A STUDY OF THE RADIATION SHIELDING CHARACTERISTICS OF BASIC CONCRETE STRUCTURES AT THE TOWER SHIELDING FACILITY

In the first of a series of experiments performed to investigate the protection afforded by various typical structures against prompt weapons radiation, radiationintensity measurements were made at the Tower Shielding Facility in two concrete-shielded bunkers and in an interconnecting tunnel. Prompt weapons radiation was simulated by the Tower Shielding Reactor II, which was operated 100 ft above the ground. The distance between the reactor and the bunkers was approximately 700 ft. The bunkers were each 12-ft cubes and were constructed so that the shield thickness on the front face of one and on the top face of the other could be varied in 4-in. steps from 0 to 20 in. The thickness of concrete and dirt surrounding all other faces was sufficient to make them black to incident radiation. The immediate goals of the experiment were to study (1) the attenuation of radiations by various thicknesses of ordinary concrete slabs, (2) the buildup of radiation intensities within the cavities by scattering of radiation in the walls, and (3) the transmission of radiation down a tunnel with two right-angle bends. The gamma-ray and fastneutron dose rates and thermal- neutron fluxes measured at various positions within the bunkers and in the tunnel and the pulse-height spectra from a 3-in. sodium iodide crystal determined at one position in the top bunker and one position in the tunnel are reported. (auth)