Nuclear Engineering: Atoms for Sea Water

The problem is old and tantalizingly difficult; it has baffled man's best technology. But a solution would be as valuable as the elusive gold that beckoned to ancient alchemists. So scientists go right on searching for a practical system for converting sea water to fresh water. For all their efforts, though, water from conventional distillation plants is still too expensive to be used anywhere except at isolated military posts or desert oil centers. The freeze-separation process, which removes fresh water as ice crystals, may some day prove more economical, but the cheapest water that it promises will cost 50¢-80> per 1,000 gallons. The price is high for municipal use. and out of the question for irrigation.

A far more satisfactory system, says Physicist R. Philip Hammond of Los Alamos Scientific Laboratory, could be built around large nuclear reactors. In the magazine Nucleonics, Hammond explains that as reactors increase in size, the heat that they produce becomes cheaper and cheaper. Steam generated by a 10 million-kw. reactor costs only one-quarter as much as steam from a 1,000,000-kw. reactor. The necessary uranium fuel is relatively cheap, and most of the cost of running a nuclear reactor involves a variety of other items. But the cost of many of these increases only slightly as the plant gets bigger.

A 25 million-kw. reactor would produce heat cheaply enough for the sort of seawater distillery Physicist Hammond would like to use. But no such reactor has ever been built or seriously contemplated. The biggest one under construction in the U.S., at Bodega Bay north of San Francisco, will generate slightly more than 1,000,000 kw. of heat. For producing electric power, says Hammond, there is no present need for anything larger. But he is sure that the monsters he has in mind can be constructed without trouble. A 25 million-kw. distilling plant would suck in a river of sea water and gush out i billion gallons of fresh water a day at about 10¢ per 1,000 gallons. This is enough for a city of 4,000,000 people, and the cost is just about what New York City pays for water brought down by gravity from the rainy Catskill Mountains only 70 miles away. The price remains prohibitive for irrigation, but cities in arid districts are glad to pay even more to slake their thirst.