PiSgrgm2, Nuclear Radiation and Effects Program 2 included ten projects, which could be grouped into four categories: (1) underwater detonations, (2) high altitude detonations, (3) develop- mental shots, and (4) nuclear radiation from a very low yleld device of par- ticular interest to the Army, (discussed under Quince and Fig Results). ae Underwater Shots, Wahoo and Umbrella Shipboard Radiation Vulnerability. It was the object of this study to document the gamma radiation phenomena generated aboard three target de~ stroyers by shots Wahoo and Umbrella. Both total gamma dose and gamma dose rate histories were measured by film badge dosimetry and gamma intensity time recorders (GITR's), respectively. Unshielded GITR stations and film badges supplied data on radiation at locations representing major battle stations; underwater GITR instrumentation supplied data on radiation in the water; and directionally shielded GITR stations mounted on deck supplied toformation on radiation from remote sources. Radiation histories were obtained on only one destroyer during shot Wahoo because of ship's power failures on the two other destroyers. Radiation histories were obtained on all three ships during shot Umbrella, although some data were lost because of shock damage. Preliminary results indicate that weather-deck dose buildup ranged between 600 r received within 0.5 min at 2,000 ft from surface zero and 45 r received within 2 min at 8,000 ft. Dose reductions by factors leas than 6 were obtained for all compartments above the waterline, and dose reduction factors greater than 9 were obtained only in machinery spaces below the waterline. Transit radiation appeared to represent a high percentage of the total radiation observed aboard the ships. In the one case where data were obtained, the underwater radiation did not contribute to the total radiation measured aboard ship. Data on gammaionization decay was obtained for the period from 0.1 to 34.8 hr after Umbrella. Shipboard Contamination Ingress. This was a study of the external and internal radiation hazards existing within typical interior compartments of a destroyer-type vessel as the result of the ingress of contaminant from nearby underwater nuclear detonations. Four compartments of the DD-592 were instrumented with total and time-incremental air samplers, surface sampiers, animals (mice and guinea pigs), and GITR's. Rates of air flow for ventila- tion and boiler combustion for the instrumented compartments were controlled 80 as to be representative of those expected under nuclear-attack conditions. Due to the failure of ship's power on the DD-592 during shot Wahoo, only surface sampler and animal data were obtained. The failure of a project timing circuit during shot Umbrella resulted in loss of time-dependent air sampler data although total air samples were obtained. Estimates of the internal dose due to inhalation in the test compartments during Wahoo indicated that the doses were below the threshold for acute exposure but that possibile chronic effects might be produced. Similar estimates for Umbrella indicated that doses were below the threshold for chronic effects, with the possible exception of the internal dose received in the engine room. Umbrella estimates of the external dose rates in the test compartments due to ingress of contaminants showed them to be a smal) fraction of the 27