Conceptual Approach For Estimating Potential Air Toxics And Radionuclide Airborne Emissions From A Temporary Exhaust System For The 216-Z-9 Crib Removal Action

The 216-Z-9 Crib, located at the Hanford Nuclear Reservation in southeastern Washington State, was the site of a successful mining effort to recover plutonium from the contaminated soils at the disposal site. A CERCLA Action Memorandum (AM) issued by the U.S. Department of Energy (DOE) requires the removal of the buildings associated with this mining effort to facilitate a remedial action planned for the near future. The decontamination and demolition of the 216 Z-9 Crib facilities is required under a consent order between the DOE, the U.S Environmental Protection Agency (EPA) and the Washington State Department of Ecology (Ecology). Removal of the buildings located on and near the concrete cover slab over the 216-Z-9 Crib will require removal of the large soil-packaging glovebox located inside the 216-Z9A Building. Prior to cleaning out the glovebox, it will be necessary to provide active filtered ventilation capability to ensure a negative pressure exists between the glovebox and the adjacent airspace while hands-on work proceeds within. The glovebox floor is open to the Z-9 crib cavern environment below. For this reason the crib and glovebox currently share a common airspace. The functional requirements for safely conducting work within the glovebox include provision of a negative pressure in the box of about 0.5 inches of water gage (nominal) less than the interior of the building. In addition, the building surrounding the glovebox will be maintained at a slight negative pressure with respect to outdoor ambient pressure. In order to assess the relevant and appropriate clean air requirements for the new temporary ventilation system and associated emissions monitoring, it was necessary to reliably predict the nature of the exhaust air stream. Factors used to predict the presence and concentrations of certain radionuclide particulates and certain gases considered to be