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Certified reference materials and reference methods for nuclear safeguards and security

Confidence in comparability and reliability of measurement results in nuclear material and environmental sample analysis are established via certified reference materials (CRMs), reference measurements, and inter-laboratory comparisons (ILCs). Increased needs for quality control tools in proliferation resistance, environmental sample analysis, development of measurement capabilities over the years and progress in modern analytical techniques are the main reasons for the development of new reference materials and reference methods for nuclear safeguards and security. The Institute for Reference Materials and Measurements (IRMM) is one of the leading institutes that supplies nuclear reference materials to fulfill the existing requirements for nuclear material and environmental sample analyses. IRMM’s activities range from the preparation and certification of large quantities of the so-called "large-sized dried” (LSD) spikes for accurate measurement of the uranium and plutonium amount content in dissolved nuclear fuels by isotope dilution mass spectrometry (IDMS), over certified synthetic uranium isotope mixtures, to the development of particle reference materials applied for the detection of nuclear signatures in environmental samples. IRMM is currently replacing some of its exhausted stocks of CRMs with new ones whose specifications are up-to-date and tailored for the demands of modern analytical techniques. Some of the existing materials will be re-measured to improve the uncertainties associated with their certified values, and to enable laboratories to reduce their combined measurement uncertainty. Furthermore, IRMM initiated and coordinated the development of a Modified Total Evaporation (MTE) technique for accurate measurements of minor isotope-amount ratios of uranium and plutonium in nuclear material and, in combination with a multi-dynamic measurement technique and filament carburization, in environmental samples. Currently IRMM is engaged in a study on the development of plutonium reference materials for “age dating”, i.e. determination of the time elapsed since the last separation of plutonium from its daughter nuclides. The decay of a radioactive parent isotope and the build-up of a corresponding amount of daughter nuclide serve as chronometer to calculate the age of a nuclear material. There are no such certified reference materials available yet.