The world is power-hungry. And South Africans are sharing the lust for power. As the Earth ages, its population is using up more resources to supply their electricity needs. But the declining source of coal has made it necessary for suppliers such as Eskom to investigate other sources of power.
The new but controversial Pebble Bed Modular Reactor (PBMR) is part of Eskom’s solution to a better power-enhanced future for South Africans.
Potchefstroom University has played an important role in the development of this reactor, and its engineering department has become a world leader in taking this technology into the future.
Professor Gideon Greyvenstein, head of the PBMR research project at the University of Potchefstroom for the Council for Higher Education (CHE), says South Africa is presently the world leader in PBMR technology. He is enthusiastic about the positive impact the project could have, not only on South Africa but also on Africa’s future.
‘The project holds the promise of safe, cost-effective nuclear power that can be adapted to suit a range of environmental and industrial settings,” he said. His team’s research has been nominated for a Technology and Human Resources for Industry Programme (Thrip) award for developing a state-of-the-art test rig where this new nuclear technology can be examined.
The international demand for electricity is expected to almost double by the year 2020. In South Africa, Eskom has calculated that between 2005 and 2010, the need for electricity will exceed what South Africa’s power stations can currently produce.
A big power station releases up to 72 000 metric tons of carbon dioxide and other harmful gases into the atmosphere in a year, the equivalent of 200 000 vehicle emissions.
To produce 1 930MW a day, the power station uses more than 16 000kg of coal, which would fill 33 train-trucks. The Koeberg power station uses only 180kg of uranium a year. Nuclear energy — which generates relatively small volumes of waste and no carbon dioxide emissions or ‘greenhouse” gases that may damage the environment — has the potential to meet this need. At the end of 2002 there were 440 nuclear power plants operating around the world, with more than 30 under construction.
But nuclear reactors are not popular with green activists because of the inherent risk that radioactivity carries with it.
Scientists are exploring new ways to improve the technology and make it cheaper and safer.
The PBMR project is a product of this research. Eskom has been investigating PBMR technology since 1993 for potential application as a power source in South Africa, as well as a viable South African export.
The company purchased the technology from German company Siemens, where reactors of this kind operated successfully from the late 1960s to the 1980s.
Krygkor first showed interest in PBMR technology in the early 1990s. Since it was interested in developing a reactor for a nuclear submarine, it bought into the technology and began researching its usefulness. It soon emerged that the pebble-bed reactor was eminently suited to supplying energy to the power-consuming world.
The PBMR project is one of the highest-level technology projects in the world and South Africa’s biggest civilian high-tech scientific and engineering research and development programme. The project is a joint venture between Eskom, the Industrial Development Corporation of South Africa and British Nuclear Fuels. Eskom, which is owned by the South African government, holds the majority stake in the project.
The project developers say that if successful, the PBMR has the long-term potential to create more than 200 000 new jobs, and add R8-billion to the country’s annual gross domestic product and R10-billion in exports — even if only 2% of the world market for new power plants is captured.
The project leaders say the programme is central to the South African government’s African renaissance initiative, and the local economy stands to benefit on an unprecedented scale.
Greyvenstein and his team at Potchefstroom University have been working closely with the PBMR team to develop a test rig for its power-conversion system.
‘In September 2002 our team achieved a global first with the successful start-up of this test rig,” he said. The test rig (or micro-turbine model), represents the first closed-cycle, three-shaft, recupe-rated gas turbine in the world.
The pebble-bed reactor’s turbine test rig has provided a ‘major boost of confidence in the technical feasibility of the PBMR concept”, says Greyevenstein.
The turbine, the first closed-cycle, multi-shaft gas turbine in the world, demonstrates, on a small scale, the business end of the Potchefstroom University project. The main objective of the project is to show that, as an enterprise, it can be sustained and controlled, and that it is stable.
‘The test rig is a replica of the functional layout of the PBMR power plant, with the same control topology and degrees of freedom,” he said. ‘It accurately predicts the behaviour of the power plant, and addresses one of the main technical risks of the project, namely the integrated controllability of a three-shaft system.
‘Furthermore, the thermal hydraulic design code, Flownex — the main design and analysis tool used in the design of the plant — accurately predicts the various plant parameters, providing a major boost of confidence in the technical feasibility of the PBMR project.”
Greyvenstein explains that the Flownex system developed by the project team is unique in that it is the only programme in the world with which the PBMR can be modelled and simulated. This makes it crucial for the continuation of the whole project, and for improving the PBMR’s competitive edge in the international arena.
‘Developments in Flownex will have an enormous impact on the modelling capabilities of the programme which, in turn, will increase South Africa’s ability to compete internationally in this field,” he says. ‘Although Flownex is particularly well-suited to the modelling of the PBMR, it is a general-systems Computational Fluid Dynamics (CFD) code that finds wide application in industry.”
Greyvenstein says the code was developed over the past 15 years by M-Tech Industrial, a company in collaboration with the Faculty of Engineering at Potchefstroom University for the CHE.
‘The PBMR project has boosted the development of Flownex as a commercial product, and users include companies and universities such as Rolls Royce, Mitsubishi Heavy Industries, Kobe Steel, ConceptsNREC, Eskom, Sasol, CSIR Miningtek, Iscor, MIT, Cranfield University and Stuttgart University.”
The PBMR project has about 300 people working on it directly, and at least another 200 working through associated companies both locally and overseas. It is possibly the largest integrated nuclear design team working on an advanced design in nuclear technology today.
In the past year, 30 engineering master’s students were actively involved as research assistants and 14 doctoral students provided technical assistance. A number of technikon students were involved as part of their Bacalareus Tech and Masters Tech engineering projects, and two fourth-year engineering students completed their final-year projects on PBMR-related work.
Once government has approved the environmental impact assessment reports, the next step is to build a full-scale prototype, says Greyvenstein. A month ago the Department of Tourism and Environmental Affairs decided in favour of the pebble-bed reactor. But the government has yet to give the final go-ahead.
A 110MW class-demonstration module will be constructed at Koeberg, near Cape Town — where Africa’s only nuclear power plant is situated — and an associated fuel plant at Pelindaba, near Pretoria, where fuel for Koeberg used to be manufactured.
The demo-model will consist of one reactor, designed to produce between 110MW and 130MW — enough to sustain about 30 000 average South African homes. A prototype of the PBMR is expected to begin functioning in 2008 if the final go-ahead is given. Green activists, led by Earthlife, are concerned about the danger of nuclear power in South Africa and the dangers the pebble-bed reactor may bring to surrounding communities.
Most of the concerns raised are about the nuclear reactor’s close proximity to surrounding commu-nities and the danger of meltdown or sabotage. But the developers say all the dangers have been researched thoroughly. Greyvenstein says the system has such intrinsic safety that it does not require the costly engineered safeguarding systems that surround ‘conventional” reactors.
The reactor’s uranium ‘pebbles” are sealed with a resilient, silicon ulterior shell that will allow only the energy and not the harmful radioactive rays to pass through. He says radioactive waste will be disposed of after its useful life by sealing it in rock so that it will not endanger future generations.