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Pretoria, South Africa

The South African Nuclear Energy Corporation was established as a public company by the Republic of South Africa Nuclear Energy Act in 1999 and is wholly owned by the State. The name is correctly indicated above, although the sequence of letters in the acronym may be taken as suggesting that the name should be the "Nuclear Energy Corporation of South Africa".Necsa replaced the country's Atomic Energy Corporation. Apart from several ancillary functions, the main functions of Necsa are to undertake and promote research and development in the field of nuclear energy and related technologies; to process and store nuclear material and other restricted material; and to co-ordinate with other organisations in matters falling within these spheres. Apart from its main operations at Pelindaba, Necsa also operates the Vaalputs radioactive waste-disposal facility. The Corporation also serves the State's other nuclear institutional obligations. The chief executive officer of Necsa is Mr. Phumzile Tshelane since 1 September 2012.Necsa is organisationally divided into a commercial group, Pelindaba Technology , which conducts business in a variety of products and markets and another group, Pelindaba Nuclear Institute , which is concerned with statutory functions, R&D, support and facility operations. Pelindaba Technology is a portfolio of businesses of which Nuclear Technology Products is a division and serves the international markets for radiation-based technology and products. Also The Uranium Enrichment Corporation of South Africa, Ltd. which operated a facility at Valindaba to produce HEU.Necsa employs some 1.400 people in diverse areas such as physics, engineering, chemistry and electronics. With changes in the country’s positioning on nuclear involvement and South Africa’s re-entry into world markets in 1990, a decision was taken to focus the organisation on commercially driven projects. Today, Necsa supplies a wide range of innovative hi-technology products and services to South African and foreign market sectors with the SAFARI-1 reactor as the cornerstone of the commercial isotope production programme. This research reactor at Pelindaba, SAFARI-1, is now the most commercialised nuclear reactor in the world with ISO 9000 accreditation and is earning South Africa millions of rands' worth of foreign revenue. The 20 MW research reactor SAFARI-1 was initially used for high level nuclear physics research programmes and was commissioned in 1965. In the 1970s and 1980s the focus of activities at Pelindaba was on the exploitation of South Africa’s uranium resources through the successful design, construction and commissioning of commercial uranium hexafluoride, uranium enrichment, and nuclear fuel assembly production facilities. Wikipedia.

Kock L.D.,University of Pretoria | Kock L.D.,South African Nuclear Energy Corporation
Journal of Raman Spectroscopy

Raman microscopy is used in the analysis of glaze on a number of samples that include blue and white ceramic shards, a tile from the Citadel of Algiers and intact Ming plates. The use of the glaze depth profiling method for the study of interfacial pigments on these samples [J. Raman Spectrosc. 2007; 38: 1480] prompted the study of the glaze on the same set of samples to determine glaze type dependence of this method. Using the index of polymerization (I p) which is closely correlated with glaze composition and processing temperature, it is shown that processing temperature could be estimated from a low of about 600 °C for some of the unknown archaeological shards to about 1000°C or above for the Ming porcelain shards. Two intact porcelain plates from the Hongzhi (1488 - 1505) and Wanli (1573 - 1620) Ming imperial periods from the J. A. van Tilburg Museum of the University of Pretoria have been studied, and glaze/glass transition temperature was estimated to be above 1000°C, consistent with historical data. A SnO2-based glaze tile shard from the Citadel of Algiers was also successfully probed, and results indicated a much lower sintering temperature. Copyright © 2012 John Wiley & Sons, Ltd. Source

Venter A.M.,South African Nuclear Energy Corporation
Journal of the Southern African Institute of Mining and Metallurgy

The availability of advanced characterization techniques is integral to the development of advanced materials, not only during development phases, but in the manufactured components as well. At Necsa, two modern neutron diffractometers equipped with in-situ sample environments, as well as complementary X-ray diffraction instruments, are now available as User Facilities within the National System of Innovation in support of the South African research and industrial communities. Neutrons and X-rays, owing to their different interaction mechanisms with matter, offer complementary techniques for probing crystalline materials. Both techniques enable nondestructive investigation of phenomena such as chemical phase composition, residual stress, and texture (preferred crystallite orientation). More specifically, the superior penetration capabilities of thermal neutrons into most materials allows for the analysis of bulk or localized depth-resolved properties in a wide variety of materials and components. Materials that can be investigated include metals, alloys, composites, ceramics, and coated systems. In particular, depth-resolved analyses using neutron diffraction complements surface investigations using laboratory X-rays in many scientific and engineering topics. The diffraction techniques can add significant downstream value to the anticipated nuclear industry development activities. © The Southern African Institute of Mining and Metallurgy, 2015. Source

Bokov P.M.,South African Nuclear Energy Corporation
Science and Technology of Nuclear Installations

We discuss the estimation of the uncertainty and sensitivity parameters for a model response under the assumption that the input variables are normally distributed and block-wise correlated with the covariance matrix, which is small in some norm. These conditions may arise when considering the impact of the group-wise neutron cross-sections' uncertainties on the uncertainty of some reactor parameters such as the neutron multiplication factor. The variance-based global sensitivity analysis, considered in our work, involves the calculation of multidimensional integrals. When the input uncertainties are small, the values of these integrals can be estimated using an asymptotic analysis method called the Laplace approximation. The asymptotic formulas for the output variance and for the global sensitivity indices have been obtained using the Laplace approximation method. It is demonstrated that the asymptotic formula for uncertainty propagation matches the uncertainty propagation formula being used in the local sensitivity analysis. The applicability of the obtained asymptotic approximations was successfully demonstrated on a test problem with realistic cross-section and covariance matrix values. © 2012 Pavel M. Bokov. Source

Sofianos S.A.,University of South Africa | Adam R.M.,South African Nuclear Energy Corporation | Belyaev V.B.,Joint Institute for Nuclear Research
Physical Review C - Nuclear Physics

The description of nuclei as a system of α particles is considered using a two-variable integrodifferential equation describing A-boson systems. The method is based on the assumption that two-body forces are the dominant ones within the system. This allows the expansion of the A-body wave function in Faddeev components which in turn can be expanded in potential harmonics that result either in a coupled system of differential equations in the hyper-radius r or, when projected on the r ij space, in a single two-variable, integrodifferential equation that includes the two-body correlations exactly. The formalism can be readily applied to systems of up to A∼20. Going beyond this number one encounters increasingly difficult numerical problems stemming mainly from the structure of the kernel in the integral. However, these problems can be eliminated by transforming the equation, when A→, into a new one having a kernel which has a simple analytical form and is easy to use in calculations. We employed the transformed equation to investigate the possibility of describing nuclei consisting of A α particles. It was found that for the Ali-Bodmer potential the A=5 system, i.e., the 20Ne, is the most stable while the A=10 system, i.e., the 40Ca, the binding energy has a maximum. Various aspects concerning the formation of Aα nuclei are discussed. © 2011 American Physical Society. Source

van Heerden F.A.,South African Nuclear Energy Corporation
Transport Theory and Statistical Physics

This article introduces a novel coarse-grained particle transport solver, designed specifically for streaming processor architectures. The coarse particles are transported using a Monte Carlo algorithm with a locally homogenized collision operator. Local errors introduced by the homogenization procedure and the use of (deterministic) quadratures, are described and analyzed. A brief description of how the simulation is mapped to the streaming processor (Graphics Processing Unit) is also given. © 2012 Copyright Taylor and Francis Group, LLC. Source

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