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In May 1998, the US Environmental Agency (EPA) certified the US Department of Energy's (DOE) Waste Isolation Pilot Plant (WIPP) as being in compliance with all of the applicable regulations governing the permanent disposal of spent nuclear fuel, high-level waste, and transuranic radioactive waste. The WIPP, a transuranic waste repository, is the first deep geologic repository in the US to have successfully demonstrated regulatory compliance with long-term radioactive waste disposal regulations and be certified to receive wastes. Many lessons were learned throughout the 25-year history of the WIPP--from site selection to the ultimate successful certification. The experiences and lessons learned from the WIPP may be of general interest to other repository programs in the world. The lessons learned include all facets of a repository program: programmatic, managerial, regulatory, technical, and social. This paper addresses critical issues that arose during the 25 years of WIPP history and how they influenced the program.

In this paper, the authors identify the scalability bottlenecks of an unstructured grid CFD code (PETSc-FUN3D) by studying the impact of several algorithmic and architectural parameters and by examining different programming models. The authors discuss the basic performance characteristics of this PDE code with the help of simple performance models developed in their earlier work, presenting primarily experimental results. In addition to achieving good per-processor performance (which has been addressed in the cited work and without which scalability claims are suspect) they strive to improve the implementation and convergence scalability of PETSc-FUN3D on thousands of processors.