Evaluation of γ exposures on personnel monitoring films by β backscattering technique

The results of studies carried out on the use of β back-scattering technique for the evaluation of personnel monitoring film exposure, are reported. The response curves of fast and slow emulsions of two types of films for γ exposures and using 35S and 147Pm sources are shown. The results indicate that β backscattering technique can be used for evaluation of γ exposures using processed films. This method is simple and has several advantages such as easy availability of source and equipment ease of operation, independent evaluation using both sides of the film (Kodak Type 2), better sensitivity and suitability for entire range of exposures in personnel monitoring. Changes in optical density of processed film occur on storing the films for long periods thus giving rise to errors in evaluation whereas the β backscattering technique is free from this drawback since the method is based on the measurement of silver concentration. Because of the type, energy and activity of the source used, the method does not pose any radiation hazard during use. (U.K.)