VARSKIN: A Computer Code for Skin Contamination and Dosimetry Assessments (NUREG/CR-6918, Revision 4)

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Publication Information

Manuscript Completed: April 2021
Date Published: July 2021

Prepared by:
D.M. Hamby
C.D. Mangini
J.M. Luitjens
D.L. Boozer
Z.G. Tucker
C.T. Rose
R.S. Flora

Renaissance Code Development, LLC
Corvallis, Oregon

V. Shaffer, NRC Project Manager

Office of Nuclear Regulatory Research
U.S. Nuclear Regulatory Commission
Washington, DC 20555-0001

Availability Notice

Abstract

VARSKIN+ is a U.S. Nuclear Regulatory Commission (NRC) computer code used by staff members and NRC licensees to calculate occupational dose to the skin resulting from exposure to radiation emitted from hot particles or other contamination on or near the skin. These assessments are required by Title 10 of the Code of Federal Regulations (10 CFR) 20.1201(c), which states that the assigned shallow dose equivalent is to the part of the body receiving the highest exposure over a contiguous 10 cm² of skin at a tissue depth of 0.007 centimeters (7 mg/cm²). Additionally, NRC staff evaluate radioactive intakes through wounds pursuant to 10 CFR 20.1202(d). VARSKIN+ can be used to perform wound dose assessments if the metabolic modeling and dosimetry methods are consistent with NRC regulations (e.g., use of 10 cm² averaging area for skin dose assessments and tissue or organ weighting factors as defined in 10 CFR 20.1003).

The VARSKIN+ computer code, an algorithm to calculate skin dose from radioactive skin contamination, has been modified on several occasions. As in previous versions, predefined source configurations are available in VARSKIN+ to allow simulations of point, disk, cylinder, sphere, slab, and syringe sources. Improvements to earlier versions included enhanced photon and electron dosimetry models, as well as models to account for airgap and cover materials. VARSKIN+ gives the user the option to have the code automatically include all decay products in dosimetry calculations or to allow the user to manually add progeny. Both ICRP 38, “Radionuclide Transformations – Energy and Intensity of Emissions” (1983), and ICRP 107, “Nuclear Decay Data for Dosimetry Calculations” (2008), nuclide libraries are available at the user’s option and contain data on gamma rays, X rays, beta particles, internal conversion electrons, and Auger electrons. Although the user can choose any dose-averaging area, the default area for skin dose calculations is 10 square centimeters, to conform to the requirements in 10 CFR 20.1201(c). A variety of unit options are provided (including both British and International System (SI) units), and the source strength can be entered in units of total activity or distributed in units of activity per unit volume. The photon model accounts for photon attenuation, charged particle buildup, and electron scatter at all depths in skin. The model allows for volumetric sources and clothing or airgaps between source and skin. The electron dosimetry model has a robust accounting for electron energy loss and particle scatter. Dose point kernels are Monte-Carlo based and results agree very well with Electron Gamma Shower (EGS) and Monte Carlo N Particle (MCNP) probabilistic simulations.
 
With the release of VARSKIN+ three new physics modules are introduced: (1) wound dosimetry; (2) neutron dosimetry; and (3) eye dosimetry. Skin and wound dosimetry implement a new alpha dosimetry model for shallow skin assessments. The new VARSKIN+ user interface is written in Java with all scientific coding updated to Fortran 2018. A chronology of VARSKIN development since its inception in 1987 is provided below.