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Author(s): Haymond, Herman R.; Larson, Kermit H.; Maxwell, Roy D.; Garrison, Warren M.; Hamilton, Joseph G.

The cyclotron is the only practical source of many carrier-free radioisotopes. The preparation and radiochemical isolation of a number of these activities, produced in the 60-inch cyclotron of Crocker Laboratory, will be presented in this paper and in subsequent papers of this series. In most cases the carrier-free radioisotopes were prepared for use in biological systems and the final preparations were in the form of isotonic saline solutions at a range of pH from 5 to 8. The present paper reports the radiochemical isolation of carrier-free Sn{sup 113} and In{sup 114} produced by bombarding cadmium with 38 Mev alpha-particles. At this energy, Sn{sup 113} and In{sup 114} are produced in a thick target by the nuclear reactions; Cd{sup 110}({alpha},n)Sn{sup 113}, Cd{sup 111}({alpha},2n)Sn{sup 113}, Cd{sup 112}({alpha},3n)Sn{sup 113}, Cd{sup 111}({alpha},p)In{sup 114}, Cd{sup 112}({alpha},pn) In{sup 114}. The shorter-lived tin and indium activities together with the possible radioisotopes of silver produced by (n,p) reactions, were allowed to decay out prior to the chemical separations.

Radioactive fall-out after the surface detonation of nuclear weapons has been known since the Trinity detonation at Alamogordo, N. Mex., in 1945. The harmful effects from this fall-out were noted by the discovery of radiation damage to some cattle grazing in a canyon about 20 miles from the detonation. However, the possibility of widespread hazard to humans was discounted and remained so until the accidental exposure in 1954 of personnel who inhabited some islands 150 to 200 miles from Bikini Atoll. None of the native population, or the American service men who were exposed, died from the radiation. However, much study of the problem has been made since that time, to learn more about the hazard which exists and to find the best way of protecting personnel from the dangers of radiation from the fall-out. The effects of nuclear weapons are due to the fission of material (uranium-235 or plutonium-239)