~ ne a x a CHAPTER § FOTAL DOSE ESTIMATES CALCULATED VALUES 4 The total doses calculated for each of the islands for hypothet~ ad ical fallout times of 8, 12, and 16 hours are given in Table 3.1, together with the coses calculated in heference 16, in order to illuge trate the difference in the estimates due to the Later information. On wg yamma spectra, meter response, snd decay rates, ae The 12-hour fallout value is considered most probable, being rome consistant with the Rongerik film badge data (see Section 6.2}, Doses.. based on this value are multiplied by the peometry factor discussed in <: Chapter 7, in order to express them in tems of the air-dose fron a source of similar energy under bilateral exposure laboratory conditions which would have produced the same midline dose, A plot of dose rate versus time based on Figure 3.3 was used and the total dose was graphically determined by normalizing ordinates and dose rates for a given time and measuring the area under curves similar to Figure 6,1, was done assuming all three fallout times far each island, This The air-dose rates measured at later times (Table 2.),) were multi-~ plied by the total correction factor for geometry and energy dependence of the survey meter (see Section 5.2), Fallout beginning times and evacuation times used were those of Table 6,1, It was found that doses calculated using the decay exponents of Section 3,2 were in good aygreement with those determined graphically, — 8.2 DISCUSSION Figure 6.2 illustsales ine cumulative air-cose as a function of time on Rongelap atoll, tased on the 12 hour fallout assumption. It can be seen that the rate of delivery of the dose varied continuously, the major portion being received at the kipher dose rate ;revatiling in the mid-portion of the exposure period, By the time that 90 percent of the dose had been received at H+ h} heurs, for evacple, the dose rate had fallen to 2.7 r/hr, less than LC percent of its naxinua value of 7.4 r/hr at H+ 16 hours. At H+ 16 eee 25 percent of the dose had teen received, Thus the dose rate curing exposure differed markedly fron that usually enccuntered usins Xeray units, The dose values for konyerik given in Tatle 8.1 are 75 percent of the canpited values, averaged for the 2d.5-and-2h-hcur exposures, This f 38 ‘~ roe sf - s i Ae . oF Se det, MaeBaet Lie 8.1