Nuclear Fuel Process

A graph comparing nucleon number against binding energy

Nuclear fuel is any material that can be consumed to derive nuclear energy, by analogy to chemical fuel that is burned to derive energy. The mass number ( A) also called atomic mass number or nucleon number, is the total number of Protons and Neutrons (together known as Binding energy is the Mechanical energy required to disassemble a whole into separate parts Nuclear Energy is released by the splitting (fission or merging together (fusion of the nuclei of Atom (s Fuel is any material that is burned or altered in order to obtain energy Combustion or burning is a complex sequence of Exothermic chemical reactions between a Fuel and an Oxidant accompanied by the production of By far the most common type of nuclear fuel is heavy fissile elements that can be made to undergo nuclear fission chain reactions in a nuclear fission reactor; nuclear fuel can refer to the material or to physical objects (for example fuel bundles composed of fuel rods) composed of the fuel material, perhaps mixed with structural, neutron moderating, or neutron reflecting materials. In Nuclear engineering, a fissile material is one that is capable of sustaining a Chain reaction of Nuclear fission. Nuclear fission is the splitting of the nucleus of an atom into parts (lighter nuclei) often producing Free neutrons and other smaller nuclei which may A chain reaction is a sequence of Reactions where a reactive product or by-product causes additional reactions to take place This article is a subarticle of Nuclear power. A nuclear reactor is a device in which Nuclear chain reactions are initiated controlled Nuclear fuel is any material that can be consumed to derive Nuclear energy, by analogy to chemical Fuel that is burned to derive energy In Nuclear engineering, a neutron moderator is a medium which reduces the velocity of Fast neutrons thereby turning them into Thermal neutrons capable The most common fissile nuclear fuels are ²³⁵U and ²³⁹Pu, and the actions of mining, refining, purifying, using, and ultimately disposing of these elements together make up the nuclear fuel cycle, which is important for its relevance to nuclear power generation and nuclear weapons. Uranium-235 is an isotope of uranium that differs from the element's other common isotope Uranium-238, by its ability to cause a rapidly expanding fission Plutonium-239 is an Isotope of Plutonium. Plutonium-239 is the primary Fissile isotope used for the production of Nuclear weapons although The nuclear fuel cycle, also called nuclear fuel chain, is the progression of Nuclear fuel through a series of differing stages Nuclear power is any Nuclear technology designed to extract usable Energy from atomic nuclei via controlled Nuclear reactions A nuclear weapon is an explosive device that derives its destructive force from Nuclear reactions either fission or a combination of fission and fusion.

Not all nuclear fuels are used in fission chain reactions. For example, ²³⁸Pu and some other elements are used to produce small amounts of nuclear power by radioactive decay in radiothermal generators, and other atomic batteries. Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation. A radioisotope thermoelectric generator ( RTG, RITEG) is an Electrical generator which obtains its power from Radioactive decay. The terms atomic battery, nuclear battery, tritium battery and radioisotope battery are used to describe a device which uses the emissions from a Radioactive Light isotopes such as ³H (tritium) are used as fuel for nuclear fusion. Tritium (ˈtɹɪtiəm symbol or, also known as Hydrogen-3) is a radioactive Isotope of Hydrogen. In Physics and Nuclear chemistry, nuclear fusion is the process by which multiple- like charged atomic nuclei join together to form a heavier nucleus If one looks at binding energy of specific isotopes, there can be an energy gain from fusing most elements with a lower atomic number than iron, and fissioning isotopes with a higher atomic number than iron. Binding energy is the Mechanical energy required to disassemble a whole into separate parts Isotopes (Greek isos = "equal" tópos = "site place" are any of the different types of atoms ( Nuclides

Oxide fuel

The thermal conductivity of uranium dioxide is low; it is affected by porosity and burn-up. In Physics, thermal conductivity, k is the property of a material that indicates its ability to conduct Heat. Porosity is a measure of the void spaces in a material and is measured as a fraction between 0–1 or as a Percentage between 0–100% The burn-up results in fission products being dissolved in the lattice (such as lanthanides), the precipitation of fission products such as palladium, the formation of fission gas bubbles due to fission products such as xenon and krypton and radiation damage of the lattice. Fission products are the atomic fragments left after a large nucleus fissions. Terminology The Trivial name " Rare earths " is sometimes used to describe all the lanthanoids together with Scandium and Yttrium Palladium (pronounced \pəˈleɪdiəm\ is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it palladium after the Xenon (ˈzɛnɒn or) is a Chemical element represented by the symbol Xe. Krypton (ˈkrɪptən or /ˈkrɪptɒn/ from kryptos "hidden" is a Chemical element with the symbol Kr and Atomic number 36 The low thermal conductivity can lead to overheating of the center part of the pellets during use. The porosity results in a decrease in both the thermal conductivity of the fuel and the swelling which occurs during use.

According to the International Nuclear Safety Center [1] the thermal conductivity of uranium dioxide can be predicted under different conditions by a series of equations. The International Nuclear Safety Center ( INSC) which operates under the guidance of the Director of International Nuclear Safety and Cooperation (NN-30 in the United States

The bulk density of the fuel can be related to the thermal conductivity

Where ρ is the bulk density of the fuel and ρ_td is the theoretical density of the uranium dioxide. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different Uranium dioxide (2 an Oxide of Uranium, also known as urania or uranic oxide is a black radioactive crystalline powder

Then the thermal conductivity of the porous phase (K_f)is related to the conductivity of the perfect phase (K_o, no porosity) by the following equation. Note that s is a term for the shape factor of the holes.

K_f = K_o. (1-p/1+(s-1)p)

Rather than measuring the thermal conductivity using the traditional methods in physics such as lees's disk, the Forbes' method or Searle's bar it is common to use a laser flash method where a small disc of fuel is placed in a furnace. Two classes of methods exist to measure the thermal conductivity of a sample steady-state and non-steady-state methods After being heated to the required temperature one side of the disc is illuminated with a laser pulse, the time required for the heat wave to flow through the disc, the density of the disc, and the thickness of the disk can then be used to calculated to give the thermal conductivity.

λ = ρC_pα

• λ thermal conductivity
• ρ density
• C_p heat capacity
• α thermal diffusivity

If t_1/2 is defined as the time required for the non illuminated surface to experience half its final temperature rise then. In Physics, thermal conductivity, k is the property of a material that indicates its ability to conduct Heat. The density of a material is defined as its Mass per unit Volume: \rho = \frac{m}{V} Different materials usually have different Specific heat capacity, also known simply as specific heat, is the measure of the heat energy required to increase the Temperature of a unit quantity In Heat transfer analysis thermal diffusivity (symbol \alpha\ but note that the symbols \kappa D and k are all commonly

α = 0. 1388 L² / t_1/2

L is the thickness of the disc

For details see [2]

UOX

The thermal conductivity of zirconium metal and uranium dioxide as a function of temperature

Uranium dioxide is a black semiconductor solid. Uranium dioxide (2 an Oxide of Uranium, also known as urania or uranic oxide is a black radioactive crystalline powder A semiconductor' is a Solid material that has Electrical conductivity in between a conductor and an insulator; it can vary over that It can be made by reacting uranyl nitrate with a base (ammonia) to form a solid (ammonium uranate). The uranyl ion is the dipositive Cation 2+, which forms salts with acids Ammonia is a compound with the formula N[[hydrogen H3]] It is normally encountered as a Gas with a characteristic pungent Odor It is heated (calcined) to form U₃O₈ that can than be converted by heating in an argon / hydrogen mixture (700 ^oC) to form UO₂. This article pertains to the chemical element For other uses see Argon (disambiguation. Hydrogen (ˈhaɪdrədʒən is the Chemical element with Atomic number 1 The UO₂ is then mixed with an organic binder and pressed into pellets, these pellets are then fired at a much higher temperature (in H₂/Ar) to sinter the solid. Sintering is a method for making objects from powder, by heating the material (below its Melting point - solid state sintering until its particles adhere The aim is to form a dense solid which has few pores.

The thermal conductivity of uranium dioxide is very low compared with that of zirconium metal, and it goes down as the temperature goes up.

It is important to note that the corrosion of uranium dioxide in an aqueous environment is controlled by similar electrochemical processes to the galvanic corrosion of a metal surface. Electrochemistry is a branch of Chemistry that studies Chemical reactions which take place in a Solution at the interface of an electron conductor Corrosion means the breaking down of essential properties in a material due to Chemical reactions with its surroundings

MOX

Main article: MOX fuel

Mixed oxide, or MOX fuel, is a blend of plutonium and natural or depleted uranium which behaves similarly (though not identically) to the enriched uranium feed for which most nuclear reactors were designed. Mixed oxide, or MOX fuel, is a blend of oxides of Plutonium and Natural uranium, Reprocessed uranium, or Depleted uranium which behaves Depleted uranium (DU is Uranium primarily composed of the Isotope Uranium-238 (U-238 Uranium (jʊˈreɪniəm is a silvery-gray Metallic Chemical element in the This article is a subarticle of Nuclear power. A nuclear reactor is a device in which Nuclear chain reactions are initiated controlled MOX fuel is an alternative to low enriched uranium (LEU) fuel used in the light water reactors which predominate nuclear power generation. See also Nuclear power "LWR" redirects here See also LWR (disambiguation A light water reactor or LWR is Nuclear power is any Nuclear technology designed to extract usable Energy from atomic nuclei via controlled Nuclear reactions

Some concern has been expressed that used MOX cores will introduce new disposal challenges, though MOX is itself a means to dispose of surplus plutonium by transmutation. Nuclear transmutation is the conversion of one Chemical element or Isotope into another which occurs through Nuclear reactions Natural transmutation occurs

Currently (March, 2005) reprocessing of commercial nuclear fuel to make MOX is done in England and France, and to a lesser extent in Russia, India and Japan. Year 2005 ( MMV) was a Common year starting on Saturday (link displays full calendar of the Gregorian calendar. England is a Country which is part of the United Kingdom. Its inhabitants account for more than 83% of the total UK population whilst its mainland This article is about the country For a topic outline on this subject see List of basic France topics. Russia (Россия Rossiya) or the Russian Federation ( Rossiyskaya Federatsiya) is a transcontinental Country extending India, officially the Republic of India (भारत गणराज्य inc-Latn Bhārat Gaṇarājya; see also other Indian languages) is a country For a topic outline on this subject see List of basic Japan topics. China plans to develop fast breeder reactors and reprocessing. China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National The fast breeder or fast breeder reactor ( FBR) is a Fast neutron reactor designed to breed fuel by producing more Fissile material

The Global Nuclear Energy Partnership, is a U. The Global Nuclear Energy Partnership (GNEP began as a US proposal announced by United States Secretary of Energy Samuel Bodman on February 6 2006 to form an S. plan to form an international partnership to see spent nuclear fuel reprocessed in a way that renders the plutonium in it usable for nuclear fuel but not for nuclear weapons. A nuclear weapon is an explosive device that derives its destructive force from Nuclear reactions either fission or a combination of fission and fusion. Reprocessing of spent commercial-reactor nuclear fuel has not been permitted in the United States due to nonproliferation considerations. All of the other reprocessing nations have long had nuclear weapons from military-focused "research"-reactor fuels except for Japan.

Metal fuel

Metal fuels have the advantage of a much higher heat conductivity than oxide fuels but cannot survive equally high temperatures.

TRIGA fuel

TRIGA fuel is used in TRIGA (Training, Research, Isotopes, General Atomics) reactors. TRIGA is a class of small Nuclear reactor designed and manufactured by General Atomics of the USA. The TRIGA reactor uses uranium-zirconium-hydride (UZrH) fuel, which has a prompt negative temperature coefficient, meaning that as the temperature of the core increases, the reactivity decreases - so it is physically impossible for a meltdown to occur. Most cores that use this fuel are "high leakage" cores where the excess leaked neutrons can be utilized for research. TRIGA fuel was originally designed to use highly enriched uranium, however in 1978 the U. S. Department of Energy launched its Reduced Enrichment for Research Test Reactors program, which promoted reactor conversion to low-enriched uranium fuel. A total of 35 TRIGA reactors have been installed at locations across the USA. A further 35 reactors have been installed in other countries.

Actinide Fuel

In a fast neutron reactor the minor actinides produced by neutron capture of uranium and plutonium can be used as fuel. A fast neutron reactor or simply a fast reactor is a category of Nuclear reactor in which the fission Chain reaction is sustained by Fast neutrons Metal actinide fuel is typically an alloy of zirconium , uranium, plutonium and the minor actinides. The minor actinides are the Actinide elements in used Nuclear fuel other than Uranium and Plutonium, which are termed the Major actinides It can be made inherently safe as thermal expansion of the metal alloy will increase neutron leakage.

Less common chemical forms

Ceramic fuels

Ceramic fuels other than oxides have the advantage of a high heat conductivities and melting points, but they are more prone to swelling than oxide fuels and are much less well understood.

Uranium nitride

This is often the fuel of choice for reactor designs that NASA produces, one advantage is that UN has a better thermal conductivity than UO₂. Uranium nitride has a very high melting point. This fuel has the disadvantage that unless ¹⁵N was used (in place of the more common ¹⁴N) that a large amount of ¹⁴C would be generated from the nitrogen by the pn reaction. As the nitrogen required for such a fuel would be so expensive it is likely that the fuel would have to be reprocessed by a pyro method to enable to the ¹⁵N to be recovered. Nitrogen (ˈnaɪtɹəʤɪn is a Chemical element that has the symbol N and Atomic number 7 and Atomic weight 14 It is likely that if the fuel was processed and dissolved in nitric acid that the nitrogen enriched with ¹⁵N would be diluted with the common ¹⁴N. Nitric acid ( H[[nitrate NO3]] also known as Aqua fortis and spirit of nitre, is a highly corrosive and

Uranium carbide

Main article: uranium carbide

Much of what is known about uranium carbide is in the form of pin-type fuel elements for liquid metal fast breeder reactors during their intense study during the 60's and 70's. Uranium carbide, a Carbide of Uranium, is a hard refractive Ceramic material However, recently there has been a revived interest in uranium carbide in the form of plate fuel and most notably, micro fuel particles (such as TRISO particles).

The high thermal conductivity and high melting point make uranium carbide an attractive fuel. In addition, because of the absence of oxygen in this fuel (during the course of radiation, excess gas pressure can build from the formation O₂ or other gases) as well as the ability to compliment a ceramic coating (a ceramic-ceramic interface has structural and chemical advantages), uranium carbide could be the ideal fuel candidate for certain Generation IV reactors such as the gas-cooled fast reactor. Generation IV reactors (Gen IV are a set of theoretical nuclear reactor designs currently being researched The Gas-Cooled Fast Reactor (GFR system is a nuclear reactor design which is currently in development

Liquid fuels

Molten anhydrous salts

These include fuels where the fuel is dissolved in the coolant. Melting is a process that results in the phase change of a substance from a Solid to a Liquid. As a general term a substance is said to be anhydrous if it contains no Water. They were used in the molten salt reactor experiment and numerous other liquid core reactor experiments, such as the Liquid fluoride reactor. A molten salt reactor (MSR is a type of Nuclear reactor where the primary coolant is a Molten salt. A molten salt reactor (MSR is a type of Nuclear reactor where the primary coolant is a Molten salt. The liquid fuel for the molten salt reactor was LiF-BeF₂-ThF₄-UF₄ (72-16-12-0. 4 mol%), it had a peak operating temperature of 705 °C in the experiment but could have gone to much higher temperatures since the boiling point of the molten salt was in excess of 1400 °C.

Aqueous solutions of uranyl salts

The Aqueous Homogeneous Reactors uses a solution of uranyl sulfate or other uranium salt in water. The uranyl ion is the dipositive Cation 2+, which forms salts with acids A salt, in Chemistry, is defined as the product formed from the neutralisation reaction of Acids and bases. Aqueous homogeneous reactors (AHR are a type of Nuclear reactor in which soluble nuclear salts (usually Uranium sulfate or Uranium nitrate) Uranyl sulfate (UO2SO4 a Sulfate of Uranium presents as an odorless lemon-yellow sand-like solid in its pure crystalline form This homogenous reactor type has not been used for any large power reactors. One of its disadvantages is that the fuel is in a form which is easy to disperse in the event of an accident. An accident is a specific identifiable unexpected unusual and unintended external event which occurs in a particular time and place without apparent or deliberate

Common physical forms of nuclear fuel

For use as nuclear fuel, enriched UF₆ is converted into uranium dioxide (UO₂) powder that is then processed into pellet form. The pellets are then fired in a high-temperature, sintering furnace to create hard, ceramic pellets of enriched uranium. The cylindrical pellets then undergo a grinding process to achieve a uniform pellet size. The pellets are stacked, according to each nuclear core's design specifications, into tubes of corrosion-resistant metal alloy. The tubes are sealed to contain the fuel pellets: these tubes are called fuel rods. The finished fuel rods are grouped in special fuel assemblies that are then used to build up the nuclear fuel core of a power reactor.

The metal used for the tubes depends on the design of the reactor - stainless steel was used in the past, but most reactors now use a zirconium alloy. For the most common types of reactors (BWRs and PWRs) the tubes are assembled into bundles with the tubes spaced precise distances apart. These bundles are then given a unique identification number, which enables them to be tracked from manufacture through use and into disposal

PWR fuel

PWR fuel bundle The fuel bundle is from a pressurized water reactor of the nuclear passenger and cargo ship NS Savannah. Creation In 1955 President of the United States Dwight Eisenhower proposed building a nuclear-powered merchant ship as a showcase for his " Atoms for Designed and built by the Babcock and Wilcox Company.

Pressurized water reactor (PWR) fuel consists of cylindrical rods put into bundles. Pressurized water reactor ( PWR s (also VVER if of Russian design are generation II nuclear power reactors that use ordinary Water A uranium oxide ceramic is formed into pellets and inserted into Zircaloy tubes that are bundled together. Zircaloy, also incorrectly called zircalloy, is a group of high- Zirconium Alloys One of the main uses of zircaloys is in Nuclear technology, The Zircaloy tubes are about 1 cm in diameter, and the fuel cladding gap is filled with helium gas to improve the conduction of heat from the fuel to the cladding. Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical In Physics, heat, symbolized by Q, is Energy transferred from one body or system to another due to a difference in Temperature There are about 179-264 fuel rods per fuel bundle and about 121 to 193 fuel bundles are loaded into a reactor core. Generally, the fuel bundles consist of fuel rods bundled 14x14 to 17x17. PWR fuel bundles are about 4 meters in length. In PWR fuel bundles, control rods are inserted through the top directly into the fuel bundle. The fuel bundles usually are enriched several percent in ²³⁵U. The uranium oxide is dried before inserting into the tubes to try to eliminate moisture in the ceramic fuel that can lead to corrosion and hydrogen embrittlement. The Zircaloy tubes are pressurized with helium to try to minimize pellet cladding interaction (PCI) which can lead to fuel rod failure over long periods.

BWR fuel

In boiling water reactors (BWR), the fuel is similar to PWR fuel except that the bundles are "canned"; that is, there is a thin tube surrounding each bundle. A boiling water reactor ( BWR) is a type of Nuclear reactor developed by the General Electric in the mid 1950s This is primarily done to prevent local density variations from effecting neutronics and thermal hydraulics of the nuclear core on a global scale. In Nuclear engineering, the void coefficient (more properly called "void coefficient of reactivity") is a number that can be used to estimate how much the In modern BWR fuel bundles, there are either 91, 92, or 96 fuel rods per assembly depending on the manufacturer. A range between 368 assemblies for the smallest and 800 assemblies for the largest U. S. BWR forms the reactor core. Each BWR fuel rod is back filled with helium to a pressure of about three atmospheres (300 kPa).

CANDU fuel

CANDU fuel bundles Two CANDU fuel bundles, each about 50 cm in length, 10 cm in diameter. Photo courtesy of Atomic Energy of Canada Ltd.

CANDU fuel bundles are about a half meter in length and 10 cm in diameter. The CANDU reactor is a Canadian-invented Pressurized heavy water reactor developed initially in the late 1950s and 1960s by a partnership between Atomic Energy of They consist of sintered (UO₂) pellets in Zirconium alloy tubes, welded to Zirconium alloy end plates. Each bundle is roughly 20 kg, and a typical core loading is on the order of 4500-6500 bundles, depending on the design. Modern types typically have 37 identical fuel pins radially arranged about the long axis of the bundle, but in the past several different configurations and numbers of pins have been used. The CANFLEX bundle has 43 fuel elements, with two element sizes. CANFLEX; the name is derived from its function CANDU FLEXible fuelling is an advanced fuel bundle design developed by Atomic Energy of Canada Ltd It is also about 10 cm (four inches) in diameter, 0. 5 m (20 inches long) and weighs about 20 kg (44 lbs) and replaces 37-pin standard bundle. It has been designed specifically to increase fuel performance by utilizing two different pin diameters. Current CANDU designs do not need enriched uranium to achieve criticality (due to their more efficient heavy water moderator), however, some newer concepts call for low enrichment to help reduce the size of the reactors. Heavy water is water which contains a higher proportion than normal of the Isotope Deuterium, as deuterium oxide, D2O or ²H2O In Nuclear engineering, a neutron moderator is a medium which reduces the velocity of Fast neutrons thereby turning them into Thermal neutrons capable

Less common fuel forms

Various other nuclear fuel forms find use in specific applications, but lack the widespread use of those found in BWRs, PWRs, and CANDU power plants. Many of these fuel forms are only found in research reactors, or have military applications.

TRISO fuel

TRISO fuel particle which has been cracked, showing the multiple coating layers

Tristructural-isotropic (TRISO) fuel is a type of micro fuel particle. It consists of a fuel kernel composed of UO_X (sometimes UC or UCO) in the center, coated with four layers of three isotropic materials. Uranium dioxide (2 an Oxide of Uranium, also known as urania or uranic oxide is a black radioactive crystalline powder The four layers are a porous buffer layer made of carbon, followed by a dense inner layer of pyrolytic carbon (PyC), followed by a ceramic layer of SiC to retain fission products at elevated temperatures and to give the TRISO particle more structural integrity, followed by a dense outer layer of PyC. Pyrolytic carbon is a Material similar to Graphite, but with some Covalent bonding between its Graphene sheets as a result of imperfections Silicon carbide ( is a compound of Silicon and Carbon bonded together to form Ceramics but it also occurs in nature as the extremely rare mineral TRISO fuel particles are designed not to crack due to the stresses from processes (such as differential thermal expansion or fission gas pressure) at temperatures beyond 1600°C, and therefore can contain the fuel in the worst of accident scenarios in a properly designed reactor. Two such reactor designs are the pebble bed reactor (PBR), in which thousands of TRISO fuel particles are dispersed into graphite pebbles, and the prismatic-block gas-cooled reactor (such as the GT-MHR), in which the TRISO fuel particles are fabricated into compacts and placed in a graphite block matrix. The pebble bed reactor ( PBR) is a graphite- moderated, gas-cooled Nuclear reactor. The Gas Turbine Modular Helium Reactor (GTMHR is a nuclear power reactor design under development by General Atomics. Both of these reactor designs are very high temperature reactors (VHTR) [formally known as the high-temperature gas-cooled reactors (HTGR)], one of the six classes of reactor designs in the Generation IV initiative. The Very High Temperature Reactor is a Generation IV reactor concept that uses a Graphite - moderated Nuclear reactor with a once-through Generation IV reactors (Gen IV are a set of theoretical nuclear reactor designs currently being researched

TRISO fuel particles were originally developed in Germany for high-temperature gas-cooled reactors. The first nuclear reactor to use TRISO fuels was the AVR and the first powerplant was the THTR-300. The THTR-300 was a Thorium high-temperature Nuclear reactor rated at 300 MW electric (THTR-300 Currently, TRISO fuel compacts are being used in the experimental reactors, the HTR-10 in China, and the HTTR in Japan.

RBMK reactor fuel rod holder 1 - distancing armature; 2 - fuel rods shell; 3 - fuel tablets.

RBMK fuel

RBMK reactor fuel was used in Soviet designed and built RBMK type reactors. A soviet (сове́т, "council" originally was a workers' local council in late Imperial Russia. RBMK is an acronym for the Russian reaktor bolshoy moshchnosti kanalniy (Реактор Большой Мощности Канальный which means "High Power Channel This is a low enriched uranium oxide fuel. The fuel elements in an RBMK are 3m long each, and two of these sit back-to-back on each fuel channel, pressure tube. The nucler fuel that is used to make fuel for an RBMK is used (spent) fuel from possible a PWR, or VVER if of Russian design.

CerMet fuel

CerMet fuel consists of ceramic fuel particles (usually uranium oxide) embedded in a metal matrix. It is hypothesized that this type of fuel is what is used in US Navy reactors. This fuel has high heat transport characteristics and can withstand a large amount of expansion.

Plate type fuel

ATR Core The Advanced Test Reactor at Idaho National Laboratory uses plate type fuel in a clover leaf arrangement

Plate type fuel has grown out of favor over the years. The Advanced Test Reactor ( ATR) is a research reactor at the Idaho National Laboratory. The Idaho National Laboratory ( INL) is an 890-square-mile (2300-km² complex located in the Idaho desert between the town of Arco and the city of It is currently used in the Advanced Test Reactor (ATR) at Idaho National Laboratory. The Advanced Test Reactor ( ATR) is a research reactor at the Idaho National Laboratory. The Idaho National Laboratory ( INL) is an 890-square-mile (2300-km² complex located in the Idaho desert between the town of Arco and the city of

Spent nuclear fuel

Main article: Spent nuclear fuel

Used nuclear fuel is a complex mixture of the fission products, uranium, plutonium and the transplutonium metals. Spent nuclear fuel, occasionally called used nuclear fuel, is Nuclear fuel that has been irradiated in a Nuclear reactor (usually at a Nuclear power Fission products are the atomic fragments left after a large nucleus fissions. Uranium (jʊˈreɪniəm is a silvery-gray Metallic Chemical element in the The minor actinides are the Actinide elements in used Nuclear fuel other than Uranium and Plutonium, which are termed the Major actinides In fuel which has been used at high temperature in power reactors it is common for the fuel not to be homogenous; often the fuel will contain nanoparticles of platinum group metals such as palladium. The platinum group (alternatively the platinum group metals or platinum metals) is a collective name sometimes used for six Metallic elements Palladium (pronounced \pəˈleɪdiəm\ is a rare and lustrous silvery-white metal that was discovered in 1803 by William Hyde Wollaston, who named it palladium after the Also the fuel may well have cracked, swelled and been used close to its melting point. Despite the fact that the used fuel can be cracked it is very insoluble in water, and is able to retain the vast majority of the actinides and fission products within the uranium dioxide crystal lattice. History of the actinoid series From the earlier known chemical properties of actinium (89 up to uranium (92 indicating a relation to the Transition metals it was generally Fission products are the atomic fragments left after a large nucleus fissions. Uranium dioxide (2 an Oxide of Uranium, also known as urania or uranic oxide is a black radioactive crystalline powder In Mineralogy and Crystallography, a crystal structure is a unique arrangement of Atoms in a Crystal.

Oxide fuel under accident conditions

Main article: Nuclear fuel response to reactor accidents

Two main modes of release exist, the fission products can be vapourised or small particles of the fuel can be dispersed. This page is devoted to a discussion of how Uranium dioxide Nuclear fuel behaves during both normal Nuclear reactor operation and under reactor accident

Fuel behavior and post irradiation examination (PIE)

Materials in a high radiation environment (such as a reactor) can undergo unique behaviors such as swelling[3] and non-thermal creep. If there are nuclear reactions within the material (such as what happens in the fuel), the stoichiometry will also change slowly over time. These behaviors can lead to new material properties, cracking, and fission gas release:

• Fission gas release
  • As the fuel is degraded or heated the more volatile fission products which are trapped within the uranium dioxide may become free. Uranium dioxide (2 an Oxide of Uranium, also known as urania or uranic oxide is a black radioactive crystalline powder For example see J. Y. Colle, J. P. Hiernaut, D. Papaioannou, C. Ronchi, A. Sasahara, Journal of Nuclear Materials, 2006, 348, 229.

• Fuel cracking
  • As the fuel expands on heating, the core of the pellet expands more than the rim which may lead to cracking. Because of the thermal stress thus formed the fuel cracks, the cracks tend to go from the centre to the edge in a star shaped pattern.

In order to better understand and control these changes in materials, these behaviors are studied. A common experiment to do this is post irradiation examination, in which fuel will be examined after it is put through reactor-like conditions [4][5] [6] [7]. Due to the intensely radioactive nature of the used fuel this is done in a hot cell. Shielded containments are commonly referred to as Hot Cells. The word "hot" refers to Radioactive. A combination of nondestructive and destructive methods of PIE are common.

The PIE is used to check that the fuel is both safe and effective. After major accidents the core (or what is left of it) is normally subject to PIE in order to find out what happened. One site where PIE is done is the ITU which is the EU centre for the study of highly radioactive materials. The European Union ( EU) is a political and economic union of twenty-seven member states, located primarily in Radioactive decay is the process in which an unstable Atomic nucleus loses energy by emitting ionizing particles and Radiation.

In addition to the effects of radiation and the fission products on materials, scientists also need to consider the temperature of materials in a reactor, and in particular, the fuel. Too high of fuel temperatures can compromise the fuel, and therefore it is important to control the temperature in order to control the fission chain reaction.

The temperature of the fuel varies as a function of the distance from the centre to the rim. At distance x from the centre the temperature (T_x) is described by the equation where ρ is the power density (W m^-3) and K_f is the thermal conductivity. An equation is a mathematical statement, in symbols, that two things are exactly the same (or equivalent In Physics, thermal conductivity, k is the property of a material that indicates its ability to conduct Heat.

T_x = T_Rim + ρ (r_pellet² - x²) (4 K_f)^-1

To explain this for a series of fuel pellets being used with a rim temperature of 200 ^oC (typical for a BWR) with different diameters and power densities of 250 MW m^-3 have been modeled using the above equation. A boiling water reactor ( BWR) is a type of Nuclear reactor developed by the General Electric in the mid 1950s Geometry, a diameter of a Circle is any straight Line segment that passes through the center of the circle and whose Endpoints are on the Note that these fuel pellets are rather large; it is normal to use oxide pellets which are about 10 mm in diameter.

Nuclear Fuel Temperature Profiles

Temperature profile for a 20 mm diameter fuel pellet with a power density of 250 MW per cubic meter. Note the central temperature is very different for the different fuel solids.	Temperature profile for a 26 mm diameter fuel pellet with a power density of 250 MW per cubic meter.	Temperature profile for a 32 mm diameter fuel pellet with a power density of 250 MW per cubic meter.
Temperature profile for a 20 mm diameter fuel pellet with a power density of 500 MW per cubic meter. Because the melting point of uranium dioxide is about 3300 K, it is clear that uranium oxide fuel is overheating at the center.	Temperature profile for a 20 mm diameter fuel pellet with a power density of 1000 MW per cubic meter. The fuels other than uranium dioxide are not compromised.

Reference Radiochemistry and Nuclear Chemistry, G. Choppin, J-O Liljenzin and J. Rydberg, 3rd Ed, 2002, Butterworth-Heinemann, ISBN 0-7506-7463-6

Radioisotope decay fuels

Radioisotope battery

Main article: atomic battery

The terms atomic battery, nuclear battery and radioisotope battery are used interchangely to describe a device which uses the radioactive decay to generate electricity. The terms atomic battery, nuclear battery, tritium battery and radioisotope battery are used to describe a device which uses the emissions from a Radioactive The terms atomic battery, nuclear battery, tritium battery and radioisotope battery are used to describe a device which uses the emissions from a Radioactive These systems use radioisotopes that produce low energy beta particles or sometimes alpha particles of varying energies. A radionuclide is an Atom with an unstable nucleus, which is a nucleus characterized by excess energy which is available to be imparted either to a newly-created Low energy beta particles are needed to prevent the production of high energy penetrating Bremsstrahlung radiation that would require heavy shielding. Bremsstrahlung ( pronounced, from German de ''bremsen'' "to brake" and de ''Strahlung'' "radiation" i Radioisotopes such as tritium, nickel-63, promethium-147, and technetium-99 have been tested. Tritium (ˈtɹɪtiəm symbol or, also known as Hydrogen-3) is a radioactive Isotope of Hydrogen. Nickel (ˈnɪkəl is a metallic Chemical element with the symbol Ni and Atomic number 28 Promethium (prəˈmiːθiəm/ /proʊˈmiːθiəm is a Chemical element with the symbol Pm and Atomic number 61 Technetium (tɛkˈniːʃɪəm is the lightest Chemical element with no Stable isotope. Plutonium-238, curium-242, curium-244 and strontium-90 have been used. Plutonium 238, is a Radioactive isotope of Plutonium with a half-life of 87 This article is about the chemical element Curium for the ancient city also called Curium (located in Cyprus see Kourion Curium (ˈkjuːriəm This article is about the chemical element Curium for the ancient city also called Curium (located in Cyprus see Kourion Curium (ˈkjuːriəm Strontium (ˈstrɒntiəm /ˈstrɒnʃiəm/) is a Chemical element with the symbol Sr and the Atomic number 38

There are two main categories of atomic batteries: thermal and non-thermal. The non-thermal atomic batteries, which have many different designs, exploit charged alpha and beta particles. Alpha particles (named after and denoted by the first letter in the Greek alphabet, α consist of two Protons and two Neutrons bound together into a Beta particles are high-energy high-speed Electrons or Positrons emitted by certain types of Radioactive nuclei such as Potassium -40 These designs include the direct charging generators, Betavoltaics, the optoelectric nuclear battery, and the radioisotope piezoelectric generator. The terms atomic battery, nuclear battery, tritium battery and radioisotope battery are used to describe a device which uses the emissions from a Radioactive Betavoltaics are generators of Electrical current, in effect a form of battery, which use energy from a Radioactive source emitting Beta particles An optolectric nuclear battery has been developed by researchers of the Kurchatov Institute in Moscow. A Radioisotope piezoelectric generator converts energy stored in the Radioactive material directly into motion to generate electricity by the repeated deformation of a Piezoelectric The thermal atomic batteries on the other hand, convert the heat from the radioactive decay to electricity. These designs include thermionic converter, thermophotovoltaic cells, alkali-metal thermal to electric converter, and the most common design, the radioisotope thermoelectric generator.

Radioisotope thermoelectric generators

A radioisotope thermoelectric generator (RTG) is a simple electrical generator which converts heat into electricity from a radioisotope using an array of thermocouples. A radioisotope thermoelectric generator ( RTG, RITEG) is an Electrical generator which obtains its power from Radioactive decay. In Electricity generation, an electrical generator is a device that converts Mechanical energy to Electrical energy, generally using Electromagnetic In Electrical engineering and industry thermocouples are a widely used type of temperature sensor and can also be used as a means to convert thermal Potential

²³⁸Pu has become the most widely used fuel for RTGs. Plutonium 238, is a Radioactive isotope of Plutonium with a half-life of 87 In the form of plutonium dioxide it has a half-life of 87. Plutonium(IV oxide is the Chemical compound with the formula PuO2 7 years, reasonable energy density and exceptionally low gamma and neutron radiation levels. Some Russian terrestrial RTGs have used ⁹⁰Sr; this isotope has a shorter half-life and a much lower energy density, but is cheaper. Strontium (ˈstrɒntiəm /ˈstrɒnʃiəm/) is a Chemical element with the symbol Sr and the Atomic number 38 Early RTGs, first built in 1958 by the U.S. Atomic Energy Commission, have used ²¹⁰Po. The United States Atomic Energy Commission (AEC was an agency of the United States government established after World War II by Congress to foster and control Polonium (pəˈloʊniəm is a Chemical element with the symbol Po and Atomic number 84 discovered in 1898 by Marie and Pierre Curie This fuel provides phenomenally huge energy density, (a single gram of polonium-210 generates 140 watts thermal) but has limited use because of its very short half-life and gamma production and has been phased out of use in this application.

Radioisotope heater units (RHU)

Photo of a disassembled RHU

Radioisotope heater units normally provide about 1 watt of heat each, derived from the decay of a few grams of Plutonium-238. Radioisotope heater units are small devices that provide heat through Radioactive decay. The watt (symbol W) is the SI derived unit of power, equal to one Joule of energy per Second. For other uses of the words gram or gramme see Gram (disambiguation. This heat is given off continuously for several decades. A decade is a period of 10 Years (since 1594 a factor of 10 difference between two numbers, or sometimes a set or a group of ten (since 1451

Their function is to provide highly localised heating of sensitive equipment (such as electronics) in deep space. The Cassini-Huygens orbiter to Saturn contains 82 of these units (in addition to its 3 main RTG's for power generation). Cassini–Huygens is a joint NASA / ESA / ASI Robotic spacecraft mission currently studying the planet Saturn and its The Huygens probe to Titan contains 35 devices. TemplateInfobox Planet.--> Titan (ˈtaɪtən, or as

Fusion fuels

Most fusion fuels fit in here. They include tritium (³H) and deuterium (²H) as well as helium three (³He). Many other elements can be fused together if they can be forced close enough to each other at high enough temperatures. In general, fusion fuels are expected to have at least three generations based on the ease of fusing light atomic nuclei together.

First generation fusion fuel

Deuterium and tritium are both considered first-generation fusion fuels; with many permutations in which they can be fused together. Deuterium, also called heavy hydrogen, is a Stable isotope of Hydrogen with a Natural abundance in the Oceans of Earth Tritium (ˈtɹɪtiəm symbol or, also known as Hydrogen-3) is a radioactive Isotope of Hydrogen. The three most commonly cited are;

²H + ³H n (14. This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. 07 MeV) + ⁴He (3. 52 MeV)

²H + ²H n (2. This article is a discussion of neutrons in general For the specific case of a neutron found outside the nucleus see Free neutron. 45 MeV) + ³He (0. 82 MeV)

²H + ²H p (3. The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive 02 MeV) + ³H (1. 01 MeV)

Second generation fusion fuel

Second generation fuels require either higher confinement temperatures or longer confinement time than those required of first generation fusion fuels. This group consists of deuterium and helium three. The products of these reactants are all charged particles, but there may be non-beneficial side reactions leading to radioactive activation of fusion reactor components.

²H + ³He p (14. The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive 68 MeV) + ⁴He (3. 67 MeV)

Third generation fusion fuel

Main article: Aneutronic fusion

There are several potential third generation fusion fuels. Aneutronic fusion is any form of Fusion power where no more than 1% of the total energy released is carried by Neutrons Since the most-studied fusion reactions Third generation fusion fuels produce only charged particles in the primary reactions and any side reactions are relatively unimportant. Therefore, there would be little radioactive activation of the fusion reactor. This is often seen as the end goal of fusion research. ³He has the highest Maxwellian reactivity of any 3rd generation fusion fuel, but there are no significant natural sources of this substance on Earth.

³He + ³He 2p + ⁴He (12. The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive 86 MeV)

Another potential aneutronic fusion reaction is the proton-boron reaction:

p + ¹¹B → 3⁴He

Under reasonable assumptions, side reactions will result in about 0. The proton ( Greek πρῶτον / proton "first" is a Subatomic particle with an Electric charge of one positive 1% of the fusion power being carried by neutrons. With 123 keV, the optimum temperature for this reaction is nearly ten times higher than that for the pure hydrogen reactions, the energy confinement must be 500 times better than that required for the D-T reaction, and the power density will be 2500 times lower than for D-T.

See also

• nuclear fuel cycle
• Uranium market
• Reprocessed uranium
• Global Nuclear Energy Partnership

External links and references

PWR fuel

• NEI fuel schematic
• Picture of a PWR fuel assembly
• Picture showing handling of a PWR bundle
• Mitsubishi nuclear fuel Co.

BWR fuel

• Picture of a "canned" BWR assembly
• Physical description of LWR fuel
• Links to BWR photos from the nuclear tourist webpage

CANDU fuel

• CANDU Fuel pictures and FAQ
• Basics on CANDU design
• THE EVOLUTION OF CANDUÒ FUEL CYCLES AND THEIR POTENTIAL CONTRIBUTION TO WORLD PEACE
• CANDU Fuel-Management Course
• CANDU Fuel and Reactor Specifics (Nuclear Tourist)
• Candu Fuel Rods and Bundles

TRISO fuel

• TRISO fuel descripción
• NON-DESTRUCTIVE EXAMINATION OF SiC NUCLEAR FUEL SHELL USING X-RAY FLUORESCENCE MICROTOMOGRAPHY TECHNIQUE
• GT-MHR fuel compact process
• Description of TRISO fuel for "pebbles"
• LANL webpage showing various stages of TRISO fuel production

CERMET fuel

• A Review of Fifty Years of Space Nuclear Fuel Development Programs
• THORIA-BASED CERMET NUCLEAR FUEL: SINTERED MICROSPHERE FABRICATION BY SPRAY DRYING
• THE USE OF MOLYBDENUM-BASED CERAMIC-METAL (CerMet) FUEL FOR THE ACTINIDE MANAGEMENT IN LWRs

Plate type fuel

• List of reactors at INL and picture of ATR core
• ATR plate fuel

TRIGA fuel

• General Atomics TRIGA fuel website

Space reactor fuels

• Space Nuclear Conference 2005 (SNC '05)

Fusion fuel

• Advanced fusion fuels presentation