Production and Characterization of Monodisperse Plutonium, Uranium, and Mixed Uranium−Plutonium Particles for Nuclear Safeguard Applications

Abstract

In order to prevent nuclear proliferation, the isotopic analysis of uranium and plutonium microparticles has strengthened the means in international safeguards for detecting undeclared nuclear activities. In order to ensure accuracy and precision in the analytical methodologies used, the instrumental techniques need to be calibrated. The objective of this study was to produce and characterize particles consisting of U, Pu, and mixed U-Pu, suitable for such reliability verifications. A TSI vibrating orifice aerosol generator in connection with a furnace system was used to produce micrometer sized, monodispersed particles from reference U and Pu materials in solution. The particle masses (in the range of 3-6 pg) and sizes (approximately 1.5 microm) were controlled by the experimental conditions and the parameters for the aerosol generator. Size distributions were obtained from scanning electron microscopy, and energy-dispersive X-ray analysis confirmed that the particle composition agreed with the starting material used. A secondary ion mass spectrometer (SIMS) was used to characterize the isotopic composition of the particles. Isobaric and polyatomic interference in the SIMS spectra was identified. In order to obtain accurate estimates of the interference, a batch of Pu particles were produced of mainly (242)Pu. These were used for SIMS analysis to characterize the relative ionization of Pu and U hydride ions and to determine the SIMS useful yields of U and Pu. It was found that U had a higher propensity to form the hydride than Pu. Useful yields were determined at a mass resolution of 450 for U-Pu particles: (1.71 +/- 0.15) % for Pu and (0.72 +/- 0.06) % for U. For Pu particles: (1.65 +/- 0.14) % for Pu. This gave a relative sensitivity factor between U and Pu (RSF(U:Pu)) of 2.4 +/- 0.2. However, the RSF(U:Pu) showed large fluctuations during the sputtering time for each analyses of the mixed U-Pu particles, in the range of 1.9-3.4.

Characterization of uranium tetrafluoride (UF4) with Raman spectroscopy

“…[12,13] This gap in UF 4 spectral properties is particularly acute as Raman spectroscopy measurements are a convenient and straightforward characterization technique for industrial processing as well as nuclear safeguards and nuclear forensic methods focused on identification of particulate species. [14][15][16] In particular, nuclear forensics represents an application where Raman analysis can provide unique probative data of chemical speciation in a timely fashion. The non-destructive nature of Raman analysis makes it well suited for the characterization of special nuclear material forensic samples from throughout the fuel cycle, including the uranium and plutonium fluorides.…”

RIMS analysis of ion induced fragmentation of molecules sputtered from an enriched U3O8 matrix

“…A major focus for these types of measurements is on improving the sensitivity for the detection of uranium and transuranic isotopes in the presence of isobaric interferences without the need for complex and time-consuming sample preparation methods. Recently, secondary ion mass spectrometry (SIMS) has shown promise as an effective tool for the analysis of nuclear materials with high sensitivity and minimal sample preparation [8][9][10][11]. The sensitivity of SIMS is often defined by useful yield: the number of ions detected over the number of atoms removed during the analysis.…”

Direct isotope ratio analysis of individual uranium–plutonium mixed particles with various U/Pu ratios by thermal ionization mass spectrometry

“…The carbon and rhenium peaks are from the surface contaminants and evaporation filament material, respectively. The EDX spectrum indicates that the particle contains uranium and plutonium, as described in Ranebo et al (2010). Oxygen signals obviously exceeded background levels, and were detected from the particles, but the quantitative evaluation of oxygen ratio to metals could not be carried out.…”

“…Therefore, several analytical techniques have been developed to characterize U-Pu mixed samples (Esaka et al, 2011;Lee et al, 2012;Ranebo et al, 2010;Suzuki et al, 2012), which are also important for nuclear safeguards and forensics. In several cases, complex chemical separation processes must be conducted prior to analysis of the uranium and plutonium isotope ratios in U-Pu mixed samples with TIMS and ICP-MS.…”