The competing SFR design banks on a novel fission concept: bombarding uranium atoms with neutrons of much higher energy than those used in a traditional nuclear plant. This concentrated atomic assault allows the reactor to extract 100 times as much energy from uranium fuel as do current thermal reactors, which use less than 1 percent of the fuel’s potential energy. The SFR can also burn spent nuclear rods from other reactors and depleted uranium left over from the uranium-enrichment process, putting a serious dent in the nuclear waste problem. Scientists from the industry’s professional group, the American Nuclear Society, estimate the energy an SFR plant could coax from these by-products would be enough to supply all of America’s needs for more than 100 years. Reburning spent rods in an SFR also reduces their radioactive decay time; the resulting waste would have to be sequestered for only a few hundred years instead of several thousand.
Unfortunately, the sodium used to transfer heat out of the core in an SFR plant is a mixed blessing. Liquid sodium is an ideal coolant in that, unlike water, it does not impede the movement of fast neutrons. It also improves safety because it works under normal atmospheric pressure. But liquid sodium is opaque, making it hard for reactor operators to monitor heat transfer. To compensate for this difficulty, INL researchers are developing computer simulations that model the way liquid sodium acts inside a fast reactor.
A few early-model SFRs have been around for a while: Idaho’s low-power, experimental EBR-II operated for 30 years, and Russia’s 29-year-old BN-600 is still running. However, INL does not want to roll out a new prototype until researchers have finished refining the computer models. This may mean that an improved SFR plant will not appear for another 10 or 20 years.
Such a lengthy timeline, combined with hefty up-front costs and lingering public skittishness, suggests that next-generation nuclear faces an uphill battle. Current designs could cost up to $10 billion to build; new ones are likely to be even more expensive. Energy companies are reluctant to commit such sums until they are sure that the upgraded designs deliver on their promise. “We need a demo plant—that’s really what’s holding the industry back,” says David Petti, an INL technical director. “The end users have basically told us, ‘We’ll be first in line for the second plant.’”
Even if INL can persuade energy companies to sign on, long construction times guarantee that the nuclear renaissance will be gradual. “These new reactors won’t come into broad use until the second half of the century. So for the next 50 years, we are going to be relying on the current generation,” Richter says.
Maintaining today’s nuclear plants will require finding a practical, safe, and politically palatable way to dispose of waste. “As to spent fuel, love it or hate it, we have it,” Richter says. “We have 60,000 tons of it from reactors that are now running.” A refined SFR design could eventually mitigate the waste issue because of the reactor’s ability to burn spent fuel, but even in a best-case scenario, the reused fuel would retain unsafe levels of radioactivity for several centuries. The nuclear industry will also have to address widespread fears about the reactors themselves. Insiders claim that today’s nuclear plants are far safer than many people realize. After all, no one has ever died in a commercial nuclear power accident on American soil; in contrast, emissions from fossil-fuel plants kill 24,000 Americans each year, according to a 2004 report commissioned by the Clean Air Task Force, an environmental group. But in the post-9/11 mind-set, nuclear plants loom as potential terrorist targets and as possible sources of raw material for nuclear weapons.
George W. Bush was supportive of INL’s nuclear research, but so far it is not clear if the Obama administration shares that enthusiasm, McCarthy says. Still, the threat of climate change has once-skeptical environmentalists like Greenspirit’s Patrick Moore—along with environmental icons like Stewart Brand and James Lovelock—throwing their support behind nuclear energy. “I think the environmental movement made the mistake of lumping nuclear energy in with nuclear weapons,” Moore says. “It’s clear to me that no technology will do more than nuclear to reduce our use of fossil fuels.”
Going Nuclear
In its efforts to develop safer, cheaper, and more efficient nuclear reactors, the Idaho National Laboratory has researched half a dozen next-generation reactor designs; these two (the sodium-cooled fast reactor and the very-high-temperature reactor) are the most promising. Both are configured to exploit the laws of nuclear physics to make a meltdown impossible, even in the face of an engineering failure or operator error. Whether or not either design is practical is still unknown.
Illustration by David Combs/Idaho National Laboratory
