Near Surface Disposal Facilities

1. Near Surface Disposal Facilities Evaluation of the Dominant Ecological Processes Impacting the Performance of NSDFs (Clarke, Burger, Kosson and Ph.D. graduate Brooke Traynham) Incorporation of Episodic Events and Anticipated Climate Change Impacts on Cover Performance(Clarke, Abkowitz, Benson and Ph.D. Candidate Roneisha Worthy). A Systems Approach to Performance Assessment for NSDFs (Clarke, Kosson, Benson and Ph.D. Candidate Joe Rustick).

2. Evaluation of the Dominant Ecological Processes Impacting the Performance of NSDFs Importance to the DOE Current PAs are deficient from the standpoint of incorporation of ecological processes that are critical to long-term performance, especially for evapotranspiration (ET) or water balance designs that rely on ET for performance. Work products Ph.D. Thesis (Dr. Brooke Traynham) One book chapter (Traynham, Burger, Clarke) Two peer reviewed publications in review (Traynham, Burger, Waugh, Clarke)

3. Incorporation of Episodic Eventsand Anticipated Climate Change Impacts on Cover Performance • Increased confidence is needed in the predictive nature of long-term cover performance models. • These covers must be able to perform over long periods of time and accommodate potential impacts due to climate change and episodic events • The above considerations are especially important to the evaluation of evapotranspiration or water balance covers. • Model selection featured analysis of three models ending HELP was selected based on a great deal of experience with it within the DOE and contractor community. • A probabilistic approach will enable consideration of uncertainties associated with long term estimates. • Performance metric: percolation into the waste is less than 3mm/yr

4. Alternative to Conventional Cover = Evapotranspiration (ET) Covers Evapotranspiration Precipitation (P) “Sponge” (S) L Infiltration (I) Factors Affecting Storage & Percolation Water retention characteristics of soils (loam vs. sand) Meteorological conditions - amount of precipitation - distribution of precipitation - form of precipitation Type of vegetation Layering of soils Percolation if I > S

5. Work Products and Deliverables Conference presentations and peer-reviewed publications WM 10 and 11 ANS 2011 Winter Meeting Manuscripts in preparation: Cover Performance Under Precipitation and Temperature Extremes at the Monticello UMT Disposal Facility

6. A Systems Approach to Performance Assessment for NSDFs Importance to the DOE A systems approach is needed. Current evaluations and potential decision-making lack a systems approach (e.g., liners vs. no liners)

7. Our Challenge: • To develop a standardized risk-informedand performance based decision-making tool that can be used to: • Improve consistency in performance assessment (PA) methodology • Evaluate proposed low level radioactive waste (LLW) near surface disposal facilities (NSDFs) using a systems design approach • Take into account potentially important waste-specific and site-specific differences • Provide information over various timeframes (e.g., less than 100 yrs., 300-500 yrs., greater than 500 yrs.) to identify influence of time-dependent processes

8. Performance Assessment Components • Site Conceptual Models: • Link sources of contamination to potential receptors through environmental transport pathways and exposure routes • Performance Evaluation Scenarios: • Examine how the disposal facility could evolve over the life-cycle of the facility • Event Tree Analysis: • Can be used to select performance evaluation scenarios (Figure from the Ph.D. dissertation of Kevin Brown)

9. Examples of Sub-Components For a Broad Systems Approach Class A trench in 2008 – Barnwell LLW site • Design specific considerations: • Type of engineered barriers to be used • Waste-specific considerations: • Waste form • Waste package • Site-specific considerations: • Climate • Geology • Ecology

10. Performance Metrics for the Decision-Making Tool The desired decision-making tool will have the ability to: • Assess the influence of each disposal facility component on modes of disposal facility change, both individually and in connection with other components. • Provide guidance on NSDF life-cycle risks for specific combinations of site attributes and waste characteristics. • Support decisions about performance monitoring locations and parameters to monitor. • Provide a standardized methodology for selecting appropriate disposal facility components applicable for any site across the DOE complex, in a manner that is transparent, defensible, and quantitative. • Example: Site-specific, and waste-specific guidance to site engineering staff on whether or not a liner system is needed for a future disposal facility and what type of liner would be needed (if any)

11. Work Products and Deliverables • Presentations and Peer-Reviewed Papers to MW 10 and WM11 • Presentation to the WA Ecology Barriers Workshop (February 2012) • Presentation Proposal in to ANS 2012 Semi-Annual Meeting in Chicago (June 2012). • Manuscripts in Preparation: • Conceptual Model Framework for Performance Evaluation • Use of Site- and Waste-Specific Event Trees in Post Closure Performance Assessment

12. A Systems Approach to Determining Design Requirements for Near Surface Disposal Joseph H. Rustick James H. Clarke Vanderbilt University/CRESP Craig H. Benson University of Wisconsin – Madison/CRESP February 1st, 2012

13. Other CRESP Projects Development of a Risk-Informed Project Prioritization Tool for the Oak Ridge Reservation (Powers, Kosson, Burger, Brown, Krahn, Mayer, Gochfeld, Clarke) Review of RI/FS Documents for the Hanford River Corridor (Powers, Clarke) Development of a Risk-Informed Approach to D&D Priority Setting (Powers, Kosson, Mayer, Clarke) Manuscript(s) in preparation that will integrate conceptual models, event tree analyses and performance assessments (Brown, Kosson, Powers, Clarke and Traynham, Rustick)