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 riskriskThe 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 radionuclideradionuclideRadioactive 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).
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 tailingstailingsThe 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.
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.
Version 4 is the most recent version of the code and may be used to demonstrate compliance with NESHAP Subpart H. Download CAP-88 PC Version 188.8.131.52 (ZIP)(37 MB, September 2014) (includes User Manual and other supporting documentation).
- Age-dependent radionuclide dose and risk factors for ingestion and inhalation.
- Additional radionuclides.
- Changes in the file management system.
CAP-88 Version 4 incorporates dose and risk factors from DCFPAK-2.2. In addition, the CAP-88 PC database, the user interface, input files, and output files, were modified to accommodate the DCFPAK-2.2 data formats and nomenclature.
Other changes less visible to the user include new code architecture, incorporation of numerical solvers for the calculation of radioactive decay chains, including the ingrowth of decay products during air transport and ground surface deposition, enhanced error messages, updated online help, and a utility for migrating Version 3 datasets, wind files and population files to Version 4. The modifications have produced a significant improvement in speed and stability for Version 4 relative to Version 3, and eliminated the solution approximations used in Version 3.
Version 4 System Requirements
- Windows XP SP3.
- Windows Vista SP1 or later.
- Windows 7 or later.
- Windows 8.
- .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.
CAP88-PC Version 4 is not compatible with earlier versions of the Windows operating system. However, Version 3 data files can be migrated to a new Version 4 installation. To migrate a Version 3 dataset, the user must run the dataset in the most recent copy of Version 3.