[en] This paper describes current factors important to suppliers operating in the natural uranium market-place and attempts to look forward in time to identify what factors will either remain or develop to complicate the lives of producers. In the absence of effective import restrictions in the United States, the market-place will continue to be a buyers' one for at least a few years, but some of the factors causing this situation will ease with the passage of time, or perhaps more correctly with the generation of more electricity from nuclear power plants. To survive over the next several years, a producer will need not only favourable production costs but also an intelligent approach to the marketing of his product. (author)

[en] The Mika uranium mineralization is located within two parallel north-south trending shear zones about 200 km northeast of Jalingo, Taraba State, Nigeria. The host rock is part of the Pan-African basement complex and consists mainly of medium grained granite which is, in places, intruded by rhyolites and siliceous veins. Petromineralgraphic studies of the ore indicate meta-autunite and coffinite occurring as finely disseminated grains and as fine fracture-fillings. The secondary uranium ore minerals are at sub-surface level and associated with hydrated iron oxides. Pitchblende in association with sulphides as fine disseminations and milli metric veinlets occurs at deeper levels. The nature of the ore and constituent gangue minerals which are mostly silicates indicate that the extraction of the uranium in acid circuit would be feasible. Conventional agitation leaching of feed with different grain size, acid concentration, temperature of slurry and residence time as variables yielded satisfactory results. Among the process variables, leachant concentration was found to be the efficiency determining factor as this investigation has shown hat high dosage of acid (108 kg H₂SO₄/t ore) is necessary to obtain 95% uranium extraction. With half this acid dosage, acid plug-cure leaching was tested, yielding uranium extraction of over 98%

[en] Two types of fast reactor are investigated to utilize the natural uranium without enrichment and reprocessing in an equilibrium state. The first trial is SFPR. Its fuel-shuffling pattern is optimized. An obtained result gives its peak fuel burnup of 22,5%, power peaking factor of 1.5 and peak excess reactivity of 2,15%. The second trial is CANDLE burnup scheme, where distribution shapes of neutron flux and nuclide densities are constant but move in axial direction with a constant velocity. A feasible solution gives the speed of burning region of 4,1 cm/year, k_eff of 1,02 and average spent fuel burnup of 41%. (author)

[en] A recently conceived nuclear reactor design is evaluated here for theoretical burn-up characteristics which might support Global Nuclear Energy Partnership (GNEP) goals. This reactor uses natural uranium metal as fuel with beryllium moderation. The reactor also uses light water as a coolant. The reactor analysis in this work predicts the reactor to be capable of running at up to 4 GW-thermal for total burn-up values of approximately 1.4 x 10³ GW-days. This is a very simple conceptual reactor design intended solely for very preliminary feasibility studies

[en] The main reactor types based on natural uranium metallic fuel element, particularly the early types, are reviewed in this report. The reactor types are: graphite moderated air cooled, graphite moderated gas cooled and heavy water moderated reactors. The design features, fabrication technology of these reactor fuel elements and the operating experience gained during reactor operation are described and discussed. The interrelation between operating experience, fuel design and fabrication was also discussed with emphasis on improving fuel performance. (author)

[en] Tissue distribution and blood chemistry of uranium in serum levels of BUN, Creatinine, SGPT and SGOT were determined in rats after the administration of uranylnitrate. Determination of uranium in organ was done by radioactivation analysis. Radioactivity of ²³⁹Np in lung was higher than in other tissues (e.g. liver, kidneys, spleen, tibia, testes, stomach and brain). Correlations between BUN and Creatinine were positively increased after the administration of 25 mg/kg uranylnitrate. The SGPT and SGOT activities showed weak correlation with the control group. However, activities of SGPT and SGOT after the administration of 1 mg/kg uranylnitrate showed high peak at 90 min interval. Uranium uptake by liver and kidneys increased at early period and decreased immediately to the control level. Lung who confirmed to be the critical organ on toxic effect by uranylnitrate. (Author)

No abstract available

[en] This report contains all the information related to the development of the CANDU advanced fuel, so-called CANFLEX-NU, which is composed of 43 elements with natural uranium fuel. Also, it contains the compatibility study of CANFLEX-RU which is considered as a CANDU high burnup fuel. This report describes the mechanical design, thermalhydraulic and safety evaluations of CANFLEX fuel bundle. (author). 38 refs., 24 tabs., 74 figs

[en] A nuclear reactor is described which consists of: nuclear reactor fuel rods defining a nuclear reactor core; zones of enriched and natural uranium fuel defined within each of the nuclear reactor fuel rods; an upper core plate; an auxiliary upper core plate fixedly connected to a first stationary set of the nuclear reactor fuel rods and spaced below the upper core plate so as to define a plenum chamber between the upper and auxiliary upper core plates; and means disposed above the upper core plate and extending through the upper core plate so as to be connected to a second set of the nuclear reactor fuel rods for vertically moving the second set of the nuclear reactor fuel rods, and the zones of enriched and natural uranium fuel defined therein, relative to the first stationary set of the nuclear reactor fuel rods, and the zones of enriched and natural uranium fuel defined therein, within the nuclear reactor core and the plenum chamber during an operative fuel cycle for predeterminedly operatively interfacing the zones of enriched and natural uranium fuel defined within all of the nuclear reactor fuel rods so as to optimize the utilization of free or excess neutrons produced within the nuclear reactor core throughout the fuel cycle

[en] Pressure tubes and heavy water (PHW) characterize all CANDU (Canadian Deuterium Uranium) reactors. This combination has provided Canada with a nuclear power system that has acknowledged design and safety advantages. The system has the additional advantage of extracting more electrical energy from uranium fuel than any other commercially developed system. That the plants of this system are economically competive has been demonstrated through the operation of the 2000 MWe Pickering Nuclear Generating Station. (Auth.)