Doses Behind Vertical and Horizontal Barriers from a Plane Source of 1.25 MeV Gamma-Ray Photon

Abstract

Calculations were performed by the Monte Carlo method to determine the dose at various detector locations behind a vertical barrier and below an adjacent horizontal barrier. Results were obtained, using two different Monte Carlo approaches, for a 1.25-MeV simulated ground source incident on 60, 40, and 20 psf of concrete. The results of the Monte Carlo calculations were used to calculate reduction factors. The above-ground reduction factors compared with those of Spencer to within 10%. The below-ground reduction factors were compared with those calculated from the OCD Engineering Manual, and the agreement in this case was found to be unsatisfactory. In some instances, discrepancies were found to be as high as a factor of 3. For the case of the open basement, agreement among the three methods was found to lie within 10 to 20%. The results obtained by the two Monte Carlo methods used were found to be in excellent agreement. These results also compared to within 10 to 15% with results of experiments performed at Technical Operations Research. The results indicate that further investigation is necessary to determine the amount of scattered radiation within a basement.