Nuclear Fuel Sources

Nuclear power plants are based on uranium mined in surface mines, or by in situ leaching. 

Nuclear energy has been used to produce electricity for more than half a century. Worldwide, nuclear energy accounts for 6% of energy and 16% of electricity, and 23% in OECD countries (UNDP, 2004). OECD countries prodnce almost 55% of the world s uranium. The global nuclear energy consumption increased rapidly from 0.1% in 1970 to 7.4% in 1998. This increase was especially high in the 1980s. 

Fissile materials are defined as materials that are fissionable by nentrons with zero kinetic energy. In nuclear engineering, a fissile material is one that is capable of snstaining a chain reaction of nuclear fission Nuclear power reactors are mainly fueled with manium, the heaviest element that occurs in natnre in more than trace qnantities. The principal nuclear energy soiuces are maninm-235, plutonium-239, uranium-233 and thorium. 

The essence of a conventional nuclear reactor is the controlled fission chain reaction of U-235 and Pn-239. This produces heat, which is used to make steam which drives a turbine. The chain reaction depends on having a surplus of neutrons to keep it going. 

Work has been done in developing thorium cycle converter-reactor systems. Several prototypes, including the high-temperature gas-cooled reactor (HTGR) and molten salt converter reactor experiment (MSRE), have operated. While the HTGR reactors are efficient, they are not expected to become important commercially for many years because of certain operating difficulties. Thorium is recovered commercially from the mineral monazite, which contains from 3 to 9% ThO along with rare-earth minerals. Much of the internal heat the Earth produces has been attributed to thorium and uranium. 

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When a star runs out of nuclear fuel it contracts until either the temperature becomes high enough to ignite another nuclear fuel source or until electron-degeneracy provides sufficient pressure to restore hydrostatic equilibrium. Recall the hydrostatic equilibrium and mass continuity equations ... 

With the use of Cs source tomographic layer-by-layer study of nuclear fuel within a range of 5 to 12 g/sm is conducted. In the specialized tomograph the initial information measurement time is 5-30 min, the tomograms restoration time is 4-10 min. The sensitivity to a various density is about 5% when detecting local areas with a diameter exceeding 0.5mm. 

In the early years of reactor development, electricity from nuclear sources was expected to be much cheaper than that from other sources. Whereas nuclear fuel cost is low, the operating and maintenance costs of a nuclear faciHty are high. Thus on average, electric power from coal and nuclear costs about the same. 

The isotope plutonium-238 [13981 -16-3] Pu, is of technical importance because of the high heat that accompanies its radioactive decay. This isotope has been and is being used as fuel in small terrestrial and space nuclear-powered sources (3,4). Tu-based radioisotope thermal generator systems dehvered 7 W/kg and cost 120,000/W in 1991 (3). For some time, %Pu was considered to be the most promising power source for the radioisotope-powered artificial heart and for cardiovascular pacemakers. Usage of plutonium was discontinued, however, after it was determined that adequate elimination of penetrating radiation was uncertain (5) (see PROSTHETIC AND BIOMEDICAL devices). 

SEALED SOURCE A soui ce Containing any radioactive substance whose structure is such as to prevent, under normal conditions of use, any dispersion of radioactive substances into the envu onment, but it does not include any radioactive substance inside a nuclear reactor or any nuclear fuel element. 

Apart from g Pu, which is a nuclear fuel and explosive, the transuranium elements have in the past been produced mainly for research purposes. A number of specialized applications, however, have led to more widespread uses. I Pu (produced by neutron bombardment of I Np to form 93 Np which decays by jS-emission to 94Pu) is a compact heat source (0.56 Wg as it decays by a-emission) which, in conjunction with PbTe thermoelectric elements, for instance, provides a stable and totally reliable source of electricity with no moving parts. It has been... 

Uranium is used as the primai-y source of nuclear energy in a nuclear reactor, although one-third to one-half of the power will be produced from plutonium before the power plant is refueled. Plutonium is created during the uranium fission cycle, and after being created will also fission, contributing heat to make steam in the nuclear power plant. These two nuclear fuels are discussed separately in order to explore their similarities and differences. Mixed oxide fuel, a combination of uranium and recovered plutonium, also has limited application in nuclear fuel, and will be briefly discussed. 

SOURCE Uranium Inslilule, Core Issues 3/98 and Uranium Insiiiule, 1998, Global Nuclear Fuel Market, Supply Demand 1998-2020. 

HLW comprises most of the radioactivity associated with nuclear waste. Because that designation can cover radioactive waste from more than one source, the term spent nuclear fuel (SNF) will be used to discuss HLW originating from commercial nuclear reactors. LLW comprises nearly 90 percent of the volume of nuclear waste but little of the radioactivity. Nuclear power reactors produce SNF and most of the nation s LLW, although there are approximately 20,000 different sources of LLW. The name SNF is a bit of a misnomer because it implies that there is no useful material left in the fuel, when in fact some fissionable material is left in it. 

Nuclear fuel cycle, 77 545-547 safety principles and, 17 546-547 Nuclear fuel reprocessing, 10 789-790 Nuclear fuel reserves, 17 518-530 alternative sources of, 17 527 economic aspects of, 17 526-527 toxicology of uranium, 17 528-529 uranium mineral resources, 17 518-521, 522-525... 

The transition from nonrenewable fossil fuel should consider the development of technologies that can use the available energy of the sun. It is reasonable to assume that solar energy will eventually serve as a primary energy source. As we attempt to use solar energy to replace the use of fossil and nuclear fuels, this relationship between solar energy and hydrogen returns and one may not effectively work without the other. 

In New York state a reprocessing plant near Buffalo began to reprocess nuclear wastes in 1966. After 6 years Nuclear Fuel Services (NFS), a subsidiary of W.R. Grace s Davison Chemical Company, abandoned the facility. There were 2 million cubic feet of radioactive material left behind along with 600,000 gallons of radioactive liquid waste that was seeping into a creek that flows into Lake Erie the source of drinking water for Buffalo. The cost of cleanup was estimated to be 1 billion. 

Uranium production does have a notable impact on ozone depletion. The Environmental Protection Agency s (EPA) Toxic Release Inventory showed that in 1999, the nation s two commercial nuclear fuel-manufacturing plants released 88% of the ozone-depleting chemical CFC-11 by industrial sources in the U.S. and 14% of the discharges in the whole world. 

The development of thorium-based nuclear power cycles still faces various problems and requires much more R D to be commercialised. As a nuclear fuel, thorium could play a more important role in the coming decades, partly as it is more abundant on Earth than uranium and also because mined thorium has the potential to be used completely in nuclear reactors, compared with the 0.7% of natural uranium. Its future use as a nuclear source of energy will, however, depend greatly on the technological developments currently investigated in various parts of the world and the availability of and access to conventional uranium resources. 

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