DNA 1240H-2 17.5.7 Effects of Transit Radiation on Electronic Equipment It was decided to investigate the effects of transit radiation on electronic equipment because weapon-test data indicated that initial radiation might affect such equipment. Experiments carried out at USNRDL~™’ tndicate that malfunction of certain electronic equipment is probable and failure of the equipment is possible, as a result of exposure to high-level transit gamma-radiation. Components, such as photomultiplier tubes and semiconductors, were irradiated with laboratory-produced ganma rays having sinmlated intensity-time characteristics of the base surge of Shot Wahoo. It was determined that, in particular, semiconductors of the germanium type were significantly affected by doses of about 2000 r delivered under such conditions. It was concluded from the laboratory experiments that, for equipment currently in use (designed 4-5 years ago when transistors were used conservatively), complete failure is not likely; however, reliability and accuracy may be reduced as a result of such gamma irradiation. No quantitative assessment of the extent of the reduction is avaiiable at this time. It has been further estimated that, in some cases, the more completely transistorized equipment manufactured currently may fail compietely. Examples where such dangers occur are in those eircuite where exact frequency control is eesential, where diode-controlled reference voltages mst be maintained accurately, and where high-impedance circuitry is used. 17.5.8 Summary No weapons-test data exist upon which to base conclusions regarding the gamna dose rates due to transit radiation at early times after water-sur- face nursts. The target ships that were sent into the fallout areas at the surface-burst tests did not contact any contaminant earlier than an hour after detonation, by wnich time any base surge (if it existed), the major source of transit radiation, would have completely dissipated. Dur- ing fallout, at an hour or more after detonation, the transit-radiation contribution to the total recorded weather-deck dos: was estimated to be of minor significance, particulariv in comparison with the deposit dose on a ship not protected by washdowr.. Data from Shots Wahoo and Umbrella indicate that on ships with the washdown system in operation, for underwater bursts that break through the sur- face with no more thar, one bubble expansion, radiation doses were due primarily (between 95 and 93%) to transit radiation. Doses from 300 to 1000 r may be expected within the first 15 min after burst at completely unshielded locations on the weather decks of ships that are stationary from about 2000 ft upwind to about 9000 ft downwind of surface zero. At some weather-deck locations, the superstructure affords sufficient shielding from base-surge radiation to reduce the free-field dose by a factcr of 2 or more. Data also indicate that the transit-radiation doses at telow- decks locations in destroyers may vary from about 2% of the weather-deck BEST AVAILABLE COPY 17-68