When Exelon corp. wanted to add a new reactor to its plant in Clinton, Il, protesters were unable to raise much of a ruckus. By the second town meeting to discuss the project, the townspeople were 85% in favor if the project.
The U.S. nuclear construction industry was presumed dead. It is anything but. If oil prices stay high, if people worry about carbon dioxide causing global warming, if the Middle East stays violent, nuclear power stands a good chance of making a huge comeback in this country.
And reactor technology hasn't been standing still, either.
The next generation, the industry promises, will be even safer. NuStart's first new reactors will reflect all the improvements Westinghouse and GE have devised over the last 30 years. They will be smaller, simpler and cheaper to build, relying on gravity, rather than electricity, to cool reactors--or, in the unlikely event of a meltdown, to flood a reactor core. Designs still on the drawing board include a Westinghouse-backed pebble-bed reactor, where uranium fuel is encased in graphite pebbles the size of tennis balls; the graphite tempers the fission reactions the way control rods do but can withstand temperatures of up to 2,800 degrees Fahrenheit, making meltdown nearly impossible. The privately held General Atomics of San Diego is promoting a reactor that uses helium as a cooling agent, rather than water, and is built in an underground silo--a deterrent to terrorists.
What about waste?
Here's one nut the nuclear industry can't crack: disposal. The nation's commercial reactors have accumulated 50,000 tons of highly toxic waste, mostly spent uranium fuel rods. When fresh, reactor fuel consists of enriched uranium 235, which is relatively harmless (the skin blocks alpha particles). But fission transforms a small quantity of uranium into extremely radioactive isotopes, including plutonium. Walk into a room with a used fuel assembly and the exposure would kill you in minutes. Plants are running out of room for depleted uranium, yet the Energy Department, which is responsible for its permanent disposal, has nowhere to put it. The plan was to build a repository at Yucca Mountain, Nev. Yet after the spending of $7 billion and 26 years on studying and designing the site, Yucca is mired in lawsuits. <snip> Pending Yucca, there are ways to buy time. If there's room for it, spent fuel can safely sit in cooling ponds inside reactor buildings. Entergy's River Bend plant is turning to casks sitting on a concrete pad outside the reactor building. Virtually impervious to terrorism, shielded with 6 feet of radiation-blocking material, the 50-ton casks are so dense that even a direct hit by a jetliner would have as much chance of breaking containment as a raw egg would have of shattering a bowling ball. On foot, terrorists would have to get past armed guards and concertina wire, then commandeer the plant's custom-built crane to lift off the enormous 10-ton lid. They'd also need thick shielding while making a getaway to avoid dying of radiation poisoning.
Options that won't be considered include reprocessing to extract components that are useful in other applications. Plutonium, for example, can be burned in reactors for energy which, by the way, means it's not available for making bombs.
Other things that have to be considered: the absolute amount of waste on a per-person basis (pretty small), and how it compares with per-capita waste produced by other methods of generating energy. (Coal, for example, contains radioactive contaminants which are released into the environment when it's burned, and this radioactivity is not regulated.)
Also, radioactive waste breaks down over time. It's a complicated decay curve, because of the mixture of nuclides, but a good approximation is a power curve with a slope of -1.2 for the first six months, going to -2.3 thereafter. After six hundred years, nuclear waste is about as radioactive as the original ore was. After that, if you're trying to get rid of radioactivity, you're ahead of the game.
No comments:
Post a Comment