Pebble-bed reactors have been touted as the future of nuclear power. They may stay that way for a long time.
Until a few months ago, the new type of reactor, being developed by a South Africa-based consortium, was heralded as the likely prototype for next-generation nuclear power plants: smaller, cheaper and safer than existing plants being used in the United States.
The pebble-bed plants, designed by the Pebble-Bed Modular Reactor (PBMR) group, even played a key role in the Bush administration's much-publicized energy plan, which in 2001 advocated a revival of nuclear power.
"PBMR will be able to bring the technology to the United States and other countries and build safe and economical operating nuclear power plants," said the group's chief executive, David Nicholls, earlier this year.
Exelon: Reactor Plan 'Too Speculative'
That scenario looks less likely now. This spring, Exelon Corp., the biggest operator of nuclear plants in the United States, abruptly pulled out of the consortium. Exelon Chairman and CEO John Rowe said the status of the pebble-bed design was "too speculative" for the company to maintain its investment. Exelon had owned a 12.5 percent interest in the PMBR project.
The PMBR group put a positive spin on Exelon's decision. The group is still building its prototype plant in Koeberg, South Africa, and notes that Exelon will work with the consortium as the project's feasibility study is completed.
Even after Exelon's defection, Nicholls told an industry forum in April that pebble-bed reactors "could be built in the U.S. in five or six years from now."
But others think such forecasts are far too optimistic.
"Exelon's decision to pull out of the project says a lot," claims Christopher Sherry, research director of the Safe Energy Communication Council, an industry watchdog group in Washington. "The writing is on the wall."
And officials with the Nuclear Regulatory Commission say the prospective timetable for approving a new form of nuclear plant is such that even if the consortium rolled out a prototype within a couple years and found new U.S. backers, it could be a decade before any plants came on line.
"To test the fuel, it would take on the order of five to seven years," says Farouk Eltawila, director of the NRC's Division of Systems Analysis and Regulatory Effectiveness. He adds that the NRC had been looking over documents pertaining to the pebble-bed technology but "stopped after Exelon terminated the pre-application agreement."
The Promise: Cheaper Plants
The pebble-bed reactor concept has gained attention because it offers an attractive-sounding alternative to the traditional method of generating nuclear power.
Most nuclear plants use uranium fuel rods to heat water, which in turn is used to generate steam, powering turbine engines. But the pebble-bed reactors would have uranium encased in thousands of tennis-ball sized chunks of graphite, and would transfer heat via helium gas to turbine engines.
According to the PMBR team, that would make the plants more efficient. As a bonus, the technology could be safer than conventional plants, since the carbon casing would reduce the exposure of the radioactive materials.
But for the energy industry, a huge part of the attraction also lies in the economics of the pebble-bed design. The plants would be smaller and, according to the PMBR consortium, could take only two years to build. (Larger plants take six years, apart from the traditionally difficult process of securing a site for a nuclear plant.) While the new reactors would generate only one-tenth the electricity of a traditional nuclear plant, the modular design of the pebble-beds means the plants could be expanded to meet increased demand, too.
This concept is partly what caught the eye of Vice President Dick Cheney, the head of the Bush administration's energy task force, who met with Exelon officials in March 2001 to discuss the pebble-bed reactors. Two months later, when the administration's energy report was released, it called for "new advanced-technology nuclear reactors" to be "a major component of our national energy policy."
But no matter how small the size of each potential power plant, says Edwin Lyman, president of the Nuclear Control Institute in Washington, the fuel-testing program for any new nuclear technology would represent a huge up-front expense, making pebble-bed plants less attractive to almost any utility.
"The resolution of those problems was more costly than Exelon was willing to swallow," says Lyman.
Safety Still At Issue
Additionally, some observers have serious doubts about the prospective safety of the pebble-bed plan.
For his part, Eltawila says there appear to be some "merits in the safety of the design," but refrains from drawing any further conclusions — and stresses that the NRC's testing process involves examining what flaws plants might have in event of a disaster.
"We ask questions to push the envelope and go beyond the design," says Eltawila. "We have our own tests and analysis to ask, 'What if something goes wrong?'"
It's those worst-case scenarios that critics of the pebble-bed concept emphasize, citing the lack of a containment structure for the plants as just one design flaw. And as Sherry notes, "A lot of the supposed safety features would have to be based on perfect manufacture of the fuel pebbles."
The threat of the graphite pebbles catching fire is also problematic, and the possibility overheating remains an unresolved issue. In contrast to a conventional water-based reactor, says Lyman, "You can't just throw more water on it." In the event of a disaster, he adds, "You'd probably just end up burying the plant under earth and creating a big de facto waste dump, at best."
Then there are new safety issues in the post-Sept. 11 world that are also working against the momentum that had been built up for pebble-bed technology.
"I think Sept. 11 had an impact on slowing down this effort, especially for modular plants," says Lyman. For instance, the need for on-site security, he says, works against "having small nuclear plants in every backyard."
All of which means we may have to wait a generation or so before next-generation nuclear power becomes a reality.