The Disposal of Nuclear Waste: A Problem in Mass Management?

A reference repository is examined for environmental compliance utilizing minimum performance standards as established by the Nuclear Regulatory Commission and the Environmental Protection Agency. These standards stipulate the amount of time the radionuclides must be retained in the barrier, the acceptable release rates from the barrier, and the acceptable mass release that can be registered at the accessible environment over a 10,000‐year time frame. The only natural, or geologic barrier standard specified is a minimum ground‐water travel time of 1000 years from the engineered barrier to the accessible environment. Other natural barrier processes including geochemical retardation and mass transfer, dilution, and dispersion are not specified. In attempting to determine the role that these unspecified components must play in order to comply with the mass release standard, we find that their role is minimal to the extent that virtually any rock type that can satisfy the minimum ground‐water travel time of 1000 years will satisfy the mass release requirements at the accessible environment. Full compliance with a concentration standard at the accessible environment requires that the nuclides contained within the larger inventories be fully contained with the controlled zone between the engineered barrier and the accessible environment