Recent band calculations are shown to be qualitatively correct, although most calculations place the bands too close to the Fermi energy EF. From normal-emission spectra, criticalpoint energies have been determined for the occupied carbon 2s band (10-13 eV below EF) and for the occupied Ti 3d-C 2p band (元′=-6 eV, 元′=-3 eV, X4′-Δ1=-4 eV, X5′=-0.5 eV, and Δ5=-0.8 eV). Oriented single-crystal faces of TiC (100)-(1×1) and TiC (111)-Ti (1×1) have been studied with angle-resolved photoelectron spectroscopy using synchrotron radiation for 8≤hν≤70 eV. In the second part, we provide an overview of the different studies carried out on model nuclear waste matrices and model nuclear reactor structure materials in order to illustrate and discuss specific results in terms of key influence parameters in relation with thermal or radiation activated migration of helium.įinally, we show that among the key parameters we have investigated as able to influence the height of the helium migration barrier, the following can be considered as pertinent: the experimental conditions used to introduce helium (implanted ion energy and implantation fluence), the grain size of the matrix, the lattice cell volume, the Young's modulus, the ionicity degree of the chemical bond between the transition metal atom M and the non-metal atom X, and the width of the band gap. deuteron induced nuclear reaction for ³He depth profiling and high-energy heavy-ion induced elastic recoil detection analysis for ⁴He measurement. The first part of this paper is devoted to a brief description of the two main IBA methods used, i.e. The aim of this paper is to point out and to discuss some features extracted from the study of helium migration in nuclear materials performed during the last fifteen years using ion beam analysis (IBA) measurements. Clear trends in phase stability, rooted in electronic structure, are revealed upon a comparison of the calculated Ti-C and Ti-N phase diagrams with the Ti-O phase diagrams from a previous study. Monte Carlo simulations showed that the ordered rocksalts transform to a disordered rocksalt that can tolerate high vacancy concentrations at intermediate to high temperatures. A large number of vacancy-ordered rocksalt phases were found to be stable at low temperature. Density functional theory calculations were combined with the cluster-expansion approach to determine ground-state carbon-vacancy and nitrogen-vacancy orderings over the octahedral sites of hcp and fcc Ti. A first-principles statistical mechanics study was performed to predict phase stability in the Ti-C and Ti-N binaries. Titanium can dissolve unusually high concentrations of interstitial elements such as carbon and nitrogen to form a rich variety of compounds with beneficial structural and functional properties.