Results of Calculations of External Gamma Radiation Exposure Rates from Fallout and the Related Radionuclide Compositions Operation Tumbler-Snapper, 1952 ABSTRACT This report presents data on calculated gammaradiation exposure rates and grounddeposition of related radionuclides resulting from Events that deposited detectable radioactivity outside the Nevada Test Site complex. INTRODUCTION The Events which deposited detectable radioactivity outside the Nevada Test Site complex! are listed in Table. 1. RESULTS Results of the calculations of relative external gamma radiation exposure rate and related radionuclide ground deposition are given in the Appendices. These calculations are described in detail in Ref. 2. The output of the calculation has 30 decay times, 10 from 1 to 21 h, 10 from to 300d, and 10 from 1 to 50 y. For each of these times and for zero time there are values of the external gammaradiation exposure rate normalized to 1 mR/h, 1 m abovethe surface, 12 h after the event, the associated values of uCi/m? for each radionuclide, and the total «Ci/m?. The 793U, 73°U, 238U and 25%24°Pu data were omitted primarily to keep the output unclassified. Futhermore,the natural uranium contentof the soil is about one million times that received from fallout and at least half of the plutonium in Nevada and Utahsoils comes from worldwide fallout.? Surface roughness effects are simulated by using Beck’s values* of (mR/h)/(uCi/m7?) for a relaxation length of 0.16 g/cm*. According to Beck, the concentration of fallout varies exponentially with soil depth, Z, according to the relation C = C,ee. Hedefines relaxation length as 1/a. TABLE 1. Event | Yield, date and placement of Events of Operation Tumbler-Snapper, 1952. Yield (kt) Date Placement Able 1 April 1 Air drop 793 ft Baker 1 April 15 Air drop 1109 ft Charlie 31 April 22 Air drop 3447 ft Dog 19 May 1 Air drop 1040 ft Easy 12 May 7 300 ft Tower Fox 1 May 25 300 ft Tower George 15 June 1 300 ft Tower How 14 June 5 300 ft Tower 1