Considerations for the long term: perpetual is not forever

Shallow land burial is intended to provide a waste emplacement with low probability for the release of radionuclides to the environment, and to provide a barrier against encroachment on the waste by man or his activities. Additionally, the emplacement conditions are designed to insure that a potential release cannot result in unacceptable radionuclide concentrations in man's environment. Site-control requirements are intended to prevent unacceptable use or accidental excavation of the waste disposal site. Evaluation procedures generally provide definition of the containment capability of the site under present environmental conditions. Long-term care requirements can continue site control measures, and provide a continuing check on the containment capability. However, significant changes in climate, hydrology, plant cover, and land use that might alter the containment potential can occur in a time frame of tens to hundreds of years, and true ''perpetual'' care cannot be guaranteed. This paper considers the possible long-term consequences of radionuclide uptake by plants and burrowing animals, of changes in site hydrology, and of inadvertent excavation of the buried waste by man at some distant future date