One of the focus areas of the University of Pretoria’s (UP’s) Institu-tional Research Theme on Energy (IRT/E) is research on the effectiveness of using silicon carbide as a fuel cladding tube instead of Zircaloy in light-water reactors, says UP professor Johan Slabber, who lectures on nuclear engineering in the department of mechanical and aeronautical engineering.
He notes that silicon carbide technology is temperature and oxidation resistant, making it safer than Zircaloy tubing, which is not oxidation resistant when exposed to hot steam.
Slabber explains that the Fukushima Dai-ichi nuclear disaster, in Japan, which was a series of system failures and releases of radioactive materials at the Fukushima I nuclear power plant, following an earthquake and tsunami in 2011, was, besides other aspects, aggravated by the chemical oxidation reaction on the Zircaloy fuel cladding tubes.
“At Fukushima, the Zircaloy tubing, combined with hot steam, oxidised to release energy through aggressive oxidation that emitted hydrogen, which subsequently exploded,” he states.
Slabber notes that silicon carbide is safer because it is a ceramic material, which is high-temperature resistant and does not deteriorate in a hot steam environment owing to oxidation creating a passive layer of silica on the tube surface.
“We are conducting a lot of research on the manufacturing, heat transfer and strengthening capabilities of silicon carbide. One area that has not yet been researched is the sealing of a silicon carbide tube, a theme that we will explore next year,” he says.
Slabber states that, with the university’s current knowledge base in respect of high-temperature reactor fuel, the fuel element in a light-water reactor, which is its biggest weakness, can, through the use of silicon carbide, be improved dramatically.
“We want to investigate the fuel technology to reduce the consequences of a core disruptive event that could result from a loss of cooling to the core and core structures,” explains Slabber.
He adds that UP has extensive contact with US-based fuel, ser- vices, technology and plant design company Westinghouse, which relayed to UP that it wanted to also research the potential of using silicon carbide as the cladding tube of light- water reactors.
“We decided that UP could undertake that type of research because South Africa has several silicon carbide specialists and the country also had a high-temperature reactor programme,” Slabber explains, adding that the drive internationally is to make reactors less reliant on operating equipment, to ensure safety, by making the reactors passively safe.
Nuclear Research Theme
Slabber explains that UP’s nuclear research theme was rolled out in 2010 after the Pebble Bed Modular Reactor (PBMR) project had been mothballed.
“After the PBMR had been terminated, UP attempted to move the technological development that was initiated as a result of the project to form a nuclear research institute.
“However, the university wanted to broaden the institutional research theme to focus on all aspects of energy, including the improvement of energy use and renewable energy,” he notes.
The IRT/E was approved in 2011, says Slabber, and the work crosscuts with other departments relating to research involving chemistry, physics, mathematics and all other disciplines of engineering.
“Currently, the bulk of funding comes from the university and we are working on increas- ing industry support.
Companies such as construction firms Aveng and Group Five have expressed interest, but they are waiting for a confirmation date from government before they make a real commitment,” Slabber says, adding that nuclear research and development at the university are being slowed down because indus-try does not want to commit to anything nuclear until government does.
Slabber states that nuclear engineering has been offered at the university as an undergraduate course for many years and the message that part of South Africa’s planned power generation expansion is the building of six additional nuclear power plants has encouraged students to view nuclear energy as a possible future professional career.
He states that the number of students who chose the undergraduate final year nuclear engineering elective has increased significantly since 2011 and, as a result, the majority of these students have decided to continue in this field at postgraduate level.
“Currently, 21 undergraduate and ten postgraduate students are enrolled in the programme, with the main focus on light- water-cooled and -moderated reactors, as these will be a part of the future of the nuclear energy industry,” states Slabber.
He adds that the course included, as a basis, the nuclear science which supports all the important disciplines of reactor engineering, followed by an overview of the functions, characteristics, fabrication and technology required for the various classes of nuclear materials that are normally used in the design of a nuclear facility.
“This is then followed by courses in reactor physics that govern the neutron dynamics in the core and a module on the removal of heat from the heated core and core components during normal and abnormal operating conditions,” explains Slabber.
For students to proceed to master’s level, several practical nuclear engineering projects have been identified.
These projects focus on improving light-water reactor fuel technology and the passive heat-removal characteristics experienced during the cooling of the reactor-core region.
“These projects are all multidisciplinary and cooperation with practical academics in other departments is necessary to achieve a successful outcome,” concludes Slabber.