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Portland cement concrete is an ideal material for use in construction of radiation shields. Although there are other materials that could be employed for radiation shielding purposes, concrete is not only economical, but it also has the advantage of being a material that can be cast into any desired homogeneous structural shape. Concrete is now commonly used for shielding of atomic research facilities, nuclear power plants, and for radiation medical and research units or equipment. Conventional concrete of sufficient thickness can be and is being used for such purposes. However, where usable space is a major consideration, the reduction in the thickness of the shield is accomplished by the use of high-density concretes. Such high-density concretes, produced by the use of heavy aggregates, will usually have a unit weight ranging from 210 to 240 lb/ft,3 which is about 50 per cent higher than the unit weight of conventional concrete. They can, however, be produced with densities up to about 330 lb/ft3 using iron as both fine and coarse aggregate. For certain types of biological shields there is a need to include materials of low atomic weight in the concrete. At present there are no ASTM test methods or specifications for concrete or concrete-making materials written specifically for biological shield applications. However, several of the existing ASTM methods and specifications pertaining to concrete and concrete-making materials are applicable to shielding concretes. Specific references to some of these methods and to their applicability are covered later herein.
Professor of civil engineering, University of California, Berkeley, Calif.