For instance, a nuclear weapon may be carried by a fighter plane and used to shoot down an attacking bomber. Since the carrying capacity of the fighter plane is severely limited, the weapon for this purpose must be small and light. A major objective of the test program is to develop such purely defensive weapons.
The encounter between the fighter plane and the bomber may well take place in our own country over populated areas. This possibility would fill most people with alarm lest the population underneath the explosion should be hurt. Fortunately, in a recent nuclear test in Nevada, five well-informed and courageous Air Force officers demonstrated that there is complete safety to people on the ground. They did this by standing directly beneath the explosion at ground zero.
This important test took place only a few months ago—on July 19, 1957. An F-89 jet fighter plane flying at 19,000 feet above sea level delivered an air-to-air atomic rocket to a preassigned point in the sky. The ground zero men were 15,000 feet immediately below. They wore no helmets, no sun-glasses, and no protective clothing.
At the instant of the explosion the men looked up, saw the fireball and felt the heat. There was no discomfort, only a gentle warmth. Then they waited for the shock wave to arrive—approximately ten seconds. When the shock came, it was actually just a loud noise. However, one of the men ducked his head instinctively. (See pictures 9 and 10.)
The blast and the thermal pulse were over. But the Air Force men stood their ground. One question still remained: Would there be any fallout? They checked their radiation instruments and waited while the cloud drifted slowly away. There was no significant rise in the radiation level. The test had been a complete success. The effects of the explosion were utterly insignificant on the ground. But high in the air an enemy plane could have been demolished even if the nuclear explosion had missed it by a considerable distance.
In order that nuclear weapons should be effective against armed invaders, it is clear that great numbers of these weapons are needed. Such great numbers of weapons, some of which must be ground-burst, will produce a considerable amount of radioactive contamination, and this contamination will endanger friend and foe alike. In particular, the radioactivity is likely to kill people in the very country whose liberty we are trying to defend. For this reason it is most important that we should be able to use nuclear weapons which cause the least possible contamination. In recent nuclear tests more and more attention has been paid to the development of such clean weapons, and most fortunately these efforts are well on the way toward success.
The radioactive fallout from nuclear testing gives rise to a possible danger which is quite limited in size. The danger from the fallout in a nuclear war, however, would be real and great. If we stop testing now, and if we should fail to develop to the fullest possible extent these clean weapons, we should unnecessarily kill a great number of noncombatants. Not to develop the explosives with the smallest radioactive fallout would, indeed, be completely inexcusable.
The only alternative is that nuclear weapons should not be used at all. Since these weapons have been presented as purely evil instruments, most people hope that they will never be used, and indeed one should hope that wars, and therefore the use of these weapons, can be avoided.
But in our conflict with the powerful communistic countries which strive for world domination, it may be too much to hope for uninterrupted peace. If we abandon our light and mobile weapons, we shall enable the Red bloc to take over one country after another, close to their borders, as opportunities arise. The free nations cannot maintain the massive armies throughout the world which would be required to resist such piecemeal aggression. On the other hand, the flexible power of clean nuclear explosives would put us in a position where we could resist aggression in any part of the world, practically at a moment’s notice.
The announced policy of our country is to maintain peace and stability in the world. By being patient and prepared we are trying to arrive at a world order based on law and justice for all peoples. There is no doubt that this policy is supported by the overwhelming majority of Americans. Our armed forces need the greatest possible flexibility in order to give strength to this policy. Such flexibility we can possess only if we have in our possession the strongest, best developed weapons which are also the cleanest, so that they may be used for defense rather than for random destruction.
If we renounce nuclear weapons, we open the door to aggression. If we fail to develop clean explosives, we expose people to disaster from radioactive fallout in any serious military conflict. To our way of thinking these are weighty arguments in favor of continued experimentation and development of nuclear weapons. But still another, more general, point of view should be considered.
The spectacular developments of the last centuries, in science, in technology, and in our everyday life, have been based on one important premise: to explore fearlessly any consequences to which greater knowledge and improved skills can lead us. When we talk about nuclear tests, we have in mind not only military preparedness but also the execution of experiments which will give us more insight and more ability to control the forces of nature. There are many specific political and military reasons why such experiments should not be abandoned. There also exists this very general reason—the tradition of exploring the unknown. We can follow this tradition, and we can at the same time be increasingly careful that radioactivity, carelessly dispersed, should not interfere with human life.
CHAPTER XVI
Has Something Happened to the Weather?
The weather is no longer quite as unpredictable as it used to be. Yet we are hardly ever sure of it even a few hours in advance. One week is about the limit of the period of any prediction. Where the best men lack knowledge untrammeled fantasy has a field day. Weather has so far remained a safe topic of conversation and of speculation.
Nuclear explosions have, of course, been made responsible for the weather—for any kind of unusual weather. Be it rain or drought or a hard season of hurricanes—the nuclear tests are dragged in. The weather bureau says: no. But then—the weather bureau has not always been correct. Indeed it would be a miracle if the popular talk and the popular press would not have seen some connection between atomic explosions and the wayward behavior of the seasons.
In one case—and to our knowledge only in one case—there has occurred a chain of events starting with a nuclear test and ending in a copious and unusual downpour. In the spring of 1955 a test shot of moderate size was fired in Nevada. At the same time the last storm of the season was blowing itself out in California. According to the usual rules of meteorology the radioactive cloud should have been carried east by the steady westerly winds which blow over the temperate zone. But this time the cloud was caught up by the swirl of the dying California storm and some of the radioactivity was carried to the west coast.
Hours after the explosion radioactive rain began to fall in California. The activity was weak enough and did not give rise to any worry. But a remarkable thing happened. As the active cloud arrived over California the storm revived. It developed into an abundant rain which is not usual at that place and time. Did we—quite unintentionally—do something about the weather?
The weather bureau said: no. One must certainly admit that this single case proves nothing. Only greatly improved methods of weather observation and weather prediction would make it possible to decide if such a chain of events consists of the strong links of cause and effect or else of a simple sequence of haphazard occurrences.
Even though our knowledge is incomplete there is at least one simple fact which should be borne in mind. All the energy in that Nevada explosion was not quite sufficient to evaporate the water droplets in a cloud one mile broad, one mile wide, and one mile deep. This is not a very big rain cloud. Such a cloud would give about one third of an inch of rain water over one square mile—not an impressive amount. Even the biggest hydrogen bomb would give only energy enough to evaporate a cloud ten miles by ten miles and towering to the top of the “boiling” portion of our air, which we call the troposphere. This would give roughly three inches of rain over a hundred square miles—a more impressive amount but vanishing in the vastness of the Pacific Ocean.
Nuclear explosions are violent enough. But compared to the forces of nature—compared even with the daily release of energy from not particularly stormy weather—all our bombs are puny. Offhand one might guess that our nuclear fireworks could not swing the scales in the massive energy changes that we see around us in the common occurrences of wind and rain.
But the interplay of clouds and sunshine, of water evaporating, freezing, dropping and thawing—in short the vagaries of weather—are both involved and tricky. Small causes can give rise to big effects. Some processes of air masses sweeping over oceans and continents are irresistible and predictable. Others, like the first upsurge of hot air from the overheated ground, may be a question of close competition and trigger action. This is what makes it so difficult to predict the weather.
One of the most delicate processes we must think about is the formation of water droplets. When some water molecules are mixed with air molecules, we have moist air. If such air rises, expands and cools, the water molecules lose some of their agitated motion and have a greater tendency to stick together to form droplets. But it is not easy to get them started on this joint enterprise.
If two or three molecules stick together, they soon are shaken apart. If, however, two or three dozen are collected, this is enough to start a growth which ends in a droplet of water. If moist air is cooled, droplets will form, provided there is a meeting place from which the growth can start. If there is no such meeting place, there are no droplets and we get no cloud. If there are few meeting places, each will collect a rather great amount of water, we will get big drops, and we may get rain. If there is an abundance of meeting places many tiny droplets are formed which will remain suspended as a cloud. The present attempts at rain-making are connected with a birth-control of droplets.
We have seen earlier that in each radioactive decay charged particles are emitted. As these move along their paths, they tear up more atoms and leave in their wake an assembly of charged particles. These charged particles strongly attract the molecules of water. They attract the molecules of air much less. The reason is that in a water molecule positive and negative charges are separated to a considerable extent whereas in the nitrogen and oxygen molecules of air the charges are distributed more evenly. As a result the track of each particle emitted in a radioactive decay provides many meeting places for the formation of water droplets.
Actually, cooled moist air has been used for many decades to make the tracks of fast charged particles visible. In one of the photographs you can see a picture of such “vapor trails.” It is a photograph through an apparatus called the Wilson Cloud Chamber. The myriads of radioactive disintegrations in the debris of a nuclear explosion can give vapor trails which coalesce into a real cloud. In this way weather might be influenced. (See pictures 11 and 12.)
In spite of all this it remains highly probable that testing of nuclear explosions, as practiced at present, does not influence the weather. Radioactivity does furnish an opportunity for droplets to form. But other abundant sources are also available for droplet formation. Dust, smoke and many forms of air pollution will do the trick. Foam scattered from ocean waves evaporates and leaves a speck of salt behind. This particle of salt may be carried by the winds for many miles and may eventually become the germ around which a new drop will condense. The cosmic rays by which we are bombarded give rise to vapor trails similar to those produced by the radioactive decay products. Among the many processes of nature and the usual by-products of civilization the few atomic tests do not play an important role. This statement can stand, not as a certainty, but as a very good guess.
Among the many surprises that the future holds one may be closely connected with the weather. In the age of the airplane we are getting more and more information about the air masses around us. Air travel demands this information and also furnishes it. New techniques, such as radar, can detect the formation of a cloud and can measure the size of droplets at a great distance. In fact the information received is so plentiful that one may doubt whether we can properly understand it and utilize it.
Fortunately we no longer need to rely exclusively on our own brains. Human thought is a remarkable thing but it is slow. The modern computing machines, the “electronic brains,” are simpletons as compared to the apparatus which each of us wears in his skull. But the electronic computers have one advantage: they are fast. Soon they will be a million times as fast as our mental processes. The expression “fast as thought” is dated—it is a contemporary of the horse-and-buggy.
The electronic machines can digest weather information as fast as it is received. Some progress has already been made. In a few years all weather predictions may be machine-made.
This need not mean that weather can be predicted with certainty or for a long time ahead. The trigger processes which, starting from an insignificant and unnoticed spot of turbulence, can grow into the dimensions of a cyclone will set a limit to any art of prediction.
But to the extent that weather cannot be predicted it may be influenced. If small causes may have big effects then even the puny means available to man may change the weather—provided we know how and where to apply the lever.
First we shall have to acquire a better understanding of the weather-science of meteorology. Then we shall have to look for the appropriate trigger mechanism. This may be a cloud of dust of the right kind—or else a chemical—or perhaps a great number of radioactive particles. In one way or another atomic explosions may be used as the trigger but the trigger will not be effective until and unless the rest of the machinery is understood.
Of course atomic explosions cannot be used in really significant numbers unless we learn how to avoid those radioactive by-products which are really dangerous. Fortunately the use of nuclear fusion, best known from the hydrogen bomb, makes it possible to regulate the kind of radioactivity one obtains. We may make only such kinds of activity which decay before they have a chance to get into the human body.
Experience has proved that to talk about weather is not dangerous. To do something about the weather will be more risky. Shall the weather become a ward of the government? Shall we have Republican Rainstorms and Democratic Droughts? In this way we shall certainly lose the last safe topic of conversation.
In the narrower confines of Europe where sovereign nation is a few hours from sovereign nation (as the wind blows) the situation will be much more serious. But even the whole planet may prove too small for fiercely conflicting interests when more knowing fingers are placed on more sensitive triggers.
To govern the weather can be most useful. It could give ample livelihood to all the people of the earth and to many more billions. Such endeavor is surely good and it would appear peaceful. But in this case as in many other cases knowledge will lead to power and power will lead to disaster if it is not tempered by wisdom.
Yet this knowledge or some similarly dangerous knowledge will come to us in our lifetimes. Nuclear explosions do not stand alone as a potential source of mischief.
CHAPTER XVII
Safety of Nuclear Reactors
At the beginning of the scientific and industrial revolution two old ambitions were found to be impossible dreams. One was the transmutation of elements, the other the machine of perpetual motion.
Modern nuclear physicists had to retract one of these statements: elements can be transmuted. But the product is expensive, for the time being much more expensive than gold.
The perpetual motion machine remains impossible in principle but the problem may be considered solved in practice. It can be proved, of course, that a machine can do useful work only if it burns up some fuel. But the price of fuel is quite often less than the cost to operate and maintain the machine.
Nuclear fuel even today is no more expensive than conventional fuel in many parts of the United States. Nuclear fuel is neither heavy nor bulky and can be therefore transported easily. In those parts of the world where ordinary fuel is expensive, nuclear energy will soon become of great importance. Furthermore, we shall learn to use most of the energy in uranium rather than just the part contained in its rare and valuable isotope, U²³⁵.
One only has to add a neutron to common U²³⁸ to get radioactive U²³⁹. In the course of time this decays into plutonium. This element can be used like U²³⁵: It produces fission, a great amount of energy and enough neutrons to keep the process going. We shall also learn to extract energy from other nuclear fuels. Thorium acts like uranium, while deuterium can give energy by building up bigger nuclei rather than breaking them into smaller pieces. Therefore the source of energy will be universally available and quite inexpensive. This really means that we are as well off as though we had a machine of perpetual motion.
But, of course, all this does not mean that the machine will do its job free of charge. Even a perpetual motion machine would need servicing and maintenance. Unfortunately our nuclear machines need a lot of such servicing and therefore for the time being, nuclear energy is not the cheapest.
The main reason why a nuclear energy source, or a nuclear reactor is difficult and expensive to run is that the reactor after a short time of operation becomes strongly radioactive. Therefore it cannot be approached and it has to be handled by remote control. We can hardly expect that energy will be free like air or water. But when we learn how to handle inexpensively our nuclear machines, we shall be able to obtain energy for a reasonable price at any place on the earth. Sooner or later conventional fuel will become scarce. But nuclear energy will allow the industrial revolution to continue and to expand into every corner of the earth.
There can be little doubt that during the next decades nuclear reactors will greatly multiply and by the beginning of the next century they will be found everywhere. It is therefore of the greatest importance that these reactors should be operated safely. On the face of it, a nuclear reactor is a sluggish instrument which can be made to run itself. But the ease of operation is deceptive. (See picture 13.)
One need not fear that a nuclear reactor might explode like an atomic bomb. Nuclear explosives are very carefully constructed so that they can release a lot of energy in a short time. Nuclear reactors on the other hand are put together so as to make it possible that energy will be released only at a moderate rate. Some reactors if improperly handled may explode, but the violence of the explosion cannot greatly exceed that of a similar weight of high explosive.
Nevertheless a reactor accident could become exceedingly dangerous. The reactor is charged with radioactive fission products and some other radioactive substances produced by neutron absorption. Any accident which will allow even a portion of these products to escape into the air will endanger people at a considerable distance in the downwind direction. One reason why reactors can be dangerous is that in protracted operation of the reactor, fission products which have longer lives accumulate. It is precisely these longer-lived products which are more dangerous because they have a better chance to find their way into the human body.
Reactors are now planned which will produce 300,000 kilowatts of electricity. If such a reactor operates for half a year and then explodes and releases its radioactive content into the atmosphere, its radioactivity will be comparable to that of a hydrogen bomb. In one important respect such an accident would be worse than a hydrogen explosion. The nuclear explosive lifts most of its radioactive products to a high altitude and the poisonous activity gets dispersed and diluted before it descends. The activity from a reactor on the other hand will remain close to the ground and might endanger the lives of the people in an area of hundreds of square miles. It will contaminate an even greater territory.
In the extensive operation of many reactors in the United States no one has yet been killed by the radioactivity. This has been due to extremely careful operation and also to good luck. We must be prepared that sooner or later accidents will occur. On the other hand we must try to take sufficient precautions to avoid the kind of catastrophic accident which we have mentioned above. With great care such accidents can indeed be avoided.
In thinking of all kinds of man-made machines we find some which move fast and seem dangerous like, for instance, airplanes; others which are stationary and apparently harmless, like the bath tub. Yet more accidents happen in bath tubs than in air travel. The most dangerous element in all operations is the human element. We ourselves constitute the greatest safety hazard. This is a situation no different in nuclear technology than in any other kind of technology. What is new in nuclear technology is that a reactor is usually very safe but may become extremely dangerous when something unexpected happens to it. Also we dare not use the method of trial and error. An error in the reactor business could exact a far heavier toll of lives than an error in the testing of H-bombs. We cannot wait to learn by experience; we must forestall accidents.
An especially difficult safety problem is connected with the use of reactors in small countries. A serious accident could endanger the lives of people in adjacent countries. Thus modern technology may force cooperation across national boundaries.
There is only one way to avoid traffic accidents and that is care exercised by everyone, particularly the drivers. Similarly reactor safety will depend on the people who operate the reactors. At the same time a lot of help can be obtained by careful construction and scrutiny of each new reactor.
One of the first acts of the Atomic Energy Commission was to establish a Committee for Reactor Safeguards. With the passing of years this committee had to take on more heavy responsibilities. At first it had to operate under secrecy. With the wider and more public use of reactors the safety considerations are becoming more available to the public. The question of safe operation of a machine cannot be separated from a thorough understanding of the working of the machine. We cannot attempt to give an adequate description of a reactor or of the safety rules. A few general statements have to suffice.
A working reactor is full of neutrons. In a small fraction of a second these neutrons produce fission and a new generation of neutrons comes into being. In slow reactors which contain lots of light elements like hydrogen or carbon, the neutrons move with speeds little greater than that of sound and a generation may last as long as a millisecond (one thousandth of a second). In fast reactors which contain almost exclusively heavier elements like uranium or iron, neutrons move with a great speed which is about three per cent of the speed of light. In this case one generation replaces another in less than a microsecond (one millionth of a second).
Fortunately not all the neutrons get reproduced so rapidly. Some fissions produce delayed neutrons which are emitted usually with a delay of several seconds. In a steadily working reactor each generation should have the same number of neutrons as the previous one. If each succeeding generation has even a slight surplus, the reactor will become hot and may explode in a small fraction of a second. The main reason why safe operation is possible is the fact that fast multiplication can occur only if each generation becomes more populous even when one does not count the delayed neutrons. A slightly overactive reactor is easily governed, but there comes a point when the dormant dragon begins to stir. This happens when there are enough neutrons produced so that multiplication can occur without waiting for the delayed neutrons. At that point a well behaved dragon will perform a harmless action. For instance it may blow a fuse. But a vicious dragon will spit radioactive fire.
It is not easy to predict whether the dragon will be always well behaved. But with careful analysis one can make such a prediction. For instance one must look into the question of whether the reactor is stable. If it gets hotter, does this make the reactor proceed even faster so that the rate of heating increases and the reactor runs away? In a stable reactor excess heat should tend to stop the energy production and thus the reactor cools and returns to its normal operating temperature.
But too great a stability may also be dangerous. Heating may be overcompensated by the cooling mechanism; after the reactor has become too cold it may then heat up too fast and overshoot again. We must guard not only against a simple run-away, but also against increasing oscillations.
In many reactors unusual chemical compounds are used. A reactor accident may start with nothing worse than an ordinary chemical reaction between strange compounds under strange conditions. But if this chemical reaction destroys the reactor sufficiently to allow some fission products to escape, then such a chemical accident can be as bad as one of nuclear origin.
In the interior of the reactor materials are exposed to unusually strong radiation. Under this effect some materials can change their chemical properties so that what has been inert as a construction material may become dangerous during the operation of the reactor.
Perhaps the most important single item is the arrangement of mechanical controls. The reactor is adjusted by a system of sheets or rods made of a material which absorbs neutrons. This arrangement must be so constructed that the control rods can be withdrawn only at a very slow rate. But it must be possible to put them back quite fast. Any danger signal should shove the absorbers in at maximum speed. The technical expression is “scram.”
The main point, however, is that all the dangers and safety devices can be studied and after careful study a nuclear accident can be avoided. Some reactors are now so thoroughly understood that they can be safely used for training of future nuclear engineers. Other reactors which are more powerful or less well studied have to be used more carefully. Some reactors should be, and are being, enclosed in gas-tight containers. If an explosion occurs the fission products will be harmlessly confined inside the container. Of course, one must be quite sure that the reactor is of such a type that it cannot produce an explosion great enough to burst the container and what is even more important one should be quite sure that the container is closed except when the reactor is shut down and completely safe. Often it may be best to build the reactor underground.
The safety of a reactor, of course, depends to a great extent on the use to which the reactor is put. In general a power station is less likely to give trouble than a moving power source. It is not probable that nuclear locomotives will ever be safe. In nuclear ships more room is available and more room permits more safety measures. But even so the safety of nuclear motors in ships will have to be considered particularly carefully because ships will have accidents in harbors.
Between the urgent need for progress and the absolute necessity of safety it is difficult to keep a sense of balance and one can easily make the mistake of being unnecessarily cautious. Such unnecessary caution was probably exercised when the Committee on Reactor Safeguards considered the earthquake hazard of the Brookhaven reactor on Long Island. A seismologist, who is a Jesuit Father, was asked to tell the committee[15] of the possibilities and probabilities of an earthquake on Long Island. The chairman[16] of the committee subjected the expert to a long and detailed questioning. After half an hour the Committee on Reactor Safeguards ran out of questions. But the Jesuit Father had not given any signs of running out of answers. The session being at an end the expert, looking the chairman of the committee firmly in the eye and in a more authoritative voice than he had yet used, said, “Mr. Chairman, I can assure you on the highest authority that there will be no major earthquakes on Long Island in the next fifty years.”
CHAPTER XVIII
By-products of Nuclear Reactors
Nuclear reactors generate energy with the help of nuclear fission. Every time a fission occurs we are left with radioactive by-products. It is most important to prevent the uncontrolled escape of these fission products from the reactor. Fortunately the dangerous products can be retained in the reactor—if the machine has been constructed and operated with reasonable care.
In the end, however, the burnt or partly burnt uranium charge will have to be removed from the reactor and fresh charge, fresh fuel will have to be added. What will become of the fission products at this time?
During protracted operation of a reactor most of the short-lived fission products decay. Those with longer lives accumulate. The discharge of the reactor is strongly radioactive, and it will remain radioactive for many years. One certainly must not dispose of this radioactive waste in a careless manner. There are, however, many ways in which one can store such waste with reasonable safety.
One can deposit the radioactive material in well-built underground tanks. One can concentrate the activity, imprison it in concrete blocks, and deposit it at the bottom of the ocean. If one is very much worried he might even put the radioactivity in rockets and let it decay harmlessly in outer space. These procedures will cost money and will add to the expense of nuclear energy.
It would be far better if we could find a way in which the radioactive by-products could be made to serve a useful and safe purpose. Some of the by-products can be used and have been used. These uses are connected with some hazards. Furthermore, only a small fraction of the fission products have found good employment up to the present. But the importance of fission products is growing.
We are using them in research. A radioactive isotope imitates the behavior of its non-active brother in all chemical reactions and in all the intricate processes in which matter changes its form inside a living body. Furthermore a radioactive substance can be detected with the greatest ease. It can be found in a concentration which is less than a millionth of a safe radiation dose. What the microscope has been in the exploration of the structure of organisms, the radioactive elements may become in the understanding of the chemical functioning of living matter.
With better understanding there comes the possibility of using radioactive by-products for diagnosis. As with the medical use of X-rays the possible small damage due to radiation exposure should be regarded as the price for the help we can get from early and correct recognition of diseases.
In the treatment of patients, particularly in the case of persons stricken by cancer, radioactive destruction of the diseased tissue is often preferable to the use of the surgeon’s knife. Such radioactive treatment is new. There is much room for improvement. Appropriate use of radioactive substances for this purpose may become a far more powerful tool and much more widespread than it is at present.
But all these applications will use up only a vanishing fraction of the fission products. Moreover, most of the biologically important elements are not produced in the fission of uranium. Many useful activities can be produced by neutron absorption in reactors. But among the fragments of uranium perhaps only radio-iodine has been put so far to direct physiological use.
Industry deals with less sensitive objects than living tissue. Therefore greater amounts of radioactive materials can be used here. And indeed radioactivity has done a great variety of jobs. The penetrating power of X-rays has been used to control the thickness of sheets in an easy and automatic manner. Radioactivity has been incorporated into surfaces which are exposed to mechanical wear or corrosion, to check the rate at which the surface is worn away by the appearance of activity in the lubricant or other fluids which have been in contact with the surface.
By such methods industry has accumulated savings which are rapidly approaching the billion dollar mark. These savings will increase as people learn how to use the new materials. But in all these cases it is important to make sure that the activity will not hurt anyone while it is used and after it has served its purpose.
Possibly the greatest amount of radioactivity will be needed in food sterilization and preservation. One may incorporate the activities into rods which will safely retain the materials but which will allow a considerable fraction of the penetrating gamma rays to escape.
To sterilize food means to destroy all microorganisms. Many of these are radiation-resistant and may have to be exposed to 50,000 or more roentgens—that is one hundred times as much as would kill a mammal.[17] Such massive irradiation begins to affect the foodstuff itself. In some cases sterilization by irradiation changes the food more than would be the case by boiling it or freezing it. In other cases irradiation produces less undesirable side effects than any other methods.
Another way to use radiation is the preservation of agricultural products. This need not be done by the difficult procedure of sterilization. It is enough to control pests and to prevent germination of the seeds which one is trying to preserve. Thus we need here approximately one per cent of the radiation that would be required for sterilization. By so little radiation the food is not altered to a noticeable extent. It is precisely in such processes, where great amounts of materials will have to be irradiated, that a substantial fraction of the fission products might find employment.
In all applications care has to be exercised lest radioactive materials should inadvertently be scattered around. Where great amounts are needed as in food sterilization and preservation, caution has to be redoubled. That trouble may arise has been illustrated by an occurrence in Houston, Texas.
Radioactive iridium¹⁹², which is a beta and a gamma emitter, was being used by a certain industrial concern to take X-ray pictures of metal parts. A shipment of this radioactive material in the form of powder pellets was being opened by remote control when compressed gas in the container exploded and scattered some radioactivity around. The area was shielded but some of the radioactive dust escaped to the rest of the building. The two men who were operating the remote control apparatus became contaminated. They washed themselves and cleaned up the area but did not report the incident.
A few weeks later a standard radiation check showed that the plant was still radioactive. Company officials became worried and called in experts. At this late stage the plant was thoroughly decontaminated. The homes of the two men were also examined and were found to be slightly radioactive. The men and their families were temporarily moved out while their homes were being cleaned up. When they returned, neighbors and friends shunned them. The four year old son of one of the men lost his playmates. People were afraid to enter the houses. One of the houses was put up for sale but no one wanted to buy it.
The fact that the houses had been checked by radiation meters and found to be clean, and the fact that the half-life of iridium¹⁹² is only 75 days so that any trace of activity would disappear in a reasonably short time, did not dispel people’s fears.
It is fortunate that no one was seriously hurt in this incident. But there is an important lesson we can learn from it: Ignorance may hurt more than radioactivity. That a house should lose its value in spite of the fact that its radioactive contamination has been removed, that a little boy should be shunned as though radioactivity were infectious like the plague—these are examples of suffering caused by one of the greatest sources of human misery: unreasoning fear.
The greatest potentialities of fission products for the future might lie in still a different direction. Radioactivity can induce mutations. To what extent this is a danger we have discussed in an earlier chapter. In the hands of a breeder who tries to bring about changes in animals or plants radioactivity could become exceedingly useful.
Of course it is true that most mutations are harmful. It is also true that artificial mutations have been produced for many decades. But now it is possible to place simple and cheap tools in the hands of many more people. Therefore the chances will increase to find among the many wrong mutations the few and decisive changes which lead to improvement.
Do we dare to place dangerous materials in so many hands? We should not do so without making certain that only competent and responsible individuals will get radioactive materials. This can be done. Druggists have dispensed poison; doctors and biologists have bred in their laboratories the multiplying menace of germs. All this was done and is being done with safety and to the great benefit of all people.
The use of radioactivity should be even more safe because this material is easy to detect. If poisons or germs become lost, they may be hard to find. Radioactive materials, however, give unmistakable evidence of their presence. It is, of course, never easy to find a needle in a haystack. But the chance to find it is much better if it is a radioactive needle.
Radioactive by-products need not remain what they seem to be today: dirt and danger to be disposed of and hidden. But in the immediate future we shall incur some expense to keep radioactivity in a safe place.
Some gaseous by-products like the long-lived krypton⁸⁵ (half-life: 10.4 years) might continue to give rise to real difficulties and to considerable expense. The trouble is, of course, that a noble gas like krypton will not be bound to any material by strong bonds. It may be inadvisable to let long-lived gases escape. On the other hand, their adsorption or their storage at low temperature or high pressure may prove to cost a considerable amount of money.
We have been talking about the problem of handling the by-products of nuclear power. This problem will not appear in proper proportion unless we also give some thought to the by-products of the kind of power we are using at present.
That we do not like smoke and smog is obvious. To what extent these residues of incomplete burning can cause cancer or other damage we do not know. Chemistry is more tricky than radiation. Our lack of knowledge about the slow biological effects of chemicals is much greater than our remaining uncertainties about radiation.
In addition to the obvious annoyance and worry caused by the products of incomplete combustion there exists an interesting question connected with the result of complete combustion. The carbon that has been deposited through the geologic ages as coal and as oil is being used up gradually and converted to a colorless, odorless, harmless gas—carbon dioxide. There is always some carbon dioxide in our atmosphere. The amount is approximately 300 parts per million of common air. All the carbon that has been burned since the beginning of the industrial revolution could have increased the carbon dioxide in the atmosphere by ten per cent to the value of 330 parts per million.
This increase could be significant. Carbon dioxide acts like a blanket or a valve for some kinds of radiation. In the daytime we receive energy in the form of visible light from the sun. This form of radiation has no difficulty in penetrating the carbon dioxide gas. However, the incoming radiation is balanced by invisible heat radiation, which flows out from the earth into space day and night. This infrared radiation is quite similar in nature to light, only our eyes are not sensitive to it. Now the carbon dioxide gas acts like a barrier, though only a partially effective barrier, to this outgoing heat radiation. If the carbon dioxide content of our atmosphere were to increase too greatly, it would act like the glass in a greenhouse and our climate would grow warmer.
A ten per cent increase in the carbon dioxide content of the atmosphere should have produced an observable rise in temperature. Such a temperature rise has not, in fact, been observed. The reason is that not all the carbon dioxide which has been generated in the processes of combustion has actually remained in the atmosphere. Most of it has found its way into the great reservoir of our oceans. Some of it is deposited as lime at the bottom of the oceans. However, some time is required for the carbon dioxide to be removed from the atmosphere and to reach the oceans. One would expect, therefore, that there would have been at least a slight increase in the carbon dioxide content of the atmosphere. Measurements show that this is the case and that the increase is about two per cent—which is too small to have changed our climate.
If we continue to consume fuel at an increasing rate, however, it appears probable that the carbon dioxide content of the atmosphere will become high enough to raise the average temperature of the earth by a few degrees. If this were to happen, the ice caps would melt and the general level of the oceans would rise. Coastal cities like New York and Seattle might be inundated.
Thus the industrial revolution using ordinary chemical fuel could be forced to end before the advantages of civilization have spread all over the earth. However, it might still be possible to use nuclear fuel. With nuclear fuel the industrial revolution and its countless benefits for man could continue to every part of the globe. The by-products of the nuclear age are less bulky and therefore are more easily handled than the by-products of our coal- and oil-economy. The main advantage of nuclear energy may yet turn out to be this: With proper care nuclear energy may turn out to be the cleanest among the available sources of power.
CHAPTER XIX
The Nuclear Age
The future depends on people. People are unpredictable. Therefore, the future is unpredictable. However, some general conditions of mankind depend on things like the development of technology, the control won by man over nature and the limitations of natural resources. These can be predicted with a little greater confidence. The future is unknown but in some respects its general outline can be guessed.
Such guesses are important. They influence our present outlook and our present actions.
The nuclear age has not yet started. Our sources of energy are not yet nuclear sources. Even in the military field, where development has been most rapid, the structure of the armed forces has not yet adjusted itself to the facts of the nuclear age in a realistic manner. In politics the atomic nucleus has entered as a promise and as a menace—not as a fact on which we can build and with which we can reckon.
Some technical predictions seem safe:
Nuclear energy will not render our older power plants obsolete in the near future. But nuclear energy will make it possible to maintain the pace—even the acceleration—of the industrial revolution. It will be possible to produce all the energy we need at a moderate cost. Furthermore—and this is the important point—this energy will be available at any place on the globe at a cost which is fairly uniform. The greater the need for power, the sooner will it be feasible to satisfy the need with the help of nuclear reactors.
Nuclear energy can be made available at the most outlandish places. It can be used on the Antarctic continent. It can be made to work on the bottom of the ocean.
The expanding front of industrialization has been called the “revolution of rising expectations.” That nuclear energy should be involved in the current and in the turbulence of this expanding front, is inevitable.
One can say a little more about the effects of scientific and technological discoveries on the relations among the people of the globe. With added discoveries raw materials will no longer be needed with the old urgency. For most substances substitutes are being found. This may make for greater economic independence.
On the other hand, new possibilities will present themselves. We shall learn how to control the air and how to cultivate the oceans. This will call for cooperation and more interdependence.
The dangers from radioactive by-products will act in a similar direction. The radioactive cloud released from a reactor accident may be more dangerous than a nuclear explosion. Such a cloud will not stop at national boundaries. Some proper form of international responsibility will have to be developed.
What effect the existence of nuclear weapons will have upon the coexistence of nations is a question less understood and less explored than any other affecting our future. Most people turn away from it with a feeling of terror. It is not easy to look at the question with calm reason and with little emotion.
A few predictions seem disturbing but are highly probable:
Nuclear secrets will not keep. Knowledge of nuclear weapons will spread among nations—at least as long as independent nations exist.
Prohibition will not work. Laws or agreements which start with the word “don’t” can be broken and will always be broken. If there is hope, it must lie in the direction of agreements which start with the word “do.” The idea of “Atoms for Peace” succeeded because it resulted in concrete action.
An all-out nuclear war between the major powers could occur but we may have good hope that it will not occur if we remain prepared to strike back. No one will want to provoke the devastation of his own country.
Atomic bombs may be used against cities. But there will be no military advantage in destroying cities. In a short and highly mobile war neither centers of supply and communication nor massive means of production will count. If cities are bombed, this will be done primarily for reasons of psychological warfare. We must be and we are prepared for this kind of war but only as a measure of retaliation. There is good reason to believe that as long as we are prepared for all-out war, our civilian population will not suffer from a nuclear attack.
The certainty of a counterblow gives real protection against all-out war. No such protection exists against wars limited in territory and in aims. In the history of mankind such wars have been most frequent. There is no indication that these limited wars have ended. We must be prepared for these conflicts with effective and mobile units, and this requires the use of nuclear firepower.
Nuclear weapons will certainly have a profound effect upon such limited warfare. Not all of this effect need be and indeed it must not be in the direction of greater devastation.