the intensity subsequently diminished to this 5 percent value, In penetrations of the stem or mshroom, this tims corresponds closely to the tims in the visible cloud reported by the pilot. However, in pen~ etrations just below the altitude of the mushroom, the length of time in the radiation field was usually longer than that in the visible cloud by a factor comparables to the time ths plane was beneath ths over= hanging mushroom but was not in the visible cloud, The length of time in the radiation field is used in Table 3.1, since the dimensions of tha radiation field are of greater interest in this report than the dicsn~ sions of the visible cloud. The tics required to pass through ths. radiation cloud varied from 1 minute for stem penstrations to about 5 minutes for the mushroom penetrations of the clouds from the higher yield detonations, More-detailed information on cloud size as a function of tim after detonation, yield of detonation, and altitudes are presented in a later section of this report. 303 RADIATION DOSE RATES IN THE CLOUD The maximm and average radiation dose rates recorded for each penetration by the various instruments previously described are given in Table 3.1. The maximm dose rate recorded on each flight through the cloud was about twice the average dose rate recorded for the total perdod in the cloud by the same instrument, The average dose rates in ths cloud recorded by the PeMeter and Bioscel were generally 100 percent and 15 percent, respectively, bigher than that determined by film dosizstry,. This is dua to the sensitivity of this electronic instrumentation to low-energy gamma radiation to which the film is only minimally responSBive. Since film dosimetry is more widely accepted as an indicator cf whole-body radiation dosage, the film data were used to give dose rates or dosages in all figures and tahles presented in this report, unless otherwise specified, A further study will be made to determine the exact response of the various instruments to various energies of gamma radiation in cozpariSon to the response of the film to the sam energies, Dstailed results of this study will be included in the final (WT) report for this project, Appendix B shows a typical plot of the dose rates in the cloud recorded by the P-Meter and Bioscel, together with data which wre ex tracted therefrom for presentation in Table 3.1. _ The radiation dose rates observed in the cloud wre a function of three primary factors: (1) the nature of the yield of the cstonstion, 1e@e, the ratio of the fission yield to the total yield: (2) the altitude at which the penetration is made with respect to the pesition or height of the mishroem; and (3) the length of time after detonation at which the penetration is made, - 30301 Radiation Dose Rates in the Cloud versus Nature of the Yield, Since fission yisld is the primary contributor to redioactivity prevailing in the cloud, it 1s to be expected that the dose rates noted in the cloud would be proportional to the ratio of the fission yisld to the total yield. Thus, if two separate detonations of essantially the BEST AVAILABLE COPY 23-27