Comparison of Standard Radiological Risk Models and Using RESRAD to Derive Generic Risk-Based Area Factors for Final Status Surveys

The RESidual RADioactivity (RESRAD) computer code has been used for years to calculate carcinogenic risk and radiological dose from exposure to radionuclides. The basic ingestion, inhalation, and direct gamma intake equations used by RESRAD, Risk Assessment Guidance for Superfund (RAGS), and the Soil Screening Guidance for Radionuclides (SSG) are similar and can produce similar results, but there are some notable differences. Of particular interest is the fact that RESRAD incorporates sophisticated environmental transport models. Associated environmental parameters allow risk assessors to consider, among other variables, the size (i.e., surface area) of the contaminated zone, a variable not typically addressed quantitatively under the RAGS/SSG paradigm. Considering the similarities between basic RESRAD, RAGS, and SSG intake equations and given the broad acceptance of RESRAD, it stands to reason that RESRAD-derived area factors may be used to supplement RAGS/SSG human health risk calculations. This would allow risk assessors to retrofit existing results or otherwise modify standard RAGS/SSG equations for use in site closeout planning under the Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM), given a key component of the MARSSIM method is the consideration of small areas of elevated activity or "hot spots" through the use of area factors.