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 (http://www.nrc.gov/about-nrc/regulatory/research/contact-us-varskin.html).
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.
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 micro-meter to a value of 0.01 micro-meter. 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.
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).
Varskin 3 is not designed for installation on a network. Attempts to install the code on a network have been unsuccessful. QA documents and source files are included on the distribution CD but will not be copied to your hard drive by the installer.
Radiation Safety Information Computational Center
Oak Ridge National Laboratory
Oak Ridge, Tennessee, USA
Developed by: Center for Nuclear Waste Regulatory Analyses
Southwest Research Institute, San Antonio, TX, USA
U.S. Nuclear Regulatory Commission, USA
Keywords: beta-ray, contamination, energy deposition, kernels, radiation doses.