Gamma-ray shielding calculations using empirical formulas for build-up factor: application to a practical case To Professor J.J. Fletcher

Abstract

Exposure of people to external ionizing radiation is controlled by time, distance and shielding. In the latter case, the radiation dose is reduced if shielding attenuates the radiation. The present study was aimed at comparing gamma-ray shielding calculation methods, the well-known trial-and-error method and a direct calculation method that make use of build-up factor’s empirical fitting formulas. The latter method was then applied to a practical case in gamma industrial radiography. The results showed that both methods provide comparable results. For high energies and high-density materials, it has been observed that all the build-up factor forms studied provide similar values. Contrariwise, it has also been observed that the linear form of the build-up factor seemed to underestimate shielding thickness for low gamma energies (lower than ≈ 1 MeV). Furthermore, the application of the method using empirical build-up factor functions to a practical case in gamma industrial radiography showed that the calculations are in agreement with the measurements carried out on the field. This demonstrates that this method is efficient and can still be used even though more sophisticated and accurate methods are now available.