compartment's to. . dose rate. Radiological Environment. This study was to document the radiological environment resulting from underwater nuclear detonations. The gross gamma fields from shots Wahoo and Umbrella were defined by means of GITR instrumentation located on coracle platforms, as well as on the major target ships. These measurements were supplemented by those of total gamma dose made with floating film packs located throughout the target array. In- cremental collections of radioactive material deposited from the resultant base surge and cloud permitted resolution of the gross gamma fields into initial, free-field, and residual doses and dose rates. Underwater probes were used to obtain information on radiation from radioactive materials sus~pended in the water. For Wahoo and Umbrella, it was found that nearly all the total gamma dose occurred within 15 min after zero time and was due to the passage of air-borne radioactive material. However, the records of gamma dose. rate versus time obtained from the two shots show pronounced and characteristic differences in the transiting gamma fields. Gamma doses in excess of 100 r occurred within the first 15 min at downwind distances of less than 16,500 ft for Wahoo and 11,000 ft for Umbrella. On both shots the dosage due to deposited radioactive material on the ships and coracles was from light to insignificant. A study of the downwind gamma data showed that a distance of approximately 23,000 to 28,000 ft from surface zero should be maintained in order to assure a total free-field dose of less than 25 r. High Altitude Shot, Yucca Neutron flux and gamma radiation measurements for the Johnston Is- land part of the Operation are covered in the summary pertaining to Teak and Orange. Measurements of the neutron flux spectrum. and total prompt ma ray flux resulting from the detonation of shot vscce, A al- titude of approximately 90,000 ft were planned. measurements were to have been made with an detector, from which determination of the energy could be made. A similar detector, using Neutron spectra of e-of-flight neutrons es included to provide correction data for the gamma responge of the detector. types of gamma detectors were used: (1) A were D detector, Two (2) subsequently telemetered to a recording ground station. The instrumentation was contained in a canister suspended 2,750 ft below the nuclear device by means of a nylon line. Due to failure of the command transmitter, which controlled the canister operational functions, the instrumentation was inactive at zero time, and no data were obtained. Projects Participating during Developmental Shots Neutron Flux Measurements. This was a program to document the neutron flux and spectrum as a function of distance for two shots in the To achieve this objective, the project participated during shots Yellowwood and Walnut. The measurements were extended during the 28 | AFWL/HO a