Radiation damage is the effect of ionizing radiation on physical objects including non-living structural materials. It can be either detrimental or beneficial for materials.

Radiobiology Radiobiology (also known as radiation biology, and uncommonly as actinobiology) is a field of clinical and basic medical sciences that involves the study of the action of ionizing radiation on living things, especially health effects of radiation. ...

is the study of the action of ionizing radiation on living things, including the health effects of radiation in

humans Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...

. High doses of ionizing radiation can cause damage to living tissue such as

radiation burn A radiation burn is a damage to the skin or other biological tissue and organs as an effect of radiation. The radiation types of greatest concern are thermal radiation, radio frequency energy, ultraviolet light and ionizing radiation. The most ...

ing and harmful

mutation In biology, a mutation is an alteration in the nucleic acid sequence of the genome of an organism, virus, or extrachromosomal DNA. Viral genomes contain either DNA or RNA. Mutations result from errors during DNA replication, DNA or viral repl ...

s such as causing cells to become

cancerous Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal bl ...

, and can lead to health problems such as radiation poisoning.

Causes

This radiation may take several forms: *

Cosmic rays Cosmic rays are high-energy particles or clusters of particles (primarily represented by protons or atomic nuclei) that move through space at nearly the speed of light. They originate from the Sun, from outside of the Solar System in our ow ...

and subsequent energetic particles caused by their collision with the atmosphere and other materials. *Radioactive daughter products (

radioisotopes A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess nuclear energy, making it unstable. This excess energy can be used in one of three ways: emitted from the nucleus as gamma radiation; transferr ...

) caused by the collision of cosmic rays with the atmosphere and other materials, including living tissues. *Energetic

particle beam A particle beam is a stream of charged or neutral particles. In particle accelerators, these particles can move with a velocity close to the speed of light. There is a difference between the creation and control of charged particle beams and ne ...

s from a

particle accelerator A particle accelerator is a machine that uses electromagnetic fields to propel charged particles to very high speeds and energies, and to contain them in well-defined beams. Large accelerators are used for fundamental research in particle ...

. *Energetic particles or electro-magnetic radiation (

X-rays An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nbs ...

) released from collisions of such particles with a target, as in an X ray machine or incidentally in the use of a particle accelerator. *Particles or various types of rays released by radioactive decay of elements, which may be naturally occurring, created by accelerator collisions, or created in a

nuclear reactor A nuclear reactor is a device used to initiate and control a fission nuclear chain reaction or nuclear fusion reactions. Nuclear reactors are used at nuclear power plants for electricity generation and in nuclear marine propulsion. Heat fr ...

. They may be manufactured for therapeutic or industrial use or be released accidentally by nuclear accident, or released sententially by a

dirty bomb A dirty bomb or radiological dispersal device is a radiological weapon that combines radioactive material with conventional explosives. The purpose of the weapon is to contaminate the area around the dispersal agent/conventional explosion with ...

, or released into the atmosphere, ground, or ocean incidental to the explosion of a

nuclear weapon A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion reactions ( thermonuclear bomb), producing a nuclear explosion. Both bom ...

for warfare or

nuclear test Nuclear weapons tests are experiments carried out to determine nuclear weapons' effectiveness, Nuclear weapon yield, yield, and explosive capability. Testing nuclear weapons offers practical information about how the weapons function, how detona ...

ing.

Effects on materials and devices

Radiation may affect materials and devices in deleterious and beneficial ways: *By causing the materials to become radioactive (mainly by

neutron activation Neutron activation is the process in which neutron radiation induces radioactivity in materials, and occurs when atomic nuclei capture free neutrons, becoming heavier and entering excited states. The excited nucleus decays immediately by emit ...

, or in presence of high-energy gamma radiation by

photodisintegration Photodisintegration (also called phototransmutation, or a photonuclear reaction) is a nuclear process in which an atomic nucleus absorbs a high-energy gamma ray, enters an excited state, and immediately decays by emitting a subatomic particle. The ...

). *By nuclear transmutation of the elements within the material including, for example, the production of Hydrogen and Helium which can in turn alter the mechanical properties of the materials and cause swelling and embrittlement. *By radiolysis (breaking chemical bonds) within the material, which can weaken it, cause it to swell, polymerize, promote corrosion, cause belittlements, promote cracking or otherwise change its desirable mechanical, optical, or electronic properties. On the other hand, radiolysis can also be used to induce crosslinking of polymers, which can harden them or make them more resistant to watering. *By formation of reactive compounds, affecting other materials (e.g.

ozone cracking Cracks can be formed in many different elastomers by ozone attack, and the characteristic form of attack of vulnerable rubbers is known as ozone cracking. The problem was formerly very common, especially in tires, but is now rarely seen in those ...

by ozone formed by ionization of air). *By

ionization Ionization, or Ionisation is the process by which an atom or a molecule acquires a negative or positive charge by gaining or losing electrons, often in conjunction with other chemical changes. The resulting electrically charged atom or molecul ...

, causing electrical breakdown, particularly in

semiconductor A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. ...

s employed in electronic equipment, with subsequent currents introducing operation errors or even permanently damaging the devices. Devices intended for high radiation environments such as the nuclear industry and extra atmospheric (space) applications may be made ''radiation hard'' to resist such effects through design, material selection, and fabrication methods. *By introducing dopants or defects by

ion implantation Ion implantation is a low-temperature process by which ions of one element are accelerated into a solid target, thereby changing the physical, chemical, or electrical properties of the target. Ion implantation is used in semiconductor device fa ...

to modify their electrical functionality in desired ways *To treat cancer by electron, gamma or ion irradiation or via boron neutron capture therapy. Many of the radiation effects on materials are produced by

collision cascade In condensed-matter physics, a collision cascade (also known as a displacement cascade or a displacement spike) is a set of nearby adjacent energetic (much higher than ordinary thermal energies) collisions of atoms induced by an energetic par ...

s and covered by

radiation chemistry Radiation chemistry is a subdivision of nuclear chemistry which is the study of the chemical effects of radiation on matter; this is very different from radiochemistry as no radioactivity needs to be present in the material which is being chemically ...

Effects on solids

Radiation can have harmful effects on solid materials as it can degrade their properties so that they are no longer mechanically sound. This is of special concern as it can greatly affect their ability to perform in

s and is the emphasis of radiation material science, which seeks to mitigate this danger. As a result of their usage and exposure to radiation, the effects on metals and

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wid ...

are particular areas of study. For metals, exposure to radiation can result in radiation hardening which strengthens the material while subsequently embrittling it (lowers

toughness In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing.fracture to occur). This occurs as a result of knocking atoms out of their lattice sites through both the initial interaction as well as a resulting cascade of damage, leading to the creation of defects, dislocations (similar to

work hardening In materials science, work hardening, also known as strain hardening, is the strengthening of a metal or polymer by plastic deformation. Work hardening may be desirable, undesirable, or inconsequential, depending on the context. This strengt ...

and

precipitation hardening Precipitation hardening, also called age hardening or particle hardening, is a heat treatment technique used to increase the yield strength of malleable materials, including most structural alloys of aluminium, magnesium, nickel, titanium, and ...

). Grain boundary engineering through thermomechanical processing has been shown to mitigate these effects by changing the fracture mode from intergranular (occurring along grain boundaries) to transgranular. This increases the strength of the material, mitigating the embrittling effect of radiation. Radiation can also lead to segregation and diffusion of atoms within materials, leading to phase segregation and voids as well as enhancing the effects of stress corrosion cracking through changes in both the water chemistry and alloy microstructure. As concrete is used extensively in the construction of nuclear power plants, where it provides structure as well as containing radiation, the effect of radiation on it is also of major interest. During its lifetime, concrete will change properties naturally due to its normal aging process, however nuclear exposure will lead to a loss of mechanical properties due to swelling of the concrete aggregates, and thus damaging the bulk material. For instance, the biological shield of the reactor is frequently composed of

Portland cement Portland cement is the most common type of cement in general use around the world as a basic ingredient of concrete, mortar, stucco, and non-specialty grout. It was developed from other types of hydraulic lime in England in the early 19th ...

, where dense aggregates are added in order to decrease the radiation flux through the shield. These aggregates can swell and make the shield mechanically unsound. Numerous studies have shown decreases in both compressive and tensile strength as well as elastic modulus of concrete at around a dosage of around 10¹⁹ neutrons per square centimeter. These trends were also shown to exist in reinforced concrete, a composite of both concrete and steel. The knowledge gained from current analyses of materials in fission reactors in regards to the effects of temperature, irradiation dosage, materials compositions, and surface treatments will be helpful in the design of future fission reactors as well as the development of

fusion reactors Fusion power is a proposed form of power generation that would generate electricity by using heat from nuclear fusion reactions. In a fusion process, two lighter atomic nuclei combine to form a heavier nucleus, while releasing energy. Devices de ...

. Solids subject to radiation are constantly being bombarded with high energy particles. The interaction between particles, and atoms in the lattice of the reactor materials causes displacement in the atoms. Over the course of sustained bombardment, some of the atoms do not come to rest at lattice sites, which results in the creation of defects. These defects cause changes in the

microstructure Microstructure is the very small scale structure of a material, defined as the structure of a prepared surface of material as revealed by an optical microscope above 25× magnification. The microstructure of a material (such as metals, polymers ...

of the material, and ultimately result in a number of radiation effects.

Radiation damage event

# Interaction of an energetic incident particle with a lattice atom # Transfer of kinetic energy to the lattice atom, giving birth to a primary displacement atom # Displacement of the atom from its lattice site # Movement of the atom through the lattice, creating additional displaced atoms # Production of displacement cascade (collection of point defects created by primary displacement atom) # Termination of displacement atom as an interstitial

Radiation cross section

The probability of an interaction between two atoms is dependent on the thermal

neutron cross section In nuclear physics, the concept of a neutron cross section is used to express the likelihood of interaction between an incident neutron and a target nucleus. The neutron cross section σ can be defined as the area in cm2 for which the number of ...

(measured in

barn A barn is an agricultural building usually on farms and used for various purposes. In North America, a barn refers to structures that house livestock, including cattle and horses, as well as equipment and fodder, and often grain.Alle ...

). Given a macroscopic cross section of

\Sigma = \sigma \rho_A

(where

\sigma

is the microscopic cross section, and

\rho_A

is the density of atoms in the target), and a reaction rate of

R = \Phi \Sigma = \Phi \sigma \rho_A

(where

\Phi

is the beam flux), the probability of interaction becomes Pdx = N_jσ(E_i)dx = Σdx.(what do any of these symbols mean?) Listed below are the cross sections of common atoms or alloys. Thermal Neutron Cross Sections (Barn)

Microstructural evolution under irradiation

Microstructural evolution is driven in the material by the accumulation of defects over a period of sustained radiation. This accumulation is limited by defect recombination, by clustering of defects, and by the annihilation of defects at sinks. Defects must thermally migrate to sinks, and in doing so often recombine, or arrive at sinks to recombine. In most cases, D_rad = D_vC_v + D_iC_i >> D_therm, that is to say, the motion of interstitials and vacancies throughout the lattice structure of a material as a result of radiation often outweighs the thermal diffusion of the same material. One consequence of a flux of vacancies towards sinks is a corresponding flux of atoms away from the sink. If vacancies are not annihilated or recombined before collecting at sinks, they will form voids. At sufficiently high temperature, dependent on the material, these voids can fill with gases from the decomposition of the alloy, leading to swelling in the material. This is a tremendous issue for pressure sensitive or constrained materials that are under constant radiation bombardment, like

pressurized water reactor A pressurized water reactor (PWR) is a type of light-water nuclear reactor. PWRs constitute the large majority of the world's nuclear power plants (with notable exceptions being the UK, Japan and Canada). In a PWR, the primary coolant (water) i ...

s. In many cases, the radiation flux is non-stoichiometric, which causes segregation within the alloy. This non-stoichiometric flux can result in significant change in local composition near grain boundaries, where the movement of atoms and dislocations is impeded. When this flux continues, solute enrichment at sinks can result in the precipitation of new phases.

Thermo-mechanical effects of irradiation

=Hardening

= Radiation hardening is the strengthening of the material in question by the introduction of defect clusters, impurity-defect cluster complexes, dislocation loops, dislocation lines, voids, bubbles and precipitates. For pressure vessels, the loss in ductility that occurs as a result of the increase in hardness is a particular concern.

= Embrittlement

= Radiation embrittlement results in a reduction of the energy to fracture, due to a reduction in strain hardening (as hardening is already occurring during irradiation). This is motivated for very similar reasons to those that cause radiation hardening; development of defect clusters, dislocations, voids, and precipitates. Variations in these parameters make the exact amount of embrittlement difficult to predict, but the generalized values for the measurement show predictable consistency.

= Creep

= Thermal creep in irradiated materials is negligible, by comparison to the irradiation creep, which can exceed 10⁻⁶sec⁻¹. The mechanism is not enhanced diffusivities, as would be intuitive from the elevated temperature, but rather interaction between the stress and the developing microstructure. Stress induces the nucleation of loops, and causes preferential absorption of interstitials at dislocations, which results in swelling. Swelling, in combination with the embrittlement and hardening, can have disastrous effects on any nuclear material under substantial pressure.

= Growth

= Growth in irradiated materials is caused by Diffusion Anisotropy Difference (DAD). This phenomenon frequently occurs in zirconium, graphite, and magnesium because of natural properties.

= Conductivity

= Thermal and electrical conductivity rely on the transport of energy through the electrons and the lattice of a material. Defects in the lattice and substitution of atoms via transmutation disturb these pathways, leading to a reduction in both types of conduction by radiation damage. The magnitude of reduction depends on the dominant type of conductivity (electronic or

Wiedemann–Franz law In physics, the Wiedemann–Franz law states that the ratio of the electronic contribution of the thermal conductivity (''κ'') to the electrical conductivity (''σ'') of a metal is proportional to the temperature (''T''). : \frac \kapp ...

, phononic) in the material and the details of the radiation damage and is therefore still hard to predict.

Effects on gases

Exposure to radiation causes chemical changes in gases. The least susceptible to damage are

noble gas The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low ch ...

es, where the major concern is the nuclear transmutation with follow-up chemical reactions of the nuclear reaction products. High-intensity ionizing radiation in air can produce a visible ionized air glow of telltale bluish-purplish color. The glow can be observed e.g. during

criticality accident A criticality accident is an accidental uncontrolled nuclear fission chain reaction. It is sometimes referred to as a critical excursion, critical power excursion, or divergent chain reaction. Any such event involves the unintended accumulation ...

s, around

mushroom cloud A mushroom cloud is a distinctive mushroom-shaped flammagenitus cloud of debris, smoke and usually condensed water vapor resulting from a large explosion. The effect is most commonly associated with a nuclear explosion, but any sufficiently ener ...

s shortly after a

nuclear explosion A nuclear explosion is an explosion that occurs as a result of the rapid release of energy from a high-speed nuclear reaction. The driving reaction may be nuclear fission or nuclear fusion or a multi-stage cascading combination of the two, tho ...

, or inside of a damaged nuclear reactor like during the Chernobyl disaster. Significant amounts of

ozone Ozone (), or trioxygen, is an inorganic molecule with the chemical formula . It is a pale blue gas with a distinctively pungent smell. It is an allotrope of oxygen that is much less stable than the diatomic allotrope , breaking down in the lo ...

can be produced. Even small amounts of ozone can cause

in many polymers over time, in addition to the damage by the radiation itself.

Gas-filled radiation detectors

In some gaseous ionisation detectors, radiation damage to gases plays an important role in the device's ageing, especially in devices exposed for long periods to high intensity radiation, e.g. detectors for the Large Hadron Collider or the Geiger–Müller tube Ionization processes require energy above 10 eV, while splitting covalent bonds in molecules and generating

free radical A daughter category of ''Ageing'', this category deals only with the biological aspects of ageing. Ageing Ailments of unknown cause Biogerontology Biological processes Causes of death Cellular processes Gerontology Life extension Metabo ...

s requires only 3-4 eV. The electrical discharges initiated by the ionization events by the particles result in plasma populated by large amount of free radicals. The highly reactive free radicals can recombine back to original molecules, or initiate a chain of free-radical polymerization reactions with other molecules, yielding compounds with increasing molecular weight. These high molecular weight compounds then precipitate from gaseous phase, forming conductive or non-conductive deposits on the electrodes and insulating surfaces of the detector and distorting its response. Gases containing hydrocarbon quenchers, e.g.

argon Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as ...

–

methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The relative abundance of methane on Ea ...

, are typically sensitive to aging by polymerization; addition of oxygen tends to lower the aging rates. Trace amounts of silicone oils, present from outgassing of silicone elastomers and especially from traces of silicone lubricants, tend to decompose and form deposits of

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ta ...

crystals on the surfaces. Gaseous mixtures of argon (or

xenon Xenon is a chemical element with the symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the ...

) with

carbon dioxide Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...

and optionally also with 2-3% of oxygen are highly tolerant to high radiation fluxes. The oxygen is added as noble gas with carbon dioxide has too high transparency for high-energy

photon A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they a ...

s; ozone formed from the oxygen is a strong absorber of

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation ...

photons.

Carbon tetrafluoride Tetrafluoromethane, also known as carbon tetrafluoride or R-14, is the simplest perfluorocarbon ( C F4). As its IUPAC name indicates, tetrafluoromethane is the perfluorinated counterpart to the hydrocarbon methane. It can also be classified as a ...

can be used as a component of the gas for high-rate detectors; the fluorine radicals produced during the operation however limit the choice of materials for the chambers and electrodes (e.g. gold electrodes are required, as the fluorine radicals attack metals, forming fluorides). Addition of carbon tetrafluoride can however eliminate the silicon deposits. Presence of hydrocarbons with carbon tetrafluoride leads to polymerization. A mixture of argon, carbon tetrafluoride, and carbon dioxide shows low aging in high

hadron In particle physics, a hadron (; grc, ἁδρός, hadrós; "stout, thick") is a composite subatomic particle made of two or more quarks held together by the strong interaction. They are analogous to molecules that are held together by the e ...

flux.

Effects on liquids

Like gases, liquids lack fixed internal structure; the effects of radiation is therefore mainly limited to radiolysis, altering the chemical composition of the liquids. As with gases, one of the primary mechanisms is formation of

s. All liquids are subject to radiation damage, with few exotic exceptions; e.g. molten sodium, where there are no chemical bonds to be disrupted, and liquid hydrogen fluoride, which produces gaseous hydrogen and fluorine, which spontaneously react back to hydrogen fluoride.

Effects on water

Water subjected to ionizing radiation forms free radicals of hydrogen and

hydroxyl In chemistry, a hydroxy or hydroxyl group is a functional group with the chemical formula and composed of one oxygen atom covalently bonded to one hydrogen atom. In organic chemistry, alcohols and carboxylic acids contain one or more hydro ...

, which can recombine to form gaseous

hydrogen Hydrogen is the chemical element with the symbol H and atomic number 1. Hydrogen is the lightest element. At standard conditions hydrogen is a gas of diatomic molecules having the formula . It is colorless, odorless, tasteless, non-toxic ...

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

hydrogen peroxide Hydrogen peroxide is a chemical compound with the formula . In its pure form, it is a very pale blue liquid that is slightly more viscous than water. It is used as an oxidizer, bleaching agent, and antiseptic, usually as a dilute solution (3%� ...

hydroxyl radical The hydroxyl radical is the diatomic molecule . The hydroxyl radical is very stable as a dilute gas, but it decays very rapidly in the condensed phase. It is pervasive in some situations. Most notably the hydroxyl radicals are produced from the ...

s, and peroxide radicals. In living organisms, which are composed mostly of water, majority of the damage is caused by the

reactive oxygen species In chemistry, reactive oxygen species (ROS) are highly reactive chemicals formed from diatomic oxygen (). Examples of ROS include peroxides, superoxide, hydroxyl radical, singlet oxygen, and alpha-oxygen. The reduction of molecular oxygen () p ...

, free radicals produced from water. The free radicals attack the

biomolecules A biomolecule or biological molecule is a loosely used term for molecules present in organisms that are essential to one or more typically biological processes, such as cell division, morphogenesis, or development. Biomolecules include lar ...

forming structures within the cells, causing

oxidative stress Oxidative stress reflects an imbalance between the systemic manifestation of reactive oxygen species and a biological system's ability to readily detoxify the reactive intermediates or to repair the resulting damage. Disturbances in the normal ...

(a cumulative damage which may be significant enough to cause the cell death, or may cause DNA damage possibly leading to

cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...

). In cooling systems of nuclear reactors, the formation of free oxygen would promote

corrosion Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engi ...

and is counteracted by addition of hydrogen to the cooling water. The hydrogen is not consumed as for each molecule reacting with oxygen one molecule is liberated by radiolysis of water; the excess hydrogen just serves to shift the reaction equilibriums by providing the initial hydrogen radicals. The reducing environment in

s is less prone to buildup of oxidative species. The chemistry of

boiling water reactor A boiling water reactor (BWR) is a type of light water nuclear reactor used for the generation of electrical power. It is a design different from a Soviet graphite-moderated RBMK. It is the second most common type of electricity-generating nu ...

coolant is more complex, as the environment can be oxidizing. Most of the radiolytic activity occurs in the core of the reactor where the neutron flux is highest; the bulk of energy is deposited in water from

fast neutron The neutron detection temperature, also called the neutron energy, indicates a free neutron's kinetic energy, usually given in electron volts. The term ''temperature'' is used, since hot, thermal and cold neutrons are moderated in a medium with ...

s and gamma radiation, the contribution of

thermal neutron The neutron detection temperature, also called the neutron energy, indicates a free neutron's kinetic energy, usually given in electron volts. The term ''temperature'' is used, since hot, thermal and cold neutrons are moderated in a medium wi ...

s is much lower. In air-free water, the concentration of hydrogen, oxygen, and hydrogen peroxide reaches steady state at about 200 Gy of radiation. In presence of dissolved oxygen, the reactions continue until the oxygen is consumed and the equilibrium is shifted. Neutron activation of water leads to buildup of low concentrations of nitrogen species; due to the oxidizing effects of the reactive oxygen species, these tend to be present in the form of nitrate anions. In reducing environments,

ammonia Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...

may be formed. Ammonia ions may be however also subsequently oxidized to nitrates. Other species present in the coolant water are the oxidized corrosion products (e.g.

chromates Chromate salts contain the chromate anion, . Dichromate salts contain the dichromate anion, . They are oxyanions of chromium in the +6 oxidation state and are moderately strong oxidizing agents. In an aqueous solution, chromate and dichromate ...

) and fission products (e.g.

pertechnetate The pertechnetate ion () is an oxyanion with the chemical formula . It is often used as a convenient water-soluble source of isotopes of the radioactive element technetium (Tc). In particular it is used to carry the 99mTc isotope (half-life 6 hou ...

and

periodate Periodate is an anion composed of iodine and oxygen. It is one of a number of oxyanions of iodine and is the highest in the series, with iodine existing in oxidation state +7. Unlike other perhalogenates, such as perchlorate, it can exist in two ...

anions,

uranyl The uranyl ion is an oxycation of uranium in the oxidation state +6, with the chemical formula . It has a linear structure with short U–O bonds, indicative of the presence of multiple bonds between uranium and oxygen. Four or more ligands may ...

and neptunyl cations). Absorption of neutrons in hydrogen nuclei leads to buildup of

deuterium Deuterium (or hydrogen-2, symbol or deuterium, also known as heavy hydrogen) is one of two stable isotopes of hydrogen (the other being protium, or hydrogen-1). The nucleus of a deuterium atom, called a deuteron, contains one proton and one ...

and

tritium Tritium ( or , ) or hydrogen-3 (symbol T or H) is a rare and radioactive isotope of hydrogen with half-life about 12 years. The nucleus of tritium (t, sometimes called a ''triton'') contains one proton and two neutrons, whereas the nucleus of ...

in the water. Behavior of supercritical water, important for the supercritical water reactors, differs from the radiochemical behavior of liquid water and steam and is currently under investigation. The magnitude of the effects of radiation on water is dependent on the type and energy of the radiation, namely its linear energy transfer. A gas-free water subjected to low-LET gamma rays yields almost no radiolysis products and sustains an equilibrium with their low concentration. High-LET

alpha radiation Alpha decay or α-decay is a type of radioactive decay in which an atomic nucleus emits an alpha particle (helium nucleus) and thereby transforms or 'decays' into a different atomic nucleus, with a mass number that is reduced by four and an at ...

produces larger amounts of radiolysis products. In presence of dissolved oxygen, radiolysis always occurs. Dissolved hydrogen completely suppresses radiolysis by low-LET radiation while radiolysis still occurs with The presence of reactive oxygen species has strongly disruptive effect on dissolved organic chemicals. This is exploited in

groundwater remediation Groundwater remediation is the process that is used to treat polluted groundwater by removing the pollutants or converting them into harmless products. Groundwater is water present below the ground surface that saturates the pore space in the sub ...

by electron beam treatment.

Countermeasures

Two main approaches to reduce radiation damage are reducing the amount of energy deposited in the sensitive material (e.g. by shielding, distance from the source, or spatial orientation), or modification of the material to be less sensitive to radiation damage (e.g. by adding antioxidants, stabilizers, or choosing a more suitable material). In addition to the electronic device hardening mentioned above, some degree of protection may be obtained by shielding, usually with the interposition of high density materials (particularly lead, where space is critical, or concrete where space is available) between the radiation source and areas to be protected. For biological effects of substances such as radioactive iodine the ingestion of non-radioactive isotopes may substantially reduce the biological uptake of the radioactive form, and chelation therapy may be applied to accelerate the removal of radioactive materials formed from heavy metals from the body by natural processes.

For solid radiation damage

Solid countermeasures to radiation damage consist of three approaches. Firstly, saturating the matrix with oversized solutes. This acts to trap the swelling that occurs as a result of the creep and dislocation motion. They also act to help prevent diffusion, which restricts the ability of the material to undergo radiation induced segregation. Secondly, dispersing an oxide inside the matrix of the material. Dispersed oxide helps to prevent creep, and to mitigate swelling and reduce radiation induced segregation as well, by preventing dislocation motion and the formation and motion of interstitials. Finally, by engineering grain boundaries to be as small as possible, dislocation motion can be impeded, which prevents the embrittlement and hardening that result in material failure.

Effects on humans

Ionizing radiation is generally harmful and potentially lethal to living things but can have health benefits in

radiation therapy Radiation therapy or radiotherapy, often abbreviated RT, RTx, or XRT, is a therapy using ionizing radiation, generally provided as part of cancer treatment to control or kill malignant cells and normally delivered by a linear accelerator. Radi ...

for the treatment of cancer and

thyrotoxicosis Hyperthyroidism is the condition that occurs due to excessive production of thyroid hormones by the thyroid gland. Thyrotoxicosis is the condition that occurs due to excessive thyroid hormone of any cause and therefore includes hyperthyroidism. ...

. Its most common impact is the induction of cancer with a latent period of years or decades after exposure. High doses can cause visually dramatic

radiation burns A radiation burn is a damage to the skin or other biological tissue and organs as an effect of radiation. The radiation types of greatest concern are thermal radiation, radio frequency energy, ultraviolet light and ionizing radiation. The most ...

, and/or rapid fatality through acute radiation syndrome. Controlled doses are used for medical imaging and radiotherapy. Most adverse health effects of radiation exposure may be grouped in two general categories: *Deterministic effects (harmful tissue reactions) due in large part to the killing/ malfunction of cells following high doses; and *Stochastic effects, i.e., cancer and heritable effects involving either cancer development in exposed individuals owing to mutation of somatic cells or heritable disease in their offspring owing to mutation of reproductive (germ) cells.Paragraph 55 in: IRCP 2007: Ann. ICRP 37 (2-4)

References

{{Authority control Radiation effects