TR10: Traveling-Wave ReactorContinued from page 1 By Matt Wald
The trick is that the reactor itself will convert the uranium-238 into a usable fuel, plutonium-239. Conventional reactors also produce P-239, but using it requires removing the spent fuel, chopping it up, and chemically extracting the plutonium--a dirty, expensive process that is also a major step toward building an atomic bomb. The traveling-wave reactor produces plutonium and uses it at once, eliminating the possibility of its being diverted for weapons. An active region less than a meter thick moves along the reactor core, breeding new plutonium in front of it. The traveling-wave idea dates to the early 1990s. However, Gilleland's team is the first to develop a practical design. Intellectual Ventures has patented the technology; the company says it is in licensing discussions with reactor manufacturers but won't name them. Although there are still some basic design issues to be worked out--for instance, precise models of how the reactor would behave under accident conditions--Gilleland thinks a commercial unit could be running by the early 2020s. While Intellectual Ventures has caught the attention of academics, the commercial industry--hoping to stimulate interest in an energy source that doesn't contribute to global warming--is focused on selling its first reactors in the U.S. in 30 years. The designs it's proposing, however, are essentially updates on the models operating today. Intellectual Ventures thinks that the traveling-wave design will have more appeal a bit further down the road, when a nuclear renaissance is fully under way and fuel supplies look tight. "We need a little excitement in the nuclear field," says Forsberg. "We have too many people working on 1/10th of 1 percent change." See the 10 Emerging Technologies of 2009. Atomic Snapshot
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A Preassembled Nuclear Reactor
06/16/2009
Massachusetts Institute of Technology
Comments
How much will there be?
How radioactive will it be?
What is its effective half-life?
How much shielding will it require?
What is its potential for mischief?
hsfrey
02/25/2009
Posts:13
Also, what will be the volume of waste and what are the costs of dealing with the waste?
JonPaul
02/25/2009
Posts:1
What are the end product?
The end products are residual (unburned) U-238, fission products, and transuranic elements (Np, Pu, Am, and Cm)
How much will there be?
The fuel in this reactor is Pu-239. The energy content in 1 lb of Pu-239 is equivalent to more than 2,000,000 lbs of coal, so nuclear power produces an enormous amount of energy and an extremely small amount of waste.
Currently we have 104 nuclear reactors in operation in the US, which generate about 20% of our electricity. The total amount of spent fuel discharged is about 2,000 tons per year. Of this, 95% is U-238 (which could be used as fuel in the Wave reactor), 4% is fission products (waste), 1% is transuranics (TRU). Of the 1% TRU, 90% is Pu, which can be recycled as fuel. The remaining 10% (0.1% of the total) is Np, Am, and Cm, which is considered waste, but can be recycled in a fast reactor like the Wave. The amount of fission products (waste) generated each year is 4% of 2,000 tons or 160,000 lbs. There are 300 million people in the US, so the average share of the nuclear waste is 160,000 lbs / 300 million = 0.0005 lbs, or 0.2 grams per person per year. If you received 100% of your electricity from nuclear power for your entire lifetime, all of the nuclear waste generated from your use would fit in a coffee cup. Compare this to the average person's carbon footprint of 20 tons of CO2 per year.
How radioactive will it be?
The radioactivity of the end products from the Wave reactor would be essentially the same as from the current generation of reactors.
What is its effective half-life?
The half-lives of the numerous fission products vary from a fraction of a second to many years. It takes about 500 years for the fission products to decay to same level of radioactivity as the natural uranium we started with.
How much shielding will it require?
Spent fuel is stored under water for at least 5 years to allow the fuel to cool (water is also an excellent shielding material). After that the fuel can be transferred to dry storage casks, which use steel and concrete for shielding. Six inches of concrete will stop more than 90% of the radiation from the spent fuel. A typical cask has about 3 inches of steel (for gamma shielding) and almost 3 feet of heavily reinforced concrete (for both gamma and neutron shielding).
What is its potential for mischief?
None. The combination of physical security, the huge mass of the storage systems, and self-protecting nature of radioactive materials make spent fuel extremely unattractive for mischief or misuse.
pronuke
03/07/2009
Posts:4
This discussion has been moved to our discussions forum.