en underground blast ef a low-yiel4 device (Reference 3). * Zhe advent of high-yield thermonuclear weapons has resulted in a manifolA ducrease in the radiclegical hasard, and gomme radiation fron fallout bas become of greater military significance.” Operation Castle demonstrated that large quantities of redicactive material eould be deposited by high-yield weapons over areas of several thousand square wiles. This led to a military requirenent for falleut data for devices of various types and yields. Froject 2.1 was charged with documenting the residual~-gamus radiation exposures from the fallout at land stations at Bikini Atoll. during Operation Redwing. 1.3 THEORY The gama radiation enitted from e muclear detonation may be divided into two portions; initial radiation and residual radiation. The residual radiation may include radiation beth from fallout and neutroninduced activity. . Tn Chis report, the radiation emitted Garing the first 30 seconds is termed “initial radiation,” and that reeeived after 30° seconds is called "residual radiation.” i-3-1 “Initial Gamma Redistion. For a fission-type device the initial radiations are divided approximately as show in fable 1.1 (from Reference 8). Tae major contributien to initial gamma redisation is from the fiscion~product gamas and the radiation from neutron eayture by FY (n,) ) din the EB components and air. The prompt gommas are nearly all absorved in the device itself and are wf little significance outside of the device. The fission-product gammas predominate at close Aistances (Reference 8). the w” (n,/) games become increasingly important at greater distances,