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Natural and Engineered Barriers at the Waste Isolation Pilot Plant

Natural and Engineered Barriers at the Waste Isolation Pilot Plant. Frank D. Hansen Sandia National Laboratories SAND2008-6989P.

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Natural and Engineered Barriers at the Waste Isolation Pilot Plant

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  1. Natural and Engineered Barriers at the Waste Isolation Pilot Plant Frank D. Hansen Sandia National Laboratories SAND2008-6989P Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company,for the United States Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.

  2. WIPP: A Solution of a National Problem

  3. Waste Types/Packaging Various Transuranic Waste Packages

  4. Built and maintained according to Nuclear Regulatory Commission standards Tested to ensure containment of radioactive materials TRUPACT-II Shipping Container

  5. Monitored by satellite tracking system Drivers are highly trained Procedures for accident prevention Emergency responders are trained Waste Types/Packaging

  6. Unloading Typical Waste Packages

  7. CH Waste in Disposal Room

  8. Bedded Salt Was Chosen for the Siting of the US Defense Nuclear Wastes • Salt can be mined easily • Salt has a relatively high thermal conductivity • Wide geographic distribution (many potential sites) • Salt is plastic * • Salt is essentially impermeable * • Fractures in salt are self healing * • Salt has existed underground for millions of years * *Attributes of Natural Barrier

  9. Natural Barrier of the Delaware Basin 1981: First shaft completed 1996: CCA submitted to EPA 1998: WIPP certified by EPA 1999: First waste shipment received 2004: First recertification 2007: Begin RH disposal WEST EAST Castile Formation Location of WIPP

  10. WIPP Underground Layout Shaft Seal System

  11. Full Scale Behavior Figure 2. Typical Level of Agreement between Underground Test Results and Predicted Closure

  12. Salt Behavior is well Understood

  13. WIPP Disposal Room Evolution

  14. Disturbed Rock Zone around a Disposal Room

  15. WIPP Room Evolution at Time=0 years

  16. WIPP Room Evolution at Time=12 years

  17. WIPP Room Evolution at 1000 years

  18. Shaft Seal System Design Guidance • Limit hazardous constituents reaching regulatory boundaries • Restrict groundwater flow through the sealing system • Use materials possessing mechanical and chemical compatibility • Protect against structural failure of system components • Limit subsidence and prevent accidental entry • Utilize available construction methods and materials

  19. Material Specification • Functions • Material characteristics • Construction • Performance requirements • Verification methods

  20. Shaft Sealing System

  21. Shaft Seal System Conclusions • The WIPP shaft seal system effectively limits fluid flow within the seal system. • Brine flow volumes from the Rustler downward are insignificant relative to the salt-column gas saturated pore volume and the repository pore volume. • The salt column becomes an effective barrier to gas and brine migration by 100 years after closure. • Long-term flow rates within the seal system are limited.

  22. Option D Panel Closure System

  23. Proposed Panel Closure System

  24. Definition of Barriers • EPA defines barriers as “any material or structure that prevents or substantially delays movement of water or radionuclides toward the accessible environment” Barriers can be “… a geologic structure, a canister, a waste form, or a material placed over and around waste provided that material or structure substantially delays movement of water or radionuclides”

  25. MgO Engineered Barrier • MgO will act as an engineered barrier in the WIPP by decreasing actinide solubilities. • Will remove CO2 and control PCO2 and pH within favorable ranges. • Only engineered barrier recognized by EPA. • Ongoing lab studies imply MgO will effectively remove H2O and CO2.

  26. Natural and Engineered Barriers Summary • Site Selection/Characterization Studies • Geologic mapping of surface and borehole data. • Geophysical surveys for structure, brine pockets. • Geochemistry/Mineralogy for geologic process analysis. • Hydrology Program • Characterize the flow and transport in subsurface ground water through field and lab tests and describe with flow models. • Chemistry Program • Estimate the solubility and mobility of radionuclides in WIPP environment through experiments. • Sorption of actinides during transport.

  27. Natural and Engineered Barriers Summary • Rock Mechanics and Shaft Seal Design • Measure and predict behavior of salt around waste rooms • Design an effective, impermeable shaft seal system using natural and man-made materials • Performance Assessment Modeling • Comparison to the EPA standards • Compliance Certification Application

  28. Natural and Engineered Barriers Summary • Robust Site Confirmed through Selection and • Characterization Studies • Natural Barriers include Salt Formation • Room Enclosure, Fractured healing, and Entombment • Favorable Hydrological Setting • Minimal Water • Flow Characterized and Modeled • Engineered Barriers • Shaft Seals and Panel Closure Systems • MgO Assurance

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