Open Fuel Cycle Advanced Fuel Cycle

Lake, Ralph G. Bennett and John F. Kotek; Scientific American, January 2002]. In addition, generation III+ reactors are designs similar to generation III but with the advanced features further evolved. With the possible exception of high-temperature gas reactors (the pebble bed is one example), generation IV reactors are several decades away from being candidates for significant commercial deployment. To evaluate our scenario through to 2050, we envisaged the building of generation III+ light-water reactors.

The pebble-bed modular reactor introduces the interesting prospect of modular nuclear plants. Instead of building a massive 1,000-megawatt plant, modules each producing around

100 megawatts can be built. This approach may be particularly attractive, both in developing countries and in deregulated industrial countries, because of the much lower capital costs involved. The traditional large plants do have the advantage of economy of scale, most likely resulting in lower cost per kilowatt of capacity, but this edge could be challenged if efficient factory-style production of large numbers of modules could be implemented. South Africa is scheduled to begin construction of a 110-megawatt demonstration pebble-bed plant in 2007, to be completed by 2011, with commercial modules of about 165 megawatts planned for 2013. The hope is to sell modules internationally, in particular throughout Africa.

Reducing Costs based on previous experience, electricity from new nuclear power plants is currently more expensive than that from new coal- or gas-powered plants. The 2003 M.I.T. study estimated that new light-water reactors would produce electricity at a cost of 6.7 cents per kilowatt-hour. That figure includes all the costs of a plant, spread over its life span, and includes items such as an acceptable return to investors. In comparison, under equivalent assumptions we estimated that a new coal plant would produce electricity at a cost of 4.2 cents per kilowatt-hour. For a new gas-powered plant, the

▲ Activities at this uranium enrichment plant in Natanz, Iran, have been a focus of concern in recent years because the facility could be used to make weapons-grade uranium. An international agreement whereby "user" countries lease fuel from "supplier" countries such as the U.S. instead of building their own enrichment plants would help alleviate the threat of nuclear weapons proliferation.

▲ Activities at this uranium enrichment plant in Natanz, Iran, have been a focus of concern in recent years because the facility could be used to make weapons-grade uranium. An international agreement whereby "user" countries lease fuel from "supplier" countries such as the U.S. instead of building their own enrichment plants would help alleviate the threat of nuclear weapons proliferation.

cost is very sensitive to the price of natural gas and would be about 5.8 cents per kilowatt-hour for today's high gas prices (about $7 per million Btu).

Some people will be skeptical about how well the cost of nuclear power can be estimated, given past overoptimism, going back to claims in the early days that nuclear power would be "too cheap to meter." But the M.I.T. analysis is grounded in past experience and actual performance of exist-

JOHN M. DEUTCH and ERNEST J. MONIZ are professors at the Massachusetts Institute of Technology and co-chaired the 2003 interdisciplinary M.I.T. study entitled The Future of Nuclear Power. They have held several government positions. Deutch was director of energy research and undersecretary of energy (1977-1980) and later deputy secretary of defense (19941995) and director of central intelligence (1994-1996). Moniz was associate director for science in the Office of Science and Technology Policy (1995-1997) and undersecretary of energy (1997-2001). They are currently co-chairing an M.I.T. study on the future of coal.

ing plants, not in promises from the nuclear industry. Some might also question the uncertainties inherent in such cost projections. The important point is that the estimates place the three alternatives—nuclear, coal and gas—on a level playing field, and there is no reason to expect unanticipated contingencies to favor one over the other. Furthermore, when utilities are deciding what kind of power plant to build, they will base their decisions on such estimates.

Several steps could reduce the cost of the nuclear option below our baseline figure of 6.7 cents per kilowatt-hour. A 25 percent reduction in construction expenses would bring the cost of electricity down to 5.5 cents per kilowatt-hour. Reducing the construction time of a plant from five to four years and improvements in operation and maintenance can shave off a further 0.4 cent per kilowatt-hour. How any plant is financed can depend dramatically on what regulations govern the plant site. Reducing the cost of capital for a nuclear plant to be the same as for a gas or coal plant would close the gap with coal (4.2 cents per kilowatt-hour). All these reductions in the cost of nuclear power are plausible—particu-larly if the industry builds a large number of just a few standardized designs—but not yet proved.

Nuclear power becomes distinctly favored economically if carbon emissions are priced [see box on opposite page]. We will refer to this as a carbon tax, but the pricing mechanism need not be in the form of a tax. Europe has a system in which permits to emit carbon are traded on an open market. In early 2006 permits were selling for more than $100 per tonne of carbon emitted (or $27 per tonne of carbon dioxide), although recently their price has fallen to about half that. (A metric unit, one tonne is equal to 1.1 U.S. tons.) A tax of only $50 per tonne of carbon raises coal-powered electricity to 5.4 cents per kilowatt-hour. At $200 per tonne of carbon, coal reaches a whopping 9.0 cents per kilowatt-hour. Gas fares much better than coal, increasing to 7.9 cents per kilowatt-hour under a $200 tax. Fossil-fuel plants could avoid the putative carbon tax by capturing and sequestering the carbon, but the cost of doing that contributes in the same way that a tax would [see "Can We Bury Global Warming?" by Robert H. Socolow; Scientific American, July 2005].

Because it is many years since construction of a nuclear plant was embarked on in the U.S., the companies that build the first few new plants will face extra expenses that subsequent operators will not have to bear, along with additional risk in working through a new licensing process. To help over-

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Solar Stirling Engine Basics Explained

Solar Stirling Engine Basics Explained

The solar Stirling engine is progressively becoming a viable alternative to solar panels for its higher efficiency. Stirling engines might be the best way to harvest the power provided by the sun. This is an easy-to-understand explanation of how Stirling engines work, the different types, and why they are more efficient than steam engines.

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