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Fast 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, 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 comparatively rich in fissile material. The fast spectrum is key to breeder reactors, which convert highly abundant uranium-238 into fissile plutonium-239, without requiring enrichment. It also leads to high burnup: many transuranic isotopes, such as of americium and curium, accumulate in thermal reactor spent fuel; in fast reactors they undergo fast fission, reducing total nuclear waste. As a strong fast-spectrum neutron source, they can also be used to transmute existing nuclear waste into manageable or non-radioactive isotopes. These characteristics also cause fast reactors to be judged a higher n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Superphénix
Superphénix (; , SPX) was a nuclear power station prototype on the Rhône river at Creys-Mépieu, Creys-Malville in France, close to the border with Switzerland. Superphénix was a 1,242 MWe fast breeder reactor with the twin goals of reprocessing nuclear fuel from France's line of conventional nuclear reactors, while also being an economical generator of power on its own. , Superphénix remains the largest breeder reactor ever built. Construction began in 1976, the reactor went critical in 1985 and was connected to the grid in 1986. The project suffered cost overruns, delays and enormous public protests. Overall, the reactor totalized a very low operation factor of 14.4%. Despite many technical issues related to being a first-of-a-kind project most of its downtime was caused by administrative procedure: the plant was technically capable of resuming operations but was forbidden to do so. Technical problems were solved over time and, by 1996, the plant had reached an availability ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fissile Material
In nuclear engineering, fissile material is material that can undergo nuclear fission when struck by a neutron of low energy. A self-sustaining thermal chain reaction can only be achieved with fissile material. The predominant neutron energy in a system may be typified by either slow neutrons (i.e., a thermal system) or fast neutrons. Fissile material can be used to fuel thermal-neutron reactors, fast-neutron reactors and nuclear explosives. Fissile vs fissionable The term ''fissile'' is distinct from ''fissionable''. A nuclide that can undergo nuclear fission (even with a low probability) after capturing a neutron of high or low energy is referred to as ''fissionable''. A fissionable nuclide that can undergo fission with a high probability after capturing a low-energy thermal neutron is referred to as ''fissile''. Fissionable materials include those (such as uranium-238) for which fission can be induced only by high-energy neutrons. As a result, fissile materi ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Neutron Source
A neutron source is any device that emits neutrons, irrespective of the mechanism used to produce the neutrons. Neutron sources are used in physics, engineering, medicine, nuclear weapons, petroleum exploration, biology, chemistry, and nuclear power. Neutron source variables include the energy of the neutrons emitted by the source, the rate of neutrons emitted by the source, the size of the source, the cost of owning and maintaining the source, and government regulations related to the source. Small devices Spontaneous fission Some isotopes undergo spontaneous fission (SF) with Neutron emission, emission of neutrons. The most common spontaneous fission source is the isotope californium-252. 252Cf and all other SF neutron sources are made by irradiating uranium or a Transuranium element, transuranic element in a nuclear reactor, where neutrons are absorbed in the starting material and its subsequent reaction products, transmuting the starting material into the SF isotope. 252Cf n ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Nuclear Waste
Radioactive waste is a type of hazardous waste that contains radioactive material. It is a result of many activities, including nuclear medicine, nuclear research, nuclear power generation, nuclear decommissioning, rare-earth mining, and nuclear weapons reprocessing. The storage and disposal of radioactive waste is regulated by government agencies in order to protect human health and the environment. Radioactive waste is broadly classified into 3 categories: low-level waste (LLW), such as paper, rags, tools, clothing, which contain small amounts of mostly short-lived radioactivity; intermediate-level waste (ILW), which contains higher amounts of radioactivity and requires some shielding; and high-level waste (HLW), which is highly radioactive and hot due to decay heat, thus requiring cooling and shielding. Spent nuclear fuel can be processed in nuclear reprocessing plants. One third of the total amount have already been reprocessed. With nuclear reprocessing 96% of the spent fue ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fast Fission
Fast fission is fission that occurs when a heavy atom absorbs a high-energy neutron, called a fast neutron, and splits. Most fissionable materials need thermal neutrons, which move more slowly. Fast reactors vs. thermal reactors Fast neutron reactors use fast fission to produce energy, unlike most nuclear reactors. In a conventional reactor, a moderator is needed to slow down the neutrons so that they are more likely to fission atoms. A fast neutron reactor uses fast neutrons, so it does not use a moderator. Moderators may absorb a lot of neutrons in a thermal reactor, and fast fission produces a higher average number of neutrons per fission, so fast reactors have better neutron economy making a plutonium breeder reactor possible. However, a fast neutron reactor must use relatively highly enriched uranium or plutonium at the reactor startup so that the neutrons have a better chance of fissioning atoms. Fissionable but not fissile Some atoms, notably uranium-238, do not usua ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Spent 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 will have different isotopic constituents than when it started. Nuclear fuel rods become progressively more radioactive (and less thermally useful) due to neutron activation as they are fissioned, or "burnt", in the reactor. A fresh rod of low enriched uranium pellets (which can be safely handled with gloved hands) will become a highly lethal gamma emitter after 1–2 years of core irradiation, unsafe to approach unless under many feet of water shielding. This makes their invariable accumulation and safe temporary storage in spent fuel pools a prime source of high level radioactive waste and a major ongoing issue for future permanent disposal. Nature of spent fuel Nanomaterial pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Curium
Curium is a synthetic chemical element; it has symbol Cm and atomic number 96. This transuranic actinide element was named after eminent scientists Marie and Pierre Curie, both known for their research on radioactivity. Curium was first intentionally made by the team of Glenn T. Seaborg, Ralph A. James, and Albert Ghiorso in 1944, using the cyclotron at Berkeley. They bombarded the newly discovered element plutonium (the isotope 239Pu) with alpha particles. This was then sent to the Metallurgical Laboratory at University of Chicago where a tiny sample of curium was eventually separated and identified. The discovery was kept secret until after the end of World War II. The news was released to the public in November 1947. Most curium is produced by bombarding uranium or plutonium with neutrons in nuclear reactors – one tonne of spent nuclear fuel contains ~20 grams of curium. Curium is a hard, dense, silvery metal with a high melting and boiling point for an actinide. It ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Americium
Americium is a synthetic element, synthetic chemical element; it has Chemical symbol, symbol Am and atomic number 95. It is radioactive and a transuranic member of the actinide series in the periodic table, located under the lanthanide element europium and was thus named after the Americas by analogy. Americium was first produced in 1944 by the group of Glenn T. Seaborg from Berkeley, California, at the Metallurgical Laboratory of the University of Chicago, as part of the Manhattan Project. Although it is the third element in the transuranic series, it was discovered fourth, after the heavier curium. The discovery was kept secret and only released to the public in November 1945. Most americium is produced by uranium or plutonium being bombarded with neutrons in nuclear reactors – one tonne of spent nuclear fuel contains about 100 grams of americium. It is widely used in commercial ionization chamber smoke detectors, as well as in neutron sources and industrial gauges. Several u ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Isotopes
Isotopes are distinct nuclear species (or ''nuclides'') of the same chemical element. They have the same atomic number (number of protons in their nuclei) and position in the periodic table (and hence belong to the same chemical element), but different nucleon numbers (mass numbers) due to different numbers of neutrons in their nuclei. While all isotopes of a given element have similar chemical properties, they have different atomic masses and physical properties. The term isotope is derived from the Greek roots isos ( ἴσος "equal") and topos ( τόπος "place"), meaning "the same place"; thus, the meaning behind the name is that different isotopes of a single element occupy the same position on the periodic table. It was coined by Scottish doctor and writer Margaret Todd in a 1913 suggestion to the British chemist Frederick Soddy, who popularized the term. The number of protons within the atom's nucleus is called its atomic number and is equal to the number of el ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Transuranic
The transuranium (or transuranic) elements are the chemical elements with atomic number greater than 92, which is the atomic number of uranium. All of them are radioactively unstable and decay into other elements. Except for neptunium and plutonium, which have been found in trace amounts in nature, none occur naturally on Earth and they are synthetic. Overview Of the elements with atomic numbers 1 to 92, most can be found in nature, having stable isotopes (such as oxygen) or very long-lived radioisotopes (such as uranium), or existing as common decay products of the decay of uranium and thorium (such as radon). The exceptions are technetium, promethium, astatine, and francium; all four occur in nature, but only in very minor branches of the uranium and thorium decay chains, and thus all save francium were first discovered by synthesis in the laboratory rather than in nature. All elements with higher atomic numbers have been first discovered in the laboratory, with neptunium a ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Burnup
In nuclear power technology, burnup is a measure of how much energy is extracted from a given amount of nuclear fuel. It may be measured as the fraction of fuel atoms that underwent fission in %FIMA (fissions per initial heavy metal atom) or %FIFA (fissions per initial fissile atom) as well as the actual energy released per mass of initial fuel in gigawatt-days/ metric ton of heavy metal (GWd/tHM), or similar units. The amount of initial fuel in the denominator is defined as all uranium, plutonium, and thorium isotopes, not including alloying or other chemical compounds or mixtures in the fuel charge. 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 are not). In reactor operations, this percentage is difficult to measure, so the alternative ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Uranium Enrichment
Enriched uranium is a type of uranium in which the percent composition of uranium-235 (written 235U) has been increased through the process of isotope separation. Naturally occurring uranium is composed of three major isotopes: uranium-238 (238U with 99.2732–99.2752% natural abundance), uranium-235 (235U, 0.7198–0.7210%), and uranium-234 (234U, 0.0049–0.0059%). 235U is the only nuclide existing in nature (in any appreciable amount) that is fissile with thermal neutrons. Enriched uranium is a critical component for both civil nuclear power generation and military nuclear weapons. Low-enriched uranium (20% 235U, typically >85%) is used for the cores of many nuclear weapons, as well as compact reactors for naval propulsion and research, as well as breeder reactors. There are about 2,000 tonnes of highly enriched uranium in the world. Enrichment methods were first developed on a large scale by the Manhattan Project. Its gaseous diffusion method was used in the 194 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
