A Review of the Faecal Sampling Programme at A.W.E

The number of classified workers providing faecal samples at A.W.E. significantly increased with the introduction of a revised Internal Dosimetry monitoring strategy in January 2003. Classified workers assigned to the enhanced dosimetry programme i.e. those individuals assessed to have the potential to receive internal doses of >1 mSv.a1, provide, as a group, upwards of about 120 faecal samples per annum for the analysis of plutonium and uranium. The analyses are based on classic radiochemical separations, after the addition of a suitable tracer radioisotope, followed by electrodeposition and alpha spectroscopy. This review looks at the implementation of the strategy and the compliance of those classified workers required to provide samples. The data collated from the programme is analysed and the distributions of dry faecal ash weights and the concentration of plutonium and uranium in faecal ash described. The programme has identified, through alpha spectroscopy, the occurrence of disequilibrium between 234U and 238U in faecal samples. Subsequent analysis of these samples, from the original electrodeposited source, by Thermal Ion Mass Spectroscopy has confirmed this disequilibrium and through the measurement of the 235U to 238U ratio identified the uranium as originating from natural sources. The significant variability in 234U: 238U ratio and total uranium in faecal samples in unexposed individuals calls into question the reported sensitivity of alpha spectrometry and faecal sampling as a monitoring technique for routine exposures. The review finds that the faecal sampling programme meets the objectives, in terms of dose sensitivity and quality of the measurement, of the A.W.E. Internal Dosimetry monitoring strategy. The information provided to the workers, when they are asked to provide samples, has ensured that the programme is well regarded and supported. (authors)