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Burnup
In nuclear power technology, burnup (also known as fuel utilization) is a measure of how much energy is extracted from a primary nuclear fuel source. It is measured as the fraction of fuel atoms that underwent fission in %FIMA (fissions per initial metal atom) or %FIFA (fissions per initial fissile atom) as well as, preferably, the actual energy released per mass of initial fuel in gigawatt-days/metric ton of heavy metal (GWd/tHM), or similar units. Measures of burnup Expressed as a percentage: if 5% of the initial heavy metal atoms have undergone fission, the burnup is 5%FIMA. If these 5% were the total of 235U that were in the fuel at the beginning, the burnup is 100%FIFA (as 235U is fissile and the other 95% heavy metals like 238U not). In reactor operations, this percentage is difficult to measure, so the alternative definition is preferred. This can be computed by multiplying the thermal power of the plant by the time of operation and dividing by the mass of the initial f ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Plutonium
Plutonium is a radioactive chemical element with the symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, and forms a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation states. It reacts with carbon, halogens, nitrogen, silicon, and hydrogen. When exposed to moist air, it forms oxides and hydrides that can expand the sample up to 70% in volume, which in turn flake off as a powder that is pyrophoric. It is radioactive and can accumulate in bones, which makes the handling of plutonium dangerous. Plutonium was first synthetically produced and isolated in late 1940 and early 1941, by a deuteron bombardment of uranium-238 in the cyclotron at the University of California, Berkeley. First, neptunium-238 ( half-life 2.1 days) was synthesized, which subsequently beta-decayed to form the new element with atomic number 94 and atomic weight 238 (half-life 88 years). Since ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Online Refuelling
In nuclear power technology, online refuelling is a technique for changing the fuel of a nuclear reactor while the reactor is critical. This allows the reactor to continue to generate electricity during routine refuelling, and therefore improve the availability and profitability of the plant. Benefits of online refuelling Online refuelling allows a nuclear reactor to continue to generate electricity during periods of routine refuelling, and therefore improves the availability and therefore the economy of the plant. Additionally, this allows for more flexibility in reactor refuelling schedules, exchanging a small number of fuel elements at a time rather than high-intensity offline refuelling programmes. The ability to refuel a reactor while generating power has the greatest benefits where refuelling is required at high frequency, for example during the production of plutonium suitable for nuclear weapons during which low-burnup fuel is required from short irradiation periods in ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fission Product
Nuclear fission products are the atomic fragments left after a large atomic nucleus undergoes nuclear fission. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons, the release of heat energy (kinetic energy of the nuclei), and gamma rays. The two smaller nuclei are the ''fission products''. (See also Fission products (by element)). About 0.2% to 0.4% of fissions are ternary fissions, producing a third light nucleus such as helium-4 (90%) or tritium (7%). The fission products themselves are usually unstable and therefore radioactive. Due to being relatively neutron-rich for their atomic number, many of them quickly undergo beta decay. This releases additional energy in the form of beta particles, antineutrinos, and gamma rays. Thus, fission events normally result in beta and gamma radiation, even though this radiation is not produced directly by the fission event itself. The produced radionuclides have va ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Fuel
Nuclear fuel is material used in nuclear power stations to produce heat to power turbines. Heat is created when nuclear fuel undergoes nuclear fission. Most nuclear fuels contain heavy fissile actinide elements that are capable of undergoing and sustaining nuclear fission. The three most relevant fissile isotopes are uranium-233, uranium-235 and plutonium-239. When the unstable nuclei of these atoms are hit by a slow-moving neutron, they frequently split, creating two daughter nuclei and two or three more neutrons. In that case, the neutrons released go on to split more nuclei. This creates a self-sustaining chain reaction that is controlled in a nuclear reactor, or uncontrolled in a nuclear weapon. Alternatively, if the nucleus absorbs the neutron without splitting, it creates a heavier nucleus with one additional neutron. The processes involved in mining, refining, purifying, using, and disposing of nuclear fuel are collectively known as the nuclear fuel cycle. Not ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fast-neutron Reactor
A fast-neutron reactor (FNR) or fast-spectrum reactor or simply a fast reactor is a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons (carrying energies above 1 MeV or greater, on average), as opposed to slow thermal neutrons used in thermal-neutron reactors. Such a fast reactor needs no neutron moderator, but requires fuel that is relatively rich in fissile material when compared to that required for a thermal-neutron reactor. Around 20 land based fast reactors have been built, accumulating over 400 reactor years of operation globally. The largest of this was the Superphénix Sodium cooled fast reactor in France that was designed to deliver 1,242 MWe. Fast reactors have been intensely studied since the 1950s, as they provide certain decisive advantages over the existing fleet of water cooled and water moderated reactors. These are: * More neutrons are produced when a fission occurs, resulting from the absorption of a fast neutron, t ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uranium-238
Uranium-238 (238U or U-238) is the most common isotope of uranium found in nature, with a relative abundance of 99%. Unlike uranium-235, it is non-fissile, which means it cannot sustain a chain reaction in a thermal-neutron reactor. However, it is fissionable by fast neutrons, and is ''fertile'', meaning it can be transmuted to fissile plutonium-239. 238U cannot support a chain reaction because inelastic scattering reduces neutron energy below the range where fast fission of one or more next-generation nuclei is probable. Doppler broadening of 238U's neutron absorption resonances, increasing absorption as fuel temperature increases, is also an essential negative feedback mechanism for reactor control. Around 99.284% of natural uranium's mass is uranium-238, which has a half-life of 1.41 seconds (4.468 years, or 4.468 billion years). Due to its natural abundance and half-life relative to other radioactive elements, 238U produces ~40% of the radioactive heat pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Fuel Cycle
The nuclear fuel cycle, also called nuclear fuel chain, is the progression of nuclear fuel through a series of differing stages. It consists of steps in the ''front end'', which are the preparation of the fuel, steps in the ''service period'' in which the fuel is used during reactor operation, and steps in the ''back end'', which are necessary to safely manage, contain, and either reprocess or dispose of spent nuclear fuel. If spent fuel is not reprocessed, the fuel cycle is referred to as an ''open fuel cycle'' (or a ''once-through fuel cycle''); if the spent fuel is reprocessed, it is referred to as a ''closed fuel cycle''. Basic concepts Nuclear power relies on fissionable material that can sustain a chain reaction with neutrons. Examples of such materials include uranium and plutonium. Most nuclear reactors use a moderator to lower the kinetic energy of the neutrons and increase the probability that fission will occur. This allows reactors to use material with far lower c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spent Nuclear Fuel
Spent nuclear fuel, occasionally called used nuclear fuel, is nuclear fuel that has been irradiated in a nuclear reactor (usually at a nuclear power plant). It is no longer useful in sustaining a nuclear reaction in an ordinary thermal reactor and depending on its point along the nuclear fuel cycle, it may have considerably different isotopic constituents. The term "fuel" is slightly confusing, as it implies a combustion of some type, which does not occur in a nuclear power plant. Nevertheless, this term is generally accepted. Nature of spent fuel Nanomaterial properties In the oxide fuel, intense temperature gradients exist that cause fission products to migrate. The zirconium tends to move to the centre of the fuel pellet where the temperature is highest, while the lower-boiling fission products move to the edge of the pellet. The pellet is likely to contain many small bubble-like pores that form during use; the fission product xenon migrates to these voids. Some of this xen ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
World Nuclear Association
World Nuclear Association is the international organization that promotes nuclear power and supports the companies that comprise the global nuclear industry. Its members come from all parts of the nuclear fuel cycle, including uranium mining, uranium conversion, uranium enrichment, nuclear fuel fabrication, plant manufacture, transport, and the disposition of used nuclear fuel as well as electricity generation itself. Together, World Nuclear Association members are responsible for 70% of the world's nuclear power as well as the vast majority of world uranium, conversion and enrichment production. The Association says it aims to fulfill a dual role for its members: Facilitating their interaction on technical, commercial and policy matters and promoting wider public understanding of nuclear technology. It has a secretariat of around 30 staff. The Association was founded in 2001 on the basis of the Uranium Institute, itself founded in 1975. Membership World Nuclear Associatio ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
EBR-II
Experimental Breeder Reactor-II (EBR-II) is a sodium-cooled fast reactor designed, built and operated by Argonne National Laboratory at the National Reactor Testing Station in Idaho.Experimental Breeder Reactor II Argonne National Laboratory It was shut down in 1994. Custody of the reactor was transferred to after its founding in 2005. Initial operations began in July 1964 and it achieved criticality in 1965 at a total cost of more than US$32 million ($ in dollars). The original emphasis in the design and operation of EBR-II was to demonstrate a complete breeder-reactor power plant with on-site reprocessing of solid metallic fuel. Fuel elements e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Power
Nuclear power is the use of nuclear reactions to produce electricity. Nuclear power can be obtained from nuclear fission, nuclear decay and nuclear fusion reactions. Presently, the vast majority of electricity from nuclear power is produced by nuclear ''fission'' of uranium and plutonium in nuclear power plants. Nuclear ''decay'' processes are used in niche applications such as radioisotope thermoelectric generators in some space probes such as ''Voyager 2''. Generating electricity from ''fusion'' power remains the focus of international research. Most nuclear power plants use thermal reactors with enriched uranium in a once-through fuel cycle. Fuel is removed when the percentage of neutron absorbing atoms becomes so large that a chain reaction can no longer be sustained, typically three years. It is then cooled for several years in on-site spent fuel pools before being transferred to long term storage. The spent fuel, though low in volume, is high-level radioactive wa ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Argonne National Laboratory
Argonne National Laboratory is a science and engineering research national laboratory operated by UChicago Argonne LLC for the United States Department of Energy. The facility is located in Lemont, Illinois, outside of Chicago, and is the largest national laboratory by size and scope in the Midwest. Argonne had its beginnings in the Metallurgical Laboratory of the University of Chicago, formed in part to carry out Enrico Fermi's work on nuclear reactors for the Manhattan Project during World War II. After the war, it was designated as the first national laboratory in the United States on July 1, 1946. In the post-war era the lab focused primarily on non-weapon related nuclear physics, designing and building the first power-producing nuclear reactors, helping design the reactors used by the United States' nuclear navy, and a wide variety of similar projects. In 1994, the lab's nuclear mission ended, and today it maintains a broad portfolio in basic science research, e ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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