OVERVIEW OF THE PERFORMANCE ASSESSMENT FOR THE RECERTIFICATION OF THE WASTE ISOLATION PILOT PLANT

The Waste Isolation Pilot Plant (WIPP) is the only operational deep geologic repository in the world for transuranic nuclear waste. WIPP opened for disposal activities in March 1999, starting the clock for the periodic recertification required every five years until the repository is closed. The first Compliance Recertification Application (CRA) was submitted to the EPA in March 2004. The CRA includes an up-to-date performance assessment (PA), which will consider new and changed information since the first certification. Performance assessment calculates probabilistic estimates of the long-term performance of the waste disposal system.

The PA system consists of conceptual models, computational codes, parameter databases, and computer systems. Sandia National Laboratories maintains the PA system in support of compliance applications and for analyses to support changes to the disposal system.

This paper provides an overview of PA with discussion of the WIPP regulatory framework, the PA methodology, conceptual and process models, scenario development, release mechanisms, major PA codes, treatment of uncertainty, the role of conservative assumptions in PA, and a summary of the results of the CRA PA.