was spread out in very large chains and clumps of crystalline a for which the term "particle size" becomes quite meaningless, Ttacpeeet that the active aerosol material when collected was in the solid state 8 carrying no more water than the normal terperature-hunidity equilibrium amount. 4o1.2.3 General Observaticns, Shot 4 hillipores exposed topside on YAG 40 appear to kave collected a mixture of dry and liquid active aercscl material, as evidenced by the Xeray film autoradiographs in Fig. 4.5. A sample autograph of a topside MP filter from the washcom ship (YAG 39) 4s included for comparison, So far as is known, the WP filters on YAG 40 were not subjected to spray from other experirental equipment on the ship, or to natural rainfall before recovery. Again, NTB autoradicrraphs and microscopy identified the active centers as crystalline aggregates in the heavy deposits, and sometimes resolvetle crystals arranged in a ring in the areas which obvicusly were struck by radioactive liquid droplets. The droplet auto- graphs ranged from 1 to 2 mm in diameter. There was an almost contin- uous background blackening of the film due to very small low-activity crystals dispersed more or less uniformly over the face of the filter. Free NaCl crystals were generally present in low concentrations, with no associated radicactivity. Figure 4.6 comprises photomicrographs of two active centers and their autographs fron the MP filter samples collected on the YAG 40 at deckhouse and flying bridge positions. The ESP on YAG 40 functioned on Shot 4, collecting the most concentrated samples at zero plus 2 hr, and zero plus 51/2 hr. Quali- tatively, the active deposits were identical to those on the MP filters. It was observed that in every case the activity was associated with a halide-reacted spot on the film. The active spot diameters were gener- ally greater than 0.1 mm (the upper useful limit of the film); conse- quently, most of the impinging liquid droplets were smeared as the film wound onto the take-up reel, The active drop residue, distributed or aggregated within the spot boundary had the same appearance as the heavy active deposits on the MP filters, described above, The occurrence of active spots to inactive salt and fresh water drops was about 1 to 100. 4e1.2.4 General Observations, Shot 5 On this shot MP filters exposed topside on the YAG's were badly damaged, apparently due to exposure to heavy rains following the period of active aerosol sampling.* The filters were in fregmente, as show by the X-ray film autosraphs of Fig. 4.7. The filter material was very * Deduced from the recorded pressure drop across the venturi system of the ''P filter pumps. The records from the topside samplers on YAG 39 and YAG 40 show three periods of simultaneous relief valve operation, which occurs only with exeessive filter resistance. 88