abundances determined by Cook. The calculation is summarized in Table 4.5. § The dose rate expressed in Mev min~ ! em-3 may be converted to dose rate expressed in roentgens hr~! by using the factor, 9.50 x 10-4. & Therefore: for Shot 5 dy = 98.7 x 107° Mev min~! cm - = 9.37 x 1078 roentgens hr-! for Shot 6 dy = 99.5 x 1078 Mev min“! em=? = 9.45 x 1078 roentgens hr-! 4.6 CALCULATION OF DOSE RATE, d Numerical values for dr, R/I and I/A substituted into Equation 4.4 give d = 9.37 x 1078 x 3.75 x 10° x 1.59 x 10 A roentgens hr-! = 5.58 x 1077 A roentgens hr-! at H + 218 hr for Shot5. d = 9.45 x 1078 x 3.75 x 10° x 1.59 x 1078 A roentgens hr-! = 5.63 x 1077 A roentgens hr~! at H + 171 hr for Shot 6. Finally the dose rate was referred to H + 12 hours for both shots by applying the decay factor from H + 12 hours to the time of analysis of the H + 218 hour and -H + 171 hour samples for Shot 5 and Shot 6 respectively. No actual measurements of gammafield decay were made over these periods. Recently Miller (Reference 6) has shown a remarkable degree of agreement to exist among Rad-Safe data taken over each of the islands at Operation Castle when the calculated disintegration min=! curve for each shot is used to refer readings to a common time. This appeared to provide sufficient justification for use of the calculated curve in the present calculations. Decay curves were calculated as described elsewhere (Reference 3) using experimentally determined capture-to-fission ratios for various 5 Incidentally it may be shownthat: i=9 n= 25 i=l 1 = 2.91 photons min~! cm~? for Shot 5 samples, and n = 2.94 photons min~! em~? for Shot 6 samples provide a gamma emission rate, R= 1 Mev min=! cm~ since i=9 >» Ej nj = 1 Mev min~! cm~? i=1 ® The dose rate in roentgens hr7' is derived from dose rate in Mev min™! cm~ as follows: by definition 1 roentgen hr-' is the absorption of 83.8 ergs per gram in air at 20°C 760 mm (or 0.101 ergs per cm! of air). Since 1 Mev = 1.60 x 10 ergs, 1 roentgen hr-' is the absorpt!. of 6.32 x 10¢ Mev hr~! cm-3, or the absorption of 1.05 x 10° Mev min“! cm~*. Therefore dose rate (in roentgens hr7!) = dose rate (in Mev min7! em7’) x 9.5 x 1074, 68