[en] Short communication

No abstract available

[en] The expression for polarized electric dipole moment of well-deformed reflection asymmetric nuclei is obtained in the framework of the liquid-drop model in the case of geometrically similar proton and neutron surfaces. The expression for polarized electric dipole moment consists of the first- and second-order terms. It is shown that the second-order correction terms of the polarized electric dipole moment are important for well-deformed nuclei. (orig.)

[en] Reactors fuels based on thorium or its compounds are important for fuel economy in advanced converters and breeders. The development of such fuels requires considerable physical, mechanical, and other data on potential materials. Our purpose was to survey the literature on these materials, report selected data, and indicate the areas where further data are needed. 63 refs, 2 figs, 10 tabs

[en] Published in summary form only

[en] In the search for long-lived superheavy elements (SHEs) in nature the claim for the detection of a SHE species with A = 292 in a commercially available thorium solution at an abundance of (1-10) x 10^-12 relative to ²³²Th using ICP-SFMS has been raised very recently by Marinov et al. The same group also claimed the finding of four long-lived isomeric states in neutron-deficient thorium isotopes at an abundance of (1-10) x 10^-11 relative to ²³²Th using the same experimental method. The aim of our study was to examine, whether the ratios mentioned above could also be found in a natural thorium mineral, using AMS as a much more sensitive technique assuring the complete suppression of molecular background. Chemically untreated thorianite (ThO₂) was used for both measurements. In addition, commercial thorium(IV) oxide (thoria) powder was also analyzed in the SHE measurements. No events were observed in the A = 292 SHE search, resulting in an upper limit of 4 x 10^-15 for the abundance of such a species relative to ²³²Th. For two neutron-deficient thorium isotopes, ²¹¹Th and ²¹⁸Th, we find upper limits of 5 x 10^-15. For ²¹³Th and ²¹⁷Th we observed a few events - albeit uncertain - which would put their abundance also into the 10^-15 range.

[en] The present state in usage of thorium as a material for nuclear fuel conversion is considered. Some nuclearphysical characteristics of the thorium cycle are given. A general evaluation of perspective usage of thorium in nuclear power engineering is given. Possibilities and methods of thorium fuel production and regeneration are discussed, as well as the basic trends in investigations on developing the thorium cycle

[en] The elastic constants (C₁₁ , C₁₂ , and C₄₄) of all the known cubic binary phases of thorium with nonmetals, ThX (X = C, N, O, P, As, Sb, S, Se), have been calculated using the full-potential linearized augmented plane wave (FLAPW) method with an exchange-correlation potential in the generalized gradient approximation (GGA). Numerical estimates of elastic parameters of the corresponding polycrystalline ceramics (bulk compression modulus, shear modulus, Young modulus, Poisson ratio, and Lame coefficients) are obtained and analyzed for the first time

[en] The band structure of metallic Th and NaCl-type ThX (X=C, N, P, S) compounds were calculated by tight-binding method, with the parametrization improvement. Values of two-center parameters chosen so as to fit the result for Th given by Gupta and Loucks were found to be very close to two-center integrals with a suitable integration range. Applying this method for evaluating parameters, the band structures for ThX compounds were also computed. Population analysis to determine the electron populations in each orbital based on the results obtained by the method indicated that for all compounds calculated the occupied states consist mainly of sigma type bonding between metalloid p and Th d sub(γ) as well as π bonding between p and Th dsub(epsilon). (auth.)

[en] Globally, the 80's and 90's years were characterized by a significant reduction in the rate of growth of nuclear energy. However, from the 2000's, there has been a significant change in the international arena, with the 'renaissance' of interest in nuclear energy, even in countries that had abandoned nuclear power. To answer questions like security, reducing the generation of radioactive waste, control of proliferation risks and long-term sustainability, some initiatives have been adopted by some countries. In 2000, the Department of Energy - DOE - United States created the GIF - Generation IV International Forum for Nuclear Reactors. Six reactor concepts were selected based on criteria such as: reduction of radioactive wastes, safety and cost effective to meet the increasing energy demand on a sustainable basis, being resistant to diversion of materials for nuclear weapons proliferation and safer against terrorist attacks. In this context, it becomes important to use thorium as nuclear fuel for the Generation IV Advanced Reactors, with startup scheduled for 2030. Although the thorium does not present significant commercial value nowadays, in a not too distant future it will probably be an important commodity. Unfortunately, contrarily to what is happening in most developed countries in recent years, Brazil is paying little attention to the thorium, even less than in the past, despite its large reserves. Thorium is three to four times more abundant than uranium in the Earth's crust and, although not fissile, all thorium can be used to produce ²³³U, by absorption of neutrons and subsequent radioactive decay. This uranium isotope is an excellent fuel for use in almost all types of nuclear reactors. It is possible that the thorium constitutes the largest Brazilian energy reserve, supplanting much oil (despite the findings of the pre-salt) and uranium. Brazil has a long tradition in the thorium technology, from mining of monazite until the obtainment of high purity thorium compounds and IPEN accumulated since the 60's a wide experience in the purification of thorium, obtained primarily from the monazite processing. Studies were also conducted on obtaining nuclear fuel based on thorium, the reduction of ThF₄ to metallic thorium, neutronic studies and proposition of reactor concepts based on the element. It should also be recorded that there was at IPEN, during this period, the production in pilot scale of over one hundred and seventy metric tons of thorium nitrate with high purity. In this paper, we present briefly the experience accumulated at IPEN-CNEN/SP-Brazil and the different areas that comprise the Thorium Fuel Cycle, and the possibilities and advantages of thorium use in the IV Generation Advanced Reactors. (author)