The Last Great Hope.(building a pebble-bed nuclear power plant in South Africa)(Brief Article)

As a birthplace, Koeberg looks none too auspicious. It's a scrubby stretch of wasteland on South Africa's west coast, 30 miles north of Cape Town. The landscape is dominated by a pair of aging nuclear cooling towers, squatting like two pale, white stumps above a few featureless buildings. Nevertheless, Tseliso Maqubela, chief director of nuclear technology for South Africa's Department of Minerals and Energy, says he hopes this unpromising patch of dust will deliver "an African renaissance."

Or the site could be a technological dead end. It all depends on whether the government approves an international consortium's proposal to build the world's first commercial "pebble bed" reactor at Koeberg. Proponents say the reactor's innovative design is the crucial next step toward a nuclear-powered future. They argue that pebble-bed technology is safer, more efficient and more dependable than the obsolescing "light water" reactors now in general use. Opponents, convinced there's no such thing as safe nuclear power, have vowed to block the Koeberg project. And Maqubela--despite his undisguised eagerness to put South Africa at the forefront of energy technology--says his office has yet to decide who's right. "It's going to be a challenge to convince us of the safety and the economic benefits of this project," he warns.

The Koeberg plant's backers don't seem worried. The pebble-bed design aced its first field tests more than a quarter-century ago. A 15- megawatt demonstration model was built in Germany in the 1960s, and it hummed along handsomely for the next 21 years. It might be going strong to this very day if it hadn't been shut down ahead of schedule, a victim of the antinuclear panic that swept the world after the 1986 Chernobyl disaster. Too bad, pebble-bed advocates say, because their reactor's design makes a Chernobyl-style disaster virtually impossible. The plant can't get hot enough to cause a meltdown, even if operators do nothing to prevent it. The designers call it "walk-away safe."

The basic design is simple enough. Like any other nuclear power plant, the pebble-bed design uses heat from a controlled nuclear chain reaction to drive an electrical turbine. There are three main differences. The first is the way the fuel is configured. In a standard light-water reactor, the heat is generated by a fixed array of several thousand metallic fuel rods. In a pebble-bed reactor, the fuel takes the form of loose graphite spheres the size of tennis balls. Each "pebble" contains thousands of tiny ceramic-coated granules of uranium dioxide. The second difference is what drives the turbines: standard nuclear-plant turbines run on steam, while the pebble-bed system uses superheated helium gas. The third difference is scale. The Koeberg reactor, if it is ever built, will be about a 10th the size and power of a typical 1,100MW light-water plant.

Advocates say the reactor's small size is one of its biggest virtues. A pebble-bed plant can be constructed from scratch in roughly two years, about a third the time it takes to build a standard light-water plant. Pebble-bed technology would enable power companies to tailor their generating facilities to fit local needs, rather than creating massive power grids to deliver electricity across country. Best of all, ...