LONG-RANGE FALLOUT FROM SEDAN AND SMALL BOY SHOTS PHILIP W. KREY and RALPH E. FRIED Isotopes, Inc., Westwood, New Jersey ABSTRACT A sampling network was established across the United States to collect debris from the Sedan and Smail Boy shots. Gross gamma assays, gamma-decay measurements, and gamma-spectrum and radiochemical analyses were performed on retrieved samples. Sedan, an underground burst, produced a cloud that was fairly homogeneous and highly fractionated. Small Boy, a surface burst, produced a heterogeneous cloud and even greater fractionation effects than Sedan. Molybdenum-99 in both shots behaved as a refractory material and did not represent an ideal tracer of fission-product debris. OBJECTIVES In the spring of 1962, Isotopes, Inc., undertook to collect, analyze, and characterize fallout from subsurface and surface bursts at intermediate- and long-range downwind distances from ground zero. The nuclear bursts studied were the Sedan and Small Boy shots in Operation Sun Beam. Sedan was approximately a 100-kt total yield with less than 30-kt fission; Small Boy was a low-yield surface burst.’ SAMPLING SITES Three lines of sampling stations extending in a north—south direc- tion were established across the country (Fig. 1). The most westerly line for the Sedan shot consisted of 12 stations situated about 15 miles apart at a distance of approximately 630 miles from ground zero. The 82