To —E por tt =. | i 4! DISCUSSION OF CFP-SITe FaLLOUT 1 os ee aes gee Fallout off-site followed the pattem immeciately established at and adjacent to the proving ground where the cloud in genesal aoved east north easterly with prevailing winds. Task force ships southeast -of NAN received the first fallout, being om the southern edge of the main strip of contamination. Fallout om the ships ranged from ine tensities of 1500 millireentgens per hour on the BATROKO which was closest to the center of the fallout path to a fer millircectgens per hour on vessels farther south. Pallout began at Rongerik Atoll at 1348 hours, 1 March as show by a self-recording radiation detection station placed there by the NYOO AEC and operated by personnel of the Air “eather Station, This instrument went off scale at 100 mr per hour at 1418 bre 1 Larch. Based upon query from air weather personnel a monitor was dispatched With the supply PBN on the moming of 2 March. A ground reading of 2000 mr/hr was obtained at 1115 by the monitor who evacuated 8 of the personnel on his om initiation and recomended evacuation of the re- mainder as s00n as possible based upon the high radiation levels. This Was concurred in and the remaining 20 were evacuated by Fal! at 1645, 2Mareh, Calculations estimating the dose received indicated that per sonnel evacuated at 1115 would have received 85 r asd the remainder 95 r. This was in fair agreezent with readings of film badges on per sonnel, Maximum film badge reading was 98r representing 3 men, 52r for l, 44r for 1, 4Or for 9. Average dose for all personnel, 54 roatgas. Inasmuch as the data from Rongerik is the only data showing exact time the fallout occurred at any location east of the proving ground and adjacent to populated islands affected by substantial radiation, its importance is such that calculation of dosages received by native populations are based upon it for time of fallout in those locations. 4 detailed analysis of this data is therefore appended in the medical tab. . Survey of Rongelap was made by Patter ABLE of Security Patrol Squadron (Patron 29) with NYOO Scintameters aboard on 2 March and found an estimated reading of 6750 mr/hr. (Later calibration for aerial survey equipment revised this to 1350). Based on this and its proximity to Bongerik it was decided that it would protabiy be necessary to evacuate the atoll. Consequently, the PHILIP, DDE 498, was dispatched to seach Pongelap on the moming of 3 Marck. In the meantime a Pai was sent to ground survey the atoll and at 1830 hours, 2 Lareh, their grouna survey showed @ reading of 14,00 miliiroentgens per hour. Celeriation of asage to 3 Maren incicated about 110 roextgens 80 the order to evacuate was given. The destroyer PHILIP evacuated the natives by 0925 to 1025, 3 March. Calculation of the total dose indicated that 130 roentgens were received. Detailed calculations are sppenced in the medical tab. A total of 65 natives were renoved, 16 natives (the old anc sickest) by PSL and 49 by DDE, iit