In a nuclear war it will not make sense to use massed manpower. Any such concentration will provide too good a target for atomic weapons. To use big, costly and conspicuous machines of war will be unwise. Such machines will be defeated by nuclear explosions in the same way as the mailed knight went down before firearms.
Any fighting unit in a nuclear war will have to be small, mobile, inconspicuous and capable of independent action. Such units whether on sea, land or in the air cannot rely and will not rely on fixed lines of supply. There will be no possibility and no need to occupy territory and to fight at fixed and definite fronts. If a war should be fought for military reasons and for military advantage, it will consist of short and sharp local engagements involving skill and advanced techniques and not involving masses that slaughter and are being slaughtered.
If an invader adopts extreme dispersion, it will become impossible to defeat him with atomic weapons. But a very highly dispersed army can be defeated by a determined local population. Therefore the main role of nuclear weapons might well be to disperse any striking force so that the resistance of people defending their homes can become decisive. Nuclear weapons may well become the answer to massed armies and may put back the power into the hands where we believe it belongs: the hands of the people.
At this point we are brought back to the main topic of this book: radioactivity. In a limited nuclear war the radioactive fallout will probably kill many of the innocent bystanders. We have seen that the testing program gives rise to a danger which is much smaller than many risks which we take in our stride without any worry. In a nuclear war, even in a limited one, the situation will probably be quite different. That noncombatants suffer in wars is not new. In a nuclear war, this suffering may well be increased further due to the radioactive poisons which kill friend and foe, soldier and civilian alike.
Fortunately there exists a way out. Our early nuclear explosives have used fission. In the fission process a great array of radioactive products are formed, some of them intensely poisonous. More recently we have learned how to produce energy by fusion. Fusion produces fewer and very much less dangerous radioactivities. Actually the neutrons which are a by-product of the fusion reaction may be absorbed in almost any material and may again produce an assortment of radioactive nuclei. However, by placing only certain materials near the thermonuclear explosion, one may obtain a weapon in which the radioactivity is harmless. Thus the possibility of clean nuclear explosions lies before us.
Clean, flexible and easily delivered weapons of all sizes would make it possible to use these bombs as we want to use them: as tools of defense. When stopping an aggressor we would not let loose great quantities of radioactive atoms which would spread death where we wanted to defend freedom. Clean nuclear weapons would be the same as conveniently packaged high explosives. They would be nothing more.
The possibility of clean explosions opens up another development: the use of nuclear explosives for the purposes of peace. Conventional high explosives have been used in peace fully as much as in war. From mining to the building of dams there is a great variety of important jobs that dynamite has performed. Nuclear explosives have not been used in a similar way. The reason is the danger from radioactivity. Once we fully master the art of clean explosions peaceful applications will follow and another step will be made in controlling the forces of nature.
All this is of course only a small part in the process of the increasing power of man and the increasing responsibility of man. As the impossible of yesterday becomes the accomplished fact of today we have to be more and more aware of our neighbors on this shrinking planet. The arts of peace maylead to conflicting interest as easily as they may lead to fruitful cooperation. If we ever learn to control the climate of the world, a nation may find itself in the same relation to another nation as two farmers who have to use the waters of the same river.
Rivals are men who fight over the control of a river. When the same word “rivals” comes to mean cooperation for the best common use of the river or any other resource—that will be the time of law and of peace. Surely this sounds like Utopia and no one sees the way. But the general direction in which we should go is not to consider atomic explosives and radioactivity as the inventions of the devil. On the contrary, we must more fully explore all the consequences and possibilities that lie in nature, even when these possibilities seem frightening at first. In the end this is the way toward a better life. It may sound unusually optimistic in the atomic age, but we believe that the human race is tough and in the long run the human race is reasonable.
Activity: Short for radioactivity. Also the strength of a radioactive source measured in disintegrations per second.
Air burst: A nuclear explosion at such an altitude that the fireball does not touch the earth’s surface. An air burst produces very little local fallout.
Alpha ray (particle): Energetic but non-penetrating radiation emitted by heavy radioactive nuclei. An alpha particle consists of two neutrons and two protons, and is identical with the nucleus of the ordinary helium atom.
Atom: A positively charged nucleus surrounded by negatively charged electrons.
Atomic bomb: A fission bomb.
Atomic cloud: The cloud remaining after the energy of the explosion has been carried off by the shock wave and the thermal radiation. It consists of condensed water vapor, ground material, and bomb debris including the radioactivity.
Atomic energy: Energy released in nuclear reactions, for example in fission. Atomic energy and nuclear energy mean the same thing, but the latter name is more appropriate.
Atomic reactor: Same as nuclear reactor.
Background radiation: Natural radiation due to cosmic rays, and due to radioactive substances in the earth, in the atmosphere, and in our own bodies.
Beta ray (particle): An energetic electron or positron emitted by some radioactive nuclei. Practically all of the fission products are beta (electron) emitters.
Blast wave: Same as shock wave.
Cesium¹³⁷: A radioactive fission product. It emits a 0.5 million volt beta ray and a 0.7 million volt gamma ray with a half-life of 30 years. The daughter nucleus is stable barium¹³⁷.
Chain reaction: Self-maintained sequence of fissions. Neutrons released by the fission of one nucleus are used to induce fission in another nucleus.
Chromosome: A small irregularly shaped body found in cells. Chromosomes carry the genes, which are responsible for heredity.
Clean bomb: A nuclear bomb which produces heat and blast, but only a negligible amount of radioactivity. The energy of such a bomb is derived almost entirely from the fusion process.
Cobalt⁶⁰: Radioisotope—decays into nickel⁶⁰ with the emission of a weak beta ray. The half-life for this decay is 5.3 years. The nickel⁶⁰ immediately ejects two gamma rays with a total energy of 2.5 million electron-volts.
Cobalt bomb: A radiological bomb which produces a large quantity of cobalt⁶⁰.
Control rod: A rod of neutron-absorbing material used to control the power level of a nuclear reactor.
Cosmic rays: Energetic particles from outer space. They induce nuclear reactions in the earth’s atmosphere and thus contribute to the background radiation. This cosmic radiation is more intense at high altitudes than at sea level.
Counter: A device which detects nuclear radiation.
Critical mass: The amount of fissionable material required to sustain a steady chain reaction. With less than the critical amount, the reaction stops because too many neutrons are lost.
Cyclotron: A machine that accelerates charged particles to high energy. Energetic charged particles can be used to induce nuclear reactions.
Daughter: The nucleus which remains after decay of a radioisotope.
Decay: Spontaneous process in which a radioactive nucleus emits an alpha, beta, or gamma ray.
Delayed neutrons: Those released after a fraction of a second to a half-minute or so by the fission products. They comprise less than one per cent of the total number of neutrons released in the fission process but are useful for the purpose of control in reactors.
Deuterium: Stable hydrogen isotope. Its nucleus (called a deuteron) consists of one proton and one neutron.
Disintegration: Same as decay.
Dose: A quantity of radiation—usually measured in roentgens.
E = mc²: Einstein’s equation relating mass (m) and energy (E). The speed of light (c) enters as a proportionality constant. The equation asserts that one pound of mass is equivalent to ten megatons of energy. In the fission process only one-tenth of one per cent of the mass is converted. Therefore, to produce ten megatons of energy by fission 1000 pounds of uranium would be required.
Electromagnetic radiation: Includes radio waves, visible, infrared, and ultraviolet waves; also X-rays and gamma rays. The latter two are energetic, penetrating forms of radiation.
Electron: A particle having a unit negative charge and a weight equal to 1/1840 of the weight of the lightest atom (hydrogen).
Electron capture: process in which an atomic electron unites with a proton in the nucleus producing a neutron and a neutrino.
Electron-volt: The amount of energy acquired by an electron which is accelerated through an electric potential of one volt. Typically, the energy required to “knock” an electron out of an atom is a few electron-volts or so; particles ejected from radioactive nuclei have energies between a few hundred thousand and a few million electron-volts.
Element: A collection of atoms whose nuclei all have the same charge. An element may consist of many isotopes.
Enriched material: Uranium which contains a greater proportion of the 235-isotope than is found in the natural ore.
Excited state: A state of an atom, molecule, or nucleus having excess energy. As soon as possible this excess energy is released and the system goes to the ground state.
Fallout: Radioactive particles from an atomic explosion. They may be carried in the atomic cloud to large distances from ground zero and then “rained down” to the earth’s surface.
Fireball: The luminous ball of hot air and bomb material which expands and cools as the shock wave races out.
Fission: The breaking-up of a heavy nucleus into two or more fragments. A large amount of energy and some free neutrons are released in the process.
Fissionable material: Isotopes which undergo fission when bombarded byslowneutrons: uranium²³⁵ and plutonium²³⁹.
Fission products: Fission fragments and their daughters, including hundreds of different radioactive species, among them strontium⁹⁰ and cesium¹³⁷.
Fusion: The combining of light nuclei into heavier ones with arelease of energy. For example, deuteron + triton → alpha + neutron. About 18 million electron-volts are released in this process.
Gamma ray: Energetic, penetrating electro-magnetic radiation emitted by certain radioactive nuclei, frequently after a beta emission.
Genes: Parts of the chromosomes. They are big molecules that determine heredity.
Ground state: The state of least energy and greatest stability of atoms, molecules, and nuclei.
Ground zero: The point on the surface of the earth directly above or below a nuclear explosion.
Half-life: The time required for one half of a large number of identical radioactive nuclei to disintegrate.
H-bomb: Same as hydrogen bomb.
Heavy hydrogen: Same as deuterium.
Heavy water: Water with heavy hydrogen substituted for ordinary hydrogen.
Hydrogen bomb: A high-yield thermonuclear bomb.
Iodine¹³¹: A radioactive fission product with a half-life of 8 days. It emits an electron of average energy 0.2 million electron-volts and a gamma ray of energy 0.4 million electron-volts.
Ion: A charged atom or molecule. Ions are produced in abundance when energetic charged particles pass through matter.
Ionization: The process of removing electrons from neutral atoms or molecules. Neutrons and gamma rays as well as energetic charged particles are very effective in producing ionization.
Iridium¹⁹²: 75 day radioisotope. It emits an electron of averageenergy 0.2 million volts and a 0.3 million volt gamma ray.
Isotopes: Atoms whose nuclei have the same number of protons but a different number of neutrons. Such atoms have the same chemical behavior.
Kiloton: The amount of energy released by a thousand tons of TNT.
Krypton⁸⁵: A radioactive fission product. It has a ten year half-life and emits an electron of average energy 0.2 million volts and a 0.5 million volt gamma ray.
Leukemia: A usually fatal disease in which white blood cells are overproduced.
Local fallout: Radioactive fallout in the neighborhood of a nuclear explosion.
Megaton: The amount of energy released by a million tons of TNT.
Meson: A particle intermediate in weight between the electron and the proton. Actually, there are two kinds of mesons, called pi and mu. The pi meson weighs 276 times as much as the electron and is connected with the forces that hold the nucleus together. The mu meson weighs 212 times as much as the electron and contributes appreciably to the cosmic radiation.
Microsecond: One millionth of a second. It takes light 5 microseconds to go a mile.
Million volt particle: Short for million electron-volt particle.
Moderator: A material used in nuclear reactors to reduce the speed of neutrons.
Molecule: A combination of atoms held together chemically.
Mutation: A genetic change, which is transmitted to offspring andaffects hereditary characteristics. Such changes in genes may be caused by radiation as well as chemical and thermal agents.
Neutrino: A weightless, uncharged particle which carries off energy in the process of beta decay.
Neutron: A neutral particle, one of the basic constituents of the nucleus. A neutron weighs slightly more than a proton, and when free, decays into a proton plus an electron and a neutrino.
Noble gases: Helium, neon, argon, krypton, and xenon. They do not combine chemically with any elements including themselves.
Nuclear bomb: A bomb which derives its energy from nuclear fission or fusion.
Nuclear reactor: A machine for maintaining a controlled chain reaction.
Nucleus: The core of an atom, consisting of neutrons and protons. Its charge is equal to the number of protons. Its weight is equal to the number of protons plus the number of neutrons.
Periodic system: The chemical elements arranged in order of increasing atomic charge. Elements with similar chemical properties occur periodically.
Plutonium: Element with charge 94, produced by capturing a neutron in uranium²³⁸ followed by two beta emissions. Like uranium²³⁵, plutonium is valuable as an atomic fuel.
Positron: The positive counterpart of the electron.
Potassium⁴⁰: A natural radioactive isotope. It has a half-life of one billion years and emits beta and gamma rays.
Proton: A constituent of the nucleus. It has one unit of positive charge and weighs slightly less than a neutron.
Radiation: Energetic charged particles, neutrons and gamma rays which cause ionization in matter. Radiation is produced in nuclear explosions but also occurs naturally from cosmic rays and from the decay of radioactive substances in our surroundings.
Radioactivity: Spontaneous nuclear decay, releasing an alpha, beta, or gamma ray.
Radioisotope: Short for radioactive isotope.
Radiological bomb: A bomb designed to create radioactive contamination.
Radium: Element with charge 88. The principal isotope has a weight of 226 and emits an alpha particle with a half-life of 1620 years.
Range: Distance traveled by an energetic charged particle in matter before it stops. Heavy charged particles move in a straight line inside matter, but electrons frequently change their course. For this reason the range of electrons is only about one-half the total distance traveled.
Reactor: Same as nuclear reactor.
Roentgen: A measure of radiation dose—defined in terms of the amount of energy deposited per unit weight of irradiated material. A dose of 400,000 roentgens in living tissue deposits enough energy to raise the temperature by 1°C. A dose of only 400 roentgens in a human being will cause death fifty per cent of the time.
Shock wave: Expanding front of high pressure and strong winds produced by an explosion.
Spontaneous fission: Natural fission, not induced by a neutron. The half-life for this process in uranium²³⁸ is 8 × 10¹⁵ years.
Stratosphere: The atmosphere above the weather zone. The altitude of the stratosphere varies from thirty to fifty thousand feet depending on latitude and season.
Stratospheric fallout: World-wide fallout from big bombs whose clouds rise into the stratosphere. On the average the radioactivity remains in the stratosphere for about ten years and is then deposited more or less uniformly over the surface of the earth.
Strontium⁹⁰: A radioactive fission product. It has a half-life of 28 years and emits two electrons of average total energy 1.2 million electron-volts. Strontium is chemically similar to calcium and gets deposited in bones.
Thermal radiation: Electromagnetic radiation, mainly visible, but also ultraviolet and infrared, emitted from the fireball of a nuclear explosion and transmitted long distances in the surrounding cold air.
Thermonuclear bomb: A bomb which derives a significant fraction of its energy from the fusion of hydrogen isotopes.
Thermonuclear reaction: A fusion reaction induced by high temperature.
Thorium: Element with charge 90. The principal isotope has a weight of 232 and emits an alpha particle with a half-life of 14 billion years.
Trigger process: A small cause which leads to a big effect.
Tritium: An isotope of hydrogen. Its nucleus (called a triton) consists of one proton and two neutrons. Tritons are radioactive beta emitters having a half-life of 12.25 years.
Troposphere: The weather portion of the atmosphere, from sea level to about forty thousand feet.
Tropospheric fallout: World-wide fallout, mainly from small bombs (less than a megaton) whose clouds remain in the troposphere. This fallout occurs on the average two weeks to a month after the explosion and stays in a latitude close to the latitude of the explosion.
Uranium: Element with charge 92. Natural uranium contains 1 part of U²³⁵ to 139 parts of U²³⁸. U²³⁵ is a fissionable material and U²³⁸ can be converted to plutonium, which is fissionable.
X-ray: Penetrating electromagnetic radiation, usually made by bombarding a metal target with energetic electrons. X-rays and gamma rays are really the same thing.
[1]The word “noble” is perhaps a misnomer—these atoms do not even seek the company of each other.[2]Quotes are put around the word atom because, having lost one of its electrons, it is no longer an ordinary neutral atom in its ground state.[3]Yet.[4]Actually the same state may be occupied by two neutrons and two protons. The reason is that neutrons and protons are magnetic particles with a north and a south pole. Consequently the demand for a difference can be satisfied by having one neutron (or proton) with its north pole pointing up and another with its north pole pointing down.[5]It seems that neutrinos emitted in the company of electrons have the symmetry of a right screw; those emitted together with a positron have the symmetry of a left screw.[6]Actually the weights rarely add up to the original 238 because, as a rule, one or more neutrons are emitted which carry off some of the original mass.[7]Only a very few unlucky ones are overtaken by beta decay first.[8]She and her husband were the discoverers of two elements, rhenium and masurium. One of these exists.[9]A great portion of the energy might be lost if the neutron is quite fast. In this case the neutron can cause internal excitation of the nucleus.[10]There seems to be a good possibility that he died from a hepatitis entirely unrelated to the initial radiation exposure.[11]Half-lives of radioactive nuclei are uninfluenced by the extreme temperatures or pressures of the explosion, or by the state of motion of the particles or where they happen to be.[12]A small amount may drift down to the ground in the winds. This may get deposited on leaves and grass.[13]The last line of the table is based on our own estimates.[14]Recent evidence suggests this number is sometimes twenty-three.[15]Dubbed by its friends “Committee for Reactor Prevention.”[16]One of the authors.[17]This difference is not surprising. When we sterilize, we have to killallgerms, even those which are most resistant to radiation. Furthermore small organisms may escape the radiation effects by mere chance. On the other hand a big and complicated organism will cease to function when the most sensitive among its essential tissues have been destroyed.
[1]The word “noble” is perhaps a misnomer—these atoms do not even seek the company of each other.
[2]Quotes are put around the word atom because, having lost one of its electrons, it is no longer an ordinary neutral atom in its ground state.
[3]Yet.
[4]Actually the same state may be occupied by two neutrons and two protons. The reason is that neutrons and protons are magnetic particles with a north and a south pole. Consequently the demand for a difference can be satisfied by having one neutron (or proton) with its north pole pointing up and another with its north pole pointing down.
[5]It seems that neutrinos emitted in the company of electrons have the symmetry of a right screw; those emitted together with a positron have the symmetry of a left screw.
[6]Actually the weights rarely add up to the original 238 because, as a rule, one or more neutrons are emitted which carry off some of the original mass.
[7]Only a very few unlucky ones are overtaken by beta decay first.
[8]She and her husband were the discoverers of two elements, rhenium and masurium. One of these exists.
[9]A great portion of the energy might be lost if the neutron is quite fast. In this case the neutron can cause internal excitation of the nucleus.
[10]There seems to be a good possibility that he died from a hepatitis entirely unrelated to the initial radiation exposure.
[11]Half-lives of radioactive nuclei are uninfluenced by the extreme temperatures or pressures of the explosion, or by the state of motion of the particles or where they happen to be.
[12]A small amount may drift down to the ground in the winds. This may get deposited on leaves and grass.
[13]The last line of the table is based on our own estimates.
[14]Recent evidence suggests this number is sometimes twenty-three.
[15]Dubbed by its friends “Committee for Reactor Prevention.”
[16]One of the authors.
[17]This difference is not surprising. When we sterilize, we have to killallgerms, even those which are most resistant to radiation. Furthermore small organisms may escape the radiation effects by mere chance. On the other hand a big and complicated organism will cease to function when the most sensitive among its essential tissues have been destroyed.