Реферат: Uranium Essay Research Paper BackgroundUranium is a
Uranium Essay, Research Paper
Uranium is a hard, dense, malleable, ductile, silver-white element that has a symbol of U and atomic number of 92. It is chemically radioactive metallic element. Uranium is a member of the actinide series in group IIIb of the periodic table. It melts at about 1132 X C, boils at about 3818 X C, and has a specific gravity of 19.05 at 25 X C. Uranium is very dense and at about 19 grams per cubic centimeter, it is 1.6 times more dense than lead. The atomic weight of the element is 238.03. It is a highly reactive metal and reacts with almost all the nonmetallic elements and their compounds, especially at elevated temperatures. It dissolves readily in nitric and hydrochloric acids but is insoluble in alkalis. Uranium never occurs naturally in the free state but is found as an oxide or complex salt in minerals such as pitchblende and carnotite. It ranks about 48th in natural abundance in crustal rocks. It is a fairly abundant element in the earth’s crust, being about 40 times as abundant as silver. Several hundred uranium-containing minerals have been found but only a few are commercially significant. Pure uranium consists of more than 99 percent of the isotope uranium-238 (half-life 4.5 +109 years), less than 1 percent of the fissile isotope uranium-235 (half-life 7 +108 years), and a trace of uranium-234 (half-life 2.5 +105 years), formed by radioactive decay of uranium-238. Among the artificially produced isotopes of uranium are uranium-233, uranium-237, and uranium-239. Isotopes ranging from mass number 222 to 242 are known.
Uranium was discovered in 1789 in pitchblende by the German chemist Martin Heinrich Klaproth, who isolated an oxide of uranium while analyzing pitchblende samples from the Joachimsal silver mines in the former Kingdom of Bohemia, located in the present day Czech Republic and named it after the planet Uranus that was discovered only eight years earlier. However, the substance that Klaproth identified was not pure uranium but an oxide. It was first isolated fifty years later in the metallic state in 1841 by Peligot. The radioactive properties of uranium were first demonstrated about a century later from the first discover of this element in 1896 when the French physicist Antoine Henri Becquerel produced, by the action of the fluorescent salt potassium uranyl sulfate, an image on a photographic plate covered with a light-absorbing substance. Deposits of pitchblende, the richest uranium ore, are found chiefly in Canada, the Democratic Republic of the Congo and the United States. Most of the uranium mined in the United States is obtained from carnotite occurring in Colorado, Utah, New Mexico, Arizona, and Wyoming. A mineral called coffinite, discovered in 1955 in Colorado, is a high-grade ore containing nearly 61 percent uranium. The U.S. production of pure uranium concentrate was about 3417 metric tons, while Canadian production was about 8729 tons; world production totaled about 29,100 metric tons.
In 1938, Enrico Fermie at the University of Chicago produced the first self-sustaining nuclear chain reaction with uranium. This discovery paved the way for the development of the atomic bomb by those involved in the Manhattan Project. The scientists involved in the Manhattan project, and those whose previous work contributed to it had to go through many steps to come to the desired end, having an atomic bomb to use against Germany and Japan. Before the discovery of nuclear fission, the principal use of uranium (chiefly as the oxides) was in pigments, ceramic glazes, and a yellow-green fluorescent glass and as a source of radium for medical purposes. It has also been added to steels to increase their strength and toughness. However, because of the high toxicity both chemical and radiological of uranium and its compounds, and because of their importance as nuclear fuel, these earlier uses have been largely reduced. After the discovery of nuclear fission, uranium became an important metal, and its uses were at first restricted mainly to the production of nuclear weapons. In 1954 the United States government relaxed controls to permit leasing of uranium enriched in the isotope uranium-235 to various private and foreign agencies for the development of nuclear power. The first such U.S. plant, which started development at Shippingport, Pennsylvania, generates 60,000 KW and requires about 15 lb of uranium-235 per month. Conventional plants producing 60,000 KW consume about 40 million lb of coal per month. During peacetime, nuclear power is uranium’s only use aside from aiding in some medical research. But uranium’s claim to fame was the atomic bomb.
Uranium gained importance with the development of practical uses of nuclear energy. Uranium-235 can be separated from uranium-238 by a diffusion process using the gaseous hexafluoride. The potentiality of uranium as a vast source of industrial power became apparent with the launching in 1954 of the first nuclear-powered submarine, the USS Nautilus, much more useful then it being used in pigments and ceramic glazes. Uranium s potential for use, as an energy source was not manifested until the mid-20th century. By 1989, 112 nuclear power plants in the United States produced more than 101,000 megawatts electric, MW(E). In addition, there are 316 plants in 40 countries outside the United States which produced more than 213,000 MW(E). Now it is used to power nuclear reactors that produce electricity and for isotopes used for medical, industrial, and defense purposes around the world. Despite the usefulness of uranium, at the moment it is not a practical source of energy due to the problems associated with it. Uranium continues to produce dangerous radiation for a long time after it has been used. Problems of uranium also include scarcity, plant safety, and storage of radioactive uranium and plutonium waste products, however, have prevented the full realization of nuclear energy’s potential.
Me and My Element
Uranium is very important in my life, it provides energy to homes and businesses around the world, but the major downside of uranium is that if in the wrong hands, can be destructive or possibly cause nuclear world war. One such result of the destructive behavior of uranium is when the number 4 reactor at Chernobyl exploded in 1987 these radioactive elements where deposited in the environment. Strong winds that were constantly shifting directions caused the fallout to cover twenty countries in about six days. There were 600 population areas that had to be decontaminated. Frequently after 1987, areas outside of the exclusion zone, which some estimates have as large as 30,000 km, were coming up contaminated. Each time it rained anywhere within 100 km around the outside of the exclusion zone heavy radioactive contamination occurred in that area. Another is the United States attacking the Japanese with the first Atomic Bomb in two cities of Japan killing thousands and creating contamination throughout. Uranium s role in human history is rather ironic. It was used in the Second World War as a weapon that would kill thousands, but ensure peace. Since then it has been a practical deterrent for other wars. But the increasing number of countries having nuclear could cause a dangerous war with uranium bombs. Should the nations of the world stop making bombs and destroy what we have or should we keep our supply to ensure our safety? Also as a power source it’s capacity is almost infinite. However, do the risks involved outweigh the possible good? The world supply of other natural fuel is limited and decreasing, what will we do after that? Uranium can be a key to the future but can also destroy it too. These questions and issues make uranium quite a controversial element and one that affects the fate mankind directly.