Enhancing the Material Control & Accounting Measurement System at the State Scientific Center of the Russian Federation – Institute for Physics and Power Engineering named after A.I. Leypunsky

The paper presents the results of work performed on creating site-level standard reference materials (SRMs) of uranium and developing and attesting non-destructive analysis methodologies for 235U mass fraction in uranium, 235U mass in uranium dioxide and plutonium mass in accountability items. The site-level standard reference materials are created for two nuclear material strata based on the 2%-enriched uranium and the 96%-enriched uranium using the witness samples approach. The site-level SRM characteristics are described, which were obtained through destructive and non-destructive analyses. The methodology of measuring the 235U mass fraction in uranium is based on the gamma-spectrometry method with a high-resolution spectrometer and the FRAM (Function Analysis with Multiple Efficiency) analytical software. The methodology of measuring the 235U mass in uranium dioxide and the plutonium mass in plutonium dioxide containers is based on the neutron coincidence counting method with an active well coincidence counter (AWCC). The paper presents the values of the attested measurement uncertainties for a wide range of masses for 235U and plutonium in the measured SRMs for the conditions at the State Scientific Center – Russian Federation – Institute for Physics and Power Engineering.