Technology▼Solutions The next generation of nuclear power?
PBMR PT Y
Schulten came up with a novel idea: He would pack tiny particles of uranium into thousands of graphite Climate change is just one of the can firm PBMR Pty, which is conspheres, each about the size of a tenproblems linked to carbon-based structing the plant, ultimately hopes nis ball. The radioactive balls, which fuels that have sparked a renewed to build 30 pebble bed reactors he called pebbles, could be cooled interest in nuclear power. While throughout the country, says Jaco by helium gas, which would power a stakeholders debate the merits of Kriek, the company’s CEO. PBMR turbine as it flowed out of the reacthis approach, the nuclear indusPty is actively trying to license its tor vessel. The uranium itself is setry and its supporters are exploring technology in the U.S., and Westingquestered at low density within the next-generation reactors that pebbles and shielded by their might be safer and less expengraphite casings. This ensures sive than the ones used today. that the uranium can never get The pebble bed modular reactor hot enough to melt, and the ca(PBMR), which is based on a detastrophe of a nuclear meltdown cades-old German design, ranks can be avoided. among the top contenders. The idea took hold, and in PBMR’s supporters describe the mid-1960s, scientists in Gerthe technology as inherently many built a prototype pebble safe and appropriate not just for bed reactor that ran successfully rich, industrialized countries but for 21 years. A much larger, comalso for developing nations. “The mercial-scale unit went online beauty of the pebble bed reactor in the 1980s, but it was hobbled South Africa’s pilot pebble bed modular reactor fuel is that you don’t need an MIT by design flaws and a growing plant is under construction at Pelindaba, near the Ph.D. to run it,” muses Andrew environmental movement that capital city Pretoria. The facility employs dozens of Kadak, a professor at the Massashut down Germany’s nuclear Ph.D.s working to promote a nuclear power infrachusetts Institute of Technology’s structure throughout the country. power industry altogether. department of nuclear science But even as PBMR technoland engineering. “That means you house Electrical Co., owner of half ogy was fading in Germany, it was can use it even in countries that don’t the world’s nuclear power plants, re-emerging in South Africa, where have the degree of history or backrecently purchased a major stake in industry and government officials ground in nuclear technology that we the company. thought its size and scalability were have in Western Europe or here.” PBMR Pty also recently signed well suited for domestic power PBMR proponents point to anotha memorandum of understanding needs. Eskom, the largest South Afer advantage: Each reactor module with Chinergy, a Chinese company rican utility company, bought rights generates about 170 megawatts of that plans to build its own demonto the PBMR design in 1993 and electrical power (MWe), far less than stration plant near Beijing. China helped create PBMR Pty to advance the 1000 MWe produced by a stancurrently has the world’s only operathe technology. dard light water reactor. PBMR can tional PBMR plant—an experimenNow, at its R&D facility at Pelinthus be scaled according to need: tal research model in Beijing housed daba, near the capital city Pretoria, Several modules can be connected at Tsinghua University. According PBMR Pty builds on the German dein tandem to power a city, and one to Kadak, who is collaborating on sign. The facility creates the reactor’s could supply the needs of a smallPBMR development with the scienpebbles by coating uranium dioxide er town. Conceivably, the reactors tists at Tsinghua University, China’s fuel particles with alternating layers could supply small, remote villages long-term goals are to build PBMR of carbon and silicon. The coated far from an urban electricity grid. plants throughout the country’s inparticles are pressed into mixtures of South Africa, which seeks a globterior. “The size is right for their graphite powder and phenolic resin, al role in next-generation nuclear needs,” he explains. which are machined into the charactechnology, now leads PBMR’s comteristic spheres, each containing only mercial development. The country How does it work? about 9 grams (g) of uranium. expects to complete construction The pebble bed design was first conWhen operational, the reactor is on a demonstration plant near Cape ceived in the 1950s by Rudolf Schuldesigned to drop fresh pebbles into Town, a city of 3 million people, by ten, a physicist in Germany. Hoping its core while used pebbles are ex2010. What’s more, the South Afrito create a safer nuclear reactor, tracted from below. After every cycle
1382 n EnvironMEntal SciEncE & tEchnology / March 1, 2006
© 2006 american chemical Society
of the reactor, each pebble’s residual fuel level will be measured electronically. PBMR officials predict that each of the 456,000 pebbles in a typical reactor will pass through the core 6 times over a period of 3 years. The helium gas used to cool the core will get extremely hot—about 900 °C, which is nearly 3 times the temperature produced in a typical light water reactor. This intense heat makes the reactor more efficient in terms of fuel-to-energy conversion, Kadak says. However, he adds that numerous design features ensure that the reactor never reaches the minimum of 3000 °C required to melt the core and unleash an environmental disaster. For example, even if a failure occurs during operations, Kadak says, the reactor will come to a standstill and dissipate heat on a decreasing curve, without releasing radioactivity. Moreover, he adds that the helium cooling system and pebble design generate less nuclear waste than that produced by the light water reactors currently in use. A 5-reactor PBMR generates nearly 1000 MWe of power and 5–6 tons of depleted uranium per year, which is comparable to the output of a single light water reactor.
Environmentalists’ challenge Environmentalists aren’t convinced, however. In January 2005, Earthlife Africa, an environmental group, convinced the Cape Town high court to rescind approval of the proposed plant, citing omissions in PBMR Pty’s environmental impact statement. “This is a demonstration plant, and no one knows if it’s even going to work,” says Olivia Andrews, a campaign coordinator with Earthlife Africa in Cape Town. “The company is using us as guinea pigs.” Andrews, who acknowledges that the group opposes all forms of nuclear power, claims PBMR Pty withheld information about higherthan-projected costs for the project. “PBMR is financially risky, and the company’s feasibility studies are overly optimistic,” she says. Kriek acknowledges that in its early stages, PBMR won’t compete cost-effectively with coal, but he suggests that economies of scale and engineering improvements will produce savings in the long term. “You have to understand the up-front
costs for the technology are very large; we have over 50 Ph.D.s in this company.” He adds that a fresh public hearing process was launched in November 2005 and that the company plans to resubmit its environmental impact statement with additional disclosures.
The global outlook During the next 25 years, PBMR Pty plans to export as many as 75 reactors in developed and developing markets, including other countries in Europe and Africa. Kadak anticipates that nuclear proliferation risks from global PBMR use could be controlled by the International Atomic Energy Agency through a certification and oversight system to monitor operation and fuel handling. Used pebbles also constitute a poor source of material for nuclear terrorism, Kadak adds. The pebbles contain so little uranium—just 9 g each—that tens of thousands would be required to make a bomb. “The grand vision is to create a global training center for PBMR operations that would coordinate fuel supplies and waste disposal and also address problems related to infrastructure shortages,” Kadak says. A spokesman for the Nuclear Regulatory Commission (NRC), Scott Burnell, describes the PBMR’s safety record as “interesting on a small scale.” Although avoiding comment on how PBMR might fare as one of the Generation IV nuclear technologies being promoted by Bush Administration officials in the U.S. Department of Energy, he concedes that NRC is closely watching its evolution in South Africa. But Kadak insists that PBMR is the best Generation IV candidate, not just because its modularity promotes siting flexibility; he says that the high temperatures at which it operates are well suited for electrolysis reactions that split hydrogen gas from water. Thus, he argues that PBMR could play a key role in fostering an emissions-free hydrogen economy, which many see as the ultimate solution to global warming. Nevertheless, PBMR—like all nuclear technology—still faces nuclear-waste questions and worries over terrorism. The extent to which these concerns derail nuclear power and relegate its historical peak to the latter half of the 20th century remains to be seen. —CHARLIE SCHMIDT March 1, 2006 / Environmental Science & Technology n 1383
