Estimating Risks of Environmental Radionuclides Using GENII Version 2

B.A. Napier (Pacific Northwest National Laboratory)

The GENII Version 2 computer code was developed at Pacific Northwest National Laboratory to incorporate the internal dosimetry models recommended by the ICRP and the radiological risk estimating procedures of Federal Guidance Report 13 into updated versions of programs for calculating radiation dose and risk from radionuclides released to the environment. The codes were designed with the flexibility to accommodate input parameters for a wide variety of generic sites. Two editions of the GENII Version 2 code system are available, a full-featured version and a version specifically designed for demonstrating compliance with the dose limits specified in 40 CFR 61.93(a), the National Emission Standards for Hazardous Air Pollutants (NESHAPS) for radionuclides. The only differences lie in the limitation of the capabilities of the user to change specific parameters in the NESHAPS version. Data entry is accomplished via interactive, menu-driven user interfaces. Default exposure and consumption parameters are provided; however, these may be modified by the user. Source term information may be entered as radionuclide release quantities for transport scenarios, or as basic radionuclide concentrations in environmental media (air, water, soil). Decay of parent radionuclides and ingrowth of radioactive decay products prior to the start of the exposure scenario may be considered. The code package also provides interfaces, through the Framework for Risk Analysis in Multimedia Environmental Systems (FRAMES), for external calculations of atmospheric dispersion, geohydrology, biotic transport, and surface water transport. The GENII results may be presented in terms of both radiation dose and risk estimates. Risk may be estimated using dose-to-risk conversion factors, FGR-13 risk factors, or other slope factors. A comparison is made of the evolution of risk estimates, using standard coefficients, FGR-13 values, and the new BEIR VII results.

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