Long-term Performance of Near Surface Contamination Isolation Systems

Integrated Analysis of Engineered and Institutional Controls

Effect of Climate Change on the Long-term Performance of Landfill Covers

Investigators: James H. Clarke and Mark Abkowitz (Vanderbilt), Joanna Burger (Rutgers),Craig Benson (Wisconsin), and David S. Kosson, Joe Rustick (Ph.D. graduate student), Roneisha Worthy (Ph.D. Graduate Student) (Vanderbilt)

Project Summary and Goals: The overall goal of this project is the development of methodologies and analytical frameworks concerning performance assessment, design, monitoring, and maintenance of near surface contaminant isolation (CI) systems that will provide reliability, transparency, and traceability; enable risk-informed decision-making; and build confidence in containment approaches.

Relevance and Impact to DOE: Technical and economic limitations often require that contamination is isolated on-site through the use of engineered barriers (covers and bottom liners) or excavated and moved to off-site disposal facilities when contaminated sites are remediated and nuclear facilities are decommissioned. Both engineered and institutional controls are needed when contaminated materials and wastes are isolated either in on-site or off-site disposal facilities.

Regulators and other stakeholders have concerns, however, about the long time periods for which the isolated materials may pose a hazard, compared to the relatively short duration of our experience with current approaches to containment. Evaluation of contamination isolation system performance for radioactive wastes is complicated by the very long time periods for which the containment system must meet its performance objectives. For example, engineered covers, which are employed to reduce infiltration into uranium mill tailings and radon emanation form the tailings into the atmosphere, have design life requirements of 200 years (minimum) to 1000 years (DOE Order 425.1). Disposal cells containing low level radioactive wastes are expected to perform for 10,000 years (A Performance Assessment Methodology for Low Level Radioactive Waste Disposal Facilities, NRC 2000).

System design and performance assessment improvements are needed that build confidence in the ability of the system to meet performance objectives and suggest more performance-oriented monitoring approaches (performance confirmation) in addition to the compliance monitoring.

Many of the current approaches to contaminant isolation using engineered barrier lack sustainability in that they rely on extensive long-term monitoring and maintenance including the potential need for system replacement or corrective action. Ecological processes and potential climate change are not typically addressed explicitly in the performance assessment that is the major decision-making tool used to address system design and long-term performance. The same can be said about the need to ensurethat performance assessment tools can incorporate the potential impacts of episodic and seasonal events and climate change.

The research that is being done and is proposed under this section is designed to address the above issues.

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