RSICC CODE PACKAGE CCC-522
1. NAME AND TITLE
VARSKIN 3: Computer Code System to Assess Skin Dose from Skin Contamination,
Version 3.1.0.
2. CONTRIBUTORS
Center for Nuclear Waste Regulatory Analyses, Southwest Research Institute, San Antonio, Texas and the U.S. Nuclear Regulatory Commission.
3. CODING LANGUAGE AND COMPUTER
Fortran and Visual Basic; Pentium (C00522PC58606).
4. NATURE OF PROBLEM SOLVED
VARSKIN 3 calculates the radiation dose (gamma and beta) to skin from radioactive contamination of skin or protective clothing. Varskin 3 Version 3.1.0 corrects a programming error in earlier versions of Varskin 3 that occurred when calculating the percent of electronic equilibrium established for the photon dose model. In general, the correction will result in lower doses calculated for radionuclides that emit high-energy photons, especially at shallow skin depths. Although this correction makes photon dose calculations more accurate, it still assumes that the photon source is a point source; and build up as a function of depth is not modeled. Subsequent versions of Varskin will take into account distributed sources and build up. The NRC is sponsoring a further enhancement to replace the existing photon dose algorithm, develop a quality assurance program for the beta dose model, and correct technical issues reported by users. To facilitate that enhancement, we encourage you to contact NRC, if you are aware of any problems or errors associated with the VARSKIN code. Search for “VARSKIN” and read additional information here.
VARSKIN 3 is significantly easier to learn and use than VARSKIN Mod 2 and includes numerous corrections and enhancements that are noted in the User Manual. The default area for skin dose calculations was changed to 10 cm2 to conform to recent regulatory guidance. The backscatter correction and gamma dose models were upgraded. The input data file for VARSKIN Mod 2 was modified to reflect current physical data, to include the contribution to dose from internal conversion and Auger electrons, and to reflect a correction for low-energy electrons. In addition, the computer code SADDE (Scaled Absorbed Dose Distribution Evaluator) Mod 2, is incorporated into Varskin 3, thus eliminating the need for additional input from the user.
VARSKIN3 calculates the dose to 10 cm2 as a default for comparison to the 50 rad limit and also contains the capability of calculating the dose to other areas, including 1 cm2, to evaluate an exposure against the eye dose limit. The dose is computed at any depth in skin or in a volume of skin from point, disk, cylindrical, spherical, slab (rectangular), and syringe sources. Doses from multiple sources can be computed. A help file that includes all of the information from the NUREG document in addition to a tutorial has also been added to the code package.
5. METHOD OF SOLUTION
VARSKIN 3 uses improved algorithms for calculating skin dose that take advantage of the increased power of modern personal computers that improve the overall accuracy of the calculations. Source density is reset to 0.001 g/cm3 when point and 2-D models are used for calculations. The backscatter correction model has been expanded to include 3-D sources and is applied regardless of the dose-averaging area. The minimum distance between the source and target was reduced from 0.27 μm to a value of 0.01 μm. Sixty radial dose calculation points are used on the target area instead of 26 points used in VARSKIN Mod 2. Once the 60-point distribution is calculated, the distribution is evaluated at 10,000 points to increase the reliability of the calculation. VARSKIN 3 evaluates the dose at 50 depths for volume-averaged doses instead of 20 points. Once the 50 point distribution is calculated, the distribution is evaluated over 10,000 points to increase the accuracy and eliminate oscillating results. VARSKIN 3 calculates the backscatter correction factor at each of the 50 depths in the volume averaged dose distribution. In VARSKIN 3, the capability of adding multiple radionuclides was eliminated and a more accurate method of creating library files was incorporated. An improved gamma dose model was incorporated into VARSKIN 3 that calculates the gamma dose to any area up to 10 cm2. BETADATA.DAT is no longer used as the input file for VARSKIN 3. Each user builds a library that contains only the radionuclides of interest to that user. The new data files contain physical data for the average energy, maximum energy, and yield based on data generated by the computer code NUCDECAY (Oak Ridge National Laboratory, 1995, distributed by RSICC as DLC-172), which uses data published in ICRP 38 (1983). Further information in the library files includes data for gamma dose calculations and contributions from internal conversion and Auger electrons.
6. RESTRICTIONS OR LIMITATIONS
Note that VARSKIN 3 cannot accurately address the lack of charged particle equilibrium. See the User Manual for details on restrictions and comments above
7. TYPICAL RUNNING TIME
Run times for VARSKIN 3 vary from a few seconds to several minutes. The code is interactive.
8. COMPUTER HARDWARE REQUIREMENTS
VARSKIN 3 was tested at RSICC on a Pentium IV running Windows XP with Service Pack 3.0.
9. COMPUTER SOFTWARE REQUIREMENTS
VARSKIN 3 was developed under the Windows operating system on personal computers. Microsoft Visual Basic 6 (for the user interface) and Lahey Fortran 7.1 compilers were used to create the executables which are included in the package.
10. REFERENCES
a: Included in documentation:
J. S. Durham, "VARSKIN 3: A Computer Code for Assessing Skin Dose from Skin Contamination," NUREG/CR-6918 (2006).
b: Background information:
R. J. Traub, W. D. Reece, R. I. Scherpelz, and L. A. Sigalla, "Dose Calculation for Contamination of the Skin Using the Computer Code VARSKIN," NUREG/CR-4418, PNL-5610, Pacific Northwest Laboratory (August 1987).
J. W. Poston and D. M. Busche, "Software Review: VARSKIN-MOD1," Health Physics 58(5), 665.
W. D. Reece, S. Miller, and J. Durham, "SADDE (Scaled Absorbed Dose Distribution Evaluator)," NUREG/CR-5276, PNL-6761 (January 1989).
J. S. Durham, “Errata for NUREG/CR-5873, VARSKIN MOD 2 and SADDE MOD 2: Computer Codes for Assessing Skin Dose from Skin Contamination,” Health Physics Society’s Newsletter, 10, 31-32 (October 1994).
J. S. Durham, “Further Errata for NUREG/CR-5873, VARSKIN MOD 2 and SADDE MOD 2,” Health Physics Society’s Newsletter, 12, 18 (December 1994).
11. CONTENTS OF CODE PACKAGE
The package is transmitted on a CD which includes the referenced document cited in 10a.and the Fortran and Basic source files, Windows executables, built-in data libraries and on-line help. QA documents and source files are included on the distribution CD but will not be copied to your hard drive by the installer.
12. DATE OF ABSTRACT
December 1987, revised February 1993, March 1995, October 2004, November 2004 and November 2006, February 2009, May 2009.
KEYWORDS: BETA-RAY; KERNEL; RADIOACTIVITY; ENERGY DEPOSITION; CONTAMINATION