The Additional Protocol (AP) authorizes safeguards authorities to verify the absence of undeclared nuclear activities in all parts of a state’s nuclear fuel cycle as well as any other location where nuclear material is or may be present. As a part of the Additional Protocol, environmental sampling has become an important tool for the detection of non-declared nuclear activities. In environmental sampling, swipe samples are collected for bulk and particle analysis. Considering the potential consequences of the analyses, these measurements need to be subjected to a rigorous quality management system.
The Nuclear Signatures Inter-laboratory Measurement Evaluation Programme (NUSIMEP) was established in 1996 to support the growing need to trace and measure the isotopic abundances of elements characteristic for the nuclear fuel cycle present in trace amounts in the environment. NUSIMEP-8 focused on measurements of low-level uranium and plutonium in synthetic nitrate solution aiming to support EURATOM safeguards (DG ENER), the IAEA Network of Analytical Laboratories (NWAL) for bulk analysis of environmental samples and laboratories in the field.
The NUSIMEP-8 solution was prepared from mixed oxide fuel dissolved in nitric acid with addition of natural uranium and diluted to an environmental level. Participating laboratories in NUSIMEP-8 received one sample solution with undisclosed values of n(238Pu)/n(239Pu), n(240Pu)/n(239Pu), n(241Pu)/n(239Pu), n(242Pu)/n(239Pu) and n(234U)/n(238U), n(235U)/n(238U), n(236U)/n(238U) amount ratios. Those isotope amount ratios were measured by participating laboratories using their routine analytical procedures. Measurement of the major isotope ratios n(235U)/n(238U) and n(240Pu)/n(239Pu) were obligatory; measurement of the minor isotope ratios were optional. 25 laboratories registered for NUSIMEP-8, three withdrew the registration while one laboratory encountered problems with the shipment of the sample. Finally, 19 participants have reported measurement results using different analytical techniques, among those 10 NWAL laboratories. Two participants did not report their results due to technical problems. The participant measurement results have been evaluated against the certified reference values by means of z-scores and zeta-scores in compliance with ISO 13528:2005. The NUSIMEP-8 results were overall satisfactory and in compliance with the IAEA Measurement Quality Goals for the analysis of bulk environmental samples. This report presents the NUSIMEP-8 participant results; including the evaluation of the questionnaire. In addition feedback from the measurement communities in nuclear safeguards, nuclear security and environmental sciences was collected in view of identifying future needs for NUSIMEP inter-laboratory comparisons.