[en] Law of change in neptunium valence in its intermetallic compounds (IC) of NpM₂ composition, where M is the element of 3d-, 4d-, or 5d-series, Np-M₂Si₂, NpM₂Ge₂, NpM₃, is studied. It is established that 5f-AO populations determining the degree of Np atom oxidation in IC depend on the total orbital momentum, L, in d^qS² electron configuration of M atom. The degree of neptunium oxidation in NpM₂ is less if M atoms are in d⁰-, d⁵-, d¹⁰-configurations as compared to compounds, in which atoms have electron d⁶, d⁷, d⁸, d⁹ configurations. Neptunium atom is in the higher degree of oxidation with elements of d-series than p-series in IC of NpM₃, where MRh, Pd, Al, Sn, Ge

[en] We have determined the electronic structure of the heavy fermion systems UBe₁₃ and UPt₃. These two systems in which the U-U distances are very large do not exhibit local moment magnetism. That they are superconducting is also unusual for such large actinide separations. The electronic structure of UBe₁₃ was calculated using the semi-relativistic LAPW method (spin-orbit included by solving the Dirac equation on the final interaction). The UPt₃ electronic system was determined using the semi-relativistic LMTO method. The electronic structure of both systems was determined self-consistently for the observed crystal structure at zero pressure. In both systems the electronic structure effectively separates into non-uranium bands and uranium bands. The uranium states near Esub(F) are dominated by the f bands pinned at Esub(F). The calculated densities of states at Esub(F), N(0), are at least one or two orders of magnitude lower than those inferred from experimental data. (orig.)

[en] The electronic structure of UT₂Si₂, where T=Cr, Mn, Fe, Co, Ni, Cu, Ru, Rh, Pd, Os, is determined by means of self-consistent density-functional calculations treating the U 5f states as band states. A pronounced trend in the hybridization strength is exposed and is deduced to give rise to the different magnetic properties of the compounds. In agreement with experiment, the non-monotonic behavior in the subseries containing 3d elements is reproduced. The underlying physics of this fact is explained. Furthermore, special features of the heavy-fermion system URu₂Si₂ are discussed. ((orig.))

[en] Short communication

[en] Short communication

No abstract available

No abstract available

[en] It is deduced that Si would stabilize the interaction layer also during irradiation not to form gross fission gas voids. Irradiation tests, such as RERTR-6 and IRIS-3 irradiation tests, using Al-Si matrices instead of an Al matrix have shown remarkable reductions in the interaction layer growth. However, the US AFIP-1 irradiation test at ATR and the European E-FUTURE1 test showed that interaction layers grow significantly due to their high fuel temperatures. It is proposed that the performance of Si on the interaction reduction would be decreased when the interaction layer grows since the Si content in the interaction layer becomes diluted. Also it is found that it is difficult to obtain high Si content in the interaction layer by interdiffusion between the U-Mo particle and Al-Si matrix during irradiation. Post-irradiation examination (PIE) of the KOMO-3 irradiation test using U-7wt%Mo/Al-2wt%Si has shown that the concentration of Si content in the interaction layer is less than 11 at% as shown in Fig. 1. One way to enrich Si in the interaction layer higher than 11 at% is pre-irradiation annealing of U-Mo/Al dispersion fuel. As shown in Fig. 1, more than 20 at% of Si could be enriched in the interaction layer by out-of-pile annealing at 580 .deg. C. The KOMO-4 and KOMO-5 irradiation tests at HANARO have irradiated pre-irradiation annealed U-Mo/Al-Si dispersion fuel in order to estimate the performance of the Si-rich layer as a diffusion barrier during irradiation. In this study, the interdiffusion behavior of the preirradiation annealed U-Mo/Al-Si dispersion fuel and as extruded U-Mo/Al-Si dispersion fuel during irradiation are analyzed. By pre-irradiation forming of Si-rich layers, in-pile interdiffusion mechanisms depending on the Si distribution can be understood for U-7wt%Mo/Al-5wt%Si. The preferential pile up of Si at the periphery of interaction layers reduces the interaction during irradiation. The presence of Si in the interaction layers does not stabilize the composition as close to (U,Mo)(Al,Si)₃, which is different from out-of-pile diffusion test results

No abstract available

[en] Polycrystalline specimens of UFe_xAl_12-x have been synthesized for 3< x<5.1. X-ray spectral and compositional analyses of the resulting compounds have been carried out. The magnetic properties in fields up to 33 T at temperatures form 4.2 to 275 K have been investigated. A model is proposed to describe the properties of these intermetallic compounds, in which there is a transition from uncompensated antiferromagnet to ferromagnet via a spin glass phase with change of composition. (Author)