ABSTRACT The primary objective of Project 7.4 was to obtain calibration data on the nuclear and physical properties of solid, liquid, and gaseous matter associated with air-borne nuclear debris resulting from nuclear detonations. These data were obtained by the application of chemical, radio- chemical, physical, and nuclear-physical analyses to the debris collected by specialized sampling devices. The calibration data were further ex- tended by making similar masurem:nts on nuclear debris collected at great distances from the site of detonation. Nuclear~debris samples close-in to the detonation site were obtained utilizing sampling devices on F-8Z, WB-29 and B-36 aircraft. In addition, WB-29's simileriy equipped oyerated out of Hawaii for the long- range calibration samples. Sufficient fission product isotopes in particulate debris were de- termined from each detonation to establish fission-yield curves. Effects of the large fluxes of high-energy neutrons on the trough elements and right wing elements were observed; the significance of these effects are discussed. Mass spectrometric analyses of plutonium and uranium isotopes showed evidence of thermonuclear isp plutonium isotopes up to Pu? were easily measuredin in the debris. Induced activities much higher than noted for fission devices were observed; notably higher than ever measured before were [— particularly in Shots 3, 4, and 5. Modal specific beta activity values for barge shots were much higher than for island shots. Full-scale tests of gaseous debris samplers indicated that further engineering refinements were necessary although some useful samples were obtained. Measuremnts for C!4 49% Kr85, H3, and Xe!%$ did not show any consistent pattern as related to the devices tested. these data cannot be specifically attributed ty laboratory analysis, or natural fractionation a It is qualitatively inferred that\ _ icantly higher for Castlé shots thanIvy-Mike. The variation of samplingequipment, _ __ isotopes. ratios were signif- It is postulated that samples well above the troposphere are required for megaton shots to insure high-quality samples. It is generally recommended that these calibration tests, both closein and at long-range, be continued with emphasis on improving debris col- lection devices and refining analytical procedures used.