent Fuel Test - Climax Unsaturated quartz monzonite, Climax stock, Nevada Test Site Canister Drift, Transfer Vehicle Receiving Room, Canister Borehole

10. Yucca Mountain Performance Confirmation ProgramThermally Accelerated Drift Concept Source: TDR-PCS-SE-000001 Rev. 05, Fig. 3-1

11. Formulate Enhanced Alternatives; Analyze • Reference Design • Alternatives: • Low thermal • Postclosure ventilation • Enhanced access • Emplacement modes • Modular/phased Design Selection Evaluation Criteria: Preclosure performance Postclosure performance Assurance Engineering acceptance Construction/operations/maintenance Environmental Schedule Cost Independent Design Features & Analysis Yucca Mountain Repository Design Selection (1999) Boundary conditions: sited in unsaturated, fractured, welded tuff; spent fuel and defense waste streams; previous conceptual design work.

12. Yucca Mountain Repository Design Selection Independent Design Features Included: 2. PACKAGING • Corrosion resistant materials • Ceramic coatings • Canistered assemblies • Rod consolidation • Waste package fillers • Canistered assemblies 1. CONFIGURATION/THERMAL • Thermal loading/aging/blending • Preclosure ventilation • Postclosure ventilation • Drift and package diameters • Waste package spacing • Backfill • Shielding/self-shielding options • Ground support options 3. ISOLATION • Drip shield • Richards barrier • Diffusion barrier • Getters • Rock pre-treatment

13. EBS Design Panel Discussion • Repository programs have demonstrated the feasibility of EBS concepts for geologic disposal • Different EBS designs for unsaturated vs. saturated hydrologic conditions; different sealing strategies • Other design issues: • Spent fuel vs. HLW glass and other waste forms • Criticality control • Performance assessment requirements • Retrievability • Need for demonstration in situ, e.g., at pilot scale • Design selection involves multiple, non-technical factors

14. EBS Design Panel Discussion Backup Slides on Yucca Mountain Repository Design Selection

15. Point Load Line Load EBS Design Alternatives - A. Low thermal See also: Aging/blending, and drift/package diameter design features Source: B00000000-01717-4600-00123 Rev. 01

16. Warm air Natural air circulation in one postclosure loop Cool air Waste packages Emplacement drift Vertical vent raise Waste packages Open Closed - Triangle EBS Design Alternatives - B. Postclosure ventilation Source: B00000000-01717-4600-00123 Rev. 01

17. Pedestal (or rail car) Waste package Pedestal (or rail car) Waste package Ground support Temporary concrete cover Waste package support Waste package on supports Pedestal (or rail car) Waste package EBS Design Alternatives - C. Enhanced Access Source: B00000000-01717-4600-00123 Rev. 01

18. Crowned invert Plug Plug Waste package Lined borehole Waste package Waste package support Invert EBS Design Alternatives - D. Emplacement modes Source: B00000000-01717-4600-00123 Rev. 01

19. Granular Backfill Emplaced at Closure EBS Design Features - 1 f) Backfill Source: B00000000-01717-4600-00123 Rev. 01

20. Alloy 22 Alloy 22 Titanium Titanium Titanium Alloy 22 EBS Design Features - 2 a) Corrosion resistant materials Source: B00000000-01717-4600-00123 Rev. 01

21. Steel Shot or Iron Oxide Thickened Carbon Steel Supports Granular Filler Integral Filler EBS Design Features - 2 e) Waste package fillers Source: B00000000-01717-4600-00123 Rev. 01

22. Drip Shield Drip Shield Emplaced at Closure Granular Backfill Emplaced at Closure Granular Backfill Emplaced at Closure Borttom of Drip Shield End Plate EBS Design Features - 3 a) Drip shield Source: B00000000-01717-4600-00123 Rev. 01

23. Fine-Grained Backfill Emplaced at Closure Coarse-Grained Backfill Emplaced at Closure EBS Design Features - 3 b) Richards barrier Source: B00000000-01717-4600-00123 Rev. 01

24. Coarse-Grained Backfill Emplaced at Closure Diffusive Barrier Placed During Construction, Prior to Emplacement of Waste Packages EBS Design Features - 3 c) Diffusion barrier Source: B00000000-01717-4600-00123 Rev. 01

25. Fine-Grained Backfill Emplaced at Closure Getter Material Placed During Construction, Prior to Emplacement of Waste Packages EBS Design Features - 3 d) Getters Source: B00000000-01717-4600-00123 Rev. 01

26. EBS Design Panel Discussion Backup Slides on History of EBS Design Development in the U.S. Spent Fuel/HLW Repository Program

27. Short History of EBS Design Developments in the U.S. Spent Fuel Repository Program • Background: Project Salt Vault (1967)1,2 and R&D at Avery Island (1982) • Spent Fuel Test - Climax (1983)1 • Basalt Waste Isolation Project (1987)2 • Salt Repository Project (1987)2 • Yucca Mountain Site Characterization Plan Conceptual Design (1988)2 • Viability Assessment (1998)2 • Yucca Mountain License Application (2008)2 1 Advanced to in situ testing with spent fuel2 Includes a conceptual EBS design for spent fuel/HLW disposal

28. Pit Liner Concrete Shield Plug Granite Concrete Steel Shield Plug Grout Canister Support Pin Liner Assembly Canister Grout Spent Fuel Test - Climax Near-Field Configuration and Facility Layout Source: SFT-C Final Report (NNA.19870901.0052) Figures 1-1 and 12-3.

29. CONTAINER PRE-FORMED PACKING CLOSURE PLATE SHELL CONSOLIDATED SPENT FUEL RODS HOST ROCK Basalt Waste Isolation Project (1987) Horizontal Emplacement Reference Concept (not shown: backfill, seals) Source: BWIP CDR (HQZ.890410.1107) Figure 2.1-1

30. Entry and Emplacement Hole Emplacement Hole Emplacement Hole Container Counterbore Salt Backfill Shield Emplaced Disposal Container Disposal Container Borehole VERTICAL SECTION Crushed Salt Packing Material in Annulus Crushed Salt Pad Bedded Salt Repository EBS Design (1987) Horizontal and Vertical Emplacement Options (not shown: backfill, seals) Sources: Salt Repository CDR (vertical: MOL.20061122.0125, and horizontal: MOL.20061214.0266)

31. Borehole Cover Shield Plug Liner Cover Standoff Emplacement Drift Crushed Tuff Backfill Emplacement Drift Shield Plug Partial Liner Waste Container Support Plate Yucca Mountain Site Characterization Plan Conceptual Design (1988) Horizontal and Vertical Emplacement Options Source: SAND84-2641 (HQS.19880517.0945) Figures 3-12 and 3-13.

32. Yucca Mountain Repository Viability Assessment (1998) Conceptual EBS Design Source: DOE/RW-0508, Figures 5-1 and 5-2.