Uranium

“ At last he spoke.
“Darling, it has just occurred to me that there must be another isotope of osmium.”
“I’ll bet,” she smiled, “that there is.”
He was silent again for another age.
“Darling, why should one uranium live six million years while another lives only two?” ”

“ This was the only chance and here, between the hidden place where determined men had worked tirelessly and ingeniously to refine only a small capsule of pure Uranium in a year and the hidden place where other learned men waited to incorporate the product into an atomic bomb that could destroy the city of the invaders completely, lay the greatest danger of defeat. ”

“ Becquerers discovery was brought about by a lucky accident, although, like so many other apparently accidental scientific discoveries, it was the outcome of a long series of scientific experiments all trending in the same direction. He had found that uranium, when exposed to the sun's rays, appeared to possess the property of absorbing them and of then acting upon a photographic plate. Since pitch-blende contained uranium, or uranium salts, he surmised that a somewhat similar result might be obtained with the ore itself. ”

“ Radio-activity of Uranium and Thorium. Radio-active Minerals. Becquerel Rays.—The uranium rays discovered by M. Becquerel act upon photographic plates screened from the light; they can penetrate all solid, liquid, and gaseous substances, provided that the thickness is sufficiently reduced; in passing through a gas, they cause it to become a feeble conductor of electricity.
These properties of the uranium compounds are not due to any known cause. The radiation seems to be spontaneous; it loses nothing in intensity, even on keeping the compounds in complete darkness for several years ”

“ Teena said.
“Well, the reactor is about four stories high,” Eddie went on. “They call it a uranium ‘pile.’ It’s made up of hundreds and hundreds of graphite bricks. That’s where they get the name ‘pile’—from brick pile. Anyway, scattered around in between the bricks are small bits of uranium. Uranium atoms are radioactive. That is, they keep splitting up and sending out rays.”
“Why do they do that?” Teena asked.
37
“It’s just the way nature made uranium, I guess,” Eddie said. “Most atoms stay in one piece, although they move around lickety-split all of the time. ”

“ Detailed descriptions of how the metal uranium slowly and regularly breaks down in a descending series into the metal lead and the gas helium, will be found in the literature on radio-activity. For our purpose, it suffices to say that according to Barrell, an atom of uranium which breaks up will ultimately give rise as a stable product to eight atoms of helium and one atom of lead. ”

“ Further investigation showed that this photographic action was exhibited by all compounds of uranium and by the metal itself, and had nothing to do with phosphorescence. It was shown equally if the uranium were kept in darkness and did not vary appreciably with time. Becquerel showed that the rays from uranium like X rays were capable of discharging a body whether positively or negatively electrified. A uranium compound brought close to the charged plate of a gold leaf electroscope causes a rapid collapse of the gold leaves. ”

“ Whereas, the DU weapons not only penetrate armor and other hardened targets, but also burst into flames releasing quantities of aerosolized uranium particles into the environment that are easily carried by wind or water and are easily resuspended, blowing radioactive contamination to locations quite distant from battlefield locations ”

“ If a chain reaction could be started in a sizable piece of uranium, unimaginable quantities of energy would be produced. Just 1 gram of uranium, undergoing complete fission, would deliver the energy derived from the total burning of 3 tons of coal and would deliver that energy in a tiny fraction of a second.
Szilard, who had come to the United States in 1937, clearly visualized the tremendous explosive force of something that would have to be called a “nuclear bomb”. ”

“ If all the energy delivered by a gram of uranium in the course of its radioactivity over many billions of years was totalled, it was enormously greater than the energy produced by the burning of a candle with a mass equal to that of uranium. ”

“ The one per cent of argon found in the earth’s atmosphere comes almost entirely from the second reaction. These radioactivities are also interesting because appreciable amounts of potassium40 are always present in human tissue.
All nuclei at the heavy end of the periodic system are radioactive alpha emitters. Uranium, for example, has no stable isotopes; they all undergo alpha decay. But there is another 46 mode of spontaneous decay of uranium, which is much less frequent than alpha decay but is of much greater practical importance. This is the fission process. ”

“ When a neutron strikes the nucleus of uranium-235 (235U) or plutonium-239 (239Pu) , it may cause the nucleus to split into two roughly equal fragments, releasing neutrons and energy. This is the well-known process of neutron-induced fission, the method in which nuclear energy is produced in both reactors and bombs. [14] The most common uranium isotope, 238U, also breaks up by fission, but does so all by itself, without the need for any external neutrons. That process is spontaneous fission and it goes on at random, very much like radioactive decay. ”

“ Lead of radioactive origin, or isotopic lead the final product of the decay of uranium is found to vary slightly in its atomic weight according to the uranium mineral from which it is extracted.
To radioactivity is ascribed the well-known “pleochroic haloes”—tiny spots or borders of deeper colour surrounding microscopic inclusions—long ago observed in certain rock-forming minerals (cordierite, andalusite, mica, etc.) when micro-sections of rocks are examined in polarized light. ”

“ Uraninite consists essentially of oxides of uranium (UO2 + UO3 = 75 to 85 per cent.) , associated with thoria, zirconia, rare earths, beryllia, and oxides of lead. Traces of lime, iron oxides, silica, bismuth, and arsenic are also sometimes present, with water in widely varying quantities. Nitrogen and helium are always found in it, and, of course, radium. Groth regards pitchblende as uranous uranate Uiv (UviO4) 2, the uranium in the acidic radicle being hexavalent and in the basic radicle tetravalent, and in the latter condition partially replaced by lead, thorium, and rare earths. ”

“ We might think of a single uranium atom breaking down and shooting off an alpha particle. We might also think of a single carbon atom combining with 2 oxygen atoms to form carbon dioxide. The uranium atom would give off 2,000,000 times as much energy in breaking down, as the carbon atom would in combining.
The energy of radioactivity is millions of times as intense as the energy released by chemical reactions. ”

“ After the discovery of the radioactive properties of uranium by Henri Becquerel in 1896, it was noticed that some minerals of uranium, such as pitchblende, were more active than the element itself, and this circumstance suggested that such minerals contained small quantities of some unknown substance or substances possessing radioactive properties in a very high degree. ”

“ In this respect, as in some others, the universe seems like a clock running down, with no mechanism for winding it up again. All the uranium in the world is breaking down, and we know of no source from which new uranium can come. Under these circumstances it seems strange that there should be any uranium. But if, like some insects, we lived only for a single spring day, we should think it strange that there should be any ice in the world, since we should find it always melting and never being formed. ”

“ In uranium, we have the one obvious derivative uranium-X, and the question remains whether this one descent can be connected with any other individual or family. Uranium is long-lived, and emits only alpha-rays. Uranium-X decays to half value in 22 days, giving out beta- and gamma-rays. Since our evidence goes to show that radio-activity is generally accompanied by the production of new elements, it is natural to search for the substance of uranium-X in other forms, and perhaps under other names, rather than to surrender immediately our belief in the conservation of matter. ”

“ All the minerals which showed radio-activity contained uranium or thorium: their activity is therefore not surprising, but the intensity of the action in certain cases is unexpected. Thus pitchblendes (ores of uranium oxide) are found which are four times as active as metallic uranium. Chalcolite (double phosphate of copper and uranium) is twice as active as uranium. Autunite (phosphate of uranium and calcium) is as active as uranium. These facts do not accord with previous conclusions, according 16to which no mineral should be so active as thorium or uranium. ”

“ There's a big cylinder of metallic uranium inside, and we play our disintegrating rays on the under surface of this cylinder from those oblique tubes below. When the rays hit the uranium in the cylinder, the atoms explode, and the decomposition products are shot off downward at almost the velocity of light. A back pressure is thus produced which lifts the Ring exactly like a rocket. ”

“ However, such bombs might very well prove to be too heavy for transportation by air.
The United States has only very poor ores of uranium in moderate quantities. There is some good ore in Canada and the former Czechoslovakia, while the most important source of uranium is Belgian Congo. ”

“ But, surrounded by a shield through which no neutron could escape, any mass of material on earth would become an atomic pile!
A single molecule of uranium in any mass of rock will sooner or later disintegrate, giving off high-speed neutrons. Normally they travel indefinitely and are harmless. Some go up into the air and may ionize a single molecule. Some may find a fissionable atom and disrupt it. ”

“ The rays that get out strike the uranium plate and cause the surface layer of molecules to disintegrate, their products being driven off by the atomic explosions with a velocity about equal to that of light, and it's the recoil that deflects and swings the plate. The amount of uranium decomposed in this experiment couldn't be detected by the most delicate balance—small mass, but enormous velocity. See?"
"Yes, I understand," answered Thornton. "It's the old, 'momentum equals mass times velocity,' business we had in mechanics." ”

“ One striking fact about uranium fission was the large amount of energy it released. In general, when a very massive nucleus is converted to a less massive one, energy is released because of the change in the mass defect, as Aston had shown in the 1920s. When the uranium nucleus breaks down through the ordinary radioactive processes to become a less massive lead nucleus, energy is given off accordingly. When, however, it breaks in two to become the much less massive nuclei of barium and krypton (or others in that neighborhood) much more energy is given off. ”

“ The world appeared to have far greater sources of energy than had been expected. The “fossil fuels”—coal, oil and natural gas—were being used at such a rate that many speculated that the gas and oil would be gone in decades and the coal in centuries. Was it possible that uranium might now serve as a new source that would last indefinitely?
It was rather disappointing that it was uranium-235 which underwent fission, because that isotope made up only 0.7% of the uranium that existed. ”

“ Then 2 beta particles are given off so that the thorium-233 becomes first protactinium-233 and then uranium-233.
If a thorium shell surrounds a nuclear reactor, fissionable uranium-233 is formed within it and is easily separated from the thorium. In this way, thorium is also added to the list of earth’s potential nuclear fuels. [4]
If all the uranium and thorium in the earth’s crust (including the thin scattering of those elements through granite, for instance) were available for use, we might get up to 100 times as much energy from it as from all the coal and oil on the planet. ”

“ Solution and Separation.—The compounds of uranium are soluble in acids. Powder the substance and evaporate with an excess of nitric acid. Take up with hydrochloric acid, dilute, pass sulphuretted hydrogen, and filter. Peroxidise the filtrate with a little nitric acid, add an excess of ammonic carbonate and some ammonium sulphide, and filter. Render the solution acid, boil; and precipitate the uranium by means of ammonia. Filter off, and wash it with dilute ammonic chloride. Ignite, and weigh [Pg 313] as protosesqui-oxide, U3O8. ”

“ The disintegration of a gram of uranium, or thorium, or radium, sets free at least a million times as much energy as that which is represented in any known chemical change taking place within a gram weight of any known compound substance. The experiments of the last eight years have then marked a remarkable advance in science in that they have proved the existence of an immense store of subatomic energy. ”

“ One isotope of plutonium, plutonium-239, which resulted from the absorption of a neutron by a 238U nucleus and the emission of two beta particles, was discovered to be as fissionable as 235U and hence theoretically just as feasible for a bomb. Since plutonium is chemically different from uranium, it offered the tremendous advantage that it could readily be concentrated by conventional chemical techniques.
The way to manufacture usable amounts of plutonium, an element that had never before been detected on earth, is to expose uranium to a very intense neutron bombardment. ”

“ The nuclear force is so short-range, it barely reaches from end to end of a large nucleus like that of uranium. Left to itself, it holds together most of the time, but with the added energy of an entering neutron, we might imagine shock waves going through it and turning the nucleus into something like a quivering drop of liquid. Sometimes the uranium nucleus recovers, keeps the neutron, and then goes on to beta-particle emission. And sometimes the nucleus stretches to the point where the nuclear force doesn’t quite hold it together. ”