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Risk Assessment
Risk Assessment and Federal Guidance Programs:  


Risk Assessment

The GENII System provides a state-of-the-art, fully documented set of software for calculating radiation dose and risk from radionuclides released to the environment. The GENII-NESHAPS edition automatically incorporates specific requirements of the NESHAPS regulations. However, EPA has not been approved it for demonstrating compliance with NESHAPS Subparts H and I.

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Download Software, Instructions, and Documentation

For information on obtaining the most recent version of GENII, please visit the Pacific Northwest National Laboratory's GENII Version 2 web page.


The U.S. Department of Energy released GENII Version 1.0 in 1988. The U.S. Environmental Protection Agency developed a new version of the software in 2002, GENII Version 2.0, incorporating improved transport models, exposure options, dose and risk estimation, and user interfaces.

In 2002, a new edition, GENII-NESHAPS, was developed as an alternative for demonstrating compliance with the dose limits specified in 40 CFR 61.93(a), the National Emission Standards for Hazardous Air Pollutants for radionuclides. In 2003, the software was peer reviewed. The Agency has since decided not support alternative models for compliance purposes. CAP-88 remains the only model supported by EPA for demonstrating compliance.

Both editions of the GENII Version 2.0 software system can be downloaded:

The GENII-NESHAPS edition offers limited capability to change parameters, but the advantage is that it automatically incorporates specific requirements of the NESHAPS regulation. The original GENII edition allows you to change specific parameters. Both GENII and GENII-NESHAPS have been reviewed and tested extensively.

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Regulatory Context

GENII-NESHAPS has not been approved by EPA for demonstrating compliance with the National Emission Standards for Hazardous Air Pollutants in 40 CFR 61, Subparts I and H.

Application Niche Exit EPA Disclaimer

GENII-NESHAPS incorporates the internal dosimetry models recommended by the International Commission on Radiological Protection in ICRP 56-72 and the radiological risk estimating procedures of Federal Guidance Report 13 into updated versions of existing environmental pathway analysis models. The software was designed with the flexibility to accommodate input parameters for a wide variety of generic sites. GENII-NESHAPS functions within the Framework for Risk Analysis in Multimedia Environmental Systems (FRAMES), which allows GENII to run in conjunction with and provide inputs to related software.

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Strengths and Limitations


GENII-NESHAPS includes the dosimetric models of ICRP Publications 56 through 72, and the related risk factors published in Federal Guidance Report 13. These dosimetry and risk models are considered to be state of the art by the international radiation protection community and have been adopted by most national and international organizations as their standard dosimetry methodology.

Dose Calculations

The GENII-NESHAPS system calculates radiation doses from chronic atmospheric releases. Air transport calculations use a chronic (annual average) plume model, which allows use of an effective stack height or calculation of plume rise from buoyant or momentum effects (or both).

Risk Estimates

The system calculates health risks to individuals or populations by applying appropriate risk factors to either the effective dose, the effective dose equivalent, or the organ dose. It also estimates cancer risk to specific organs or tissues using risk factors from Federal Guidance Report 13.

Data Entry, Use, and Available Parameters

GENII-NESHAPS offers interactive, menu-driven user interfaces for entering data. It provides default exposure and consumption parameters for the maximally exposed individual. It accepts radionuclide source term information in formats appropriate for different exposure scenarios --as release quantities where transport is involved or as concentrations in environmental media (air, water, soil) in the absence of transport. The model also considers decay of parent radionuclides and in-growth of radioactive decay products prior to the start of the exposure scenario for either basic or derived concentrations. Because the system works sequentially on individual decay chains, unlimited numbers of radionuclides, including the source term and accumulated decay products, can be processed in a single run.

Exposure Pathways

The radial grid used in GENII-NESHAPS allows consideration of both the distance and direction to target individuals and populations. The model accommodates scenarios involving chronic releases to air from ground level and/or elevated sources. Exposure pathways include direct exposure from surface sources (soil) and air (semi-infinite cloud and finite cloud geometries) as well as inhalation and ingestion. The tritium model includes consideration of both gas and vapor, conversion of gas into vapor, and biological conversion of both into organically-bound tritium.

Hardware Requirements


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