Application of MCNP5 software for efficiency calculation of a whole body counter

Abstract

Efficiency of a whole body counter was calculated using MCNP5 code and measured experimentally. Measurements were performed using standard phantoms filled with water and a dissolved 137Cs isotope. The results obtained by calculation agree very well with the experimental ones for a set of different distances and axial shifts. The ORNL phantom of a human body was applied to investigate how representative the experimental calibration source is of the measured human subjects. Differences were found to be up to 20%, so corrections should be made if an accurate value of activity in the human body is desired. Experimental and theoretical work presented in this paper is related to a sodium iodide (NaI) detector, which has relatively low resolution. However, such systems are still in use in many laboratories. On the other hand, detection efficiency of a low-resolution system is larger than that for HpGe detectors, which might be important in an accidental situation when shorter measuring time is very important. Copyright © 2012 Health Physics Society.