Using VARSKIN for Hot Particles Ingestion Dosimetry Evaluation (NUREG/IA-0535)

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Publication Information

Manuscript Completed: March 2020
Date Published: September 2022

Prepared by:
Shlomi Halfon, Ph.D.

Soreq Nuclear Research Centre
Yavne 81800 Israel

Vered Shaffer, Ph.D., NRC VARSKIN Project Manager
S. Bush-Goddard, Ph.D., NRC RAMP Project Manager
J. Tomon, CHP, NRC RPB Branch Chief

K. Tien, NRC Project Manager

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

Prepared as part of
The Agreement on Research Participation and Technical Exchange
Under the Radiation Protection Computer Code Analysis and Maintenance Program (RAMP)

Availability Notice

Abstract

Small highly radioactive particles referred to as "hot particles" have been a radiological concern and dosimetry challenge in the last few decades, especially in and around nuclear industry facilities. VARSKIN has been used for decades to calculate hot particles dose in the case of skin exposure largely due to contamination scenarios. To test the feasibility of VARSKIN for dosimetry analysis of hot particle ingestion scenarios, VARSKIN was benchmarked against Monte Carlo N-Particle (MCNP) simulations and data from the literature, to evaluate its ability to be used for the calculation of beta doses to the digestive tracts in the case of hot particles
ingestion.

VARSKIN was found to a large extent in alignment with the calculation of the maximum dose from ingested hot particles. The VARSKIN code results were found to be within approximately 10 percent of those from MCNP, for electron energies between 0.2 to 2.5 megaelectronvolts (MeV) and hot particle sizes no larger than a few hundred micrometers in diameter. 

However, to perform such calculation in VARSKIN, it was found that few enhanced parameters must be included in the calculation. The first is to cancel the backscatter correction. Second an appropriate volume averaging parameter according to the International Commission on Radiological Protection (ICRP) organ model must air be included. Third, the user must set the averaging area to give the maximum Dose Area Product (DAP). 

With these enhanced parameters, the dosimetry from VARSKIN will be able to estimate the worst case for the hot particle exposure which will mainly relate to the local dose for a potential ulceration risk or the average dose for cancer risk. 

The dose distribution around a cylindrical brachytherapy source inside the body was also calculated using VARSKIN. VARSKIN results compared well to MCNP version 6.2 and the Electron Gamma Shower (EGSnrc) software package when a point source was modeled without self-attenuation with the source at distances more than approximately 1 millimeter (mm) away from the source. When realistic source composition was included in the models, VARSKIN produced results that were approximately 30 percent lower than those from EGSnrc.