Pelindaba, South Africa – Scientists from southern Africa no longer need to travel tens of thousands of kilometres to conduct materials research using thermal energy neutron beams, thanks to a recent installation of upgraded diffraction beam line facilities at the Safari-1 research reactor near Pretoria, South Africa. Neutron diffraction is a neutron scattering technique applied to determine the atomic and/or magnetic structure of materials (see the Science box).
"Being able to do the research closer and faster will be beneficial to the competitiveness of our industry and academia," said Andrew Venter, Scientific Section Leader at the South African Nuclear Energy Corporation (Necsa) in charge of the project. The modernized neutron diffraction facilities provide state-of-the-art capabilities of international standard to researchers from various scientific disciplines.
While a developing country like South Africa will not be able to afford the extensive suite of equipment major research institutions in the developed world can offer, it can successfully focus on niche research areas, Venter said. "We need to find such niches and build expertise around them."
The recent upgrade was carried out with support from the IAEA, which included donations of some of the high-precision equipment and contracting of international experts to advise on its design, fabrication and installation. The IAEA, through its Technical Cooperation Programme, also facilitated training of Necsa staff at leading international research centres.
Recent applications
Several researchers from universities and industry across the country have already used the equipment that includes the Powder Instrument for Transition in Structure Investigations and the Materials Probe for Internal Strain Investigations. In addition, collaborative initiatives are under way with scientists from the wider region as well, Venter said.
The fact that a neutron has a magnetic moment enables the study of magnetic structure in materials at the atomic level. These studies are fundamental to understanding the magnetic properties of materials. While most of the research is of academic interest, extensive studies of dilute alloys of chromium have also taken place at the facility.
Research support is also provided in applied themes of industrial interest such as steel production. A team from the University of Pretoria, for instance, now routinely uses the equipment to obtain more precise characterization of iron ore samples, identifying the various types of oxides in the ore. Fundamental understanding of compositional and formation mechanisms contributes towards improving the efficiency of sintering processes.
Venter is also working with a research team to study methods to improve the performance of steels using a process called austenization. It involves heating steel to a temperature at which it changes crystal structure, and then quickly cooling it back to maintain some of the austenite structure. Neutron beams present a high sensitivity probe for the precise characterization of the steel both before and after the austenization process to evaluate its effectiveness. Steel prepared this way typically has greater toughness and is used in environments that require high strength such as critical components in electricity generation plants.
Other steel-related diagnosis, made possible using neutron diffraction, relates to measuring the effectiveness of post-welding heat treatments of steel aimed at reducing inevitable detrimental stresses caused during weld joining processes.
The new facilities at Necsa formed an integral part of the 1st Research Reactor School organized earlier this year by the IAEA and the African Regional Cooperative Agreement for Research, Development and Training Related to Nuclear Science and Technology (AFRA) for researchers from the ten research reactors across Africa.
Further neutron science expansions
Necsa is developing various other instruments awaiting regulatory approval, Venter said. These include small-angle neutron scattering (SANS) and neutron imaging (NI) techniques. SANS uses elastic neutron scattering at small scattering angles (0.5 – 10°) to investigate the structure of various substances at a mesoscopic scale of about 1-1000 nanometer and provides a powerful diagnostic toll to explore the world at nanometre scale. It is widely used to study the shape and size of particles dispersed in homogeneous mediums in chemistry, biology and solid state physics. NI is a transmission technique to study heterogeneous materials, taking advantage of scattering and/or absorption contrast between different elements. If the sample is rotated and many different views are taken, a tomographic three-dimensional reconstruction of that internal distribution can be performed. This non-destructive technique has a wide range of application in the areas of cultural heritage research, porosity and water movement in concretes and minerals and hydrogen diagnostic capabilities for renewable energy studies.
