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 Events and 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
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
What we have learned is that episodic events are primarily responsible for failure. Exploit the natural water storage capacity of finer textured soils. Regions where precipitation < potential evapotranspiration (ET). Better in regions where snowpack is minimal. Western states, western Canada (excluding coastal areas) Can be impractical in eastern states because there is too much water to manage. ET covers may not be practical for all sites.
Exploit the water removal capabilities of evaporation and transpiration.
Key: Design for sufficient storage capacity to retain water that accumulates during winter with limited drainage; 4

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-informed and 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., 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
Design specific considerations:
Type of engineered barriers to be used
Waste-specific considerations:
Waste form
Waste package
Site-specific considerations:
Climate
Geology
Ecology
Class A trench in 2008 – Barnwell LLW site

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)