Resuspension Consequence Assessment of the WIPP Release

On 14 February 2014, there was a release of radiological material at the Waste Isolation Pilot Plant in New Mexico due to improper waste packaging. The resulting chemical reaction released 241Am as airborne contamination in the Waste Isolation Pilot Plant underground repository. This incident caused a small leak through the bypass dampers, creating effluent in an airborne plume of radiological contamination consisting of primarily 241Am. The original ground deposition was determined using validated plume modeling for the precipitation to ensure the release was below regulatory limits. Building upon this data allows for the assessment of long-term, off-site doses downwind of the facility. Using the health physics code HOTSPOT, air source terms were generated across the ground deposition plume in grid format to allow for a detailed analysis of the full scope of the ground deposition plume. The individual squares of the grid, or "kernels" were summed to calculate the dose at different offsite locations from the inhalation pathway. The lifetime integrated total effective dose equivalents (TEDEs) of these areas were all found to be, conservatively, on the order of millisievert or less and thus negligible from a radiobiological perspective. Additionally, further resuspension of this material was accounted for using three of the four different methods available in HOTSPOT. Using conservative assumptions, the wind-adjusted upper bound lifetime doses of all off-site locations were found to be substantially less than the average yearly background dose of around 3.10 mSv and are thus negligible.