Te TR eeee gammaradiations. In addition, beta and gammaenergies and decay rates were determined as required. The techniques used are described in detail in the first draft of the “Manual for the Radiological Field Laboratory.” Briefly, beta activities were determined with the end-window tubes, shielded in lead pigs, connected to either decade or binary scalers. Gamma activities were obtained with the same setup but with a lead-aluminum~-lead sandwich between the sample and the detector to acreen out the betas. This sandwich unavoidably absorbed some soft gammas. Calculations indicate that about 8 per cent of gammas with energies of 1.2 Mev and 50 per cent of gammaenergies below 9.3 Mev are removed by the sandwich and are therefore included in the beta rather than in the gamma count. The reported beta and gamma activities should therefore be regarded as indicating soft and hard radiations, respectively, rather than strictly betas and gammas. Alpha activities were measured with a scintillation probe coupled to a scaler. Beta energies were obtained by Feather analysis using aluminum absorbers, and gamma energies were TR PNTE TRE determined by absorption with lead. Decay rates were determined by plotting beta-gammaactivities as a function of time. The accuracy of the data was ensured by calibration of the counting equipment win standard radioactive sources. Each setup was checked by a dally determination of its standard factor and a periodic chi-square analysis. The nine-tenths error of the raw count was maintained at a level below 1 per cent, whereas the over-all precision of the results was held to 2 maximum spread of +5 per cent. Results were reported daily to RIC. Duta on activities were turned in the same day that the samples were received. Because of the evacuation of personnel from land bases for Mike shot, the field laboratory was stationed on the hangar deck of the USS Rendova, CVE 114. Electrical power and water were obtained from the ship. The operating personnel consisted of four enlisted men w:th chemical backgrounds provided by the Army Chemica! Center ard supervised by P. Shapiro, chemist from SCEL. Capt R. Dempsey, assigned to the Rad-Safe Unit from SCEL, was in chargeof the laboratory. Since the enlisted men had no previous experience with this radiological laboratory, a 3-week training period was given in which practice exercises illustrating Pee the techniques required during the operation were carried out. 6.38.1 Radiological Assays The specific data obtained were reported as completed and will not be repeated here. A total of 275 samples were analyzed. Table 6.1 summarizes the types of samples assayed and the operations performed. The airborne material analyzed was of three types. The first type was collected by a vacuum -operated air filter, run continuously just outside the field laboratory, sampling air from the hangar deck of the USS Rendova. No significant radioactivity was found here. The CEP EYTye ro second type was obtained from portable air samplers. One stationed on the flight deck of the USS Rendova acter Mike shot showed no radioactivity. Another, carried during an aerial survey immediately after Mike shot, showed significart beta and gamma but no alpha activity (see Table 10.27). The third type was taken from filters in aircraft which had flown through the cloud resulting from Mike shot. These showed excremely high beta counts and considerable gammaactivity but no significant aipha activity. Cascade-impactor samples were assayed to obtain information on the activity present in various particle sizes of airborne particulate matter. One series taken immediatelyafter Mike shot showed beta and gamma activity or, all stages, with most of the activity orslides $ and 4. Another series taken M +6 day showed only beta activity, most of which was found on slides 2 and 3 and on the filter paper beyoud slide 4. As can be seen from Table 6.1, most of the samples analyzed were sea water taken at various stations in Eniwetok Lagoon at two levels, at the surface and at a depth of 30 ft. The results obtained were utilized by TG 152.3 to govern the return of naval vessels into the lagoon after the evacuation and to control the intake water to evaporators on the ships. 31