The erection of a concrete biological shield at Hanford, Washington presented several unique construction problems. This shield encloses the radioactive core of a reactor and is designed to protect operating personnel from the harmful effects of pile neutrons and associated gamma radiation. Permanent steel forms were erected to close tolerance around the reactor and filled with high density concrete by means of prepacked method. Prefabricated sections of the steel forms, or crates, were five to eight feet deep and weighed up to 18 tons each. During erection, the process holes through successive crates were kept within 0.012 in. of their nominal distance. The left side, top shield, and right side of this biological shield were constructed integrally to form a rigid frame. The front and rear crates, which contain numerous process holes, were keyed into the side and top shields so as to permit relative expansions of shield components and to provide for their lateral support. These massive steel and concrete walls provide considerable resistance to blast and earthquake forces, support numerous process facilities, contain pile gas, as well as protect personnel from nuclear radiation.

A number of the questions which have been posed to us in the subject references are commented upon below. These have been reviewed by personanel of the Research and Engineering Operation and the Facilities Engineering Operation, Chemical Processing Department, and of the Chemical Research and Development Operation, Hanford Laboratories Operation. Particular acknowledment is given G. J Alkire, J. P. Duckworth, J. B. Fecht, R. G. Geier, E. R. Irish, H. M. Jones, G. C. Oberg, A. M. Platt, W. H. Reas, W. C. Schmidt, R. J. Sloat, W. H. Swift, M. T. Walling and L. L. Zahn of these organizations for assistance given assembling this information.