Nuclear fuel

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https://en.wikipedia.org/wiki/Nuclear_fuel 

Nuclear Fuel Process

 

A graph comparing nucleon number against binding energy

 

Close-up of a replica of the core of the research reactor at the Institut Laue-Langevin

Nuclear fuel is material used in nuclear power stations to produce heat to power turbines. Heat is created when nuclear fuel undergoes nuclear fission.

Most nuclear fuels contain heavy fissile actinide elements that are capable of undergoing and sustaining nuclear fission. The three most relevant fissile isotopes are uranium-233, uranium-235 and plutonium-239. When the unstable nuclei of these atoms are hit by a slow-moving neutron, they frequently split, creating two daughter nuclei and two or three more neutrons. In that case, the neutrons released go on to split more nuclei. This creates a self-sustaining chain reaction that is controlled in a nuclear reactor, or uncontrolled in a nuclear weapon. Alternatively, if the nucleus absorbs the neutron without splitting, it creates a heavier nucleus with one additional neutron.

The processes involved in mining, refining, purifying, using, and disposing of nuclear fuel are collectively known as the nuclear fuel cycle.

Not all types of nuclear fuels create power from nuclear fission; plutonium-238 and some other elements are used to produce small amounts of nuclear power by radioactive decay in radioisotope thermoelectric generators and other types of atomic batteries.

Nuclear fuel has the highest energy density of all practical fuel sources.

Oxide fuel

For fission reactors, the fuel (typically based on uranium) is usually based on the metal oxide; the oxides are used rather than the metals themselves because the oxide melting point is much higher than that of the metal and because it cannot burn, being already in the oxidized state.

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

Uranium dioxide

Uranium dioxide is a black semiconducting solid. It can be made by heating uranyl nitrate to form UO
₃

${\displaystyle {\ce {UO2(NO3)2.6H2O-> UO3 + 2NO2 + 1/2O2 + 6H2O(g)}}}$

This is then converted by heating with hydrogen to form UO₂. It can be made from enriched uranium hexafluoride by reacting with ammonia to form a solid called ammonium diuranate, ${\displaystyle {\ce {(NH4)2U2O7.}}}$ This is then heated (calcined) to form UO
₃ and U₃O₈ which is then converted by heating with hydrogen or ammonia to form UO₂.

The UO₂ is 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.

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

Corrosion of uranium dioxide in water is controlled by similar electrochemical processes to the galvanic corrosion of a metal surface.

While exposed to the neutron flux during normal operation in the core environment a small percentage of the Uranium-238 in the fuel absorbs excess neutrons and is transmuted into U-239. U-239 rapidly decays into Neptunium-239 which in turn rapidly decays into Plutonium-239. The small percentage of Plutonium-239 has a higher neutron cross section than Uranium-235. As the Plutonium-239 accumulates the chain reaction shifts from pure Uranium-235 at initiation of the fuel use to a ratio of about 70% Uranium-235 and 30% Plutonium-239 at the end of the 18 to 24 month fuel exposure period.

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.

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.

Reprocessing of commercial nuclear fuel to make MOX was done in the Sellafield MOX Plant (England). As of 2015, MOX fuel is made in France (see Marcoule Nuclear Site), and to a lesser extent in Russia (see Mining and Chemical Combine), India and Japan. China plans to develop fast breeder reactors (see CEFR) and reprocessing.

The Global Nuclear Energy Partnership, was a U.S. proposal in the George W. Bush Administration 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. Normally, with the fuel being changed every three years or so, about half of the Pu-239 is 'burned' in the reactor, providing about one third of the total energy. It behaves like U-235 and its fission releases a similar amount of energy. The higher the burn-up, the more plutonium in the spent fuel, but the lower the fraction of fissile plutonium. Typically about one percent of the used fuel discharged from a reactor is plutonium, and some two thirds of this is fissile (c. 50% Pu-239, 15% Pu-241). Worldwide, some 70 tonnes of plutonium contained in used fuel is removed when refueling reactors each year.

Metal fuel

Metal fuels have the advantage of a much higher heat conductivity than oxide fuels but cannot survive equally high temperatures. Metal fuels have a long history of use, stretching from the Clementine reactor in 1946 to many test and research reactors. Metal fuels have the potential for the highest fissile atom density. Metal fuels are normally alloyed, but some metal fuels have been made with pure uranium metal. Uranium alloys that have been used include uranium aluminum, uranium zirconium, uranium silicon, uranium molybdenum, and uranium zirconium hydride (UZrH). Any of the aforementioned fuels can be made with plutonium and other actinides as part of a closed nuclear fuel cycle. Metal fuels have been used in water reactors and liquid metal fast breeder reactors, such as EBR-II.

TRIGA fuel

TRIGA fuel is used in TRIGA (Training, Research, Isotopes, General Atomics) reactors. The TRIGA reactor uses UZrH fuel, which has a prompt negative fuel temperature coefficient of reactivity, meaning that as the temperature of the core increases, the reactivity decreases—so it is highly unlikely 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. That is, they can be used as a neutron source. 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 US. 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. Metal actinide fuel is typically an alloy of zirconium, uranium, plutonium, and minor actinides. It can be made inherently safe as thermal expansion of the metal alloy will increase neutron leakage.

Molten plutonium

Molten plutonium, alloyed with other metals to lower its melting point and encapsulated in tantalum, was tested in two experimental reactors, LAMPRE I and LAMPRE II, at Los Alamos National Laboratory in the 1960s. "LAMPRE experienced three separate fuel failures during operation."

Non-oxide ceramic fuels

Ceramic fuels other than oxides have the advantage of high heat conductivities and melting points, but they are more prone to swelling than oxide fuels and are not understood as well.

Uranium nitride

Main article: 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 (n,p) 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 pyroprocessing to enable 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. Fluoride volatility is a method of reprocessing that does not rely on nitric acid, but it has only been demonstrated in relatively small scale installations whereas the established PUREX process is used commercially for about a third of all spent nuclear fuel (the rest being largely subject to a "once through fuel cycle"). All nitrogen-fluoride compounds are volatile or gaseous at room temperature and could be fractionally distilled from the other gaseous products (including recovered uranium hexafluoride) to recover the initially used nitrogen. If the fuel could be processed in such a way as to ensure low contamination with non-radioactive carbon (not a common fission product and absent in nuclear reactors that don't use it as a moderator) then Fluoride volatility could be used to separate the ¹⁴
C produced by producing carbon tetrafluoride. ¹⁴
C is proposed for use in particularly long lived low power nuclear batteries called diamond battery.

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 reactors during their intense study during the 1960s and 1970s. 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 makes uranium carbide an attractive fuel. In addition, because of the absence of oxygen in this fuel (during the course of irradiation, excess gas pressure can build from the formation of O₂ or other gases) as well as the ability to complement 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. While the neutron cross section of carbon is low, during years of burnup, the predominantly ¹²
C will undergo neutron capture to produce stable ¹³
C as well as radioactive ¹⁴
C. Unlike the ¹⁴
C produced by using Uranium nitrate, the ¹⁴
C will make up only a small isotopic impurity in the overall carbon content and thus make the entirety of the carbon content unsuitable for non-nuclear uses but the ¹⁴
C concentration will be too low for use in nuclear batteries without enrichment. Nuclear graphite discharged from reactors where it was used as a moderator presents the same issue.

Liquid fuels

Liquid fuels are liquids containing dissolved nuclear fuel and have been shown to offer numerous operational advantages compared to traditional solid fuel approaches.

Liquid-fuel reactors offer significant safety advantages due to their inherently stable "self-adjusting" reactor dynamics. This provides two major benefits: - virtually eliminating the possibility of a run-away reactor meltdown, - providing an automatic load-following capability which is well suited to electricity generation and high-temperature industrial heat applications.

Another major advantage of the liquid core is its ability to be drained rapidly into a passively safe dump-tank. This advantage was conclusively demonstrated repeatedly as part of a weekly shutdown procedure during the highly successful 4 year Molten Salt Reactor Experiment.

Another huge advantage of the liquid core is its ability to release xenon gas which normally acts as a neutron absorber (¹³⁵
Xe is the strongest known neutron poison and is produced both directly and as a decay product of ¹³⁵
I as a fission product) and causes structural occlusions in solid fuel elements (leading to the early replacement of solid fuel rods with over 98% of the nuclear fuel unburned, including many long-lived actinides). In contrast, Molten Salt Reactors (MSR) are capable of retaining the fuel mixture for significantly extended periods, which not only increases fuel efficiency dramatically but also incinerates the vast majority of its own waste as part of the normal operational characteristics. A downside to letting the ¹³⁵
Xe escape instead of allowing it to capture neutrons converting it to the basically stable and chemically inert ¹³⁶
Xe, is that it will quickly decay to the highly chemically reactive long lived radioactive ¹³⁵
Cs, which behaves similar to other alkali metals and can be taken up by organisms in their metabolism.

Molten salts

Molten salt fuels have nuclear fuel dissolved directly in the molten salt coolant. Molten salt-fueled reactors, such as the liquid fluoride thorium reactor (LFTR), are different from molten salt-cooled reactors that do not dissolve nuclear fuel in the coolant.

Molten salt fuels were used in the LFTR known as the Molten Salt Reactor Experiment, as well as other liquid core reactor experiments. The liquid fuel for the molten salt reactor was a mixture of lithium, beryllium, thorium and uranium fluorides: 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 operated at 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 (AHRs) use a solution of uranyl sulfate or other uranium salt in water. Historically, AHRs have all been small research reactors, not large power reactors. An AHR known as the Medical Isotope Production System is being considered for production of medical isotopes.

Liquid metals or alloys

The Dual fluid reactor has a variant DFR/m which works with eutectic liquid metal alloys, e.g. U-Cr or U-Fe.

Common physical forms of nuclear fuel

See also: Active fuel length

Uranium dioxide (UO₂) powder is compacted to cylindrical pellets and sintered at high temperatures to produce ceramic nuclear fuel pellets with a high density and well defined physical properties and chemical composition. A grinding process is used to achieve a uniform cylindrical geometry with narrow tolerances. Such fuel pellets are then stacked and filled into the metallic tubes. 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 which, in addition to being highly corrosion-resistant, has low neutron absorption. The tubes containing the fuel pellets are sealed: these tubes are called fuel rods. The finished fuel rods are grouped into fuel assemblies that are used to build up the core of a power reactor.

Cladding is the outer layer of the fuel rods, standing between the coolant and the nuclear fuel. It is made of a corrosion-resistant material with low absorption cross section for thermal neutrons, usually Zircaloy or steel in modern constructions, or magnesium with small amount of aluminium and other metals for the now-obsolete Magnox reactors. Cladding prevents radioactive fission fragments from escaping the fuel into the coolant and contaminating it. Besides the prevention of radioactive leaks this also serves to keep the coolant as non-corrosive as feasible and to prevent reactions between chemically aggressive fission products and the coolant. (e.g. The highly reactive alkali metal Caesium which reacts strongly with water, producing hydrogen, and which is among the more common fission products)

• 

  Nuclear Regulatory Commission (NRC) photo of unirradiated (fresh) fuel pellets.

• 

  NRC photo of fresh fuel pellets ready for assembly.

• 

  NRC photo of fresh fuel assemblies being inspected.

PWR fuel assembly (also known as a fuel bundle) This fuel assembly is from a pressurized water reactor of the nuclear-powered passenger and cargo ship NS Savannah. Designed and built by the Babcock & Wilcox Company.

PWR fuel

Pressurized water reactor (PWR) fuel consists of cylindrical rods put into bundles. A uranium oxide ceramic is formed into pellets and inserted into Zircaloy tubes that are bundled together. The Zircaloy tubes are about 1 centimetre (0.4 in) in diameter, and the fuel cladding gap is filled with helium gas to improve heat conduction from the fuel to the cladding. 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 14×14 to 17×17. PWR fuel bundles are about 4 m (13 ft) long. 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 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. This is primarily done to prevent local density variations from affecting neutronics and thermal hydraulics of the reactor core. 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 BWR in the U.S. form the reactor core. Each BWR fuel rod is backfilled with helium to a pressure of about 3 standard atmospheres (300 kPa).

CANDU fuel bundles Two CANDU ("CANada Deuterium Uranium") fuel bundles, each about 50 cm long, 10 cm in diameter.

CANDU fuel

CANDU fuel bundles are about 0.5 metres (20 in) long and 10 centimetres (4 in) in diameter. They consist of sintered (UO₂) pellets in zirconium alloy tubes, welded to zirconium alloy end plates. Each bundle weighs roughly 20 kilograms (44 lb), 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. It is also about 10 cm (4 inches) in diameter, 0.5 m (20 in) long and weighs about 20 kg (44 lb) and replaces the 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 the lower neutron absorption in their heavy water moderator compared to light water), however, some newer concepts call for low enrichment to help reduce the size of the reactors. The Atucha nuclear power plant in Argentina, a similar design to the CANDU but built by German KWU was originally designed for non-enriched fuel but since switched to slightly enriched fuel with a ²³⁵
U content about 0.1 percentage points higher than in natural uranium.

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.

A magnox fuel rod

Magnox fuel

Main article: Magnox

Magnox (magnesium non-oxidising) reactors are pressurised, carbon dioxide–cooled, graphite-moderated reactors using natural uranium (i.e. unenriched) as fuel and Magnox alloy as fuel cladding. Working pressure varies from 6.9 to 19.35 bars (100.1 to 280.6 psi) for the steel pressure vessels, and the two reinforced concrete designs operated at 24.8 and 27 bars (24.5 and 26.6 atm). Magnox alloy consists mainly of magnesium with small amounts of aluminium and other metals—used in cladding unenriched uranium metal fuel with a non-oxidising covering to contain fission products. This material has the advantage of a low neutron capture cross-section, but has two major disadvantages:

• It limits the maximum temperature, and hence the thermal efficiency, of the plant.
• It reacts with water, preventing long-term storage of spent fuel under water - such as in a spent fuel pool.

Magnox fuel incorporated cooling fins to provide maximum heat transfer despite low operating temperatures, making it expensive to produce. While the use of uranium metal rather than oxide made nuclear reprocessing more straightforward and therefore cheaper, the need to reprocess fuel a short time after removal from the reactor meant that the fission product hazard was severe. Expensive remote handling facilities were required to address this issue.

TRISO fuel

0.845 mm TRISO fuel particle which has been cracked, showing multiple layers that are coating the spherical kernel

Tristructural-isotropic (TRISO) fuel is a type of micro-particle fuel. A particle consists of a kernel of UO_X fuel (sometimes UC or UCO), which has been coated with four layers of three isotropic materials deposited through fluidized chemical vapor deposition (FCVD). The four layers are a porous buffer layer made of carbon that absorbs fission product recoils, followed by a dense inner layer of protective 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 particles are then encapsulated into cylindrical or spherical graphite pellets. 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 up to 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 prismatic-block gas-cooled reactor (such as the GT-MHR) and the pebble-bed reactor (PBR). Both of these reactor designs are high temperature gas reactors (HTGRs). These are also the basic reactor designs of very-high-temperature reactors (VHTRs), one of the six classes of reactor designs in the Generation IV initiative that is attempting to reach even higher HTGR outlet temperatures.

TRISO fuel particles were originally developed in the United Kingdom as part of the Dragon reactor project. The inclusion of the SiC as diffusion barrier was first suggested by D. T. Livey. The first nuclear reactor to use TRISO fuels was the Dragon reactor and the first powerplant was the THTR-300. Currently, TRISO fuel compacts are being used in some experimental reactors, such as the HTR-10 in China and the High-temperature engineering test reactor in Japan. Spherical fuel elements utilizing a TRISO particle with a UO₂ and UC solid solution kernel are being used in the Xe-100 in the United States.

QUADRISO fuel

QUADRISO Particle

In QUADRISO particles a burnable neutron poison (europium oxide or erbium oxide or carbide) layer surrounds the fuel kernel of ordinary TRISO particles to better manage the excess of reactivity. If the core is equipped both with TRISO and QUADRISO fuels, at beginning of life neutrons do not reach the fuel of the QUADRISO particles because they are stopped by the burnable poison. During reactor operation, neutron irradiation of the poison causes it to "burn up" or progressively transmute to non-poison isotopes, depleting this poison effect and leaving progressively more neutrons available for sustaining the chain-reaction. This mechanism compensates for the accumulation of undesirable neutron poisons which are an unavoidable part of the fission products, as well as normal fissile fuel "burn up" or depletion. In the generalized QUADRISO fuel concept the poison can eventually be mixed with the fuel kernel or the outer pyrocarbon. The QUADRISO concept was conceived at Argonne National Laboratory.

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. This is a low-enriched uranium oxide fuel. The fuel elements in an RBMK are 3 m long each, and two of these sit back-to-back on each fuel channel, pressure tube. Reprocessed uranium from Russian VVER reactor spent fuel is used to fabricate RBMK fuel. Following the Chernobyl accident, the enrichment of fuel was changed from 2.0% to 2.4%, to compensate for control rod modifications and the introduction of additional absorbers.

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 United States 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. The blue glow around the core is known as Cherenkov radiation.

Plate-type fuel has fallen out of favor over the years. Plate-type fuel is commonly composed of enriched uranium sandwiched between metal cladding. Plate-type fuel is used in several research reactors where a high neutron flux is desired, for uses such as material irradiation studies or isotope production, without the high temperatures seen in ceramic, cylindrical fuel. It is currently used in the Advanced Test Reactor (ATR) at Idaho National Laboratory, and the nuclear research reactor at the University of Massachusetts Lowell Radiation Laboratory.

Sodium-bonded fuel

Sodium-bonded fuel consists of fuel that has liquid sodium in the gap between the fuel slug (or pellet) and the cladding. This fuel type is often used for sodium-cooled liquid metal fast reactors. It has been used in EBR-I, EBR-II, and the FFTF. The fuel slug may be metallic or ceramic. The sodium bonding is used to reduce the temperature of the fuel.

Accident tolerant fuels

Accident tolerant fuels (ATF) are a series of new nuclear fuel concepts, researched in order to improve fuel performance under accident conditions, such as loss-of-coolant accident (LOCA) or reaction-initiated accidents (RIA). These concerns became more prominent after the Fukushima Daiichi nuclear disaster in Japan, in particular regarding light-water reactor (LWR) fuels performance under accident conditions.

The aim of the research is to develop nuclear fuels that can tolerate loss of active cooling for a considerably longer period than the existing fuel designs and prevent or delay the release of radionuclides during an accident. This research is focused on reconsidering the design of fuel pellets and cladding, as well as the interactions between the two.

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. In fuel which has been used at high temperature in power reactors it is common for the fuel to be heterogeneous; often the fuel will contain nanoparticles of platinum group metals such as palladium. Also the fuel may well have cracked, swollen, and been heated 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. The radiation hazard from spent nuclear declines as its radioactive components decay, but remains high for many years. For example 10 years after removal from a reactor, the surface dose rate for a typical spent fuel assembly still exceeds 10,000 rem/hour, resulting in a fatal dose in just minutes.

Oxide fuel under accident conditions

Main article: Behavior of nuclear fuel during a reactor accident

Two main modes of release exist, the fission products can be vaporised or small particles of the fuel can be dispersed.

Fuel behavior and post-irradiation examination

Main article: Post Irradiation Examination

Post-Irradiation Examination (PIE) is the study of used nuclear materials such as nuclear fuel. It has several purposes. It is known that by examination of used fuel that the failure modes which occur during normal use (and the manner in which the fuel will behave during an accident) can be studied. In addition information is gained which enables the users of fuel to assure themselves of its quality and it also assists in the development of new fuels. After major accidents the core (or what is left of it) is normally subject to PIE 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.

Materials in a high-radiation environment (such as a reactor) can undergo unique behaviors such as swelling 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.

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.

According to the International Nuclear Safety Center 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

Where ρ is the bulk density of the fuel and ρ_td is the theoretical density of the uranium dioxide.

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 such as Lees' disk, the Forbes' method, or Searle's bar, it is common to use Laser Flash Analysis 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 calculate and determine 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.

α = 0.1388 L²/t_1/2

• L is the thickness of the disc

For details see K. Shinzato and T. Baba (2001).

Radioisotope decay fuels

Radioisotope battery

Main article: Atomic battery

An atomic battery (also called a nuclear battery or radioisotope battery) is a device which uses the radioactive decay to generate electricity. These systems use radioisotopes that produce low energy beta particles or sometimes alpha particles of varying energies. Low energy beta particles are needed to prevent the production of high energy penetrating bremsstrahlung radiation that would require heavy shielding. Radioisotopes such as plutonium-238, curium-242, curium-244 and strontium-90 have been used. Tritium, nickel-63, promethium-147, and technetium-99 have been tested.

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. These designs include the direct charging generators, betavoltaics, the optoelectric nuclear battery, and the radioisotope piezoelectric generator. 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 generator

Inspection of Cassini spacecraft RTGs before launch

 

Main article: Radioisotope thermoelectric generator

A radioisotope thermoelectric generator (RTG) is a simple electrical generator which converts heat into electricity from a radioisotope using an array of thermocouples.

²³⁸
Pu
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 ⁹⁰
Sr
; 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 ²¹⁰
Po
. 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 for this application.

Photo of a disassembled RHU

Radioisotope heater unit (RHU)

Main article: Radioisotope heater unit

A radioisotope heater unit (RHU) typically provides 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.

Their function is to provide highly localised heating of sensitive equipment (such as electronics in outer space). The Cassini–Huygens orbiter to Saturn contains 82 of these units (in addition to its 3 main RTGs for power generation). The Huygens probe to Titan contains 35 devices.

Fusion fuels

Main article: Fusion power § Fuels

Fusion fuels are fuels to use in hypothetical Fusion power reactors. They include deuterium (²H) and tritium (³H) as well as helium-3 (³He). Many other elements can be fused together, but the larger electrical charge of their nuclei means that much higher temperatures are required. Only the fusion of the lightest elements is seriously considered as a future energy source. Fusion of the lightest atom, ¹H hydrogen, as is done in the Sun and stars, has also not been considered practical on Earth. Although the energy density of fusion fuel is even higher than fission fuel, and fusion reactions sustained for a few minutes have been achieved, utilizing fusion fuel as a net energy source remains only a theoretical possibility.

First-generation fusion fuel

Deuterium and tritium are both considered first-generation fusion fuels; they are the easiest to fuse, because the electrical charge on their nuclei is the lowest of all elements. The three most commonly cited nuclear reactions that could be used to generate energy are:

²H + ³H → n (14.07 MeV) + ⁴He (3.52 MeV)

²H + ²H → n (2.45 MeV) + ³He (0.82 MeV)

²H + ²H → 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, but generate fewer neutrons. Neutrons are an unwanted byproduct of fusion reactions in an energy generation context, because they are absorbed by the walls of a fusion chamber, making them radioactive. They cannot be confined by magnetic fields, because they are not electrically charged. This group consists of deuterium and helium-3. The products are all charged particles, but there may be significant side reactions leading to the production of neutrons.

²H + ³He → p (14.68 MeV) + ⁴He (3.67 MeV)

Third-generation fusion fuel

Main article: Aneutronic fusion

Third-generation fusion fuels produce only charged particles in the primary reactions, and side reactions are relatively unimportant. Since a very small amount of neutrons is produced, there would be little induced radioactivity in the walls of the fusion chamber. This is often seen as the end goal of fusion research. ³He has the highest Maxwellian reactivity of any 3rd generation fusion fuel. However, there are no significant natural sources of this substance on Earth.

³He + ³He → 2 p + ⁴He (12.86 MeV)

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

p + ¹¹B → 3 ⁴He (8.7 MeV)

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.

Iconoclasm

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Iconoclasm 

"Triumph of Orthodoxy" over iconoclasm under the Byzantine Empress Theodora and her son Michael III. Late 14th – early 15th-century icon.

 

In this Elizabethan work of propaganda, the top right of the picture depicts men busy pulling down and smashing icons, while power is shifting from the dying King Henry VIII at left, pointing to his far more staunchly Protestant son, the boy-king Edward VI at centre.
National Portrait Gallery, London

Iconoclasm (from Greek: εἰκών, eikṓn, 'figure, icon' + κλάω, kláō, 'to break') is the social belief in the importance of the destruction of icons and other images or monuments, most frequently for religious or political reasons. People who engage in or support iconoclasm are called iconoclasts, a term that has come to be figuratively applied to any individual who challenges "cherished beliefs or venerated institutions on the grounds that they are erroneous or pernicious."

Conversely, one who reveres or venerates religious images is called (by iconoclasts) an iconolater; in a Byzantine context, such a person is called an iconodule or iconophile. Iconoclasm does not generally encompass the destruction of the images of a specific ruler after his or her death or overthrow, a practice better known as damnatio memoriae.

While iconoclasm may be carried out by adherents of a different religion, it is more commonly the result of sectarian disputes between factions of the same religion. The term originates from the Byzantine Iconoclasm, the struggles between proponents and opponents of religious icons in the Byzantine Empire from 726 to 842 AD. Degrees of iconoclasm vary greatly among religions and their branches, but are strongest in religions which oppose idolatry, including the Abrahamic religions. Outside of the religious context, iconoclasm can refer to movements for widespread destruction in symbols of an ideology or cause, such as the destruction of monarchist symbols during the French Revolution.

Early religious iconoclasm

Ancient era

Main article: Akhenaten

 

Amun

In the Bronze Age, the most significant episode of iconoclasm occurred in Egypt during the Amarna Period, when Akhenaten, based in his new capital of Akhetaten, instituted a significant shift in Egyptian artistic styles alongside a campaign of intolerance towards the traditional gods and a new emphasis on a state monolatristic tradition focused on the god Aten, the Sun disk—many temples and monuments were destroyed as a result:

In rebellion against the old religion and the powerful priests of Amun, Akhenaten ordered the eradication of all of Egypt's traditional gods. He sent royal officials to chisel out and destroy every reference to Amun and the names of other deities on tombs, temple walls, and cartouches to instill in the people that the Aten was the one true god.

Public references to Akhenaten were destroyed soon after his death. Comparing the ancient Egyptians with the Israelites, Jan Assmann writes:

For Egypt, the greatest horror was the destruction or abduction of the cult images. In the eyes of the Israelites, the erection of images meant the destruction of divine presence; in the eyes of the Egyptians, this same effect was attained by the destruction of images. In Egypt, iconoclasm was the most terrible religious crime; in Israel, the most terrible religious crime was idolatry. In this respect Osarseph alias Akhenaten, the iconoclast, and the Golden Calf, the paragon of idolatry, correspond to each other inversely, and it is strange that Aaron could so easily avoid the role of the religious criminal. It is more than probable that these traditions evolved under mutual influence. In this respect, Moses and Akhenaten became, after all, closely related.

Judaism

According to the Hebrew Bible, God instructed the Israelites to "destroy all [the] engraved stones, destroy all [the] molded images, and demolish all [the] high places" of the indigenous Canaanite population as soon as they entered the Promised Land.

In Judaism, King Hezekiah purged Solomon's Temple in Jerusalem and all figures were also destroyed in the Land of Israel, including the Nehushtan, as recorded in the Second Book of Kings. His reforms were reversed in the reign of his son Manasseh.

Iconoclasm in Christian history

Saint Benedict's monks destroy an image of Apollo, worshiped in the Roman Empire

Scattered expressions of opposition to the use of images have been reported: in 305–306 AD, the Synod of Elvira appeared to endorse iconoclasm; Canon 36 states, "Pictures are not to be placed in churches, so that they do not become objects of worship and adoration." Proscription ceased after the destruction of pagan temples. However, widespread use of Christian iconography only began as Christianity increasingly spread among gentiles after the legalization of Christianity by Roman Emperor Constantine (c. 312 AD). During the process of Christianisation under Constantine, Christian groups destroyed the images and sculptures expressive of the Roman Empire's polytheist state religion.

Among early church theologians, iconoclastic tendencies were supported by theologians such as: Tertullian, Clement of Alexandria, Origen, Lactantius, Justin Martyr, Eusebius and Epiphanus.

Byzantine era

Byzantine Iconoclasm, Chludov Psalter, 9th century

 

Main article: Byzantine Iconoclasm

The period after the reign of Byzantine Emperor Justinian (527–565) evidently saw a huge increase in the use of images, both in volume and quality, and a gathering aniconic reaction.

One notable change within the Byzantine Empire came in 695, when Justinian II's government added a full-face image of Christ on the obverse of imperial gold coins. The change caused the Caliph Abd al-Malik to stop his earlier adoption of Byzantine coin types. He started a purely Islamic coinage with lettering only. A letter by the Patriarch Germanus, written before 726 to two iconoclast bishops, says that "now whole towns and multitudes of people are in considerable agitation over this matter," but there is little written evidence of the debate.

Government-led iconoclasm began with Byzantine Emperor Leo III, who issued a series of edicts between 726 and 730 against the veneration of images. The religious conflict created political and economic divisions in Byzantine society; iconoclasm was generally supported by the Eastern, poorer, non-Greek peoples of the Empire who had to frequently deal with raids from the new Muslim Empire. On the other hand, the wealthier Greeks of Constantinople and the peoples of the Balkan and Italian provinces strongly opposed iconoclasm.

Pre-Reformation

Peter of Bruys opposed the usage of religious images, the Strigolniki were also possibly iconoclastic. Claudius of Turin was the bishop of Turin from 817 until his death. He is most noted for teaching iconoclasm.

Reformation era

Further information: Beeldenstorm and Iconophobia § Iconophobia and the English Reformation

The first iconoclastic wave happened in Wittenberg in the early 1520s under reformers Thomas Müntzer and Andreas Karlstadt, in the absence of Martin Luther, who then, concealed under the pen-name of 'Junker Jörg', intervened to calm things down. Luther argued that the mental picturing of Christ when reading the Scriptures was similar in character to artistic renderings of Christ.

In contrast to the Lutherans who favoured certain types of sacred art in their churches and homes, the Reformed (Calvinist) leaders, in particular Andreas Karlstadt, Huldrych Zwingli and John Calvin, encouraged the removal of religious images by invoking the Decalogue's prohibition of idolatry and the manufacture of graven (sculpted) images of God. As a result, individuals attacked statues and images, most famously in the beeldenstorm across the Netherlands in 1566. However, in most cases, civil authorities removed images in an orderly manner in the newly Reformed Protestant cities and territories of Europe.

• Calvinist iconoclasm during the Reformation
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  Destruction of religious images by the Reformed in Zurich, 1524.

• 

  Remains of Calvinist iconoclasm, Clocher Saint-Barthélémy, La Rochelle, France.

Extent (in blue) of the Beeldenstorm through the Spanish Netherlands

 

16th-century iconoclasm in the Protestant Reformation. Relief statues in St. Stevenskerk in Nijmegen, the Netherlands, were attacked and defaced by Calvinists in the Beeldenstorm.

The belief of iconoclasm caused havoc throughout Europe. In 1523, specifically due to the Swiss reformer Huldrych Zwingli, a vast number of his followers viewed themselves as being involved in a spiritual community that in matters of faith should obey neither the visible Church nor lay authorities. According to Peter George Wallace "Zwingli's attack on images, at the first debate, triggered iconoclastic incidents in Zurich and the villages under civic jurisdiction that the reformer was unwilling to condone." Due to this action of protest against authority, "Zwingli responded with a carefully reasoned treatise that men could not live in society without laws and constraint."

Significant iconoclastic riots took place in Basel (in 1529), Zurich (1523), Copenhagen (1530), Münster (1534), Geneva (1535), Augsburg (1537), Scotland (1559), Rouen (1560), and Saintes and La Rochelle (1562). Calvinist iconoclasm in Europe "provoked reactive riots by Lutheran mobs" in Germany and "antagonized the neighbouring Eastern Orthodox" in the Baltic region.

The Seventeen Provinces (now the Netherlands, Belgium, and parts of Northern France) were disrupted by widespread Calvinist iconoclasm in the summer of 1566. This period, known as the Beeldenstorm, began with the destruction of the statuary of the Monastery of Saint Lawrence in Steenvoorde after a "Hagenpreek," or field sermon, by Sebastiaan Matte on 10 August 1566; by October the wave of furor had gone all through the Spanish Netherlands up to Groningen. Hundreds of other attacks included the sacking of the Monastery of Saint Anthony after a sermon by Jacob de Buysere. The Beeldenstorm marked the start of the revolution against the Spanish forces and the Catholic Church.

Looting of the Churches of Lyon by the Calvinists in 1562 by Antoine Caron.

During the Reformation in England, which started during the reign of Anglican monarch Henry VIII, and was urged on by reformers such as Hugh Latimer and Thomas Cranmer, limited official action was taken against religious images in churches in the late 1530s. Henry's young son, Edward VI, came to the throne in 1547 and, under Cranmer's guidance, issued injunctions for Religious Reforms in the same year and in 1550, an Act of Parliament "for the abolition and putting away of divers books and images." During the English Civil War, Bishop Joseph Hall of Norwich described the events of 1643 when troops and citizens, encouraged by a Parliamentary ordinance against superstition and idolatry, behaved thus:

Lord what work was here! What clattering of glasses! What beating down of walls! What tearing up of monuments! What pulling down of seats! What wresting out of irons and brass from the windows! What defacing of arms! What demolishing of curious stonework! What tooting and piping upon organ pipes! And what a hideous triumph in the market-place before all the country, when all the mangled organ pipes, vestments, both copes and surplices, together with the leaden cross which had newly been sawn down from the Green-yard pulpit and the service-books and singing books that could be carried to the fire in the public market-place were heaped together.

Protestant Christianity was not uniformly hostile to the use of religious images. Martin Luther taught the "importance of images as tools for instruction and aids to devotion," stating: "If it is not a sin but good to have the image of Christ in my heart, why should it be a sin to have it in my eyes?" Lutheran churches retained ornate church interiors with a prominent crucifix, reflecting their high view of the real presence of Christ in Eucharist. As such, "Lutheran worship became a complex ritual choreography set in a richly furnished church interior." For Lutherans, "the Reformation renewed rather than removed the religious image."

Lutheran scholar Jeremiah Ohl writes:

Zwingli and others for the sake of saving the Word rejected all plastic art; Luther, with an equal concern for the Word, but far more conservative, would have all the arts to be the servants of the Gospel. "I am not of the opinion" said [Luther], "that through the Gospel all the arts should be banished and driven away, as some zealots want to make us believe; but I wish to see them all, especially music, in the service of Him Who gave and created them." Again he says: "I have myself heard those who oppose pictures, read from my German Bible.… But this contains many pictures of God, of the angels, of men, and of animals, especially in the Revelation of St. John, in the books of Moses, and in the book of Joshua. We therefore kindly beg these fanatics to permit us also to paint these pictures on the wall that they may be remembered and better understood, inasmuch as they can harm as little on the walls as in books. Would to God that I could persuade those who can afford it to paint the whole Bible on their houses, inside and outside, so that all might see; this would indeed be a Christian work. For I am convinced that it is God's will that we should hear and learn what He has done, especially what Christ suffered. But when I hear these things and meditate upon them, I find it impossible not to picture them in my heart. Whether I want to or not, when I hear, of Christ, a human form hanging upon a cross rises up in my heart: just as I see my natural face reflected when I look into water. Now if it is not sinful for me to have Christ's picture in my heart, why should it be sinful to have it before my eyes?

The Ottoman Sultan Suleiman the Magnificent, who had pragmatic reasons to support the Dutch Revolt (the rebels, like himself, were fighting against Spain) also completely approved of their act of "destroying idols," which accorded well with Muslim teachings.

A bit later in Dutch history, in 1627 the artist Johannes van der Beeck was arrested and tortured, charged with being a religious non-conformist and a blasphemer, heretic, atheist, and Satanist. The 25 January 1628 judgment from five noted advocates of The Hague pronounced him guilty of "blasphemy against God and avowed atheism, at the same time as leading a frightful and pernicious lifestyle. At the court's order his paintings were burned, and only a few of them survive."

Other instances

From the 16th through the 19th centuries, many of the polytheistic religious deities and texts of pre-colonial Americas, Oceania, and Africa were destroyed by Christian missionaries and their converts, such as during the Spanish conquest of the Aztec Empire and the Spanish conquest of the Inca Empire.

Many of the moai of Easter Island were toppled during the 18th century in the iconoclasm of civil wars before any European encounter. Other instances of iconoclasm may have occurred throughout Eastern Polynesia during its conversion to Christianity in the 19th century.

After the Second Vatican Council in the late 20th century, some Roman Catholic parish churches discarded much of their traditional imagery, art, and architecture.

Muslim iconoclasm

Further information: Aniconism in Islam

Islam has a much stronger tradition of forbidding the depiction of figures, especially religious figures, with Sunni Islam forbidding it more than Shia Islam. In the history of Islam, the act of removing idols from the Ka'ba in Mecca has great symbolic and historic importance for all believers.

In general, Muslim societies have avoided the depiction of living beings (both animals and humans) within such sacred spaces as mosques and madrasahs. This ban on figural representation is not based on the Qur'an, instead, it is based on traditions which are described within the Hadith. The prohibition of figuration has not always been extended to the secular sphere, and a robust tradition of figural representation exists within Muslim art. However, Western authors have tended to perceive "a long, culturally determined, and unchanging tradition of violent iconoclastic acts" within Islamic society.

Early Islam in Arabia

The first act of Muslim iconoclasm dates to the beginning of Islam, in 630, when the various statues of Arabian deities housed in the Kaaba in Mecca were destroyed. There is a tradition that Muhammad spared a fresco of Mary and Jesus. This act was intended to bring an end to the idolatry which, in the Muslim view, characterized Jahiliyyah.

The destruction of the idols of Mecca did not, however, determine the treatment of other religious communities living under Muslim rule after the expansion of the caliphate. Most Christians under Muslim rule, for example, continued to produce icons and to decorate their churches as they wished. A major exception to this pattern of tolerance in early Islamic history was the "Edict of Yazīd", issued by the Umayyad caliph Yazīd II in 722–723. This edict ordered the destruction of crosses and Christian images within the territory of the caliphate. Researchers have discovered evidence that the order was followed, particularly in present-day Jordan, where archaeological evidence shows the removal of images from the mosaic floors of some, although not all, of the churches that stood at this time. But Yazīd's iconoclastic policies were not continued by his successors, and Christian communities of the Levant continued to make icons without significant interruption from the sixth century to the ninth.

Egypt

The Sphinx profile in 2010, without the nose

Al-Maqrīzī, writing in the 15th century, attributes the missing nose on the Great Sphinx of Giza to iconoclasm by Muhammad Sa'im al-Dahr, a Sufi Muslim in the mid-1300s. He was reportedly outraged by local Muslims making offerings to the Great Sphinx in the hope of controlling the flood cycle, and he was later executed for vandalism. However, whether this was actually the cause of the missing nose has been debated by historians. Mark Lehner, having performed an archaeological study, concluded that it was broken with instruments at an earlier unknown time between the 3rd and 10th centuries.

Ottoman conquests

Certain conquering Muslim armies have used local temples or houses of worship as mosques. An example is Hagia Sophia in Istanbul (formerly Constantinople), which was converted into a mosque in 1453. Most icons were desecrated and the rest were covered with plaster. In the 1934 the government of Turkey decided to convert the Hagia Sophia into a museum and the restoration of the mosaics was undertaken by the American Byzantine Institute beginning in 1932.

Contemporary events

Further information: Destruction of early Islamic heritage sites in Saudi Arabia and Destruction of cultural heritage by ISIL

Certain Muslim denominations continue to pursue iconoclastic agendas. There has been much controversy within Islam over the recent and apparently on-going destruction of historic sites by Saudi Arabian authorities, prompted by the fear they could become the subject of "idolatry."

A recent act of iconoclasm was the 2001 destruction of the giant Buddhas of Bamyan by the then-Taliban government of Afghanistan. The act generated worldwide protests and was not supported by other Muslim governments and organizations. It was widely perceived in the Western media as a result of the Muslim prohibition against figural decoration. Such an account overlooks "the coexistence between the Buddhas and the Muslim population that marveled at them for over a millennium" before their destruction. The Buddhas had twice in the past been attacked by Nadir Shah and Aurengzeb. According to art historian F. B. Flood, analysis of the Taliban's statements regarding the Buddhas suggest that their destruction was motivated more by political than by theological concerns. Taliban spokespeople have given many different explanations of the motives for the destruction.

During the Tuareg rebellion of 2012, the radical Islamist militia Ansar Dine destroyed various Sufi shrines from the 15th and 16th centuries in the city of Timbuktu, Mali. In 2016, the International Criminal Court (ICC) sentenced Ahmad al-Faqi al-Mahdi, a former member of Ansar Dine, to nine years in prison for this destruction of cultural world heritage. This was the first time that the ICC convicted a person for such a crime.

The short-lived Islamic State of Iraq and the Levant carried out iconoclastic attacks such as the destruction of Shia mosques and shrines. Notable incidents include blowing up the Mosque of the Prophet Yunus (Jonah) and destroying the Shrine to Seth in Mosul.

Iconoclasm in India

Further information: Religious violence in India

In early Medieval India, there were numerous recorded instances of temple desecration by Indian kings against rival Indian kingdoms, which involved conflicts between devotees of different Hindu deities, as well as conflicts between Hindus, Buddhists, and Jains.

In 642, the Pallava king Narasimhavarman I looted a Ganesha temple in the Chalukyan capital of Vatapi. In c. 692, Chalukya armies invaded northern India where they looted temples of Ganga and Yamuna.

In the 8th century, Bengali troops from the Buddhist Pala Empire desecrated temples of Vishnu Vaikuṇṭha, the state deity of Lalitaditya's kingdom in Kashmir. In the early 9th century, Indian Hindu kings from Kanchipuram and the Pandyan king Srimara Srivallabha looted Buddhist temples in Sri Lanka. In the early 10th century, the Pratihara king Herambapala looted an image from a temple in the Sahi kingdom of Kangra, which was later looted by the Pratihara king Yasovarman.

During the Muslim conquest of Sindh

Records from the campaign recorded in the Chach Nama record the destruction of temples during the early 8th century when the Umayyad governor of Damascus, al-Hajjaj ibn Yusuf, mobilized an expedition of 6000 cavalry under Muhammad bin Qasim in 712.

Historian Upendra Thakur records the persecution of Hindus and Buddhists:

Muhammad triumphantly marched into the country, conquering Debal, Sehwan, Nerun, Brahmanadabad, Alor and Multan one after the other in quick succession, and in less than a year and a half, the far-flung Hindu kingdom was crushed ... There was a fearful outbreak of religious bigotry in several places and temples were wantonly desecrated. At Debal, the Nairun and Aror temples were demolished and converted into mosques.

• Iconoclasm during the Muslim conquests in the Indian subcontinent
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  The Somnath Temple in Gujarat was repeatedly destroyed by Islamic armies and rebuilt by Hindus. It was destroyed by Delhi Sultanate's army in 1299 CE. The present temple was reconstructed in Chaulukya style of Hindu temple architecture and completed in May 1951.

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  The Kashi Vishwanath Temple was repeatedly destroyed by Islamic invaders such as Qutb al-Din Aibak.

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  Ruins of the Martand Sun Temple. The temple was destroyed on the orders of Muslim Sultan Sikandar Butshikan in the early 15th century, with demolition lasting a year.

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  The armies of Delhi Sultanate led by Muslim Commander Malik Kafur plundered the Meenakshi Temple and looted it of its valuables.

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  Kakatiya Kala Thoranam (Warangal Gate) built by the Kakatiya dynasty in ruins; one of the many temple complexes destroyed by the Delhi Sultanate.

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  Rani ki vav is a stepwell, built by the Chaulukya dynasty, located in Patan; the city was sacked by Sultan of Delhi Qutb-ud-din Aybak between 1200 and 1210, and it was destroyed by the Allauddin Khilji in 1298.

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  Artistic rendition of the Kirtistambh at Rudra Mahalaya Temple. The temple was destroyed by Alauddin Khalji.

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  Exterior wall reliefs at Hoysaleswara Temple. The temple was twice sacked and plundered by the Delhi Sultanate.

Chola to Paramara dynasty

In the early 11th century, the Chola king Rajendra I looted temples in a number of neighbouring kingdoms, including:

• Durga and Ganesha temples in the Chalukya Kingdom;
• Bhairava, Bhairavi, and Kali temples in the Kalinga kingdom;
• a Nandi temple in the Eastern Chalukya kingdom; and
• a Siva temple in Pala Bengal.

In the mid-11th century, the Chola king Rajadhiraja plundered a temple in Kalyani. In the late 11th century, the Hindu king Harsha of Kashmir plundered temples as an institutionalised activity. In the late 12th to early 13th centuries, the Paramara dynasty attacked and plundered Jain temples in Gujarat.

The Somnath temple and Mahmud of Ghazni

Perhaps the most notorious episode of iconoclasm in India was Mahmud of Ghazni's attack on the Somnath temple from across the Thar Desert. The temple was first raided in 725, when Junayad, the governor of Sind, sent his armies to destroy it. In 1024, during the reign of Bhima I, the prominent Turkic-Muslim ruler Mahmud of Ghazni raided Gujarat, plundering the Somnath temple and breaking its jyotirlinga despite pleas by Brahmins not to break it. He took away a booty of 20 million dinars. The attack may have been inspired by the belief that an idol of the goddess Manat had been secretly transferred to the temple. According to the Ghaznavid court-poet Farrukhi Sistani, who claimed to have accompanied Mahmud on his raid, Somnat (as rendered in Persian) was a garbled version of su-manat referring to the goddess Manat. According to him, as well as a later Ghaznavid historian Abu Sa'id Gardezi, the images of the other goddesses were destroyed in Arabia but the one of Manat was secretly sent away to Kathiawar (in modern Gujarat) for safekeeping. Since the idol of Manat was an aniconic image of black stone, it could have been easily confused with a lingam at Somnath. Mahmud is said to have broken the idol and taken away parts of it as loot and placed so that people would walk on it. In his letters to the Caliphate, Mahmud exaggerated the size, wealth and religious significance of the Somnath temple, receiving grandiose titles from the Caliph in return.

The wooden structure was replaced by Kumarapala (r. 1143–72), who rebuilt the temple out of stone.

Mamluk dynasty onward

Historical records compiled by Muslim historian Maulana Hakim Saiyid Abdul Hai attest to the religious violence during the Mamluk dynasty under Qutb-ud-din Aybak. The first mosque built in Delhi, the "Quwwat al-Islam" was built with demolished parts of 20 Hindu and Jain temples. This pattern of iconoclasm was common during his reign.

During the Delhi Sultanate, a Muslim army led by Malik Kafur, a general of Alauddin Khalji, pursued four violent campaigns into south India, between 1309 and 1311, against the Hindu kingdoms of Devgiri (Maharashtra), Warangal (Telangana), Dwarasamudra (Karnataka) and Madurai (Tamil Nadu). Many Temples were plundered; Hoysaleswara Temple and others were ruthlessly destroyed.

In Kashmir, Sikandar Shah Miri (1389–1413) began expanding, and unleashed religious violence that earned him the name but-shikan, or 'idol-breaker'. He earned this sobriquet because of the sheer scale of desecration and destruction of Hindu and Buddhist temples, shrines, ashrams, hermitages, and other holy places in what is now known as Kashmir and its neighboring territories. Firishta states, "After the emigration of the Bramins, Sikundur ordered all the temples in Kashmeer to be thrown down." He destroyed vast majority of Hindu and Buddhist temples in his reach in Kashmir region (north and northwest India).

In the 1460s, Kapilendra, founder of the Suryavamsi Gajapati dynasty, sacked the Saiva and Vaishnava temples in the Cauvery delta in the course of wars of conquest in the Tamil country. Vijayanagara king Krishnadevaraya looted a Bala Krishna temple in Udayagiri in 1514, and looted a Vittala temple in Pandharpur in 1520.

A regional tradition, along with the Hindu text Madala Panji, states that Kalapahad attacked and damaged the Konark Sun Temple in 1568, as well as many others in Orissa.

Some of the most dramatic cases of iconoclasm by Muslims are found in parts of India where Hindu and Buddhist temples were razed and mosques erected in their place. Aurangzeb, the 6th Mughal Emperor, destroyed the famous Hindu temples at Varanasi and Mathura, turning back on his ancestor Akbar's policy of religious freedom and establishing Sharia across his empire.

In modern India, the most high-profile case of iconoclasm was from 1992. Hindus, led by the Vishva Hindu Parishad and Bajrang Dal, destroyed the 430-year-old Islamic Babri Masjid in Ayodhya.

Iconoclasm in East Asia

China

Further information: Four Buddhist Persecutions in China and Anti-Western sentiment in China

There have been a number of anti-Buddhist campaigns in Chinese history that led to the destruction of Buddhist temples and images. One of the most notable of these campaigns was the Great Anti-Buddhist Persecution of the Tang dynasty.

During and after the 1911 Xinhai Revolution, there was widespread destruction of religious and secular images in China.

During the Northern Expedition in Guangxi in 1926, Kuomintang General Bai Chongxi led his troops in destroying Buddhist temples and smashing Buddhist images, turning the temples into schools and Kuomintang party headquarters. It was reported that almost all of the viharas in Guangxi were destroyed and the monks were removed. Bai also led a wave of anti-foreignism in Guangxi, attacking Americans, Europeans, and other foreigners, and generally making the province unsafe for foreigners and missionaries. Westerners fled from the province and some Chinese Christians were also attacked as imperialist agents. The three goals of the movement were anti-foreignism, anti-imperialism and anti-religion. Bai led the anti-religious movement against superstition. Huang Shaohong, also a Kuomintang member of the New Guangxi clique, supported Bai's campaign. The anti-religious campaign was agreed upon by all Guangxi Kuomintang members.

There was extensive destruction of religious and secular imagery in Tibet after it was invaded and occupied by China.

Many religious and secular images were destroyed during the Cultural Revolution of 1966–1976, ostensibly because they were a holdover from China's traditional past (which the Communist regime led by Mao Zedong reviled). The Cultural Revolution included widespread destruction of historic artworks in public places and private collections, whether religious or secular. Objects in state museums were mostly left intact.

South Korea

According to an article in Buddhist-Christian Studies:

Over the course of the last decade [1990s] a fairly large number of Buddhist temples in South Korea have been destroyed or damaged by fire by Christian fundamentalists. More recently, Buddhist statues have been identified as idols, and attacked and decapitated in the name of Jesus. Arrests are hard to effect, as the arsonists and vandals work by stealth of night.

Angkor

Further information: Angkor

Beginning around 1243 AD with the death of Indravarman II, the Khmer Empire went through a period of iconoclasm. At the beginning of the reign of the next king, Jayavarman VIII, the Kingdom went back to Hinduism and the worship of Shiva. Many of the Buddhist images were destroyed by Jayavarman VIII, who reestablished previously Hindu shrines that had been converted to Buddhism by his predecessor. Carvings of the Buddha at temples such as Preah Khan were destroyed, and during this period the Bayon Temple was made a temple to Shiva, with the central 3.6 meter tall statue of the Buddha cast to the bottom of a nearby well.

Political iconoclasm

Damnatio memoriae

Main article: damnatio memoriae

Revolutions and changes of regime, whether through uprising of the local population, foreign invasion, or a combination of both, are often accompanied by the public destruction of statues and monuments identified with the previous regime. This may also be known as damnatio memoriae, the ancient Roman practice of official obliteration of the memory of a specific individual. Stricter definitions of "iconoclasm" exclude both types of action, reserving the term for religious or more widely cultural destruction. In many cases, such as Revolutionary Russia or Ancient Egypt, this distinction can be hard to make.

Among Roman emperors and other political figures subject to decrees of damnatio memoriae were Sejanus, Publius Septimius Geta, and Domitian. Several Emperors, such as Domitian and Commodus had during their reigns erected numerous statues of themselves, which were pulled down and destroyed when they were overthrown.

The perception of damnatio memoriae in the Classical world was an act of erasing memory has been challenged by scholars who have argued that it "did not negate historical traces, but created gestures which served to dishonor the record of the person and so, in an oblique way, to confirm memory," and was in effect a spectacular display of "pantomime forgetfulness." Examining cases of political monument destruction in modern Irish history, Guy Beiner has demonstrated that iconoclastic vandalism often entails subtle expressions of ambiguous remembrance and that, rather than effacing memory, such acts of de-commemorating effectively preserve memory in obscure forms.

During the French Revolution

Throughout the radical phase of the French Revolution, iconoclasm was supported by members of the government as well as the citizenry. Numerous monuments, religious works, and other historically significant pieces were destroyed in an attempt to eradicate any memory of the Old Regime. A statue of King Louis XV in the Paris square which until then bore his name, was pulled down and destroyed. This was a prelude to the guillotining of his successor Louis XVI in the same site, renamed "Place de la Révolution" (at present Place de la Concorde). Later that year, the bodies of many French kings were exhumed from the Basilica of Saint-Denis and dumped in a mass grave.

Some episodes of iconoclasm were carried out spontaneously by crowds of citizens, including the destruction of statues of kings during the insurrection of 10 August 1792 in Paris. Some were directly sanctioned by the Republican government, including the Saint-Denis exhumations. Nonetheless, the Republican government also took steps to preserve historic artworks, notably by founding the Louvre museum to house and display the former royal art collection. This allowed the physical objects and national heritage to be preserved while stripping them of their association with the monarchy. Alexandre Lenoir saved many royal monuments by diverting them to preservation in a museum.

The statue of Napoleon on the column at Place Vendôme, Paris was also the target of iconoclasm several times: destroyed after the Bourbon Restoration, restored by Louis-Philippe, destroyed during the Paris Commune and restored by Adolphe Thiers.

Other examples

St. Helen's Gate in Cospicua, Malta, which had its marble coat of arms defaced during the French occupation of Malta

 

Statue of William of Orange formerly located on College Green, in Dublin. Erected in 1701, it was destroyed in 1929—one of several memorials installed during British rule which were destroyed after Ireland became independent.

Other examples of political destruction of images include:

• There have been several cases of removing symbols of past rulers in Malta's history. Many Hospitaller coats of arms on buildings were defaced during the French occupation of Malta in 1798–1800; a few of these were subsequently replaced by British coats of arms in the early 19th century. Some British symbols were also removed by the government after Malta became a republic in 1974. These include royal cyphers being ground off from post boxes, and British coats of arms such as that on the Main Guard building being temporarily obscured (but not destroyed).
• With the entry of the Ottoman Empire to the First World War, the Ottoman Army destroyed the Russian victory monument erected in San Stefano (the modern Yeşilköy quarter of Istanbul) to commemorate the Russian victory in the Russo-Turkish War of 1877–1878. The demolition was filmed by former army officer Fuat Uzkınay, producing Ayastefanos'taki Rus Abidesinin Yıkılışı—the oldest known Turkish-made film.
• In the late 18th century, the Brabant Revolutionaries sacked Brussels' Grand Place, destroying statues of nobility and symbols of Christianity. In the 19th century, the place was renovated and many new statues added. In 1911, a marble commemoration for the Spanish freethinker and educator Francisco Ferrer, executed two years earlier and widely considered a martyr, was erected in the Grand Place. The statue depicted a nude man holding the Torch of Enlightenment. The Imperial German military, which occupied Belgium during the First World War, disliked the monument and destroyed it in 1915. It was restored in 1926 by the International Free Thought Movement.
• In 1942 the pro-Nazi Vichy Government of France took down and melted Clothilde Roch's statue of the 16th-century dissident intellectual Michael Servetus, who had been burned at the stake in Geneva at the instigation of Calvin. The Vichy authorities disliked the statue, as it was a celebration of freedom of conscience. In 1960, having found the original molds, the municipality of Annemasse had it recast and returned the statue to its previous place.
• The Battle of Baghdad and the regime of Saddam Hussein symbolically ended with the Firdos Square statue destruction, a U.S. military-staged event on April 9, 2003 where a prominent statue of Saddam Hussein was pulled down.
  

• United States Marines destroy a statue of Saddam Hussein.
  Subsequently, statues and murals of Saddam Hussein all over Iraq were destroyed by US occupation forces as well as Iraqi citizens.
• In 2016, paintings from the University of Cape Town were burned in student protests as symbols of colonialism.
• In November 2019 the statue of Swedish footballer Zlatan Ibrahimović was vandalized by Malmö FF supporters after he announced he had become part-owner of Swedish rivals Hammarby. White paint was sprayed on it; threats and hateful messages towards Zlatan were written on the statue, and it was burned. In a second attack the nose was sawed off and the statue was sprinkled with chrome paint. On 5 January 2020 it was finally toppled.
• On June 4, 2020, Virginia governor Ralph Northam ordered the monument to Robert E. Lee in Richmond to be removed in response to George Floyd protests. It was removed on September 8, 2021.

In the Soviet Union

Demolition of the Cathedral of Christ the Saviour, Moscow, 5 December 1931

During and after the October Revolution, widespread destruction of religious and secular imagery in Russia took place, as well as the destruction of imagery related to the Imperial family. The Revolution was accompanied by destruction of monuments of tsars, as well as the destruction of imperial eagles at various locations throughout Russia. According to Christopher Wharton:

In front of a Moscow cathedral, crowds cheered as the enormous statue of Tsar Alexander III was bound with ropes and gradually beaten to the ground. After a considerable amount of time, the statue was decapitated and its remaining parts were broken into rubble.

The Soviet Union actively destroyed religious sites, including Russian Orthodox churches and Jewish cemeteries, in order to discourage religious practice and curb the activities of religious groups.

During the Hungarian Revolution of 1956 and during the Revolutions of 1989, protesters often attacked and took down sculptures and images of Joseph Stalin, such as the Stalin Monument in Budapest.

The fall of Communism in 1989-1991 was also followed by the destruction or removal of statues of Vladimir Lenin and other Communist leaders in the former Soviet Union and in other Eastern Bloc countries. Particularly well-known was the destruction of "Iron Felix", the statue of Felix Dzerzhinsky outside the KGB's headquarters. Another statue of Dzerzhinsky was destroyed in a Warsaw square that was named after him during communist rule, but which is now called Bank Square.

In the United States

The Sons of Liberty pulling down the statue of George III of the United Kingdom on Bowling Green (New York City), 1776

During the American Revolution, the Sons of Liberty pulled down and destroyed the gilded lead statue of George III of the United Kingdom on Bowling Green (New York City), melting it down to be recast as ammunition. Similar acts have accompanied the independence of most ex-colonial territories. Sometimes relatively intact monuments are moved to a collected display in a less prominent place, as in India and also post-Communist countries.

In August 2017, a statue of a Confederate soldier dedicated to "the boys who wore the gray" was pulled down from its pedestal in front of Durham County Courthouse in North Carolina by protesters. This followed the events at the 2017 Unite the Right rally in response to growing calls to remove Confederate monuments and memorials across the U.S.

2020 demonstrations

Main article: List of monuments and memorials removed during the George Floyd protests

During the George Floyd protests of 2020, demonstrators pulled down dozens of statues which they considered symbols of the Confederacy, slavery, segregation, or racism, including the statue of Williams Carter Wickham in Richmond, Virginia.

Further demonstrations in the wake of the George Floyd protests have resulted in the removal of:

• the John Breckenridge Castleman monument in Louisville, Kentucky;
• plaques in Jacksonville, Florida's Hemming Park (renamed in 1899 in honor of Civil War veteran Charles C. Hemming), which were in remembrance of deceased Confederate soldiers;
• the monumental obelisk of the Confederate Soldiers and Sailors Monument and a statue of Charles Linn in Linn Park, Birmingham, Alabama;
• a statue of Junípero Serra in Golden Gate Park, San Francisco;
• a statue of Confederate Gen. Robert E. Lee in Montgomery, Alabama;
• the Appomattox statue in Alexandria, Virginia, leaving the monument's base empty but intact.

Multiple statues of early European explorers and founders were also vandalized, including those of Christopher Columbus, George Washington, and Thomas Jefferson.

• Christopher Columbus was removed in Virginia, Minnesota, Chicago and beheaded in Boston MA.
• George Washington statue was toppled in Portland, Oregon.

A statue of the African-American abolitionist statesman Frederick Douglass was vandalised in Rochester, New York, by being torn from its base and left close to a nearby river gorge. Donald Trump attributed the act to anarchists, but he did not substantiate his claim nor did he offer a theory on motive. Cornell William Brooks, former president of the NAACP, theorised that this was an act of revenge from white supremacists. Carvin Eison, who led the project that brought the Douglass statues to Rochester, thought it was unlikely that the Douglass statue was toppled by someone who was upset about monuments honoring Confederate figures, and added that "it's only logical that it was some kind of retaliation event in someone’s mind". Police did not find evidence that supported or refuted either claim, and the vandalism case remains unsolved.