(FO,,) and the corresponding field radiction intensity, (Ry); (2) aeter- mining the fallout per unit area over water, (FQ;) and; (3) calculating the radiation field, (Ry) which would have occurred had the water areas been land, from the assumed rel-tionship, Aa FQ Fo,d RL -—— (2.1) 2.1 =R, This method of approach required the following measurements: (a) Fallout per unit area on available islands of the test atolis (o) (c) Gamma fields produced at sampling locations. Fallout per unit area in the lagoon and over the surrounding in terms of yuantity of radioactivity. ocean, It was also important to obtsain inforwation concerning particle size and note times of errival and cessation of the rallout as well as the variations in the radiation field with time, Zelel Predicted Camma Fields Estimates of the extent and level of gamma fields expected from the fallout were made for each of the originally planned shots, These predictions were based on scaled surface JANGLs data using the cube root relaticnship with modifications in the crosswind and upwind ;atterns indicated by IVY data.7/ It was estimated that the fallout would carry downwind at the rate of 15 miles per hour and that the durationaf falleut at any one point would be 2 hr for megaton yields. Values calculeted for 2 and 3 hr after detonation represent the levels thet would exist haa the fallout deposited over extended land areas, Table 2.1 sumzarizes the predictions for three of the detonations; the effect of decay and the dulay in arrivai of fallout on the gamma fields can be noted. discussion of this scaling is presented in Cection 5.2.8. 2elee A sempling Stetions On the basis of the predictions given in the prec. ding section, it appeared thet the minimum area of military interest would extend to a distance of 50 miles from tue shot point and vould have a maximum width of 20 miles, Since it was not possible to predict the sector in which the primary fallout would arrive sufficientiy in advance of shot time to permit proper placement and activetion of sampling ststions, an array completely surrounding the shot point was needed. sxperience at IVY showed that, it would not be feasible to document the fallout more than 50 miles from grcund zero with available lozistic support. The radial array of sampling staticns chown 1m Fig. 2.1 was evolved from these criteria, This plan was modified within the atolls to take advantage of available islands and to permit the placement of simple rectangular grid arrays in the lagoons. In addition, limited sampling stutions were arranged at a number of outlying islands. Operationally, Project 2.5a was divided into two phases - one ‘requiring the collection of data from land and lagoon stations, and the other from sea stetions. Logistic support for the lend and lagoon phase involved the use of smell poats and helicopters while mounting of the 22 OTNIEaOMENSNE