suggested that “disposal in cavities mined in salt beds and salt domes” promises “the most practical immediate solution of the problem,” and (3) noted that solidifying the waste into an insoluble form would simplify disposal (NRC 1957). That early report noted that a great deal of research was still needed. Indeed, institutions charged with planning and carrying out geologic disposal have encountered major political and technical difficulties. Most communities are not receptive to hosting a HLW repository,1 and some groups oppose disposal because of concerns about environmental damage and as a way to strike at nuclear power.
Most of the technical challenges are related in some way to uncertainty. Understanding the mechanisms and characterizing the features of environmental systems is a much more difficult task than it was thought to be 45 years ago. Understanding the disposal environment and how it interacts with the engineered facilities and packages placed in it provide the basis for predicting behavior. Scientists must make predictions spanning, in some cases, tens of thousands of years to respond to regulatory guidance and requirements. Such predictions necessarily involve uncertainties, even when the physical, chemical, and biological phenomena involved are well understood. The time and effort expended in countries that have geologic disposal programs attest to the difficulties, and scientific understanding of the phenomena involved is still evolving.
A recent report by an international committee of the National Research Council nonetheless concludes that geologic disposition is the only long-term end point that does not require continued management and resource expenditures (NRC 2001a). Worldwide, no engineered geologic repository for HLW has been designed and operated as yet, although the Waste Isolation Pilot Plant (WIPP) in the United States is an operating geologic repository for long-lived transuranic waste. The WIPP is approximately 700 meters underground, mined out of bedded salt.
The committee draws from previous studies by the National Academies in recommending a risk-based approach to management and disposition of HLW and SNF and cleanup of contaminated sites. These studies were not specific to the United States—