A Review of Applications of Radioisotopes to Engineering

Abstract

Radioisotopes are radioactive versions of the natural chemical elements, differing from these only in their nuclear mass and in their ability to emit radiations. They are produced mainly by neutron bombardment of ordinary materials in a nuclear reactor. The most important radiations are beta particles (fast electrons of nuclear origin) and gamma rays (penetrating electromagnetic radiations). These are detected with ionization chambers, Geiger counters or scintillation counters. In production control, the absorption or scattering of radiations is used as a measure of material thickness, and in some cases, of its atomic number. Radioactive tracers aid in production research in rapid determination of mixing efficiencies and hold-up times. Tracers are also used in the non-destructive testing of materials and components and in more basic research into alloy structure. In this latter research, photographic films are used to produce autoradiographs which show the microscopic distribution of radioactively labelled constituents. Radioactivation by neutron irradiation enables certain impurities to be assayed at sub-microgram levels without chemical separation. The wear of engine parts can be measured, in a fraction of the time taken for orthodox methods, by making the parts in question radioactive and measuring the worn radioactive debris in circulating lubricant. Cutting tools can be measured similarly by assaying radioactive debris attached to the swarf. For many purposes gamma radiography supplements X-radiography or replaces it as a cheaper alternative. The greater manoeuvrability of gamma-ray sources is of especial advantage in the radiography of assembled engines.