410861 Long Term Activity Estimates For The Northern Marshall Islands ~ This paper provides preliminary upper-bound estimates of the residual gamma activity on the northern Marshall Islands due to U.S. atmospheric testing at Bikini. These estimates are intended to be indicative of the activity to be determined by up-coming deteiled Surveys. Estimates are also provided for islands in the Enewetak atol} and compared with the 1972 survey. Finally, an analysis of wind pro- files and fallout patterns is presented which serves to delineate those _morthern Marshal] islands which were uncontaminated by fallout froz the Bikini tests. BEST COPY AV, AVAILABLE ST COPY APPROACH 1. After 20 years or so, the principal fission procucts of interest are 590 and cs 3? whose characteristics are summarized below. Isotope gr20 cs 29? Curies/kt of Fission at H+] 110 - 329 Fraction of Total Curies 2.1x107” 6.1x1077 Half Life _ Decay Mode 29y 30y B only 2(100%) and ¥ (932) “ The fractional contribution of Cs 137 to the one-hour dose rate is mot the same as the fraction of total Curies at one hour since the cs}9? Y energy is lower than that average energy for all fission products (.66 MeV vs. 2 MeV). This results in a roentgen response for cs??? that ts 0.4) times that for the inventory taken as a whole. At some time after burst, when cs}3? fis the only remaining fission product voemitter, the dose rate is given by DOE ARCHIVES D(T) = O(1 hr) [6.1x107” x 0.42) (0.5)*/3° Note that beta activity is not being considered here on the presumption that the survey techniques distinguish between where T is in years. Enclosure (2) 2°