30 WORLDWIDE EFFECTS OF ATOMIC WEAPONS Using this relationship, and extrapolating to January 1, 1953, it is found that after the close-in fa!!out is subtracted, a total of 1.68 8 Mc of activity remains to be accounted for. If this remainder of 1.68 8 Mc were distributed evenly over the remaining 157 X 10° mi? of the earth, the average fallout for the 157 X 10° mi? would be 1.68 * 10° == 1.07 eS 157 * 10° or x -\: : 10°? curies /mi?, / | -1.07 & 10° ~ . 1.256 * 10° ; == 852 d/min/ft?. / / This is clearly higher than would be expected in view of the average of 212 d/min/ft? measured for the 37.4 * 10° mi? just to the east of the United States, over which the westerly winds must carry the radioactive clouds before they spread out over the rest of the world. Since the gummed paper may not retain 100 per cent of the activity falling onto it, particularly if rainfall containing the radioactive material falls on the paper, it is of interest to assume some reasonable value for the average fallout that might be expected over the portion of the world not sampled and to calculate the factor by which the gummed-paper readings would need to be multiplied if all the TUMBLER/SNAPPER activity were to be accounted for. It would appear that unless the efficiency of collection of the gummed paper was as low as 10 to 15 per cent, 80 per cent or more of the TUMBLER/SNAPPER activity remained suspended in the atmosphere for periods after June 18, 1952, or that large quantities of activity fell in areas not sampled. + rr Ff Fallout data from Operation Ivy, extrapolated to January 1, 1953, were reported for forty-four stations in the United States and for forty-nine worldwide stations. The worldwide sampling covers a muchlarger fraction of the earth’s surface than was the case for TUMBLER/SNAPPER, although DISTRIBUTION OF RADICACTIVE DEBRIS 31 there are still large areas in the polar regions and south of the equator, and, of course, behind the Iron Curtain, that were not sampled. In all, the samples cover some 111 X 10° mi’. For purposes of accounting for the activity from ivy, the sampled area was divided into four parts and the average fallout for each atea was computed. From these averages the total measured fallout was determined. These data are summarized in Table 3 on page 32. The range of fallout was from 330,000 d/min/ft? at Iwo Jima to 20 d/min/ft? at Lagos, Nigeria. In Area 3, the large reading at Iwo Jima was assigned to an area of 100 degrees squated by noting the relative position of the nearest surrounding stations. A simple numerical average of the fourteen stations in this area would give 35,111 d/min/ft?, which would certainly be too high a weight for this exceptionally high reading. If the 330,000 d/min/ft? had been omitted entirely, the average for Area 3 would have been 12,428 d/min/ft’. The average fallout for the 111 X 10° mi? sampled was 5.07 X 10° curies/mi’, or 4037 d/min/ft’. The average for the forty-six United States stations was 1609 d/min/ft?’. The average of six stations south of the equator and twostations north of latitude 60° N was 371 d/min/ft’. If this last figure is taken as representative of the 86 < 10° mi? not included in Table 3, the worldwide total activity measured during the 61 days following MIKE can be.calculated. The total for the 86 X 10° mi? not accounted for in Table 3 is 0.40 B Mc and the total ivy fallout for the world, measured during the Gi days following the test and extrapolated to January 1, 1953, is 6.03 8 Mc. This is a very small fraction of the total 8 activity produced in tvy. To account for the low measured activity during ivy, by means of the unknown efficiency of collection by the gummed papers, would require that in TUMBLER/SNAPPER more than ten times the activity actually produced would have been measured by the fallout experiments. Only two possibilities remain to explain the result: (1) either most of erTreeareryenrel-edanitebnceiiiiaeieatinesnbeice exceeding 2 months, or (2) large quantities fell out in areas not ade- quately covered by the sampling network. Since the stations nearest to the test site reporting fallout for the entire period were more than 500 mi from Fniwetok, a considerable quantity of activity could have fallen in