Analysis of potential airborne radionuclide emissions during and after fires through contaminated soil areas on the INL
Date
2021
Authors
Williams, Connor, author
Johnson, Thomas, advisor
Brandl, Alexander, committee member
Lindsay, James, committee member
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Abstract
The risk of wildfires burning through legacy soil contamination areas of the Idaho National Laboratory (INL) facility with consequent airborne radiological releases has been a concern for some time and this concern has only increased in recent years with an increasing number and size of wildfires burning through the property. The question of personnel safety has been raised in terms of firefighters and other first responders who might be in close proximity to an ongoing fire as well as the health risks to facility staff and members of the general public. As a result, this study seeks to update the current soil nuclide inventory of the known legacy contamination sites which pose a fire risk as well as update previous fire resuspension studies made of INL contamination sites through the use of updated modeling techniques and inputs available in more recent literature. Baseline soil contamination values were developed for the contaminated areas starting with average measured radionuclide concentrations in soil, using in-situ gamma spectroscopy or decay correcting the best available data from previous reports. Soil-to-plant uptake fractions from the literature were used to estimate radionuclide concentrations in plants growing on the sites. Worst case estimates of plant biomass were used to yield release estimates during a fire. Doses to first responders or other high-exposure individuals were estimated through a comparison to the minimum soil screening concentrations calculated specifically for the INL facility in the literature. This study involved using dynamic dispersion models to determine the minimum soil and plant concentration, for various common nuclides found at INL, which would be necessary to produce an exposure of 10 mrem or greater either during a fire due to release of radionuclides from plant tissue, or after a fire due to resuspension of rootless soil. Based on the relatively low level of soil radionuclide concentrations in even the most contaminated sites, the low soil-to-plant transfer coefficients of the specific measured nuclides remaining in the soil and the likely quick dispersion and dilution of any released nuclides in the smoke/dust column, the overall exposure is likely to be small. Therefore, it is hypothesized that that any measurable radiological doses which could be expected to any given individual would be well below current occupational or public exposure limits and thus would not present a health hazard.
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Subject
Idaho National Laboratory
radiation protection
wildfire
nuclide resuspension
health physics
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