Application of HRGS for forensic characterization of uranium oxides, pure uranium metals and uranium alloys

Highlights: • Forensic characterization of U oxides, U metal and its alloys by HRGS was carried out. • Matrix density, U assay, U isotope masses were determined by non-destructive method. • Iterative quasi-Newton–Broyden method combined with experimental HRGS data were used. • The HRGS results were confirmed by IDMS, XRF, XRD analytical techniques. A nondestructive iterative method for uranium-bearing material characterization with HRGS developed earlier in Burdeinyi et al. (2020) is applied to determine matrix densities, uranium mass fraction and uranium isotope masses of uranium ore, ${\mathrm{UO}}_2$ and $U_3{O}_8$ powders, fuel elements in the form of ${\mathrm{UO}}_2$ microspheres, uranium metal and uranium alloys. It is shown that $U_3{O}_8$ powders with uranium mass fraction of about 84% can be distinguished from the powders of ${\mathrm{UO}}_2$ with uranium mass fraction of about 87%; uranium products in the form of liquid or loose powder with matrix density of 0.5–2.0${\mathrm{g/cm}}^3$ can be distinguished from uranium products in the form of compacted fuel elements with matrix density of 6.0–10.0${\mathrm{g/cm}}^3$ and from pure metal uranium and uranium alloys with matrix density of 14.0–19.0 ${\mathrm{g/cm}}^3$. In fuel microspheres based on ${\mathrm{UO}}_2$ the uranium mass fraction 88.02% measured by HRGS is consistent, within the measurement uncertainties, with the results of isotope dilution mass spectrometry $87.76\pm 0.64\text{\%}$ and also is confirmed by X-ray diffraction technique. The uranium mass fraction of the uranium ore estimated as 0.08% by HRGS is consistent, within the measurement uncertainties, with the value $0.09\pm 0.01\text{\%}$ determined with WDXRF. Densities of two different uranium metal samples, estimated as $18.42{\mathrm{g/cm}}^3$ and $19.33{\mathrm{g/cm}}^3$ by HRGS are consistent with values $18.24\pm 0.55{\mathrm{g/cm}}^3$ and $18.86\pm 0.59{\mathrm{g/cm}}^3$, respectively, obtained by the gas pycnometry technique.