Computational Study of Actinide-Noble Gas systems

  • Lin Yang

Student thesis: Phd


This thesis reports studies of systems containing actinide (An) and noble gas (Ng) elements, in both the nuclear materials and coordination chemistry fields. Among nuclear fuel fission products, noble gases (especially Kr and Xe) have low solubility and may release to the fuel-clad gap, which will lead to fuel swelling and thermal conductivity degradation. For the safe and efficient use of nuclear fuel, it is important to have a comprehensive understanding of fission gas release behaviours. However, the fission gas release model in actinide nitrides, promising candidates for use as a fuel in Generation IV reactors, is rudimentary. Chapter 3 studies the effect of non-stoichiometry of UN on point defect formation energy and Ng solution energy. The most stable defect types and the preferred trap sites of Ng under different stoichiometric conditions are reported. Chapter 4 investigates the diffusion of Ng in UN, and finds that the Ng diffusion is governed by the U vacancy-assisted mechanism. The calculated diffusion coefficients are in good agreement with the experiments. Chapter 5 extends the binary UN work to ternary (U, Pu)N. Actinide vacancy formation energy and Ng incorporation energy are found to be highly dependent on the chemical environment around the defects (i.e., the number of U atoms in the first (NU(1NN)) and second (NU(2NN)) nearest-neighbour shell), which increase as NU(1NN) increases while decrease as NU(2NN) increases. In coordination chemistry, An-Ng (especially He) complexes are candidate molecules for achieving high coordination numbers. Chapter 6 investigates the geometries, electronic structures, and bond properties of early An-Ng complexes, reporting 18-coordinate Th3+-He and Th4+-He systems for the first time. The covalency of the An-He bond in the group valent AnHe17q+ (An = Ac-U) species increases from AcHe173+ to UHe176+, while Ac-Ng bond covalency in AcNg123+ increases as the Ng gets heavier.
Date of Award1 Aug 2023
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorNikolas Kaltsoyannis (Supervisor) & Nicholas Chilton (Supervisor)


  • Fission gas release
  • High coordination number
  • Density functional theory
  • Actinide nitride fuels

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