An intercomparison exercise on the determination of neptunium-237 in an environmental material

An intercomparison exercise has been carried out on the measurement of²³⁷Np in a sample of sea-born sediment taken from the estuary of the River Esk in Cumbria, United Kingdom. The sediment had been contaminated by radioactive liquid discharges from the nuclear fuels reprocessing plant at Sellafield. The measure of agreement between the submitted values was such that one would accept with confidence²³⁷Np analyses reported by the participating laboratories. The exercise was arranged by the Analysts' Informal Working Group (AIWG). The AIWG is a small group of chemists from several Government laboratories in the United Kingdom having an interest in radionuclides in the environment. From time-to-time the Group arranges intercomparison exercises; these exercises are in addition to the members' normal quality assurance schemes, and in addition to intercomparison exercises arranged by other organizations. So far as the authors are aware, there has been no report of such an exercise involving²³⁷Np, and there appear to be no natural matrix reference materials available for environmental²³⁷Np.