Fission 84 Isotope

All compounds as well as metallic uranium are radioactive—some more so than others. The main hazard from radioactive isotopes is radiation poisoning. Of course, another potential hazard is using fissionable isotopes of uranium and plutonium for other than peaceful purposes, but such purposes involve pohtical decisions, not science. 

The essential ingredients for producing heat in a thermal fission nuclear reactor are the fuel and a moderator. A heat transport system with its coolant is necessary to convey the heat from the reactor to boilers where steam is produced to drive the turbogenerator. The natural materials available for fuel and moderator are uranium ore and water natural uranium extracted from the ore comprises the fissionable isotope uranium-235 and water contains hydrogen which is a good moderator. (Table I)... 

But nature provides only 0.7% of the fissionable isotope U in natural uranium, the rest being 238u and although the predominant hydrogen isotope in water is a good moderator, it absorbs too many neutrons to allow a reaction to be maintained with the low content of natural uranium. However, the heavy hydrogen... 

Uranium-233, like uranium-235 and plutonium-239, forms a fissionable isotope used as nuclear fuel. This isotope can be made from natural thorium by irradiation with neutrons, as follows ... 

One of the fascinating features of fission power is the breeding of fission fuel from nonfissionable uranium-238. Breeding occurs when small amounts of fissionable isotopes are mixed with uranium-238 in a reactor. Fission liberates neutrons that convert the relatively abundant nonfissionable uranium-238 to uranium-239, which beta-decays to neptunium-239, which in turn beta-decays to fissionable plutonium-239. So in addition to the abundant energy produced, fission fuel is bred from relatively abundant uranium-238 in the process. 

The original reactor built in 1942 was just barely critical because the natural uranium that was used contained less than 1 percent of the fissionable isotope U-235 (half-life 713 million years). What if, in 1942, Earth had been 9 billion years old instead of... 

Uranium (233U) is a fissionable isotope of uranium produced artificially by bombarding thorium-232 with neutrons. Used as an atomic fuel in molten salt reactor and is a possible fuel in breeder reactors. Half-life 1.62 x 105 years. 

The most abundant isotope of uranium, 238U, does not undergo fission. In a breeder reactor, however, a 238U atom captures a neutron and emits two /3 particles to make a fissionable isotope of plutonium, which can then be used as fuel in a nuclear reactor. Write a balanced nuclear equation. 

Of all the elements, fluorine is the most reactive and the most electronegative (a measure of tendency to acquire electrons). In its chemically combined form, it always has an oxidation number of -1. Fluorine has numerous industrial uses, such as the manufacture of UF6, a gas used to enrich uranium in its fissionable isotope, uranium-235. Fluorine is used to manufacture uranium hexafluoride, SF6, a dielectric material contained in some electrical and electronic apparatus. A number of organic compounds contain fluorine, particularly the chlorofluorocarbons used as refrigerants and organofluorine polymers, such as DuPont s Teflon. 

Uranium-233. A second fissionable isotope uranium-233, can be produced from naturally occurring thorium. It does not present an economically attractive option at present because of its dependence on highly enriched U-235 to bring the thorium cycle into operation and the large R D expenditures required... 

At a meeting of the American Physical Society at Columbia University on February 17, 1939, they advanced a theory of uranium fission which postulated that not all the uranium employed as target actually fissioned. They believed that less than one percent of their uranium target disintegrated because only one of the three isotopes of uranium was actually capable of fission. This fissionable isotope first discovered in 1935 by Arthur Dempster of the University of Chicago, has an atomic weight of 235 instead of 238 which is the atomic weight of 99.3% of the uranium mixture found in nature. U-238 is extremely stable its half-life has been estimated to be four billion years. 

Natural uranium contains close to 0.72% by weight of the only fissionable isotope and more than 99% non-fissionable U, and a trace quantity of U. For uranium to be useful as the fuel to the nuclear reactor, the level needs to reach 1 to 5% (more often 3 to 5%) while most of the nuclear weapons and submarines require a concentration of at least 90% The separation of those uranium isotopes, very similar in properties, can not be effected by chemical means. 

In order to develop the atomic bomb, it was necessary to separate the more easily fissionable isotope from Because the natural abundance of is only 0.7%, its isolation... 

Fermi s work made two developments possible (1) the exploitation of nuclear fission for the controlled generation of energy in nuclear reactors and (2) the production of a slow- and fast-neutron fissionable isotope of plutonium, as an... 

Plutonium-239 is the fissionable isotope produced in breeder reactors it is also produced in ordinary nuclear plants and in weapons tests. It is an extremely poisonous substance with a half-life of 24,100 years. 

The fissionable isotopes are U-233, U-235, Pu-239, and Pu-241. The fertile isotopes U-238 and Th-232 are converted to fissionable isotopes by neutron absorption (U-238 into plutonium isotopes and Th-232 into U-233). Natural uranium contains 0.71% U-235, 99.28% U-238, and 0.006% U-234. Fuel enriched in U-233 and plutonium must be produced from thorium and U-238, respectively (Fig. 1) by neutron capture the neutrons are provided initially by fission of U-235. 

Adapted from Radiokhimiya, 11 (2), Zvara I, Chuburkov YuT, Caletka R, Shalaevskii MR, Experiments on chemistry of element 104II. Chemical study of the spontaneous fission isotope, 163-174, 1969, with permission from Academizdat Nauka Publishers. 

Reproduced (adapted) from JINR Report R7-86-322, Domanov VP, Timokhin SN, Zhuikov BL, Chun KS, Eichler B, Chepigin VI, Zvara I, Search for spontaneously fissioning isotopes of elements 107-110 in the products of the interaction of 235U +40 Ar, 1986, with permission from Joint Institute for Nuclear Research. 

Use Source of fissionable isotope uranium-235, source of plutonium by neutron capture, electric power generation. 

The total amount of uranium in the identified reactor zones is estimated to be of the order of 800 tons. Burn-up of the 235U was really astonishing, amounting to about 15,000 megawatt-years of energy released in fission. Isotopic composition of the most depleted ore samples is 0.3% 235U, compared to 0.7% for normal uranium (3,6). Bear in mind that 1.8 billion years ago when the reaction went critical normal uranium contained over 3% 235U, comparable to the enrichment used in modern day reactors. 

The important fissionable isotopes of plutonium and uranium—Pu-239, U-235, and U-233—can be used in controlled chain reactions to produce atomic energy. 

The uranium(IV) oxide, UO2, used as fuel in nuclear power plants has a higher percentage of the fissionable isotope uranium-235 than is present in the UO2 found in nature. To make fuel grade UO2, chemists first convert uranium oxides to uranium hexafluoride, UFg, whose concentration of uranium-235 can be increased by a process called gas diffusion. The enriched UFg is then converted back to UO2 in a series of reactions, beginning with... 

In this manner the nonfissionable uranium-238 is transmuted into the fissionable isotope pIutonium-239 (Figure 23.13). 

Another fertile isotope is 90 Th. Upon capturing slow neutrons, thorium is transmuted to uranium-233, which, like uranium-235, is a fissionable isotope ... 

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