X-ray diffraction Phase Analysis of Single Hot Particles from Chornobyl

Nearly four decades after the Chornobyl accident, the structural stability of dispersed nuclear fuel particles is still not fully understood, limiting accurate environmental risk assessment. To date, no phase analyses of these particles have been published. We present a comprehensive phase analysis of individual nuclear fuel hot particles and crystal diffraction data that have not been previously reported in literature. By combining high-resolution synchrotron X-ray diffraction with triple-axis rotation, we were able to collect full Bragg reflection data and determine which phases remained stable in real-world conditions. The analysis revealed the presence of UO 2 , U 3 O 8 , U 4 O 9 and Zr-mixed phases. The detection of largely intact UO 2 and U 4 O 9 suggests their structural frameworks have remained stable and are likely to continue acting as containment matrices for incorporated fission products and actinides in the near future. These results provide a basis for further investigation into the extent to which uranium oxide matrices have retained their integrity after long-term environmental exposure in soil and asphalt within the Chornobyl Exclusion Zone (CEZ) and support further development of contamination models and waste management strategies at nuclear accident sites. • Synchrotron XRD reveals crystalline uranium oxide phases in individual CEZ particles • Comprehensive phase analysis identifies uranium and zirconium oxides in hot particles • XANES measurements confirm cubic-ZrO 2 phase in a hot particle