Validation of Non-Standard Analytical methods Used in Nuclear Material Measurement for Safeguards Purposes

The Analytical Service (AS) of the Nuclear Safeguards and Forensics unit of the European Commission's Joint Research Centre is the laboratory responsible for performing the destructive analysis for nuclear safeguards in the frame of the EURATOM treaty. The AS operates a pool of analytical techniques to determine the concentration and isotopic composition of uranium and plutonium, and also to measure the level of impurities in uranium materials. Because of the sensitive nature of these measurements, it is crucial to ensure the quality of the delivered results which should be unbiased, with a proper uncertainty and in accordance with the International Target Values. Some of the methods in use have been adapted from existing commercial instruments and from established norms while some others have been fully developed in-house (Hybrid K-edge Densitometry for U/Pu assay, \"COMPUCEA\" for U concentration /enrichment or \"ELANA\" for light element analysis). In the latter case the validation of the methods requires a complete study to identify, characterise and control the key parameters (such as the repeatability, reproducibility and robustness) of the method. This characterisation may be hindered by the lack of certified reference materials with a suitable matrix. To address this issue, the laboratory has to gain confidence in the robustness of its methods by other means such as inter- or intra- laboratory comparison exercises or simulation models. This paper presents the pool of analytical techniques used for nuclear safeguards purposes in the Analytical Service of JRC Karlsruhe and describes the approaches implemented to validate these methods.