CHAPTER 17 were positioned at various distances from surface zero, from 2900 to 8900 ft for shot Wahoo and from 1900 to 7900 ft for shot Umbrella. 23, 32, 33 Reference 34 summarizes experiments the British conducted in 1949 aboard a cruiser, the Arethusa, to determine the shielding afforded by the ship's structures against the F.P.C. ganma radiation resulting from @ nuclear airburst. Ganma radiation emitted by cobalt-60 and sodium-24 sources was used to similate the F.P.C. gamma radiation aboard a ship located beyond the range of complete destruction from an air burst. However, since the angle of elevation of the source from the water line was only 10°, it is estimated that the results may also be used to indicate levels of F.P.C. gamma radiation for water-surface bursts, although the isotope gamma energies were only about 1/6 (Co-60) to 1/3 (Na-24) of the F.P.C.-gamma-radiation energies for a nuclear burst. Radiation levels were measured in three groups of compartments, that were in vertical alignment and in some compartments that extended across the width of the ship, such as the mess decks and.the 4th-deck engine and boiler rooms. Several significant conclusions were reached as a result of these experiments, relating geometry and ship orientation to F.P. gamma dose. It was found that, in general, the protection afforded by t ship was greatest (by as much as a factor of 30) for bow exposures, and least for exposures on the beam. This effect was particularly noticeable in compartments situated below the upper deck, and was due, presumably, to the added protection afforded by bulkheads near the bow of the ship. As would be expected, the ship orientation did not affect to so great an extent the exposures at locations in compartments within the bridge etructure. It was also found that for compartments that extended across the full width of the ship, there was a considerable variation (by as mich as a factor of 11) between the dose received at the near-incident and near-exit sides of a compartment relative to the source of radiation. 17.4.5 Effects of F.P.C. Radiation on Shipboard Electronic Equipment The possibility that shipboard electronic equipment might malfunction as @ result of exposure to the high rapidly delivered radiation exposures emanating from a muiclear detonation was indicated by laboratory tests carried out in 1956.% ‘hese preliminary high-intensity short-duration neutron-irradiation tests, in which the Los Alamos Scientific Laboratory's Godiva pulse reactor was the neutron source, indicated the sensitivity of semiconductors to neutron irradiation. At Operation Plumbbob, in Nevada, mumerous components used in electronic circuits were exposed to F.P.C. radiation from airburst Shots Hood and Priecille.%© It was concluded that, of components normally used in electronic circuits, semiconductor devices are the most susceptible to damage by nuclear radiation, and in locations where physical survivel of equipment is possible, fast-neutron bombardment alone could be responsible for permanent damage to semiconductor devices. Data indicated 17-3] vee ne ane nee ee ne Rm I ene mee Ey nee aoe ere Smear mary commer y FS