6.5-Mt vicld to be approximately 4 x 10° r, whereas (2) particle and drop-size rangcs of fallout and airborne materials at ground leve], (3) amount and measurements for Shot 4 indicated that only 1.55 < in! r were received. At approximately 4,500-yard distribution of radioactive materials in fallout and range. this handbook shows a prediction of about airborne materials, and (4) gros3 gamma and beta- $00 r; measurements showed that only about 84 r gamma decay rates of radioactive materials (some gamma field measurements were also made for cor- were received. \t would uppear that the {nitial-~gamma radiation relation purposes). ig of negligible significance, since the blast and thermai effects in the same range of distances are so great that personnel could only survive tf they were disposcd inside blast- and thermal-proof bunkers. The distribution and intensity of fallout from all shots was investigated. The residual gamma pattern and some data on gamma decay and particle-size distribution was established for Shot 1. The fallout from Shot 1 was adr~-white particulate, irregular in shape; many particles were flaky in nature. Gamma levels of military significance were found to exist at downwind distances to at least 280 nautical miles. ‘The fallout from Shot 2 was more nearly characteristic of an aerosol with no evidence of large Project 2.3 “Neutron Flux Measurements” (WT-914), Naval Research Laboratory; T D. Hans- coms, Project Officer. This project was assigned the problem of meas-~ urtag tne neutron flux encountered in the detonation of the nuclear devices at Castle, using the same particulate. Th. fragmentary data on the residual gamma ficld show the level of activity 5 hours aftcr techniques as used at Snapper and Upshot-Knothole. detonation to be 145 r/hr at a downwind distance of Gold, sulfur, and tantalum were used to measure the flux in the thermal region and the regioa above 3 Mev. The fission detectors were used to measure 45 nautica] auics. Project 2.5b ‘Fallout Studies” (WT~-916}, Chemi- the 1-Mev region of the neutron spectrum and to give an iaea of the shape of the spectrum above that point. cal WarfareLaboratories, Army Chemical Center; E. F. Wilscy, Project Officer. Because of the short half tives of some of the in-~ cuced activities, it wag necessary to provide counting facilities in the field: two trailers were installed on (1) the characteristics of fallout from land-surface and water-surface bursts, (2) the evaluation of the hazards associated with the residual contamination finec Igslacd for this purpose, and were equipped from such bursts, (3) the evaluation of the contam- nigm. The remaining samples were sent to the Naval bursts, and (4) :nformation for the evaluation of mechanisms of particle formation and distribution. Inter- The objectives of this project were to determine to hancle the counting of gold,! and pluto- inating characteristics of fallout debris from such Research Laboratcry for counting. The plutonium. samples were included to provide data in the region above 200 ev, the Oak Ridge National Laboratory supplicd these samples and the personnel to handle them. Because of the unanticipated delays and shotschedule revisions after the firing of Shot 1, the participation of Project 2.3 was considerably modified. Samples were exposed on the first two shots only, and because of shifts in shot sitea and the modifica~ tion of the Shot 5 device, further participation was curtailed. The data acquired from Shots 1 and 2 indicated that the neutron flux is relatively amal! outside the mittent fallout collectors located at Bikini and Eniwetok Atolls were used to sample and collect the fallout. Most of the data, except the survey dala, were obtained from Shot 1. Shot 1 activities which were sampled ranged up to 290 millicuries for areas of 0.6 in? at the downwind stations. The greatest amount of radioactive fallout reached the downwindstation east and southeast of ground zero atH + 5 to H + 15 minutes. The main downwind stations received a second wave from H + 25 to H + 60 minutes, and one station sampled a third and smaller wave [rom H + 4 to H +5 hours. Fallout continued to occur in very small quantities up to H + 12 hours. radius of extreme damage caused by blast and ther- The average Shot 1 decay slopes were ~1.69 for mal radiation. Project 2.5a “Distribution and Intensity of Fallout” (WT-915), U. S. Naval Radiological Defense Labora- tory; RL. Steton, Project Officer. The gathering of fallout data at Castle was a logical extension of previous fallout documentation. The variation in yields as well as the opportunity to docu- the period from H + 210 to H + 450 hours, and ~1 37 from H + 400 to H + 1,700 hours. The Shot 1 fallout consisted primarily of particles that appeared to be coral and salt. Most of the activity associated with the larger particles was located near the particle surfaces, while for smaller particles the activity appeared to be distributed regularly or irregularly throughout the particle. ment surface water detonations for the first time made this study of fallout extremely important. The specific objectives were to sample and analyze fallout material to determine: (1) time and rate of arrival of the fallout and its final distribution patterns, 109 Project 2.6a “Chemical, Physical, and Radio- chemical Characteristics of the Contaminant” (WT-917), U. S. Naval Radiological Defense Labora-