Effects of Simulated Transit Radiation on Digital Circuits

This paper describes results of tests made to determine the performance of digital computer circuits in a transit radiation environment. These tests were sponsored by the Bureau of Ships under direct cognizance of the Naval Radiological Defense Laboratory as part of a study of nuclear radiation effects on shipboard electronic equipment. The transit radiation is emitted by airborne weapon fission products after the fireball and cloud column have dispersed. The transit radiation was simulated by use of cobalt-60 gamma radiation to a maximum dose rate of 3 × 105 roentgens/ hour and to a maximum dose of 1.5 x 104 roentgens. The circuits tested consisted of conventional transistor digital circuitry with 11 to 32 components mounted on each printed wire card. A total of 72 cards of twelve types were actively tested using the manufacturer´s acceptance specifications as a basis for determining proper performance. Circuit performance was recorded by photographing the oscilloscope display of circuitwaveforms at regular intervals during a test. As a result of the radiation measurable changes occurred in the output waveforms of some of the circuits, but in no instance did the circuit performance become unacceptable because of the radiation.