National Geographic : 1972 Nov
predicts that the year 2000 will see 75 percent of our total energy and half of our electricity still coming from whatever fossil fuels we have not yet exhausted. But there are new promises that the energy problem-at least for electricity-eventually will be licked. I have seen much evidence of these promises in recent travels around this country and abroad. New and more effective nuclear reactors are being developed. I have found scientists enthusiastically seeking to extract energy from the sun, from the tides, from the wind, from the furnace deep inside the earth, even from seawater. Some-perhaps all-of these schemes will work in time. Our own government is spend ing 620 million dollars this year on overall energy research. Nuclear Power Brings New Problems The most immediate solution, of course, is the nuclear reactor, which taps the mighty energy released when uranium atoms fission, or split. Twenty-eight commercial nuclear power plants are already operating in the United States, including the pioneering plant at Shippingport, Pennsylvania, that went on line 15 years ago. Forty-nine additional plants are under construction, and another 67 are on order. When all the new ones are completed, they will add more than 30 percent to the Na tion's 370-million-kilowatt total capacity. Nuclear power plants bring their own prob lems. Even more than conventional generat ing plants fired by fossil fuels, they produce large amounts of waste heat. Safeguards must be provided against leakage of radiation from the reactor itself, and also from the radio active wastes that the process produces. Finally, there is a scarcity of inexpensive uranium. According to the Atomic Energy Commission, relatively low-cost nuclear fuel will probably be exhausted by the end of the century if we continue to build only the types of nuclear power plants operating today. Fortunately there is a major development in nuclear reactors that may meet some of these problems. It is the liquid-metal fast breeder reactor. To understand how it works, you need to know something about the con ventional water-cooled reactor now in use. Fast Breeder Makes Its Own Fuel If you could examine the core of a conven tional reactor, you would find it made up of thousands of zirconium-alloy tubes, called pins. About twice the thickness of a lead pen cil and usually 12 feet long, they are inserted into the reactor in bundles. Constantly bathed with water, these pins hold a mixture of ordi nary uranium 238, which does not fission, and a small amount of the scarcer uranium 235, which is the actual fuel. Heat given off when uranium atoms split is carried away by the circulating water and used to produce steam for a turbine generator, just as in a coal- or oil-fired plant. One pound of uranium, about the size of a golf ball, stores as much energy as 15 carloads of coal. But in the water-cooled reactor barely one percent of that energy can be tapped. That's where the breeder reactor comes in. The alchemist of old, who sought to turn base metals into gold, would have been entranced by the breeder, for it transmutes elements, producing more fuel than it consumes. Pins holding uranium 238 are placed in a blanket around the core. As atoms split in the core, they give off heavy nuclear particles called neutrons, which bombard the uranium Commuter car built in Illinois can scoot quietly along on bat tery power. Designed for smog beset cities, it can go 100 miles at 30 mph. Electric cars, re charging at night when pow er plants have surplus capacity, would shift a major pollution source from exhaust pipes to power-station smokestacks, which can be more easily con trolled. Transportation now burns more than half the oil consumed in the U. S.