Frequently Asked Questions About CAP88-PC v2.0
Q: Can CAP88-PC be used to estimate the dose to a resident who is closer than 100 meters to the release point?
A: This is not specifically disallowed in the rule, but is not good practice. For close-in distances,
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should be used because it accounts for building wake effects.
F.A. Gifford, Jr., writing in Volume 17 of Nuclear Safety, "Turbulent Diffusion Typing Schemes - Review", page 68 (issued 1976) notes a limitation to the Briggs modification of the Pasquill-Gifford formulation: the various expressions given by Briggs for the Sigma-y and Sigma-z parameters for turbulence classes A thru F are limited to distances between 100 and 10,000 meters, diverging from available data beyond those ranges. This is referred to the Air Resources Atmospheric Turbulence and Diffusion Laboratory 1973 Annual Report.
The Briggs dispersion coefficient recommendations were developed for an elevated point source and optimized for some TVA air concentration data. These are used in CAP88-PC.
Another effect at shorter receptor distances is building wake.
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uses various different equations for distances within an estimated wake perturbation field; CAP88-PC has no accounting for wake effects. The fields will persist for downstream distances that depend on building frontal area and elevation of the release point above the building.
Q: Why do I keep getting the following error message: "Couldn't find installable ISAM"?
A: Windows 95 (and higher) will automatically attempt to install CAP88-PC v2.0 in the directory "c:\Program Files\". The CAP88-PC v2.0 program will not run properly under this Program Files directory, because it is a Windows3.1 application that does not recognize directories with more than eight characters.
To correct this problem, you will have to un-install the program and re-install it.
The instructions for un-installing the program are in the user guide, which is on the web at:
cap88v2_userguide.pdf
2.11. Uninstall CAP88-PC Version 2.0
The Uninstall icon will uninstall only those files that were installed with CAP88-PC Version 2.0. Any extracted or created Population and Wind Files, as well as any Datasets and Output Files, will not be deleted. If the Uninstall icon has been removed, run the UNWISE.EXE program located in the CAP88-PC install directory.
To re-install the program correctly, first click on the C2.EXE file to download, and save it to your c:\ drive. Then open Windows Explorer, and double click on the C2.EXE file. The "Welcome" dialogue box will appear and ask if you want to install the program. Click "OK" to proceed.
When the "Select Destination Directory" dialog box appears, change the path
from: c:\Program Files\CAP88PC2
to: c:\CAP88PC2
then click "OK."
Follow the directions in the proceeding dialogue boxes to complete installation of the program.
Also, be sure to download and execute the
"Y2K/Windows95 patch"
immediately after installing the program, and before running the program for the first time.
Q: What is the technical basis to CAP88-PC?
A: CAP88-PC uses a modified Gaussian plume equation 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 tailings. Plume rise can be calculated assuming either a momentum or buoyancy-driven plume. Assessments are done for a circular grid of distances and directions with a radius of 80 kilometers (50 miles) around the facility.
The program computes radionuclide concentrations in air, rates of deposition on ground surfaces, concentrations in food and intake rates to people from ingestion of food produced in the assessment area. 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 U.S. Nuclear Regulatory Commission Regulatory Guide 1.109 terrestrial food chain models.
Dose and risk estimates from CAP88-PC are applicable only to low-level chronic exposures, since the health effects and dosimetric data are based on low-level radionuclide intakes.
Q: Why Does CAP88-PC Version 2.0 Requires English (United States)?
A: CAP88-PC v.2.0 runs calculations using FORTRAN, which recognizes commas as field delimiters only. Numbers to the right of a comma are assigned to the next variable in the program. For example, suppose FORTRAN reads variables X and Y from a European input file that supplies values 1,2 and 3,4 respectively. FORTRAN would read the value for 1 as X and 2 as Y. All calculations based on these inputs would be incorrect. To be read correctly, the input file must use a period to designate the decimal place: e.g., 1.2 and 3.4.
Please note that this issue may affect any FORTRAN application running under the Windows 95 operating system. You may wish to confirm that your Windows 95 Regional Settings are configured correctly for FORTRAN applications.
Q: Why do I get error messages when I go to add a decay chain, such as U-238 or Th-230? When the program dialog box asks me if I want to include the entire chain, I clicked on "Yes", and I received the following two
error messages: "Disk I/O error during read" and "User defined error," then the program ends.
A: This error occurs if you manually type in the radionuclide name, instead of choosing it by scrolling down and selecting it from the pick list. If you select the parent radionuclide from the pick list, the decay chain will load without error.
Q: Is there a way to import files from the Version 1 into Version 2?
A: Yes. Look at the options in the File menu, you'll see one that says "Convert .SCR file". That option allows you to take input from version 1 and use it for version 2. When you run version 1, it saves all the data in a 'screen' file. Screen files have the format *.SCR, where * is the name you assigned to the assessment.
Q: When I run a population assessment on CAP88-PC, why do the distances in my report not match the distances in the population file?
A: This looks confusing, but the program is actually doing exactly what it was designed to do. The distances in the population file are the 'outer edge' distances; that is, it is the distance from the center of the circular array to the outer edge of each particular sector segment, which contains the population.
But, when it's time to calculate concentrations, you want to figure what the
concentration is in the middle of each sector segment. The program thus interpolates between the inner and outer edge of each sector segment, calculates the concentration at the midpoint, and applies that concentration uniformly to everyone within the sector. So, a sector segment that starts at zero and ends at 250 gets calculated at 125, the next one starts at 250 and ends at 750, so the midpoint is 500, and so on. The midpoints are the distance that are reported in the output; hence the discrepancy.
Q: My facility has more than the six sources allowed by CAP88-PC. Do I have to do multiple runs?
A: No. On the number of sources, remember what it is that CAP88-PC is really doing with your releases. While you can specify up to 6 different sources, the only difference it makes is if the sources have really different heights or momentum/buoyant release data. Mathematically, it's as if all 6 sources are located together at the same point, with different plumes emanating from that point. If your sources all have similar heights, for example, if they're fume hoods at the same height, just group the releases together and it comes out the same.
Q: When I try to run the program and select "New Datafile" from the file menu or toolbar, it says "Select * from Dataset" isn't a valid path, then it exits the program. Why is this?
A: This is a result of using Windows95. By default, Windows95 installs programs in the subdirectory `Program Files', which is not recognized by CAP88-PC, version 2.0, because the subdirectory name has more than 8 characters To correct the problem, re-install the program and override the default to install the program in the directory c:\cap88pc2\ for
best results.
Q: What is CAP93-PC?
A: In 1993 EPA created a variant of CAP88-PC that has an altered wet deposition model. In CAP93-PC, rainfall is entered as the percentage of time that rain occurs annually, whereas in CAP88-PC it is taken as the total cm/year rainfall rate. The change was made to account for scenarios where rainfall is episodic and in which all rainfall is not equally effective in deposition. At the time this FAQ was prepared, EPA had no plans to release CAP93-PC for public use, nor allow it for NESHAPS compliance determinations.
Q: I tried to run CAP88-PC on my local area network, and I got the message, "couldn't lock file; share.exe hasn't been loaded." Is there a fix?
A: SHARE.EXE is a DOS program that controls the number of allowable users for a given file. CAP88-PC requires that only 1 user have its files open at any time. To do this, you should have SHARE.EXE either in your CAP88-PC directory or in your DOS directory. And, most importantly, please add this line to your AUTOEXEC.BAT file, after the PATH statement, if you have a PATH statement in your AUTOEXEC.BAT:
Load SHARE.EXE /L:500 /F:5100
Alternately, SHARE can be loaded in "high memory" with this statement in your AUTOEXEC.BAT file:
LH SHARE.EXE /L:500 /F:5100
As always, to make this change effective, you must re-boot your PC. A "warm boot" (control-alt-delete) is OK, as this runs the AUTOEXEC.BAT file.
Q: How do I model short-term or 'accident' releases in CAP88-PC?
A: CAP88-PC is not appropriate for modeling short term or accidental releases. There are several reasons for this. First, the dose/risk conversion factors in CAP88-PC are all predicated on chronic, low-level exposures. Second, the Gaussian model is, by definition, a long-term model, and CAP88-PC is written to only accept weather data that has a joint-frequency distribution typical of annual averages.
Also, CAP88-PC only models four pathways; ingestion, inhalation, immersion and ground surface. The dominant pathway in an acute release is usually skyshine, which CAP88 ignores. And, you get little ingestion in an acute release, so CAP88 would overestimate that pathway.
To model accidental releases, I recommend the HOTSPOT code by Steve Homann at Lawrence Livermore National Laboratory.
The code is available for download at the HOTSPOT website.
Q: The deposition velocity data used in CAP88-PC seems high compared to published measurements. Is this an oversight?
A: No. The deposition velocities are set artificially high to account for both the foliar deposition of particles, which adds to deposition over time, as well as the actual velocity of deposition from gravitational settling.
Q: How do I account for building wake or tip downwash of the plume?
A: CAP88-PC does not account for these effects explicitly. However, generally speaking the effect of building wake or tip downwash at the release point is to depress the plume. A conservative approach to modeling building wake/downwash is to set the release height to one meter, like that of a ground level release.
Q: Do I have to use the weather data that is supplied with CAP88-PC?
A: No. Quite the contrary, users are encouraged to use on-site weather data for CAP88-PC assessments. The weather data that is supplied is solely for convenience and is not endorsed in any way. CAP88-PC version 2.0 comes with a utility for converting on-site meteorological data into a format usable by CAP88-PC.
Q: Version 1.0 hangs up if I make changes to the DEFAULT.DAT file. It works fine if I don't change DEFAULT.DAT. Why does it do this?
A: Version 1.0 needs to have ANSI.SYS specified in your CONFIG.SYS file. The entry should be in this form:
DEVICE=drive:\directory name\ANSI.SYS
where 'drive' is the hard drive where your operating system is located, and 'directory name' is the directory or subdirectory where the operating system resides.
The reason for this error is that when you change the DEFAULT.DAT, CAP88-PC displays a warning message with a colored background to the screen. Because the program uses ANSI.SYS to change the background color, the program will fail if ANSI.SYS is not specified.
Model Limitations for CAP88-PC
Co-location of release points: While up to six stack or area sources can be modeled, all the sources are modeled as if located at the same point.
Plume Rise: The same plume rise mechanism (buoyant or momentum) is used for all sources.
Area Sources: Area sources are treated as uniform.
Complex Terrain: Variation in radionuclide concentrations due to complex terrain cannot be modeled.
Accidental Releases: Dose and risk estimates from CAP88-PC are applicable only to low-level chronic exposures, since the health effects and dosimetric data are based on low-level chronic intakes. CAP88-PC cannot be used for either short-term or high-level radionuclide intakes.
The User's Guide for CAP88-PC Version 1.0 has a typographical error concerning absolute humidity. In section 8.1.8 (page 8-11, second sentence) the figure provided for absolute humidity--8 milligrams/m3--is incorrect. The correct units are grams; the figure should be 8 grams/m3.
EPA 520/1-89-005 Risk Assessment Methodology: Draft Environmental Impact Statement for Proposed NESHAPS for Radionuclides, Volume 1, Background Information Document, United States Environmental Protection Agency, Office of Radiation Programs, Washington, D.C. 20460, February 1989.
Fields, D.E.; Miller, C.W.; Cotter, S.J. Validation of the AIRDOS-EPA computer code by simulating intermediate range transport of Kr-85 from the Savannah River Plant. Atmos. Environ. 18:2029-2036; 1984.
Gifford, F.A., Jr., "Turbulent diffusion-typing schemes: A review", Nuclear Safety 17(1):68-86, 1976.
Griggs, G.A., "Plume Rise, AEC Critical Review Series", TID-25075, 1969.
Little, C. A. and C. W. Miller, The Uncertainty Associated with Selected Environmental Transport Models, ORNL-5528 (November, 1979)
Maheras, S.J.; Ritter, P.D.; Leonard, P.R.; and Moore, R. Benchmarking of the CAP-88 and GENII computer codes using 1990 and 1991 monitored atmospheric releases from the Idaho National Engineering Laboratory, Health Phys. 67:509-517; November 1994.
Miller, C. W. And L. M. Hively, A Review of Validation Studies for the Gaussian Plume Atmospheric Dispersion Model, Nuclear Safety, Vol. 28, No. 4, October-December 1987, pp. 522-531.
Moore, R.E., Baes, C.F.III, McDowell-Boyer, L.M., Watson, A.P., Hoffman, F.O., Pleasant, J.C., Miller, C.W., "AIRDOS-EPA: A Computerized Methodology for Estimating Environmental Concentrations and Dose to Man from Airborne Releases of Radionuclides", (Reprint of ORNL-5532), EPA 520/1-79-009, U.S. EPA Office of Radiation Programs, Washington, D.C., 20460.
Pasquill, F., "The Estimation of the Dispersion of Windborne Material", Meterology Magazine, 90:33, 1961.
Rupp, E.M., Beall, S.E., Bornwasser, L.P., Johnson, D.H., "Dilution of Stack Gases in Cross Winds", USAEC Report AECD-1811 (CE-1620), Clinton Laboratories, 1948.
Simpkins, A. A. and D. M. Hamby, Predicted Versus Measured Tritium Oxide Concentrations at the Savannah River Site, Health Phys. 72:170-185; February 1997.
Till, J.E.; Meyer, R.M.; Radiological Assessment, A Textbook on Environmental Dose Analysis, US NRC, NUREG/CR-3332 ORNL-5968, September 1983.
Turner, D.B. "Workbook of Atmospheric Dispersion Estimates", Air Pollution Control Administration, Cincinnati, Ohio, 1969.
