This TNR archive piece is available online for the first time as part of a conversation about America's energy future, sponsored by Southern Company.
In 1947, just two years after Hiroshima and Nagasaki, this magazine published an article that considered the tremendous peaceful potential of nuclear energy for powering homes and businesses. At the time, nuclear power was still associated with the war. But today 20 percent of U.S. electricity is generated in this country's nuclear plants.
The biggest single industrial enterprise in the United States today is not General Motors or U.S. Steel but the Atomic Energy Commission and all that it controls. Apart from being the world's ultimate military threat, atomic energy is also fast becoming the basis of what one might call the alchemical industry. It sprawls across the country, half-secret, little understood, but with almost limitless possibilities.
In trying to assess these possibilities, we may as well begin at the beginning—with the process on which this industry of the future depends.
The basis of the atomic-energy industry is a process known as the "fission chain reaction." A chain reaction is established when a mass of fissionable material such as uranium is bombarded with high-speed nuclear particles known as neutrons, and when each release of a neutron in turn releases another neutron. When this reaction is fast and violent, the result is the atomic bomb. Slower, and under careful control, it provides the atomic energy that may turn the wheels and drive the turbines of the industry of the future.
The only species of nucleus found in nature that will support a chain reaction is the famous light isotope of uranium, U-235. It is present wherever uranium is found, and always in the same proportion: one part out of 139 will be the light isotope of uranium. The other 138 parts will be U-238. A piece of metal made from U-235 has the same blue-brown color as a piece of normal uranium; it is dissolved by the same acids in the same way; it can be cut and scratched in the same way. It differs only in its weight and in its spectacular nuclear properties.
Before atomic energy can be developed or a chain reaction started, ore must be dug and purified until some compound of uranium is obtained. The processes are like those used to prepare any rather rare chemical; they might be compared to the mining and refining of tungsten for the filaments of light bulbs. Some of our uranium comes from the remote mines of the Haut Katanga in the high tropical plateau of the Belgian Congo; some comes from a Canadian mine at Great Bear Lake near the Arctic Circle, and some from mines in western Colorado and Utah.
Refining, in turn, is carried on at widely separated small chemical plants all working under contract with the Atomic Energy Commission.
All this is just the beginning. No technique of chemistry will suffice to separate the light U-235 atoms from the pure uranium compound that has now been produced. That must be done in the unique and costly plants of Oak Ridge—a government-owned city of some 30,000 population along the Clinch River near Knoxville, Tennessee.
The Oak Ridge townsite alone cost about $100 million, entirely apart from the plants; it grew in one wartime year from a quiet countryside to a great guarded reserve holding the most remarkable technical and engineering structures of this century. Now Oak Ridge is working continuously for the Atomic Energy Commission, and its job is to separate the light isotope of uranium, U-235. This process, which until 1942 had been accomplished only in laboratories, is carried on by different methods at two Oak Ridge plants.
The enormous plant called K-25, that is operated by the Carbide and Carbon Chemicals Corporation (a subsidiary of Union Carbide), employs about 5,000 persons and separates U-235 by diffusion. The plant cost about $500 million to design and construct, with another $50 million or so going to the research and development behind the process. Its miles of corridors run past the most highly developed automatic-process machinery in the world.
The plant pumps gas containing uranium through invisible holes contained in a number of finely constructed barriers. Because the molecules of U-235 are a little lighter than those of U-238, they move a bit faster, and so diffuse more quickly through the holes in the tiny barrier. The difference is slight, but since the gas is run and rerun through the barriers literally thousands of times, the result is the separation of the light isotope. Gas containing a high concentration of U-235 appears after a long time at one end of the plant; gas depleted of the valuable isotope concentrates as waste at the other.
A SECOND large plant at Oak Ridge, called Y-12 and operated by the Tennessee Eastman Corporation, separates U-235 by another method. Here, uranium atoms are made to travel in a high vacuum under the deflecting forces of electric and magnetic fields. Again the difference in weight between the U-235 atoms and those of U-238 is the key to the process. Heavy and light isotopes travel slightly different paths and are collected in different boxes at the ends of their paths. This is but the magnification on a vast scale of what the physicist has long done for tiny quantities in his laboratory.
The Y-12 electromagnetic plant was relatively easy to build and was the first completed unit of the project. It has always been expensive to operate; the air of bustle that accompanies the magnified laboratory operations of this plant was always in sharp contrast to the quiet and aseptic halls of the diffusion plant. In recent months employment at Y-12 has sharply dropped. This change probably reflects the full functioning of the diffusion plant, which by now must be separating nearly all the U-235 that the U.S. produces.
Plutonium an end product
BUT the U-235 obtained in this way is not the only material which can be used as a nuclear fuel or explosive. A second type is plutonium—which, although a form of an element, is not found in nature but can be successfully synthesized. Another alternative is U-233, a component of uranium which is so short-lived (i.e., disintegrates so rapidly from intense radioactivity) that it is not found in natural uranium.
Both plutonium and U-233 can be made by transmutation—that is, by bombarding the nuclei of another atomic species with neutrons. In the first case, neutrons smashing at the nuclei of heavy uranium atoms (U-238) give us plutonium 239. In the second case, atoms of thorium (Th-232) gobble up neutrons and are transformed eventually into uranium atoms with weight 233.
The only known source of neutron ammunition in quantity sufficient to produce large-scale transmutation is the chain reaction itself. But the chain reaction also needs nuclear fuel. The dilemma is solved by the very ingenious method of the pile. Normal uranium will maintain a chain reaction if it is arranged in lumps in an appropriate geometrical lattice with carbon filling in the boxes of the lattice to slow down the neutrons. The carbon is usually in the form of graphite and the total arrangement looks something like a Tinker Toy.
By various means the intensity of the neutron bombardment—which comes from the uranium 235 atom—may be increased to any desired value. The neutrons are absorbed by the U-238 present, and plutonium is formed. The uranium metal in the pile, after it has been allowed to react with neutrons for some time, can be removed. The plutonium, present in the once pure uranium, together with scores of radioactive fission products, can now be separated by ordinary chemical means. Plutonium is therefore an end product of the same type of chain reaction in which it will be used later as a nuclear fuel or explosive.
Plutonium is produced in three large chain-reacting normal-uranium piles near Hanford, Washington, on the Columbia River, whose waters are passed through the machines to remove the heat generated in the pile. The process raises the river temperature several degrees. Plutonium from Hanford and U-235 from Oak Ridge are at present being shipped to Los Alamos, New Mexico, where they are shaped into parts that make up an atomic-bomb assembly.
Fuel of the future
IN addition to their use in the bomb, plutonium and uranium 235 are also the raw materials for industrial atomic energy. Many of the laboratories that did the research for the bomb are now concentrating on non-military uses of atomic power. The Oak Ridge electromagnetic plant, with its great high-vacuum systems and huge magnets, was the outcome of the work of the research laboratory operated by the University of California under the indefatigable Ernest Lawrence, inventor of the cyclotron. It was the great magnet of the unfinished giant cyclotron which in 1941 formed the basis for the Y-12 development at Oak Ridge. The California laboratory, with its magnificent shops and its brilliant talent, is still at work. Rather than uranium fission, its major effort is directed today toward the new high-energy physics, the study of the fundamental nature of the nuclear forces. Even though atomic energy has been released and harnessed, these forces are not well understood.
Similar advances with important future applications are being made in the low hills of a county forest preserve about 30 miles west of Chicago. After the first chain reaction was produced on the University of Chicago campus late in 1942, the uranium pile was moved outside the city to a place called the Argonne Laboratory. In 1944 a second pile for research purposes was completed at the Argonne. It consists of a medium-sized tank surrounded by a concrete shield wall and uses heavy water instead of graphite to slow the neutrons. The reactor on which the Germans were working when the war ended was of this type; a larger version than that at the Argonne is now operating successfully at Chalk River, in Ontario. Heavy water is simply water, H20, in which the hydrogen present is not ordinary hydrogen but its isotope of weight two. This is in many ways the easiest isotope to prepare in pure form. The Germans had a few tons of heavy water, which was made at the famous electrochemical plant in Norway. The Atomic Energy Commission has made heavy water in considerable quantity, at several plants in this country and at one in British Columbia. Heavy water looks exactly like the water that runs from your bathroom faucet, but costs about $100 a pint.
The Argonne is at present operated on a cooperative basis by a group of Midwestern universities, under contract to the commission, as a “national laboratory.” At Brookhaven, Long Island, another nuclear-physics and pile laboratory is now being set up for the commission under the sponsorship of Eastern universities.
AT Oak Ridge, the duPont Company built a semi-production pile, or pilot plant, that was the first to operate at high power. Contained within the Clinton Laboratories that are now operated by the Monsanto Chemical Company, this development is a graphite pile, with pieces of metallic normal uranium placed in rows in long channels in the graphite. An air blast down the channels cools the metal, removing the heat generated by fission and sending hot air up a large smokestack. The energy generated by the plant would be sufficient for a town of about 3,000 population if it were converted to electrical power instead of being wasted.
The Clinton Laboratories pile also produces large amounts of radioactive materials which may be purchased from the commission by research institutions, hospitals, scientists, and anyone else who meets the conditions set forth in the McMahon-Douglas Atomic Energy Act. Radioactive substances are used for therapy in such diseases as leukemia and hyperthyroidism; they have a vastly more important use in tracer research in biology and chemistry. The supply of these isotopes cheaply and in quantity is a valuable and growing part of the alchemical industry.
More fame for Los Alamos
LOS ALAMOS itself belongs in the research parade. The tools of the nuclear physicist—the cyclotron, the high-voltage machine, the betatron—were brought to the high New Mexico mountains. Los Alamos has developed techniques in the handling of materials whose very names are not known elsewhere, and is carrying out an important research program despite its burdens of isolation, secrecy and bomb-making.
From the viewpoint of atomic energy for non-military uses, the concentration of power is the most spectacular and the most promising property of nuclear fuels. The power of a city like Pittsburgh would require the consumption of no more than two or three pounds of nuclear fuel a day. Initially the energy appears as simple heat—the interior of the pile heats up from the controlled chain reaction. But heat itself is not too useful; it must be converted into a form of energy that can produce electrical power, the most flexible and useful form of energy on a large scale.
The conversion of heat into electrical energy is done every day in every coal-burning power plant. Atomic power will simply replace the fire-box under the steam boiler. Some substance—a gas, like steam; or a liquid, like molten sodium metal—will be circulated through the hot interior of the pile, as water and steam go through the boiler tubes of a locomotive. This flowing substance will then be directed to turn the spinning blades of a turbine, which drives the electric generator.
Among the practical problems of applying atomic energy to industry is that of building a chain reactor which can get hot without disintegrating. The conversion of heat into useful power is efficient only when high temperatures are involved. There is a whole family of possible chain reactors, from the large ones using normal uranium and weighing a thousand tons or so, down to a bomblike "critical mass" of pure plutonium not as big as your hand. So far only two small, low-power, low-temperature enriched reactors have been made. Both are at Los Alamos. But scientists of the Monsanto firm at Oak Ridge are now working on the design of a power reactor that will probably be cooled by helium gas and with which they hope to be driving turbines by the end of 1948. And certainly it is likely that someone, somewhere, will have perfected a high-power nuclear reactor giving electrical power by the end of 1950. Which of the diverse routes it will follow no one knows. Whether the cooling and working substance will be a gas like helium, or a molten metal, or high-pressure steam—and whether the reactor will use normal uranium in a large pile, or partly enriched U-235 or even pure nuclear fuel—are questions for the future.
But the decisive question about industrial atomic power remains that of cost. In the United States nuclear energy must compete with cheap and abundant coal. Only construction and continued operation of a number of different plants under careful accounting will determine the cost of atomic energy. But there are competent engineers who maintain that uranium power can compete right now with any but the cheapest coal-generated power.
British hammer and anvil
THE impact of atomic energy on the economy of the U.S. will not be great for some time to come, but consider what a few million-kilowatt plants could mean to a Great Britain, now caught between the hammer of rising needs for power and the anvil of lower coal production. All of Britain's electric-power needs could be met by the "burning" of about 20 pounds of nuclear fuel a day. The labor cost of coal in the U.S. is less than $2 per ton; in Britain, it is nearly $5. In such a situation, atomic power may well prove economic in a few years' time.
Another uncertainty in the development of industrial atomic power has to do with the choice between using normal uranium as it comes from the ground, or partially or wholly enriched nuclear fuel. The decision will depend on the problems of getting high temperatures, and on the economics of raw-material supply as compared with the cost of the complicated chemical processes involved in reworking the exposed uranium for its content of plutonium. The fact that power can be obtained either with or without the simultaneous production of nuclear fuel and explosive is evidently of great concern in the problem of international control, and the distinction made (as in the Acheson-Lilienthal report) between activities "safe" for national or private enterprise and those too "dangerous" to be operated save by an international authority, depends upon this fact.
Fifty tons of shielding
DESPITE much loose talk, the immediate prospects for a small-sized, long-running atomic engine capable of powering aircraft or automobiles are remote. A small, reacting critical mass of plutonium, properly cooled, could generate thousands of horsepower. But it would have to be surrounded with a minimum of some 50 tons of dense metal shielding to prevent the neutrons and gamma-radiation which necessarily accompany fission from producing radiation sickness in the men who operate the reactor. The shielding properties of matter depend on its fundamental atomic and nuclear structure; it is not possible to expect a new alloy or an ingenious arrangement which would reduce the 50-ton minimum very much. Unless your vehicle is large enough to accommodate a 50-ton power plant, you cannot hope to gain much from nuclear energy.
Ships, naval or merchant, can certainly be freed from the need to refuel. Small aircraft probably cannot, but the cost of their power is of minor importance anyway. No one burns coal in aircraft, though it is much cheaper than 100-octane gasoline. Large aircraft may exploit the possibilities of the atom. At Oak Ridge, a group under the direction of the Fairchild Aircraft and Engine Corporation are trying to propel aircraft by nuclear energy. Most of the large aviation concerns are represented in the effort.
The use of atomic energy for super-weapons, like the intercontinental rockets or pilotless robot aircraft of long range, is more likely to develop successfully. Here, crew and passengers are absent, and shielding is required only to protect instruments.
While scientists apply their ingenuity to developing atomic energy for industrial purposes, the production of atomic bombs continues at Los Alamos. What one can expect is not a notable change in the bomb itself, or any great increase in the power of its explosion, but rather a reworking of the many technical features of the bomb which determine its tactical employment. It is clear that it can be turned into a flexible weapon, suited to kill the people of a town by explosion high in the air, to demolish the heaviest of underground fortifications by detonation deep in the ground, or to attack naval targets with great effect. The devastating effect of the blast, of the heat and of the enormous instantaneous gamma-radiation are now known. Less clear is the effect of the radioactive "debris" which the bomb may leave behind. But conservative calculations show that it may take months or even years before an area contaminated by such debris becomes safe again.
The common and unauthorized talk about bombs "thousands of times more powerful" than those used so far is discounted by most specialists. That the possibility exists is certainly true; that any realization is at hand seems most unlikely. In the unfortunate absence of clear official statements, it is better to realize that the present bomb is quite bad enough. The number "a thousand times" is easy to say; but it is hardly possible to describe with equanimity the results of an even vaster explosion, with its heat and its radioactive debris, than the one which was witnessed by Dr. Sasaki, by the Jesuit priest, and by the agonized mother of Hiroshima.