Determination of 237Np at trace level:: evaluation of various analytical procedures

Np-237 is a long-lived actinide (2.14 x 10(6) y), an a emitter, which is present either in the fuel cycle or in the environment as a result of local fallout. Due to the low concentration level encountered in bioassays or environmental samples, a preconcentration is necessary and several analytical tools can be used, namely: alpha-spectrometry, PERALS (Photon Electron Rejecting Alpha Liquid Scintillation) or ICP-MS (Inductively Coupled Plasma-Mass Spectrometry). In the case of actinide mixtures where interference can occur, a radiochemical separation is necessary prior to measurement in order to obtain a pure fraction of each actinide. In this paper different approaches, still in use for actinide mixtures and based on ion exchange, extraction chromatography and solvent extraction, are investigated and compared for Np-237 analysis on synthetic solutions. In addition, the suitability of the various procedures is discussed for Np regarding several criteria such as the constraints of the analytical tool, the concentration level, the time needed for the analysis and waste generation.