detonation site, thus these persons would have received fallout with similar gra- nule diameters as that given in Fig. 1 for Bikini Ash. Their location was fur- ther south than the location reported for the 5th Lucky Dragon (Ts57) thus less debris fell on Sifo Island. The fallout encountered by these people was estimated to be off the centerline of the BRAVO cloud by about 30 km. 4, A Simple Model for Exposure Rate History at Rongelap, Sifo and Utirik Islands The exposure rate survey by the crew members of the USS PHILIP (0C68), the early fallout decay exponents indicated by Miller (0C68) and the time of arrival of fallout on the surface of Rongelap were combined to estimate the exposure rate history at Rongelap Island prior to evacuation (see Table 3) (Cr56). This exposure rate history would not include the contribution from non~fission fragment nuclides since it was based on fission product decay expo- nent given by Miller (0C68). The total integrated exposure at Rongelap Island from the onset of fallout until evacuation was 180 R for one meter above the surface. The maximum exposure rate of about 12 Rh 1 was estimated to occur about 5 hours post detonation, however, it was assumed that all the fallout was on the ground at this time, that is, an instantaneous rise in exposure rate. of the U.S.S. The crew PHILIP also surveyed Sifo Island and the crew of the USS RENSHAW surveyed Utirik Island during their evacuation efforts (0C68). The exposure rate histories for Utirik Island and Sifo Island were given in Table 3. In sum- mary, the exposure rates in Table 3 were based on Miller's decay estimates and do not account for build-up of exposure rate but are in agreement with initial estimates. A more refined estimate of external exposure rate history was based on Bikini Ash as follows. 14