tern variations since the atolls present a heterogeneous exposure rate environ- ment (Gr77). External exposure calculations are based on Figures 24 to 26 which were derived from data listed in Cr56, Sh57, Un59, and Gr77. The area under straight line portions of the curve was determined by yu eta - A, n+] | (6) where X = external exposure during straight line interval, mR, R,, = exposure rate at the end of the interval, mh), R = exposure rate at the beginning of the interval, kh, ty = time post detonation at the end of interval, hours, ty = time post detonation at the beginning of interval, hours, n slope of a straight Line. = Data from 11 detonations during May, June, and July of 1958 (Sh57) mean fallout deposition exponent of 18.8. indicated a This mean value was observed at Utirik, Rongelap, Parry, and Wotho and was applied to early time post detonation of BRAVO to obtain the initial increasing exposure rate history shown on Figures 24 and 26. This method yielded a fallout deposition period of 5.5 hours on Rongelap and 12 hours on Utirik. This time compares well with the original observations reported by the Marshallese and by U.S. Navy personnel stationed in the area (Sh57). Initial dose equivalents on "acute doses" are developed in greater detail in another report. 46