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Encyclopedia > Nuclear fuel
Nuclear Fuel Process
A graph comparing nucleon number against binding energy

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. Light isotopes such as 3H (tritium) are used as fuel for nuclear fusion. 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. General Name, Symbol, Number Plutonium, Pu, 94 Chemical series Actinides Period, Block 7 , f Density, Hardness 19816 kg/m3, no data Appearance silvery white metal Atomic properties Atomic weight 244. ... Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting radiation in the form of particles or electromagnetic waves. ... A radioisotope thermoelectric generator (RTG) is a simple electrical generator which obtains its power from radioactive decay. ... The terms atomic battery, nuclear battery and radioisotope battery are used to describe a device which uses the charged particle emissions from a radioactive isotope to directly generate electricity. ... Tritium (symbol T or 3H) is a radioactive isotope of hydrogen. ... The deuterium-tritium (D-T) fusion reaction is considered the most promising for producing fusion power. ... Binding energy is the energy required to disassemble a whole into separate parts. ... For other uses, see Isotope (disambiguation). ...

The thermal conductivity of uranium dioxide is low; it is affected by porosity and burn-up. 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. 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. In physics, thermal conductivity, k, is the intensive 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 0â€“1, or as a percentage between 0â€“100%. The term porosity is used in multiple fields including manufacturing, earth sciences and construction. ... Fission products are the residues of fission processes. ... The lanthanide series is the 14 rare earth chemical elements which lie between lanthanum and ytterbium on the periodic table. ... For other uses, see Palladium (disambiguation). ... Look up bubble in Wiktionary, the free dictionary. ... General Name, Symbol, Number xenon, Xe, 54 Chemical series noble gases Group, Period, Block 18, 5, p Appearance colorless Standard atomic weight 131. ... For other uses, see Krypton (disambiguation). ... Look up lattice in Wiktionary, the free dictionary. ...

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 bulk density of the fuel can be related to the thermal conductivity For other uses, see Density (disambiguation). ...

p = (ρtd-ρ)/ρ

Where ρ is the bulk density of the fuel and ρtd is the theoretical density of the uranium dioxide. UO2 A black, radioactive, crystalline powder, once used in the late 1800s to mid-1900s in ceramic glazes. ...

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

Kf = Ko.(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. 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 = ρCpα

If t1/2 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 intensive property of a material that indicates its ability to conduct heat. ... For other uses, see Density (disambiguation). ... To meet Wikipedias quality standards, this article or section may require cleanup. ... In heat transfer analysis, thermal diffusivity (symbol: ) is the ratio of thermal conductivity to heat capacity. ...

α = 0.1388 L2 / t1/2

L is the thickness of the disc

For details see [2]

### UOX

Uranium dioxide is a black semiconductor solid. It can be made by reacting uranyl nitrate with a base (ammonia) to form a solid (ammonium uranate). It is heated (calcined) to form U3O8 that can than be converted by heating in an argon / hydrogen mixture (700 oC) to form UO2. 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. The aim is to form a dense solid which has few pores. UO2 A black, radioactive, crystalline powder, once used in the late 1800s to mid-1900s in ceramic glazes. ... A semiconductor is a solid whose electrical conductivity is in between that of a conductor and that of an insulator, and can be controlled over a wide range, either permanently or dynamically. ... The uranyl ion, showing the U-O bond order of 3 Diagram of a uranyl ion. ... For other uses, see Ammonia (disambiguation). ... General Name, symbol, number argon, Ar, 18 Chemical series noble gases Group, period, block 18, 3, p Appearance colorless Standard atomic weight 39. ... General Name, Symbol, Number hydrogen, H, 1 Chemical series nonmetals Group, Period, Block 1, 1, s Appearance colorless Atomic mass 1. ... Sintering is a method for making objects from powder, increasing the adhesion between particles as they are heated. ...

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

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

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. Image File history File links Download high-resolution version (979x598, 4 KB) Other versions w:Image:ZrUthermalcond. ... Image File history File links Download high-resolution version (979x598, 4 KB) Other versions w:Image:ZrUthermalcond. ... Drinking water This article focuses on water as we experience it every day. ... Electrochemistry is the study of the electronic and electrical aspects of chemical reactions. ... In biology, galvanism is the contraction of a muscle that is stimulated by an electric current. ... For the hazard, see corrosive. ...

### 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. MOX fuel is an alternative to low enriched uranium (LEU) fuel used in the light water reactors which predominate nuclear power generation. Mixed oxide, or MOX fuel, is a blend of plutonium and natural uranium or depleted uranium which behaves similarly (though not identically) to the enriched uranium feed for which most nuclear reactors were designed. ... General Name, Symbol, Number plutonium, Pu, 94 Chemical series actinides Group, Period, Block n/a, 7, f Appearance silvery white Standard atomic weight (244) gÂ·molâˆ’1 Electron configuration [Rn] 5f6 7s2 Electrons per shell 2, 8, 18, 32, 24, 8, 2 Physical properties Phase solid Density (near r. ... Depleted uranium storage yard. ... General Name, symbol, number uranium, U, 92 Chemical series actinides Group, period, block n/a, 7, f Appearance silvery gray metallic; corrodes to a spalling black oxide coat in air Standard atomic weight 238. ... Core of a small nuclear reactor used for research. ... A light water reactor or LWR is a thermal nuclear reactor that uses ordinary water, also called light water, as its neutron moderator. ... This article is about applications of nuclear fission reactors as power sources. ...

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. // Transmutation is the conversion of one object into another. ...

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. China plans to develop fast breeder reactors and reprocessing. Year 2005 (MMV) was a common year starting on Saturday (link displays full calendar) of the Gregorian calendar. ... For other uses, see England (disambiguation). ... The fast breeder or fast breeder reactor (FBR) is a fast neutron reactor designed to breed fuel by producing more fissile material than it consumes. ...

The Global Nuclear Energy Partnership, is a U.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. 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. The Global Nuclear Energy Partnership, announced by U.S. Department of Energy secretary Samuel Bodman on February 6, 2006, is a 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... The mushroom cloud of the atomic bombing of Nagasaki, Japan, 1945, rose some 18 km (11 mi) above the epicenter. ...

## 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. 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. TRIGA is a class of small nuclear reactor designed and manufactured by General Atomics of the USA. TRIGA is an acronym of Training, Research, Isotopes, General Atomics. This type of reactor can be installed without a containment building, and is designed for use by scientific institutions and universities for purposes...

### Actinide Fuel

In a fast neutron reactor the minor actinides produced by neutron capture of uranium and plutonium can be used as fuel. Metal actinide fuel is typically an alloy of zirconium , uranium, plutonium and the minor actinides. It can be made inherently safe as thermal expansion of the metal alloy will increase neutron leakage. Shevchenko BN350 nuclear fast reactor and desalination plant situated on the shore of the Caspian Sea. ... The minor actinides are the actinide elements in spent fuel other than uranium and plutonium, these are termed major actinides. ...

## Less common chemical forms

#### Ceramic fuels

Ceramic fuels 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. 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. General Name, symbol, number nitrogen, N, 7 Chemical series nonmetals Group, period, block 15, 2, p Appearance colorless gas Standard atomic weight 14. ... The chemical compound nitric acid (HNO3), also known as aqua fortis and spirit of nitre, is an aqueous solution of hydrogen nitrate (anhydrous nitric acid). ...

##### 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. 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). Uranium carbide, a carbide of uranium, is a hard refractive ceramic material. ...

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 Generation IV reactor concept that features a fast-neutron spectrum and closed fuel cycle for efficient conversion of fertile uranium and management of actinides. ...

#### Liquid fuels

##### Molten anhydrous salts

These include fuels where the fuel is dissolved in the coolant. They were used in the molten salt reactor experiment and numerous other liquid core reactor experiments. 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. Physics In physics, melting is the process of heating a solid substance to a point (called melting point) where it turns liquid. ... As a general term, a substance is said to be anhydrous if it contains no water. ... A molten salt reactor is a type of nuclear reactor where the working fluid is a molten salt. ...

##### Aqueous solutions of uranyl salts

The Aqueous Homogeneous Reactors uses a solution of uranyl sulfate or other uranium salt in water. 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. Drinking water This article focuses on water as we experience it every day. ... The uranyl ion, showing the U-O bond order of 3 Diagram of a uranyl ion. ... For other meanings of the word salt see table salt or salt (disambiguation). ... Aqueous homogeneous reactors (AHR) are a type of nuclear reactor in which soluble nuclear salts (usually uranium sulfate or uranium nitrate) have been dissolved in water. ... Uranyl sulfate (U02S04) a sulfate of uranium presents as an odorless lemon-yellow sand-like solid in its pure crystaline form. ... A railing accidentally collapses at a college football game, spilling fans onto the sidelines An accident is something going wrong unexpectedly. ...

## 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. Designed and built by the Babcock and Wilcox Company.

### 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. This is primarily done to prevent local density variations from effecting neutronics and thermal hydraulics of the nuclear core on a global scale. 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). The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ... 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 thermal output of a nuclear reactor increases (or decreases, if negative) as voids (steam bubbles) form in the reactor moderator or coolant. ...

### 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.

## 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 UOX (sometimes UC or UCO) in the center, coated with four layers of three isotropic materials. 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. 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 pebble bed modular reactor (PBMR), in which thousands of TRISO fuel particles are dispersed into graphite pebbles, and a 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. Both of these reactor designs are high-temperature gas-cooled reactors (HTGR), which is a type of very high temperature reactors (VHTR), one of the six classes of reactor designs in the Generation IV initiative. Image File history File links TRISO.gif Summary This likely SEM photo of a cracked TRISO fuel pellet showing its layered nature was taken from the US Department of Energy, Office of Nuclear Energy, Science and Technology website. ... Image File history File links TRISO.gif Summary This likely SEM photo of a cracked TRISO fuel pellet showing its layered nature was taken from the US Department of Energy, Office of Nuclear Energy, Science and Technology website. ... UO2 A black, radioactive, crystalline powder, once used in the late 1800s to mid-1900s in ceramic glazes. ... UC may refer to: MC++, also Î¼C++ and uC++, an extension of the C++ programming language designed for concurrent programming Microcontroller, as uC derived from Î¼C, a computer-on-a-chip used to control electronic devices Ultra Cricket, a play-by-e-mail cricket game created by Tim Astley Ulcerative... Pyrolytic carbon is a material similar to graphite, but with some covalent bonding between its graphene sheets. ... Except where noted otherwise, data are given for materials in their standard state (at 25 Â°C, 100 kPa) Infobox disclaimer and references Silicon carbide (SiC) is a ceramic compound of silicon and carbon that is manufactured on a large scale for use mainly as an abrasive but also occurs in... Graphite Pebble for Reactor The pebble bed reactor (PBR) or pebble bed modular reactor (PBMR) is an advanced nuclear reactor design. ... The Gas Turbine Modular Helium Reactor (GTMHR) is a nuclear power reactor design under development by General Atomics. ... Very high temperature reactor scheme. ... 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 (HTGR). The first nuclear reactor to use TRISO fuels was the AVR and the first powerplant was the THTR-300. Currently, TRISO fuel compacts are being used in the experimental reactors, the HTR-10 in China, and the HTTR in Japan. The THTR-300 was a thorium high-temperature nuclear reactor rated at 300 MW electric (THTR-300). ...

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

Image File history File links Download high resolution version (685x1739, 60 KB) Description Object: RBMK reactor fuel rods holder Description: 1 - distancing armature; 2 - fuel rods shell; 3 - fuel tablets. ... Image File history File links Download high resolution version (685x1739, 60 KB) Description Object: RBMK reactor fuel rods holder Description: 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. This is a low enriched uranium oxide fuel. The fuel elements in an RBMK are extremely long, on the order of 7 meters. The Chernobyl reactor was a 1GWe RBMK reactor. Soviet redirects here. ... RBMK is an acronym for the Russian reaktor bolshoy moshchnosti kanalniy (Russian: Ð ÐµÐ°ÐºÑ‚Ð¾Ñ€ Ð‘Ð¾Ð»ÑŒÑˆÐ¾Ð¹ ÐœÐ¾Ñ‰Ð½Ð¾ÑÑ‚Ð¸ ÐšÐ°Ð½Ð°Ð»ÑŒÐ½Ñ‹Ð¹) which means reactor (of) high power (of the) channel (type), and describes a now obsolete class of graphite-moderated nuclear power reactor which was built only in the Soviet Union. ... This article is about the city of Chernobyl. ...

#### 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. It is currently used in the Advanced Test Reactor (ATR) at Idaho National Laboratory. Image File history File links No higher resolution available. ... Image File history File links No higher resolution available. ... The Advanced Test Reactor is a research reactor at the Idaho National Laboratory. ... The Idaho National Laboratory (INL) is an 890 square mile (2,300 kmÂ²) complex located in the Idaho desert between the towns of Arco and Idaho Falls. ... The Advanced Test Reactor is a research reactor at the Idaho National Laboratory. ... The Idaho National Laboratory (INL) is an 890 square mile (2,300 kmÂ²) complex located in the Idaho desert between the towns of Arco and Idaho Falls. ...

## Spent nuclear fuel

Main article: Used nuclear fuel

Used nuclear fuel is a complex mixture of the fission products, uranium, plutonium and the transplutonium metals. In fuel which has been used at high temperature in power reactors it is common for the fuel to not be homogenous often the fuel will contain nanoparticles of platinum group metals such as palladium. 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. Used low enriched uranium nuclear fuel is an example of a nanomaterial which existed before the term nano became fashionable, in the oxide fuel intense temperture gradients exist which cause fission products to migrate. ... Fission products are the residues of fission processes. ... General Name, symbol, number uranium, U, 92 Chemical series actinides Group, period, block n/a, 7, f Appearance silvery gray metallic; corrodes to a spalling black oxide coat in air Standard atomic weight 238. ... General Name, Symbol, Number plutonium, Pu, 94 Chemical series actinides Group, Period, Block n/a, 7, f Appearance silvery white Standard atomic weight (244) gÂ·molâˆ’1 Electron configuration [Rn] 5f6 7s2 Electrons per shell 2, 8, 18, 32, 24, 8, 2 Physical properties Phase solid Density (near r. ... The minor actinides are the actinide elements in spent fuel other than uranium and plutonium, these are termed major actinides. ... Look up nano in Wiktionary, the free dictionary. ... The platinum group or platinum metals is the collective name sometimes used for six chemical elements within the periodic table. ... For other uses, see Palladium (disambiguation). ... The actinide series encompasses the 14 chemical elements that lie between actinium and nobelium on the periodic table with atomic numbers 89 - 102 inclusive. ... Fission products are the residues of fission processes. ... UO2 A black, radioactive, crystalline powder, once used in the late 1800s to mid-1900s in ceramic glazes. ... In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms in a crystal. ...

### Oxide fuel under accident conditions

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 conditions such as overheating. ...

## 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: Irradiation is the process by which an item is exposed to radiation. ...

• 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. 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. A combination of nondestructive and destructive methods of PIE are common. UO2 A black, radioactive, crystalline powder, once used in the late 1800s to mid-1900s in ceramic glazes. ... A robotic manipulator for a Hot cell A Hot Cell is a heavily shielded room in which radioactive materials can be handled remotely using robotic manipulators (see picture) and viewed through shielded windows. ...

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. This article is about the location. ... Radioactive decay is the set of various processes by which unstable atomic nuclei (nuclides) emit subatomic particles. ...

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 (Tx) is described by the equation where ρ is the power density (W m-3) and Kf is the thermal conductivity. An equation is a mathematical statement, in symbols, that two things are the same (or equivalent). ... In physics, thermal conductivity, k, is the intensive property of a material that indicates its ability to conduct heat. ...

Tx = TRim + ρ (rpellet2 - x2) (4 Kf)-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 Wm-3 have been modeled using the above equation. Note that these fuel pellets are rather large; it is normal to use oxide pellets which are about 10 mm in diameter. A boiling water reactor (BWR) is a light water reactor design used in some nuclear power stations. ... In geometry, a diameter (Greek words diairo = divide and metro = measure) of a circle is any straight line segment that passes through the center and whose endpoints are on the circular boundary, or, in more modern usage, the length of such a line segment. ...

Temperature profile for a 20 mm diameter fuel pellet with a power density of 250 W 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 W per cubic meter.
Temperature profile for a 32 mm diameter fuel pellet with a power density of 250 W per cubic meter.
Temperature profile for a 20 mm diameter fuel pellet with a power density of 500 W 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 W per cubic meter. The fuels other than uranium dioxide are not compromised.

Main article: atomic battery

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) is a simple electrical generator which obtains its power from radioactive decay. ... This article is about machines that produce electricity. ... Electric redirects here. ... In electronics, thermocouples are a widely used type of temperature sensor and can also be used as a means to convert thermal potential difference into electric potential difference. ...

238Pu has become the most widely used fuel for RTGs. In the form of plutonium dioxide it has a half-life of 87.7 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. Early RTGs, first built in 1958 by the U.S. Atomic Energy Commission, have used 210Po. 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. Plutonium 238, is an isotope of plutonium with a half-life of 86. ... Prepared during the reprocessing of nuclear fuel by calcination of plutonium(IV) oxalate, Pu(C2O4)2. ... General Name, Symbol, Number strontium, Sr, 38 Chemical series alkaline earth metals Group, Period, Block 2, 5, s Appearance silvery white metallic Standard atomic weight 87. ... Almost a year after World War II ended, Congress established the United States Atomic Energy Commission to foster and control the peace time development of atomic science and technology. ... General Name, Symbol, Number polonium, Po, 84 Chemical series metalloids Group, Period, Block 16, 6, p Appearance silvery Standard atomic weight (209) gÂ·molâˆ’1 Electron configuration [Xe] 4f14 5d10 6s2 6p4 Electrons per shell 2, 8, 18, 32, 18, 6 Physical properties Phase solid Density (near r. ...

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. This heat is given off continuously for several decades. Image File history File links Photo of a disassembled RHU File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Photo of a disassembled RHU File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Similar to a tiny radioisotope thermoelectric generator (RTG), these units normally provide about 1 watt of heat each, derived from the decay of a few grams of plutonium 238. ... For other uses, see Watt (disambiguation). ... BIC pen cap, about 1 gram. ... A decade is a set or a group of ten, commonly a period of 10 years in contemporary English, or a period of 10 days in the French revolutionary calendar. ...

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). The Huygens probe to Titan contains 35 devices. Outer space (also called just space), as a name for a region, refers to the relatively empty parts of the Universe, outside the atmospheres of celestial bodies. ... Cassini-Huygens is a joint NASA/ESA/ASI unmanned space mission intended to study Saturn and its moons. ... Atmospheric characteristics Atmospheric pressure 140 kPa Hydrogen >93% Helium >5% Methane 0. ... Titan (, from Ancient Greek Î¤á¿‘Ï„Î¬Î½) or Saturn VI is the largest moon of Saturn and the only moon known to have a dense atmosphere. ...

## 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. The three most commonly cited are; Deuterium, also called heavy hydrogen, is a stable isotope of hydrogen with a natural abundance in the oceans of Earth of approximately one atom in 6500 of hydrogen (~154 PPM). ... Tritium (symbol T or 3H) is a radioactive isotope of hydrogen. ...

2H + 3H $rightarrow$ n (14.07 MeV) + 4He (3.52 MeV)
2H + 2H $rightarrow$ n (2.45 MeV) + 3He (0.82 MeV)
2H + 2H $rightarrow$ p (3.02 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 $rightarrow$ p (14.68 MeV) + 4He (3.67 MeV)

For other uses, see Proton (disambiguation). ...

### Third generation fusion fuel

There are several potential third generation fusion fuels. Third generation fusion fuels produce only charged particles in the fusion process and there are no side reactions. Therefore, there would be no radioactive activation of the fusion reactor. This is often seen as the end goal of fusion research. 3He is the first 3rd generation fusion fuel that is likely to be used since it has the lowest Maxwellian reactivity in comparison to other 3rd generation fusion fuels.

3He + 3He $rightarrow$ 2p + 4He (12.86 MeV)

Another aneutronic fusion reaction may be the proton-boron reaction: For other uses, see Proton (disambiguation). ...

p + 11B → 34He

Under reasonable assumptions, side reactions will result in about 0.1% 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. If the percentage of D-T is higher, spontaneous combustion might occur and damage the system. For other uses, see Proton (disambiguation). ...

The nuclear fuel cycle, also called nuclear fuel chain, is the progression of nuclear fuel through a series of differing stages. ... 10 countries are responsible for 94 % of the global uranium extraction. ... Reprocessed uranium (RepU) is the uranium recovered from nuclear fuel reprocessing. ... The Global Nuclear Energy Partnership, announced by U.S. Department of Energy secretary Samuel Bodman on February 6, 2006, is a 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...

### 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

Results from FactBites:

 nuclear fuel cycle: Information from Answers.com (3963 words) Since nuclear materials are radioactive, it is important to ensure that radiation exposure of both those involved in the transport of such materials and the general public along transport routes is limited. A nuclear reactor core is composed of a few hundred "assemblies", arranged in a regular array of cells, each cell being formed by a fuel or control rod surrounded, in most designs, by a moderator and coolant, which is water in most reactors. The spent fuel rods are usually stored in water, which provides both cooling, the spent fuel continues to generate decay heat as a result of residual radioactive decay, and shielding to protect the environment from residual ionizing radiation, although after several years of cooling they may be moved to dry cask storage.
 Nuclear fuel - Wikipedia, the free encyclopedia (3716 words) Nuclear fuel is any material that can be consumed to derive nuclear energy, by analogy to chemical fuel that is burned to derive energy. H (tritium) are used as fuel for nuclear fusion. Metal actinide fuel is typically an alloy of zirconium, uranium, plutonium and the minor actinides.
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