MCNP model of the EEAE ACCUSCAN Whole Body Counter

Monte Carlo simulations and verification measurements for the efficiency calibration of the ACCUSCAN shadow-shield type Whole Body Counter (WBC) of the Greek Atomic Energy Commission (EEAE) are presented. A model of the counter and RMC-II anthropomorphic phantom was developed using the MCNP code. Full energy peak efficiencies for different phantom positions were calculated for 60Co and 137Cs sources. The deviations between computational and experimental efficiencies were found to be less than 12 % for 60Co and 4 % for 137Cs for the Ge detector and less than 25 % for 60Co and 4 % for 137Cs for the NaI detector. This work contributes to the accurate quantification of internal contamination in individuals accidentally exposed in Greece by the Greek Atomic Energy Commission Laboratories and moreover demonstrates the effectiveness of using computational tools for understanding the calibration of radiation detection systems used for in vivo monitoring.

Effect of Radon Concentration in Air on the Quality of Radioactivity Measurements in the Human Body

A prototype shadow-shield whole body counter is used at the University of Ioannina Medical Physics Laboratory as a tool in radiation protection and in biomedical research. In this study the effect of natural airborne radioactivity on the measurement quality features was investigated and performance improvements were developed. Radon air concentration in the counting room was assessed using electret and track detectors over short and long time periods, respectively under various ventilation conditions. A method based on the assessment of the 214Bi 1.76 MeV spectral region was developed to correct for the interference of the radon products to the lower energies of the spectrum. Moreover airborne radioactivity in the counting room was controlled by forced ventilation. Double measurements were carried out in anthropomorphic phantoms and in adult volunteers to assess the impact of the room ventilation module in the measurement precision. Radon control coupled with corrections for the interference of its decay products improved substantially the counter performance characteristics.