[en] Two experimental methods were developed for determining U-235/U-238 ratio in uranium solutions. The isotopic was measured by high resolution ratio gamma-ray spectrometry (G.S.) and neutron activation analysis (N.A.A.). The precision obtained was similar for both methods, but better sensitivity was obtained by N.A.A. The accuracy in both cases was stablished by comparison with samples previously analyzed by mass spectrometry, the results were satisfactory for both techniques. Studies involving the influence of the nitric acid concentration on the isotopic ratio measurement, also were done. In addition, computer programs for faster data reduction were developped, in the case of N.A.A. (author)

[en] We report the results obtained from study the spectral narrowing of a tunable dye laser, pumped by a doubled Nd:YAG laser, as a function of lasers configurations with a frequency selective element inserted into the optical cavity. (author)

[en] An uranium-thorium anomaly has been discovered east of Copiapo. The outcrops of the area, selected by an airbone survey, consist of Upper Cretaceous rocks, mainly volcanic and silicif-sericitic fine grain granites. Associated to shear zones and veins that affect granites, up to 10,000 cps and 11,000 ppm of Th has been measured. In veins, the contents of uranium reaches 100 ppm; no uranium mineralization was observed. This and other anomalies located in shear zones and breccia pipes of the surrounding area, increases the U-Th favorability of the contact between volcanic and intrusive rocks of Upper Cretaceous to Terciary Age. (author)

[en] A computational design for the principal equipment involved in the absorption and desorption sections of a heavy water production plant (Girdler-sulphide method) is described. the programs were developed in FORTRAN. A detailled description of transport equations for the desorption tower, which are applicable for the absorption one is included. The optimization criteria used for the equipment design were mainly economic; the results were obtained under the optimal conditions for the towers. The programs may be used in the long term, for the simulation of the absorption and desorption sections together with the isotopic exchange sectionts (author)

[en] The main factors which fall upon the acceptance or rejection of Nuclear Energy are analyzed. A wide view of the nuclear development reached so far in the world and, especially of the evolution observed in Chile is given. The problem of public acceptance of Nuclear Energy is stated within the Energetic Forum. A synthesis of the activities of Diffusion comprised in the National Plan for Diffusion of C.CH.E.N. is given. (Author)

[en] Chemical exchange chromatography as applied to isotope separation has undergone a constant development during the last few years. The results so far indicate that this method could eventually become commercially useful. This work presents a critical review of the experimental methods presently under study by principal research groups, and which have not get been compared. (Author)

[en] This work shows the statistical relationship between phosphorous and uranium for the most important Chilean phosphatic ore deposits, Mejillones (II Region) and Bahia Inglesa (III Region). Geochemical data showed that the Mejillones phosphorites have a lognormal character and its correlation coefficient is 0.85. Phosphatic ore deposit at Bahia Inglesa, has a similar distribution, but in this case the correlation coefficient is smaller about 0.81. It is concluded that the genetic relation between phosphorous and uranium at the Mejillones phosphates is more closer than those of Bahia Inglesa being this more economically feasible. (Author)

[en] Many works discuss martensitic transformation in austenitic stainless steels, and especially transformations induced by temperature or monotonic charges. Some studies have focused on the propagation of fissures by fatigue in metastable austenitic test pieces, which display reduced propagation speed of fissures when martensite is induced at the end of the fissure. However, controversy still persists with regard to the role of different parameters in the fatigue behavior of these steels. This work presents preliminary analysis results of fissure propagation by fatigue using test pieces obtained from 1 mm thick sheets of austenitic steel EN 1.4318 (AISI 301LN) with 17% Cr, 7% Ni, low C and alloyed with N. The tests were performed at R charge relations (relation between minimum and maximum charge) of 0.1, 0.3, 0.5 and 0.7. The results were analyzed applying the concepts of the two driving forces concept (cw)

[en] There are five intermetallic compounds in the Al-Mo system that are stable at low temperatures. Of these, the richest phases in some of the two components are the compounds Al₁₂Mo and AlMo₃, whose Pearson symbols are cI26 and cP8, respectively. In both structures, the atoms of the minority component occupy positions bcc and each one of them is surrounded by 12 atoms first neighbors of the other component. These 13 atoms form icosahedron shaped units or heaps. Unlike what occurs in Al₁₂Mo, the AlMo₃ heaps are superposed by sharing atoms from the majority component. The neighboring environment of the majority component is mixed but differs considerably in one or another intermetallic. In each structure, the sites occupied by any given species are crystallographically equivalent, that is, they can self generate from one of the positions and from the crystalline structure's elements of symmetry. This work studies the energy of vacancies and antisites in both compounds and the atomic-jump processes to vacant sites. Computer simulation techniques were used based on minimizing the system's energy. Many-body embedded-atom potentials were used to represent the atomic interactions. The potential mixture used resulted in an adjustment to the crystalline structure of the AlMo₃ phase at low temperatures and to its formation energy (cw)

[en] The production of components of Ti alloys, specifically Ti-6Al-4V, involves some difficulties in obtaining the final desired microstructure, producing decrease in the material's mechanical properties. In the specific case of materials to be used for surgical implants an equiaxial fine grain microstructure of α phase a with an homogenously precipitated β phase is needed. The modification of certain microstructural features is not possible based on simple thermal treatments. Thermomechanical treatments are effective for transforming the lamellar α phase into equiaxial α, but these methods include major deformations in the (α + β) two-phase field. In order to avoid this stage, thermo-hydrogenating processes were used (THP). The THP involve a treatment of β solubilization before, during or after the hydrogenation, a possible isothermal treatment below the β hydrogenated transus temperature and the final vacuum dehydrogenation. The development of treatments using hydrogen as a temporary alloying element creates a new class of microstructures, which are finer than equiaxial structures and respond well to resistance to traction and fatigue. Since the THP do not include the working of the material to control the microstructure, they are more appropriate for use with shaped components close to the end, like those obtained by powder metallurgy or smelting. Different thermo-hydrogenating treatments in Ti-6Al-4V to modify the microstructure were studied. Final microstructures of α fine phase and β disperse phase were obtained using THP in samples with initial lamellar α phase separated by thin sheets of β phase. The characterization of the initial material and of the transformed material was carried out using optic and scanning electron microscopy (CW)