Chopter 3 NUCLEAR - RADIATION MEASUREMENTS AND FALLOUT STUDIES The nuclear-radiation program had two major objectives: (1) the documentation of the uitial radiation, neutron and gamma, from megaton-range nuclear detonations and (2) the documentation of faitlou: from land-surface and water-surface bursts of multimegaton devices. The unexpectedly high yield of Shot 1 had two influences on the execution of the program: First, much of the sparc equipment was destroyed on Site Tare, and instrumentation for subsequent shots was curtailed. Second, the importance of fallout in terms of effects of military signiZicance over large areas beyond the blast~ and thermal~damage envelopes was demonstrated dramatically. This realization, together with the observation that activity dissolved in sea water could be a measure cf the fallout intensity, provided the impetus for the water and aerial surveys that yielded valuable data after Shots 3 and 6. Prior to Operation Castle, only one multimegaton detonation had provided data on nuclear--radiation effects-— Shot Mike of Operation Ivy. The initial-radiation data consisted of records of initial gamma versus time at two stations, total initial-gamma exposure at a numberof distances, and a few neutron-flux measurements using Au, and [ activation detectors. There had been an extensive array of fallout-documentatton stations a.ong the islands and in the lagoon of Eniwetok Atoll; however, these collected data on the crosswind and upwind fallout only, since the more-extensive downwind fallout occurred on the ocean toward the north. The fallout from the few kiloton~range surface and underground shots prior to Castle had also been documented. Measurements of initial radiation from fission devices up to 500 kt had been performed extensively. The initial-radiation data were not adequate prior to Castle because (1) the scaling laws are not simple and do not lend themselves to extrapolation from kiloton-range to multimegaton yields and (2) the neutron dose from neutrons in the energy band above thermal but below 3 Mev had not been measured due io the lack of detectors with thresholds in this region. The objectives of the Castle nuclear-radiation experiments were aimed at obtaining data to eliminate the deficiencies mentioned above. In particular, the objectives were to document for multimegaton landsurface and water-surface detonations (1) distribution of fallout; (2) physical, chemical, and radiochemical nature of fallout; (3) rate of delivery and total initial-gamma radiation at vcrious distances; (4) energy spectrum of and dosage from neutrons at various distances; and (5) the applicability of fission threshold neut: »n detectors and germanium neutron~dose detectors. 3.1 INITIAL-GAMMA RADIATION The total exposure from initial-gamma radiation was detected at a number of locations using film-badge and chemical-dosimeter systems. Only a part of the anticipated data was obtained because of extensive destruction of stations and supplies during Shot 1. 41