ATTENUATION OF FALLOUT RADIATION AS A FUNCTION OF CONCRETE BLOCKHOUSE WALL THICKNESS

This experiment was conducted to verify theoretical calculations of wall thickness effect on the shielding characteristics of a concrete blockhouse in a uniformly contaminated fallout field. Two gamma emitters, cobalt 60 and cesium 137, were used to simulate uniform planes of contamination. The dose rates at various locations within blockhouses with wall thickness of 48 psf, 93. 7 psf, and 139 psf were measured with ionization-chamber dosimeters. Reduction factors were calculated from the data taken at the center detector positions and compared with reduction factors computed from the theoretical calculations of National Bureau of Standards. Experimental and theoretical reduction factors 3 feet and 6 feet above the center of the concrete blockhouse agreed within =15% for a uniformly contaminated plane of cobalt 60, and with =20% for cesium 137. Cobalt 60 and cesium 137 radiation show approximately exponential attenuation of dose rate as a function of wall thickness ranging from 48 to 139 psf for detector heights of 0 (ground level), 3, and 6 feet.