Assessment of the progress of steel oxidation in gas cooled nuclear reactors by a remote measurement technique

An instrument is described which has been developed for the measurement of oxide thickness on structural components in the nuclear core region of Magnox power stations. Using a ruby laser and a helium-neon laser the equipment can measure oxide thicknesses in the range from a few microns to more than a millimetre. The technique is essentially non-destructive and the equipment need not be in direct contact with components on which measurements are being made. The need for such an instrument, the technique of measurement, stability requirements and the methods of calibration are discussed. The performance of the instrument is illustrated using a set of in-pile results obtained at Oldbury nuclear power station in 1974. The future development potential is briefly discussed. (author)