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

Precipitation (P)

L

“Sponge”(S)

Infiltration (I)

Percolation if I > S

Evapotranspiration

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

Alternative to Conventional Cover = Evapotranspiration (ET) Covers

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 DOEA systems approach is needed.

Current evaluations and potential decision-making lack a systems approach (e.g., liners vs. no liners)

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., 300-500 yrs., greater than 500 yrs.) to identify influence of time-dependent processes

7

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)

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

9

Class A trench in 2008 – Barnwell LLW site

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)

10

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. RustickJames H. Clarke

Vanderbilt University/CRESPCraig H. Benson

University of Wisconsin – Madison/CRESPFebruary 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)