407587 Long Term Activity Estimates For The Northern Marshall Islands This paper provides preliminary upper-bound estimat s of the residual gamma activity on the northern Marshall Islands du to U.S. atmospheric testing at Bikini. to be These estimates are intende indicative of the activity to be determined by up-comine de éiled Surveys. Estimates are also provided for islands in the En wetek ato} and compared with the 1972 survey. Finally, an analysis of Wind pro- files and fallout patterns is presented which serves to del neate those northern Marshall islands which were uncontaminatec by felldut froz the Bikini tests. I. BEST COPY AVAILABLE _ APPROACH After 20 yeers or so, the principal fission product of interest are 5790 and cs}?? whose Characteristics are summarized beldy. Isotope gr? cs9? Curies/kt of Fission et Ht] Fraction of Total Curies 110 - 320 2.1x1077 6.1x107” Half Life _ Decay Mode 29y 30y B only B(100z) and ¥ (93%) dose rate The fractional contribution of cst9? to the one-houy is not the same as the fraction of total Curies at one hour[since the cs 23? that average energy for all fi sion pro- y energy is lower than ducts (.66 MeV vs. 2 MeV). This results in a roentgen respgnse for cs}9? that is 0.41 times that for the inventory taken as a whole. At some time after burst, when cs)9? is the only remaining fisgion product syeemitter, the dose rate is given by b(t) = B(1 hr) [6.1x2077 x 0.41) (0.57/20 where T is in years. DDE ARCHIVES Note that beta activity is not being gonsidered here on the presumption that the survey techniques distinguish between Enclosure (4) —_ ea