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Radiation Protection


The CAP-88 (Clean Air Act Assessment Package - 1988) computer model is a set of computer programs, databases and associated utility programs for estimating dose and riskHelpriskThe probability of injury, disease or death from exposure to a hazard. Radiation risk may refer to all excess cancers caused by radiation exposure (incidence risk) or only excess fatal cancers (mortality risk). Risk may be expressed as a percent, a fraction, or a decimal value. For example, a 1% excess risk of cancer incidence is the same as a 1 in a hundred (1/100) risk or a risk of 0.01. from radionuclideHelpradionuclideRadioactive forms of elements are called radionuclides. Radium-226, Cesium-137, and Strontium-90 are examples of radionuclides. emissions to air. CAP-88 is a regulatory compliance tool under the National Emissions Standard for Hazardous Air Pollutants (NESHAP).

Version 4.1 is now available, as is the STARGET utility to convert meteorological data.

Earlier versions of CAP-88 PC are available in the EPA Archives. Search EPA Archive

On this page:

Version 4.1

Version 4.1 is the most recent version of the code and may be used to demonstrate compliance with NESHAP Subpart H. 

IMPORTANT NOTE TO USERS: Installing Version 4.1 on your computer will uninstall Version 4.0. If you wish to use Version 4.0 for the current compliance cycle, please wait to install Version 4.1 until you have submitted your reports. If you have previously installed the beta version of Version 4.1, please uninstall it before downloading CAP-88 PC Version 4.1. To uninstall, open “Control Panel,” click on “Programs and Features,” highlight the CAP88-PC Version 4.1 beta program, then right-click and select “uninstall."

Download CAP-88 PC Version 4.1 and supporting documents. 

CAP-88 PC Version is compatible with Windows 10. Version 4.1 has a full set of dose conversion factors from DCFPAK 3.02. In Version 4.1, report files are opened in word-processing programs to facilitate printing.
Version 4.1 System Requirements

  • Windows 7 or later.
  • NET Framework version 4.
  • 32-bit x86 architecture. 64-bit installation not supported but the 32-bit version can be installed on 64-bit systems.


A beta version of the STARGET Utility is available to convert meteorological data in STAR format to a *.wnd file for use in CAP-88 PC Version 4.1
Download  STARGET Utility and supporting documents.

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Version 4.0

Version 4.0, the previous version of the code, may still be used to demonstrate compliance with NESHAP Subpart H. CAP-88 PC Version 4.0 has age-dependent radionuclide dose and risk factors for ingestion and inhalation.

Download CAP-88 PC Version (ZIP) (37 MB, September 2014) (includes User Manual and other supporting documentation).

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Modeling Capabilities

Plume Modeling

CAP-88 PC uses a modified Gaussian plume model to estimate the average dispersion of radionuclides released from up to six sources. The sources may be either elevated stacks, such as a smokestack, or uniform area sources, such as a pile of uranium mill tailingsHelptailingsThe remaining portion of a metal-bearing ore after some or all of a metal, such as uranium, has been extracted.. While up to six stacks or area sources can be modeled, all the sources are modeled as if located at the same point; that is, stacks cannot be located in different areas of a facility. Uniform contamination is assumed for area sources.

Plume rise can be calculated assuming either a momentum or buoyancy-driven plume. The same plume rise mechanism (buoyant or momentum) is used for each source. Assessments are done for a circular grid of 16 sectors by setting distance and direction within a radius of 80 kilometers (50 miles) around the facility. Errors arising from these assumptions will have a negligible effect for assessments where the distance to exposed individuals is large compared to the stack height, area or facility size.

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Radionuclide Concentration Modeling

The program computes radionuclide concentrations in air, rates of deposition on ground surfaces and plants, and concentrations in food. It uses intake rates to people from ingestion of food produced in the assessment area and inhalation of airborne radionuclides. Estimates of the radionuclide concentrations in produce, leafy vegetables, milk and meat consumed by humans are made by coupling the output of the atmospheric transport models with the terrestrial food chain models in the U.S. Nuclear Regulatory Commission, Regulatory Guide 1.109 (PDF)(64 pp, 3.03 M, About PDF).

Variation in radionuclide concentrations due to complex terrain cannot be modeled; all assessments assume a flat plain.

Risk Estimate Modeling

Dose and risk estimates from CAP-88 PC are applicable only to low-level chronic exposures, since the health effects and dosimetric data are based on low-level chronic intakes. CAP-88 PC cannot be used for either short-term or high-level radionuclide intakes.

CAP-88 PC provides the CAP-88 methodology for assessments of both collective populations and maximally-exposed individuals and allows users to edit some environmental transport variables. A complete set of dose and risk factors, census data, and stability array data used in CAP-88 is provided, however, site specific data can be entered by the user.

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