X-ray spectroscopic study of chemical state in uranium carbides.

Sergei M Butorin,Aaron Beck,Lucia Amidani,Stephan Weiss,Stephen Bauters,Olivier Tougait,Tonya Vitova

doi:10.1107/s160057752101314x

Abstract

UC and UMeC2 (Me = Fe, Zr, Mo) carbides were studied by the high-energy-resolution fluorescence-detected X-ray absorption (HERFD-XAS) technique at the U M4 and L3 edges. Both U M4 and L3 HERFD-XAS reveal some differences between UMeC2 and UC; there are differences also between the M4 and L3 edge results for both types of carbide in terms of the spectral width and energy position. The observed differences are attributed to the consequences of the U 5f, 6d-4d(3d) hybridization in UMeC2. Calculations of the U M4 HERFD-XAS spectra were also performed using the Anderson impurity model (AIM). Based on the analysis of the data, the 5f occupancy in the ground state of UC was estimated to be 3.05 electrons. This finding is also supported by the analysis of U N4,5 XAS of UC and by the results of the AIM calculations of the U 4f X-ray photoelectron spectrum of UC.

Highlights

Mixed carbides (U, Pu)C are considered as promising fuels for the generation-IV nuclear reactors
Compared with standard mixed oxide fuel (U, Pu)O2, mixed carbides are expected to improve reactor performance due to higher thermal conductivity and higher metal atom density, better structural stability compared with standard nuclear fuels and better chemical compatibility with fuel cladding materials, such as stainless steel
We report HERFD-XAS measurements at the U M4 edge of UC and their analysis within the framework of Anderson impurity model (AIM)

Summary

Introduction

Mixed carbides (U, Pu)C are considered as promising fuels for the generation-IV nuclear reactors. For UC, research groups which measured X-ray photoemission (XPS) spectra (Erbudak & Keller, 1979; Ishii, 1993; Ejima et al, 1993; Ito et al, 2001; Eckle et al, 2004), probing the valence band, and inverse photoemission spectra (Ejima et al, 1993), probing the conduction band, compared these spectra with conventional band structure calculations. By making such a comparison, they suggested that the states in UC have a completely itinerant character. UMoC2 can exist as a fission product (Peniel et al, 2012)

Experimental

Computational details

Results and discussion

Conclusion