South African Nuclear Energy Corporation Research Articles

Evaluation of the Basic Neutronics and Thermal-Hydraulics for the Safety Evaluation of the Advanced Micro Reactor (AMR)

South Africa requires safe affordable distributed base load energy, one way to achieve this is to use nuclear power integrated with renewable energy sources on a decentralized basis. This suggests the development of its own micro modular nuclear reactor, to supply energy to towns, small communities, mines and processing plants. Large Light Water Reactors (LWRs) are expensive and require a large infrastructure development. A High Temperature Reactor (HTR) called the Advanced Micro Reactor (AMR) is in the process of being developed and the design philosophy is to design for inherent safety, maximally using technology that has been developed and validated in previous HTR programs albeit in a completely different and unique configuration. The concept is based on existing knowhow and experience/expertise in South Africa during the time of the Pebble Bed Modular reactor (PBMR) project. These AMR reactors are to be factory built to obtain good quality control and rolled out to various sites. Once the reactor has reached its end of life, it would be returned to a licensed organisation for refuelling. The AMR produces 10MW of thermal power. The reactor configuration uses hexagonal graphite blocks for structural and moderator material, which are arranged to form a cylindrical core layout. The fuel assemblies are silicon carbide tubes that house coated particle fuel, immersed in a lead-bismuth eutectic alloy (LBE). Each fuel assembly is contained in a boring within the graphite moderator that allows an annulus for cooling. There are 420 fuel assemblies in the core. Low enriched fuel in the form of UO₂ or UCO is used. Helium gas is used as coolant. The coolant enters the core at 450°C and exits at 750°C. The mechanical, neutronic and thermal-hydraulic design of the AMR, is being evaluated with assistance from STL Nuclear (Pty) Ltd., the University of Pretoria (UP), the North-West University and the South African Nuclear Energy Corporation (NECSA). The OSCAR-5 code package, together with the Serpent neutronic code were used to perform the basic neutronic studies while the Flownex package was used to determine the thermal-hydraulic and safety evaluation for the Design Base Accident (DBA) specifically the Depressurized Loss of Forced Cooling (DLOFC) event.

Buccal and palatal alveolar bone dimensions in the anterior maxilla: A micro-CT study.

Anterior maxillary immediate implant placement has become a popular procedure. It has aesthetic and functional risks. A prerequisite for success is sufficient alveolar bone for primary stability. Many cone-beam computed tomography (CBCT) studies have assessed alveolar bone dimensions in the anterior maxilla, with varying results. More accurate information on the alveolar bone dimensions in the anterior maxilla is required. The objective of the present study was to evaluate bone dimensions in the anterior maxilla using micro-CT, a high-resolution imaging tool. Seventy-two human skulls were scanned using micro-CT at the South African Nuclear Energy Corporation. Specialized software was used for 3-D rendering, segmentation, and visualization of the reconstructed volume data. Axial planes were created over each alveolus/tooth from canine to canine. Buccal and palatal bone dimensions were measured at crestal, 3 mm, 6 mm, and 9 mm levels. Buccal bone rarely exceeded 0.5 mm, consisting of bundle bone only for all investigated teeth at all levels. Up to a third of teeth showed buccal fenestrations. Alveolar bone on the palatal side was thicker than buccal and increased from <1 mm at crestal level up to 3.77 mm, 4.56 mm, and 5.43 mm for centrals, laterals, and canines at the 9 mm level, respectively. Immediate implants in the anterior maxillae has anatomical risks. Alveolar bone on the buccal aspect is very thin, with fenestrations in certain positions. Therefore, a thorough planning and individual approach are needed to avoid possible complications and achieve stable aesthetic and functional results in the long-term.

Relevance of Palladium to Radiopharmaceutical Development Considering Enhanced Coordination Properties of TE1PA.

Invited for the cover of this issue are the group of Raphaël Tripier and Nathalie Le Bris at the University of Brest (UMR CNRS 6521 CEMCA; France), Cathryn H. S. Driver from the South African Nuclear Energy Corporation in Pretoria (South Africa), and their collaborators. The image depicts the beginning of a new area of research into palladium and complexation of its radioisotopes for applications in nuclear medicine. Read the full text of the article at 10.1002/chem.202200942.

Validation of computational fluid dynamics method through experimental investigation of the plasma spraying process

Numerical modelling has emerged as a powerful predictive tool to enhance plasma sprayed coatings quality and process efficiency. In the present work, a comprehensive Computational Fluid Dynamics model of a gas heating inside a direct current arc plasma torch, is developed, using the simulation software Ansys Fluent. It is therefore sought to test its accuracy and limitations by comparing its predictions to actual data generated in the South African Nuclear Energy Corporation plasma spraying laboratory. In this regards, titanium powder of respective size distributions, 0-63 μm, and 63-75 μm, is sprayed onto a metal piece work. The transport medium is an argon-nitrogen plasma jet, generated from a direct current torch running under an induced power of 12.8 – 13.1 kW. The spraying distance and powder carrier gas flow rate are varied throughout the experiment, from 75 to 85 mm, and 3.9 to 5.8 kg/h, respectively. Comparison of laboratory and simulation-based results were mostly in agreement, in terms of the plasma jet shape, the effect of power increase on the torch exit temperature, the effects of particle size distribution, and carrier gas variation on particle melting and trajectory.

Foreword

The Advanced Materials Initiative (AMI) programme was established in 2003 by the Department of Science and Innovation (DSI)( formerly the Department of Science and Technology (DST)) and Science Councils that contribute towards research and development on materials science, namely, the Council for Scientific and Industrial Research (CSIR), Council for Mineral Technology (MINTEK) and South African Nuclear Energy Corporation (NECSA).The objective of establishing this initiative was to research, develop and innovate across the advanced materials value chain. In this context, the advanced materials are defined as all materials that provide opportunities for creating new products and utilising advanced properties through the application of new technologies. From the DSI‘s strategic consideration, the AMI‘s key objectives are: to foster the creation of new industries, to improve the competitiveness of old and existing industries, and to promote technology localisation.The significance of the AMI programme through high-end beneficiation of South Africa’s mineral wealth is to position the science councils and universities to contribute towards the provision of solutions to the priority needs of our country, especially South Africa’s urgent need to create jobs and assist in the alleviation of our beloved country’s Triple Challenge of Poverty, Unemployment and Inequality. This is also part of the government’s nine-point plan - adding value to our mineral wealth by advancing beneficiation and support to the engineering and metals value chain.The Conference of the South African Advanced Materials Initiative (CoSAAMI), is an evolution of the Advanced Materials Initiative (AMI) series of conferences which offered a platform for local and international researchers and students, to present their work on topics related to the themes of the conference. The thematic areas of the conference are: powder metallurgy, materials for extreme environment, smart materials, corrosion, light weighting, computational materials science (modelling and simulation), political economy of materials science, advanced manufacturing, alloy development, polymers, ceramics, composites, nanomaterials and novel energy materials.All papers submitted to the CoSAAMI 2019 were peer-reviewed by a panel of expert referees in accordance with the IOP Peer Review Guidelines. A total of 95 manuscripts were received and through a rigorous review process where each paper received three reviews, only 50 were selected for publishing in a conference proceedings. The papers that were not accepted for publication were offered an option for presentation as a poster.The support of our panel of reviewers is tremendously appreciated and this conference proceedings would not be possible if it were not for their tireless and committed effort. The CoSAAMI 2019 team thanks you.

Foreword

ForewordThe Advanced Materials Initiative (AMI) was established by the three science councils working in metallurgy and materials science, viz. Mintek, the Council for Scientific and Industrial Research (CSIR) and the South African Nuclear Energy Corporation Ltd. (Necsa). It is supported by the Department of Science and Technology (DST) to facilitate research, development and innovation across the materials value chain. The goal is to target significant export income and new industries for South Africa by 2020 through the country becoming a world leader in sustainable materials production and manufacturing via technological competence and optimal, sustainable local manufacturing of value-added products while reducing environmental impact.The key objectives of the programme are to create new industries, support existing industries, and localise technology. The AMI takes an integrated (vertical and lateral) approach across the entire value chain from resource development to materials production and the manufacture of end-products, to achieve its goal.The AMI consists of various technology networks, each focussing on different commodities that are of strategic importance to South Africa. The AMI promotes collaborative research between the science councils, tertiary education institutions and industry, both local and internationally. Human resource development is critical for the networks to expand the country’s technical capacity, develop the use of materials in new applications and more diverse industries, and develop industrial localisation.The Conference of the South African Advanced Materials Initiative (CoSAAMI’18) is the culmination of the annual peer review mechanism of the AMI. It particularly encourages the interaction of students and developing academics with the more established academic community and industry in an informal setting to present and discuss new and current work.The organising committee received 93 papers covering about 10 topics. Based on over 141 reviews from the technical committee and external reviewers, 50 papers appear in this proceedings. Each paper received at least 3 reviews. These proceedings will furnish scientists and engineers in the field of materials science with an excellent reference book and furthermore be an impetus to stimulate further study and research in these areas.The success of the AMI depends completely on the effort, talent and energy of researchers in the field of materials science who have written and submitted papers on various topics, as well as the reviewers who have invested significant time in analysing and assessing multiple papers to maintain a high standard of quality for this conference. We thank all authors and participants for their contributions.

A micro-CT study of the greater palatine foramen in human skulls.

The greater palatine foramen (GPF) is an important anatomical landmark and has substantial clinical relevance in dental surgery. Knowledge of its precise location and dimensions is required for proper planning of surgical procedures involving the posterior maxilla. We used microfocus computed tomography to determine the location and dimensions of the GPF, and any sex and race variations in those measurements, in 77 human skulls scanned at the South African Nuclear Energy Corporation. Specialized software was used for three-dimensional rendering, segmentation, and visualization of the reconstructed volume data. GPF location ranged from adjacent to the first molar to distal of the third molar. The most common GPF location was near the third molar (66.7% of skulls), and the GPF was as close as 6.31 mm (mean distance 12.75 ± 3 mm). The mean GPF dimensions were 5.22 mm on the anterior-posterior axis and 2.81 mm on the lateral-medial axis. We noted no significant differences in relation to race, sex, or age in the sample. The GPF was adjacent or posterior to the third maxillary molar in most skulls.

Visualization Within the Ventricles of the Brain: A Micro-Focus X-Ray Study.

Conceptualization of the ventricular system of the brain by macroscopic studies is complicated by the lack of physical structure of these interconnected cavities. Dissection procedures designed to display the structures in the walls of the ventricles are destructive and not conducive for the appreciation of the ventricular system in its entirety. The application of Micro-focus X-ray tomography affords the possibility to appreciate hidden structures in a nondestructive manner. The aim of this study was to explore the possibility of using micro-focus X-ray tomography in the three-dimensional (3D) visualization of the ventricular system as well as the various neuroanatomical structures within its walls for educational purposes. Randomly selected embalmed human cadaver brains were scanned at Necsa (South African Nuclear Energy Corporation) housing the MIXRAD laboratory consisting of a Nikon XTH 225 ST micro-focus X-ray tomography facility. A 3D flythrough video of the ventricular system was reconstructed from these scans using software to view the inner surface of the ventricles. Micro-focus X-ray tomography provides feasible means of delivering high-resolution images in a nondestructive way to design a representation of the ventricular system. In addition, structures in the walls of the ventricular system could be appreciated in a novel way. It is envisaged that this 3D-fly-through video of the ventricular system will be valuable when integrated with standard prosections and atlas pictures in the educational setting. Further studies evaluating the use of this integrative visualization of the ventricular system of the brain for its applicability in the educational setting should be performed. Anat Rec, 301:1138-1147, 2018. © 2017 Wiley Periodicals, Inc.

The effect of α-irradiation from enriched uranium on the leaching properties of PTFE

Abstract In the uranium enrichment plants of the South African Nuclear Energy Corporation SOC Ltd (Necsa), sintered polytetrafluoroethylene (PTFE) filters were used to remove gas entrained solid particles, in order to prevent blocking of the isotope separating elements. When these plants were decommissioned and dismantled, the filters which mostly contained solid uranium fluoride and uranium oxyfluoride compounds and compressor ring dust, were broken into pieces, put into metal drums, and stored. This waste contains enriched uranium and can't be disposed of at the current disposal site (Vaalputs), which only accepts low and intermediate level waste. Initial attempts, directly after removal from the enrichment plants, to decontaminate these filters using various aqueous solutions, were unsuccessful probably because of the known non-wettability of PTFE surfaces. However, recent attempts to leach the absorbed enriched uranium were successful. This resulted in a study to determine the effect of mainly α-irradiation from the enriched uranium on the morphology of PTFE. A Monte Carlo N-Particle transport code (MCNP), a general purpose radiation transport code modelling the interaction of radiation with materials that simulate nuclear processes, was used to determine the rate of PTFE radiolysis. The results confirmed that the dose rate received from mainly the α-particles (97%) during the storage period had caused significant structural damage to the PTFE depending on the enrichment grade and the amount of uranium on the filters. To confirm the modelling data, analytical techniques, including micro X-ray tomography, thermogravimetric analysis and X-ray diffraction were used to study the morphology changes in the PTFE structure of the research samples. Experimental results indicated that the crystallinity increased while the molecular weight of the PTFE decreased. This could be attributed to the radiation induced degradation of the PTFE by the absorbed enriched uranium.

The Importance of Maintaining a Mosaic of Different Plant Communities for Arthropod Biodiversity Conservation at the Vaalputs Radioactive Waste-Disposal Site, Bushmanland, South Africa

Effective biodiversity monitoring and rehabilitation relies on a good understanding of the factors that influence species distributions and assemblage composition. Here we investigated the influence of plant community characteristics on arthropod diversity, abundance and community composition at the radioactive waste-disposal facility of the South African Nuclear Energy Corporation (NECSA), Northern Cape Province. Plant alpha-diversity and cover was similar between all five plant communities surveyed. Similarly, total arthropod alpha-diversity did not differ between these plant communities. In contrast, arthropod abundance differed between the different plant communities and was negatively correlated with plant alpha-diversity and positively correlated to vegetation cover. Also, more beta-diverse plant communities did not necessarily support greater beta-diversity of arthropods. However, different plant communities generally had different arthropod communities. This highlights the importance of maintaining a mosaic of different plant communities for the effective conservation of arthropod biodiversity in this semi-arid region.

Samarium oxide as a radiotracer to evaluate the in vivo biodistribution of PLGA nanoparticles

Nuclear Technologies in Medicine and the Biosciences Initiative (NTeMBI), a national technology platform developed and managed by the South African Nuclear Energy Corporation (Necsa) and funded by the Department of Science and Technology

Coupled 3D neutronics/thermal hydraulics modeling of the SAFARI-1 MTR

The purpose of this study was to develop a coupled accurate multi-physics model of the SAFARI-1 Material Testing Reactor (MTR), a facility that is used for both research and the production of medical isotopes. The model was developed as part of the SAFARI-1 benchmarking project as a cooperative effort between the Pennsylvania State University (PSU) and the South African Nuclear Energy Corporation (Necsa). It was created using a multi-physics coupling of state of the art nuclear reactor simulation tools, consisting of a neutronics code and a thermal hydraulics code.The neutronics tool used was the PSU code NEM, and the results from this component were verified using the Necsa neutronics code OSCAR-4, which is utilized for SAFARI-1 core design and fuel management. On average, the multiplication factors of the neutronics models agreed to within 5pcm and the radial assembly-averaged powers agreed to within 0.2%.The thermal hydraulics tool used was the PSU version of COBRA-TF (CTF) sub-channel code, and the results of this component were verified against another thermal hydraulics code, the RELAP5-3D system code, used at Necsa for thermal–hydraulics analysis of SAFARI-1. Although only assembly-averaged results from RELAP5-3D were available, they fell within the range of values for the corresponding assemblies in the comprehensive CTF solution. This comparison allows for the first time to perform a quantification of steady-state errors for a low-powered MTR with an advanced thermal–hydraulic code such as CTF on a per-channel basis as compared to simpler and coarser-mesh RELAP5-3D modeling. Additionally, a new cross section representation was used to ensure that the thermal hydraulic feedback effects on the core neutronics were captured as accurately as possible. This cross section representation was applied to SAFARI-1 core calculations for the first time in this work. Such implementation helps to quantify the effect of detailed modeling of thermal–hydraulics feedback effects on neutronics results in multi-physics simulations.The outcome of the study is the intended coupled neutronics/thermal–hydraulics model of the SAFARI-1 reactor.

Production of high specific activity 195mPt‐cisplatinum at South African Nuclear Energy Corporation for Phase 0 clinical trials in healthy individual subjects

Platinum agents continue to be the main chemotherapeutic agents used in the first-line and second-line treatments of cancer patients. It is important to fully understand the biological profile of these compounds in order to optimize the dose given to each patient. In a joint project with the Australian Nuclear Science and Technology Organisation and the Nuclear Medicine Department at Steve Biko Academic Hospital, South African Nuclear Energy Corporation synthesized and supplied (195m) Pt-cisplatinum (commonly referred to as cisplatin) for a clinical pilot study on healthy volunteers. Enriched (194) PtCl2 was prepared by digestion of enriched (194) Pt metal (>95%) followed by thermal decomposition over a 3 h period. The (194) PtCl2 was then placed in a quartz ampoule, was irradiated in SAFARI-1 up to 200 h, then decay cooled for a minimum of 34 h prior to synthesis of final product. (195m) Pt(NH3 )2 I2 , formed with the addition of KI and NH4 OH, was converted to the diaqua species [(195m) Pt(NH3 )2 (H2 O)2 ](2+) by reaction with AgNO3 . The conversion to (195m) Pt-cisplatinum was completed by the addition of concentrated HCl. The final product yield was 51.7% ± 5.2% (n = 5). The chemical and radionuclidic purity in each case was >95%. The use of a high flux reactor position affords a higher specific activity product (15.9 ± 2.5 MBq/mg at end of synthesis) than previously found (5 MBq/mg). Volunteers received between 108 and 126 MBq of radioactivity, which is equivalent to 6.8-10.0 mg of carrier cisplatinum. Such high specific activities afforded a significant reduction (~50%) in the chemical dose of a carrier cisplatinum, which represents less than 10% of a typical chemotherapeutic dose given to patients. A good manufacturing practice GMP compliant product was produced and was administered to 10 healthy volunteers as part of an ethically approved Phase 0 clinical trial. The majority of the injected activity 27.5% ± 5.8% was excreted in the urine within 5 h post injection (p.i.). Only 8.5% ± 3.1% of cisplatinum remained in blood pools at 5 h, which gradually cleared over the 6-day monitoring period p.i. At the end of the study (6 days p.i.), a total of 37.4% ± 5.3% of the product had cleared from the blood into urine, and approximately 63% remained in the body. The significantly lower concentration of carrier cisplatinum used for imaging resulted in a well-tolerated product.

Efficiency of neutron tomography in visualizing the internal structure of metal artefacts from Mapungubwe museum collection with the aim of conservation

Estimating physical stability as well as revealing signs of fabrication in metal artefacts via two complementary nondestructive methods, neutron- and X-ray tomography were the main goals of this study. To aid conservation management of metal artefacts improved knowledge of the internal structure and degree of corrosion therein is highly desired. In this study, neutron- and X-ray tomography were chosen as two complementary noninvasive visualization techniques to study internal structure and corrosion of five representative examples of archaeological metal artefacts from the Mapungubwe museum collection. Tomography was performed at the Neutron Radiography (SANRAD) facility of the South African Nuclear Energy Corporation where thermal neutrons as well as complementary X-rays are conveniently available under one roof. Comparative studies revealed neutron tomography to be generally superior to X-ray tomography due to the enhanced penetration properties of neutrons through the metal objects. In this paper the rich capability of neutron tomography as a nondestructive visualization aid for scientific conservation purposes is introduced and supported by results achieved for the five selected real artefacts.

Contributions of Natural Radionuclides in the Domestic Water of Two Critical Gold Mining Communities in Ghana

A study of the possible radiological impact as a result of usage of water in two critical mining communities of Dumasi and Chujah at Bogoso in the Western Region of Ghana was carried out. Water samples collected from boreholes and treated water supplied by a gold mining company were analyzed for important radionuclides such as 238U, 234U, 226Ra, 210Po, 230Th, 232Th and 224Ra, using extractive techniques in the RadioAnalytical Laboratory of the South African Nuclear Energy Corporation. None of the radionuclide concentrations found exceeded the world averages in drinking water. The 238U/235U ratios were also found to fall within those for natural environmental materials. The dose contributions of the radionuclides for different age groups were evaluated using the IAEA recommended dose conversion factors. The lifetime average dose for all the communities are lower than 0.1 mSv/a as recommended by WHO; however, if age group classification is considered, infants less than 1 year old in Chujah are exposed to 0.11 mSv/a when the treated water is used.

Effectiveness of neutralization process in reducing heavy metals concentrations in discharged sludge from the treatment of sulphide ore for gold using instrumental neutron activation analysis

The effectiveness of the neutralization process on heavy metals precipitated in sludge has been evaluated using instrumental neutron activation analysis (INAA) facilities at the South African Nuclear Energy Corporation (Necsa). The elemental concentrations of Th, Fe, Ag, Co, Cr, As, Au and K were reduced after the neutralization process with the exception of Mn and Sn which appeared to be enhanced by the neutralization process. Even though the neutralization process was targeted at the basic ferric arsenate compound, it was found to be effective in reducing other elemental concentrations. The variations in the geochemical compositions of the sulphidic ores during treatment at various stages also showed that physical processing stages do not significantly alter the elemental concentrations in the feed materials, however, the chemically active processing stages do. Also, the enhancement of the elements at the chemical stages depends on total quality control, where the application was not very repeatable the pattern of variation of elements at some stages was found to be irregular irrespective of the ore grade. The elements; Sn, Fe, Th, K, Au, Ag, As, Cr, and Co were enhanced in almost all the chemically active stages. Au was much more enhanced during flotation and bio-oxidation processes. Correlation analysis performed to determine the distribution patterns show that Fe, As, Ag and Co are geochemically associated and might be enriched simultaneously.

A density‐functional theory approach to the separation of K2ZrF6 and K2HfF6 via fractional crystallization

AbstractBecause of the low absorption cross‐section for thermal neutrons of zirconium (Zr) as opposed to hafnium (Hf), Zr‐metal must essentially be Hf‐free (&lt;100 ppm Hf) to be suitable for use in nuclear reactors. However, Zr and Hf always occur together in nature, and due to very similar chemical and physical properties, their separation is particularly difficult. Separation can be achieved by traditional liquid–liquid extraction or extractive distillation processes, using Zr(Hf)Cl4 as feedstock. However, the production of K2Zr(Hf)F6 via the plasma dissociation route, developed by the South African Nuclear Energy Corporation Limited (Necsa), could facilitate the development of an alternative separation process. In this theoretical study, the results of density‐functional theory (DFT) simulations of K2Zr(1‐z)HfzF6 solid solutions [using Cambridge Serial Total Energy Package (CASTEP)] are presented, for which the supercell approach was applied in an attempt to determine whether solid solution formation during crystallization from aqueous solutions (fractional crystallization) is thermodynamically possible, which would hinder the separation efficiency of this method. Consequently, the calculated thermodynamic properties of mixing were used to evaluate the separation efficiency of Zr and Hf by fractional crystallization using a thermodynamic model to calculate the relative distribution coefficients. The small mixing enthalpies that were calculated from the DFT results, indicates that lattice substitution of Zr(IV) by Hf(IV) in K2ZrF6 could occur with relative ease. This is not surprising, considering the close similarities between Zr and Hf, and it was therefore concluded that K2Zr(1‐z)HfzF6 solid solution formation might well restrict the separation efficiency of Zr and Hf by fractional crystallization of K2Zr(Hf)F6. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011

Fluorine research in South Africa and four benchmarking countries: Comparative mapping and assessment

Fluorine research has been identified as a priority area in South Africa and the South African Nuclear Energy Corporation (NECSA) is embarking in an effort to expand its hydrogen fluoride and aluminium trifluoride production capacity. On the eve of those efforts this article reports the findings of an effort to map and assess fluorine research in South Africa in comparison to four other countries i.e. Malaysia, Australia, Germany and Italy.

The role of SAFARI-1 in industry and academia

The South African Nuclear Energy Corporation (NECSA) owns and operates the SAFARI-1 20 MW Research Reactor. In fulfilling its mandate from government to apply radiation technology for scientific purposes, NECSA is constantly exploring opportunities to employ the neutrons from its beam line facilities to benefit both academia and industry in research and technological development. This goal is approached through joint ventures with industry and academia. This paper outlines the facilities available at SAFARI-1 and their application to various fields.