must not contribute to the exposure of the public in excess of these amounts. Permissible levels of radioactivity would, therefore, depend on the ability of the disposal system to retain the radionuclides. Additionally, all exposures must be limited to "as low as reasonably achievable" levels.

DOE Order 5820.2A deals with radioactive waste management, including high-level waste, TRU waste, and LLW, and contains a number of provisions that meet and extend the regulatory criteria established by the USNRC. The order, promulgated in 1988, requires that the concept of waste minimization, including waste segregation, be applied in process design and operation. The order also requires a PA for all disposal facilities. There are two objectives that must be addressed in PA models (DOE, 1996c).

The first objective is to assure that the disposed waste will not cause an exposure (effective dose equivalent) greater than 25 mrem/yr to any member of the public. DOE has interpreted this to include all pathways of possible exposure during the period of 1,000 years following closure of the disposal facility. To increase confidence in the outcome of the modeling, analysis beyond 1,000 years (but not exceeding 10,000 years) may be done (DOE, 1996c).

The second applicable performance objective addresses inadvertent intrusion after the institutional control period (100 years), requiring that the effective dose equivalent received by an individual who might inadvertently intrude into the facility not exceed 100 mrem/yr for continuous exposure or 500 mrem for a single acute exposure. PA modeling of this scenario beyond 1,000 years post-closure is not recommended.

In addition to the waste treatment and disposal regulations that were discussed in the previous section, controls may be imposed at waste treatment or disposal sites through the mechanism of WAC. All DOE facilities are required to have WAC for waste received by that facility for treatment or disposal (DOE Order 5820.2A). As indicated by