TABLE 3.14 — Averages of Cumulative Fer Cent of Radioactive Particles Under Stated Sise Ranges Shot Under 5 1 3 Under 10 p 20 8.8 Under 20m| 43 74 31 68 The Shot 1 particles were also found to have 43 per cent of the parti- cles under 10 p, which was about 14 times as many particles in the same size range as those collected from Shot 3. However, the percentage of particles under 20 p was approximately the same (about 70 per cent) in the samples collected from both shots. Apparently, Shot 1 produced a larger percentage of particles under 5 p and 10 p than did Shot 3. The size range umer 5 p is the range of particles which is most likely to be deposited at som: point in the respiratory system2 except for particles below 0.1 yp or 0.2 p, which tend to be exhaled.23/ These results also indicete that Shot 1: particles would be harder to decontaminate than particles from Shot 3. The Shot 1 percentages are higher than those that have been found at previous tests and may be due to improvements in analytical technique, but it is felt that the difference in the results is mre likely to be due to the differences of the particle characteristics themselves. 3e9el Activity in Size-Fractionated Particles. The percentage of total activity of each fraction of a size fractionated sample, which was collected from How Island after Shot l, was determined by Project 2.6b. 12/ It should be pointed out that these particles were primarily fractionated for radiochemical analysis. Particles below 44 pp were separated by a roller analyzer so some age glomerates were probably broken up. The particles above 44 p were fractionated by sieves so fewer agglomerates were probably broken up. Table 3.15 presents data which is a by product of the radiochemical analysis procedures. The per cent of total activity in the two smllest fractions is about 23.4 per cent of the activity found in the entire sample and second only to the activity in the largest fraction (32.9 per cent). The activity in these two smllest frac- tions would constitute the principal pulmonary hazard in this fallout. However, the internal hazard caused by these particles is almst always overshadowed by the external radiation hazard existing in the same region and so the internal respiratory hazard may be relatively unimportant. It should also be poimed out that these results 89