In a notice filed February 10 by the U.S. Environmental Protection Agency (EPA), the agency notes that updated National Emission Standards for Radionuclides have been put into place and that version 4 of EPA’s CAP88-PC model is now available.

CAP88-PC version 4 is approved by the EPA to demonstrate compliance with National Emission Standards for Hazardous Air Pollutants (NESHAP) that apply to radionuclides, but EPA says numerous changes and improvements have been added to the model under Version 4.

Any facility subject to requirements for radionuclide NESHAP found in Title 40 of the U.S. Code of Federal Regulations, Part 61, Subpart H, is potentially affected by this action; and EPA has established a public docket on the matter which can be found at www.regulations.gov/#!docketDetail;D=EPA-HQ-OAR-2002-0050.   

From a user perspective, EPA notes that the most significant changes included in Version 4 are the incorporation of age-dependent radionuclide dose and risk factors for ingestion and inhalation. Additionally, the number of radionuclides covered by the NESHAP has been increased. Changes in the file management system used by the program have also been included.

This is significant for those in the nonwovens industry who produce filtration media intended to capture air emissions of radionuclides.
Several nonwoven technologies that meet this application have been in place since at least 1988, and numerous solutions are available from a variety of nonwoven materials.  

According to EPA, version 4 of CAP88-PC has other changes that are “less visible” to the user. Included in these changes are:  new code architecture; incorporation of numerical solvers for the calculation of radioactive decay chains (including the in-growth 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 agency notes that these modifications have produced significant improvements in speed and stability relative to version 3 and have eliminated solution approximations that were used in Version 3.

EPA originally issued a NESHAP to control radionuclide emissions from a number of different source categories on December 15, 1989, (docket number EPA-HQ-OAR-2002-0050-0028), and Subpart H of 40 CFR part 61 is one of the source categories covered in the 1989 final rule.

Facilities owned and operated by the Department of Energy (DOE) are regulated under subpart H, and DOE administers many facilities across the country—including government-owned and contractor-operated facilities—that handle significant amounts of radioactive material that can be emitted to the air in various chemical and physical states. Subpart H is therefore intended to limit radionuclide emissions (except radon) from the stacks and vents at DOE facilities to ensure no member of the public receives an effective dose equivalent to more than 10 millirems per year (mrem/yr) or in SI units 0.1 millisievert per year (mSv/yr). See Title 40, U.S. Coder of Federal Regulations, Part 61.92 for more information.

The original CAP88 (Clean Air Act Assessment Package-1988) was a set of computer programs, databases and associated utility programs for estimating dose and risk from radionuclide emissions and was put into place in early 1992. It provided dose and risk assessments of collective populations, maximally-exposed individuals, and selected individuals. Versions 2.0, 2.1 and 3 were released in 1999 and 2007 respectively.

While Version 4 doesn’t modify calculations contained in previous versions, according to EPA, modifications have been made to add flexibility, enhance stability of the code and make it easier for users—all while improving the model’s quality assurance. The agency has also implemented an extensive testing and documentation program in version 4 to address user concerns with previous versions. This enhanced documentation allows greater compatibility with user software quality assurance programs according to EPA.

The total number of radionuclides available has also been increased from 825 under Version 3 to 1252 in Version 4; and the maximum number of radionuclides that can be included in any single case has been increased from 256 in Version 3 to 500 in Version 4.
Like all models, however, EPA notes that there are some limitations in the CAP88-PC system.

For instance, while up to six stacks or sources can be modeled, all the sources are modeled as if they are located at the same point (i.e., stacks cannot be located in different areas of a facility). The same plume rise mechanism—buoyant or momentum—is also used for each source, and multiple sources are treated as uniform.  The agency further notes that variation in radionuclide concentrations due to complex terrain cannot be modeled, but errors that arise from these assumptions should have a negligible impact on assessments where the distance of exposed individuals is large compared to the stack height, area, or facility emissions.

Docket materials are available through www.regulations.gov or in hard copy at the Air and Radiation Docket in the EPA Docket Center (EPA/DC), EPA West, Room B 102, 1301 Constitution Avenue NW, Washington, DC. For those in the DC area, EPA’s Docket Center Public Reading Room is open from 8:30 a.m.-4:30 p.m., Monday through Friday, except legal holidays. The telephone number for the Public Reading Room is 202-566-1744, and the telephone number for the Air and Radiation Docket is 202.566.1742.

Copies of the CAP88-PC Version 4 model are also available electronically at http://www.epa.gov/radiation/assessment/CAP88/index.html.

For more information, please contact Reid J. Rosnick in EPA’s Radiation and Indoor Air, Radiation Protection Division (6608T). Rosnick can be reached in care of EPA, 1200 Pennsylvania Avenue NW, Washington, DC 20460, or by phone at 202.343.9200. E-mail can be addressed to [email protected]. n


Peter Mayberry is president of Mayberry & Associates in Washington, DC. Peter is a third-generation Washingtonian and government relations professional whose career spans more than three decades. He served as INDA’s Director of Government Affairs from 1989-2009 and has a deep understanding of legislative and regulatory issues facing our industry. Peter is also the author of www.nonwovensregs.com and can be reached via e-mail addressed to [email protected].