Published online 23 February 2010 | Nature 463, 1008-1009 (2010) | doi:10.1038/4631008b

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Pebble-bed nuclear reactor gets pulled

South Africa cuts funding for energy technology project.

Bedtime for pebbles?Pebble Bed Modular Reactor (Pty)

Hopes for the development of pebble-bed nuclear reactor technology, long held up as a safer alternative to conventional nuclear power, have suffered a blow. Last week, the South African government confirmed that it will effectively stop funding a long-term project to develop the technology.

The development company, Pebble Bed Modular Reactor (PBMR), based near Pretoria, says that it is now considering axing three-quarters of its 800 staff, about half of whom are scientists or engineers. "The resources available to the company will not sustain the current cost structure," the company says. The cuts could trigger an exodus of nuclear expertise from South Africa, although some argue that government funding has kept the project going for too long in the face of growing problems.

South Africa started to develop its pebble-bed reactor design in the mid-1990s, hoping that it would deliver cheap electricity and open up a lucrative export industry. It licensed the technology from Germany's Jülich Research Centre, which abandoned a working prototype reactor in 1991 after citing poor business opportunities.

Eskom, South Africa's main electricity generator, based in Johannesburg, set up the PBMR in 1999 to develop the technology into a economically viable reactor. "It caught the mood in South Africa, and the feeling among South Africans was that their technology was as good as anybody's," says Steve Thomas, an energy-policy researcher at the University of Greenwich, London. "This was their chance to show the world what they could do."

The proposed reactor would have used enriched uranium fuel embedded within tennis-ball-sized graphite spheres ('pebbles'). These should enable it to run at temperatures of between 750 °C and 1,600 °C yet resist a core meltdown even if the helium-gas coolant is lost, an attractive safety feature.

“This was South Africa’s chance to show the world what it could do.”


But several of the firm's biggest investors, including the utility firm Exelon in Chicago, Illinois, withdrew during the feasibility phase, which ended in 2004. In the four years up to March 2007, the South African government contributed 7.2 billion rands (US$935 million) in funding, on the condition that the PBMR "attract additional investment through investors other than government, and that it secure a customer for its product", according to a government statement. However, despite a revised business model and product offering, the firm has been unable to do either of these, the government says. Funding was last week slashed to 11 million rands over the next three years, which is "not enough to keep a nuclear design and engineering company going", according to the PBMR.

Runaway costs and technical problems helped to doom the project, says Thomas. "In 1998, they were saying that they would have the demo plant online in 2003" at a cost of 2 billion rands, he says. "The final estimate was that the demo plant would be online in 2018 and it would cost 30 billion rands." Furthermore, he adds, the PBMR has never been held to account for why costs rose every year, why the completion date was continually pushed back or the nature of its design problems.

In a final twist, the PBMR announced last year that it was indefinitely shelving plans to build a demonstration plant. The programme's demise will not help South Africa's goal of doubling its 35,000-megawatt power-generating capacity by 2025.

One problem was that the design became too ambitious, says John Walmsley, past president of the South African branch of the Nuclear Institute, a professional society for nuclear engineers. The PBMR hoped to push the reactor's operating temperature as high as possible to enable not just electricity generation, but also 'process heat' applications such as turning coal into liquid fuels, he says. It also aimed to boost the power output to the very limits of the design to make the reactor more economical. "They tried to build a BMW when they maybe should have started with a Morris Minor," he says.

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Although many scientists had hoped that the safety system of the pebble-bed design would win over opponents of nuclear power, a 2008 report from the Jülich Research Centre cast doubt on those claims, suggesting that core temperatures could rise even higher than the safe threshold.

Tsinghua University in Beijing now hosts the only operational prototype pebble-bed reactor, although similar reactors are being developed in the United States and the Netherlands. But the PBMR's problems are not unique, says Thomas. "Every nuclear nation in the world has had a programme to commercialize this type of reactor, and they all got nowhere." 

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