Results of Calculations of External Gamma Radiation Exposure Rates from Local Fallout and the Related Radionuclide Compositions of Selected U.S. Pacific Events Abstract This report presents data on calculated gammaradiation exposure rates and local surface deposition of related radionuclides resulting from selected U.S. Pacific events. Introduction In the past, we have calculated the normalized external gammaradiation exposurerates that resulted from local fallout from the Nevada Test Table 1. the reconstruction of radiation doses downwind Mike Site (NTS).' These calculations have been used in of NTS. More recently, we were asked to make similar calculations to assist in the reconstruction of doses to personnelparticipating in nuclear tests in the Pacific. This report contains the results of these calculations that we made and that were used by the Nuclear Test Personnel Reviewof the Date, placement, and yield of se- lected U.S. Pacific events. Event Bravo Romeo Yankee Zuni Tewa Date Oct. 31, 1952 Feb. 28, 1954 Mar. 26, 1954 May 4, 1954 May27, 1956 July 20, 1956 Placement Yield (MT) Surface 10.4 Surtace Barge Barge Surface 13.5 3.5 Barge 15.0 11.0 5.0 Defense Nuclear Agencv and its contractors. The selected U.S. Pacific events” are listed in Table 1. Results Results of the calculationsof relative external gammaradiation exposure rate and related radionuclide ground deposition are given in the Appendices. These calculations are described in detail in Ref. 3. The output of the calculation has 30 decav times: 10 from 1 to 21 h, 10 from 1 to 300 d, and 10 from 1 to 50 y. For each of these times and for zero time, there are values of the external gamma radiation exposure rate normalhzed to i mR/h, 1 m above the surface, 12 h after the event; the associated values of uCi/m* for each the concentration of fallout varies exponentially with soil depth, Z, according to the relation C = C,e~*4. He defines relaxation length as 1/a. Fractionation effects were simulated by the removal of a fraction of the refractory nuclides from the calculation. Calculations for each event were performed for unfractionated debris and for using Beck's values? of (mR/h)/(uCi/m?) for a relaxation length of 0.16 g/cm?. According to Beck, ternal gamma-ray exposure rates and associated radionuclide; and the total uwCi/m-. Surface roughness effects are simulated by debris with 0.5 and 0.1 of the refractorv elements present. Each Appendix contains three sets of 11 pagesof calculated results relating to one event in Table 1. Each set of 11 pages is marked Page 2 through Page 12. Page 2 of each set gives the ex- values of total microcuries per square meter at 30