Neutron radiation
Encyclopedia
Neutron radiation is a kind of ionizing radiation
which consists of free neutrons. A result of nuclear fission
or nuclear fusion
, it consists of the release of free neutrons from atoms, and these free neutrons react with nuclei of other atoms to form new isotopes, which, in turn, may produce radiation. This will result in a chain reaction of nuclear radiation, which makes radiation dangerous and harmful over great areas of space.
s may be emitted from nuclear fusion
or nuclear fission
, or from any number of different nuclear reactions such as from radioactive decay
or reactions from particle interactions (such as from cosmic rays or particle accelerators). Large neutron sources are rare, and are usually limited to large-sized devices like nuclear reactors or particle accelerators (such as the Spallation Neutron Source
).
Neutron radiation was discovered as a result of observing a beryllium
nucleus
reacting with an alpha particle
thus transforming into a carbon
nucleus
and emitting a neutron
, Be
(α
, n
)C
. The combination of an alpha particle emitter and an isotope with a large (α
, n
) nuclear reaction probability
is still a common neutron source.
neutron radiation is most commonly used for scattering
and diffraction
experiments in order to assess the properties and the structure of materials in crystallography
, condensed matter physics
, biology
, solid state chemistry, materials science
, geology
, mineralogy
and related sciences. Neutron radiation is also used in select facilities to treat
cancerous tumors due to its highly penetrating and damaging nature to cellular structure. Neutrons can also be used for imaging of industrial parts termed neutron radiography when using film, neutron radioscopy when taking a digital image, such as through image plates, and neutron tomography for three dimensional images. Neutron imaging is commonly used in the nuclear industry, the space and aerospace industry, as well as the high reliability explosives industry.
. It does not ionize atoms in the same way that charged particles such as protons and electrons do (exciting an electron), because neutrons have no charge. However, neutron interactions are largely ionizing, for example when neutron absorption results in gamma emission and the gamma ray (photon) subsequently removes an electron from an atom, or a nucleus recoiling from a neutron interaction is ionized and causes more traditional subsequent ionization in other atoms. Because neutrons are uncharged, they are more penetrating than alpha radiation or beta radiation. In some cases they are more penetrating than gamma radiation, which is impeded in materials of high atomic number
. In materials of low atomic number
such as hydrogen, a low energy gamma ray may be more penetrating than a high energy neutron.
neutron radiation is considered a fourth radiation hazard alongside the other types of radiation. Another, sometimes more severe hazard of neutron radiation, is neutron activation
, the ability of neutron radiation to induce radioactivity in most substances it encounters, including the body tissues of the workers themselves. This occurs through the capture of neutrons by atomic nuclei, which are transformed to another nuclide
, frequently a radionuclide
. This process accounts for much of the radioactive material released by the detonation of a nuclear weapon
. It is also a problem in nuclear fission
and nuclear fusion
installations, as it gradually renders the equipment radioactive; eventually the hardware must be replaced and disposed of as low-level radioactive waste
.
Neutron radiation protection relies on radiation shielding. In comparison with conventional ionizing radiation based on photons or charged particles, neutrons are repeatedly bounced and slowed (absorbed) by light nuclei, so a large mass of hydrogen
-rich material is needed. Neutrons readily pass through most material, but interact enough to cause biological damage. Due to the high kinetic energy of neutrons, this radiation is considered to be the most severe and dangerous radiation available. The most effective materials are e.g. water
, polyethylene
, paraffin wax, or concrete
, where a considerable amount of water molecules are chemically bound to the cement. The light atoms serve to slow down the neutrons by elastic scattering
, so they can then be absorbed by nuclear reaction
s. However, gamma radiation is often produced in such reactions, so additional shielding has to be provided to absorb it.
Because the neutrons that strike the hydrogen nucleus (proton
, or deuteron) impart energy to that nucleus, they in turn will break from their chemical bonds and travel a short distance, before stopping. Those protons and deuterons are high linear energy transfer
particles, and are in turn stopped by ionization of the material through which they travel. Consequently, in living tissue, neutrons have a relatively high relative biological effectiveness
, and are roughly ten times more effective at causing cancers or LD-50s compared to photon or beta radiation of equivalent radiation exposure.
collision cascade
s that can produce point defects and
dislocation
s in the materials. At high neutron fluences this can lead to embrittlement
of metals and other materials, and to swelling
of some of them. This poses a problem for nuclear reactor vessels, and significantly limits their lifetime (which can be somewhat prolonged by controlled annealing
of the vessel, reducing the number of the built-up dislocations). Graphite moderator
blocks are especially susceptible to this effect, known as Wigner effect
, and have to be annealed periodically; the well-known Windscale fire
was caused by a mishap during such an annealing operation.
.
In order to achieve an effective fission chain reaction, the neutrons produced during fission must be captured by fissionable nuclei, which then split, releasing more neutrons. In most fission reactor designs, the nuclear fuel is not sufficiently refined to be able to absorb enough fast neutrons to carry on the fission chain reaction, due to the lower cross section
for higher-energy neutrons, so a neutron moderator
must be introduced to slow the fast neutrons down to thermal velocities to permit sufficient absorption. Common neutron moderators include graphite
, light water and heavy water
. A few reactors (fast neutron reactor
s) and all nuclear weapons rely on fast neutrons. This requires certain changes in the design and in the required nuclear fuel. The element beryllium
is particularly useful due to its ability to act as a neutron reflector or lens. This allows smaller quantities of fissile material to be used and is a primary technical development that led to the creation of neutron bomb
s.
.
Ionizing radiation
Ionizing radiation is radiation composed of particles that individually have sufficient energy to remove an electron from an atom or molecule. This ionization produces free radicals, which are atoms or molecules containing unpaired electrons...
which consists of free neutrons. A result of nuclear fission
Nuclear fission
In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...
or nuclear fusion
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...
, it consists of the release of free neutrons from atoms, and these free neutrons react with nuclei of other atoms to form new isotopes, which, in turn, may produce radiation. This will result in a chain reaction of nuclear radiation, which makes radiation dangerous and harmful over great areas of space.
Sources
NeutronNeutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
s may be emitted from nuclear fusion
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...
or nuclear fission
Nuclear fission
In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...
, or from any number of different nuclear reactions such as from radioactive decay
Radioactive decay
Radioactive decay is the process by which an atomic nucleus of an unstable atom loses energy by emitting ionizing particles . The emission is spontaneous, in that the atom decays without any physical interaction with another particle from outside the atom...
or reactions from particle interactions (such as from cosmic rays or particle accelerators). Large neutron sources are rare, and are usually limited to large-sized devices like nuclear reactors or particle accelerators (such as the Spallation Neutron Source
Spallation Neutron Source
The Spallation Neutron Source is an accelerator-based neutron source facility that provides the most intense pulsed neutron beams in the world for scientific research and industrial development...
).
Neutron radiation was discovered as a result of observing a beryllium
Beryllium
Beryllium is the chemical element with the symbol Be and atomic number 4. It is a divalent element which occurs naturally only in combination with other elements in minerals. Notable gemstones which contain beryllium include beryl and chrysoberyl...
nucleus
Atomic nucleus
The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The...
reacting with an alpha particle
Alpha particle
Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus, which is classically produced in the process of alpha decay, but may be produced also in other ways and given the same name...
thus transforming into a carbon
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
nucleus
Atomic nucleus
The nucleus is the very dense region consisting of protons and neutrons at the center of an atom. It was discovered in 1911, as a result of Ernest Rutherford's interpretation of the famous 1909 Rutherford experiment performed by Hans Geiger and Ernest Marsden, under the direction of Rutherford. The...
and emitting a neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
, Be
Beryllium
Beryllium is the chemical element with the symbol Be and atomic number 4. It is a divalent element which occurs naturally only in combination with other elements in minerals. Notable gemstones which contain beryllium include beryl and chrysoberyl...
(α
Alpha particle
Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus, which is classically produced in the process of alpha decay, but may be produced also in other ways and given the same name...
, n
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
)C
Carbon
Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds...
. The combination of an alpha particle emitter and an isotope with a large (α
Alpha particle
Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus, which is classically produced in the process of alpha decay, but may be produced also in other ways and given the same name...
, n
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...
) nuclear reaction probability
Cross section (physics)
A cross section is the effective area which governs the probability of some scattering or absorption event. Together with particle density and path length, it can be used to predict the total scattering probability via the Beer-Lambert law....
is still a common neutron source.
Uses
Cold, thermal and hotNeutron temperature
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 a certain temperature. The neutron energy distribution is...
neutron radiation is most commonly used for scattering
Neutron scattering
Neutron scattering,the scattering of free neutrons by matter,is a physical processand an experimental technique using this processfor the investigation of materials.Neutron scattering as a physical process is of primordial importance...
and diffraction
Neutron diffraction
Neutron diffraction or elastic neutron scattering is the application of neutron scattering to the determination of the atomic and/or magnetic structure of a material: A sample to be examined is placed in a beam of thermal or cold neutrons to obtain a diffraction pattern that provides information of...
experiments in order to assess the properties and the structure of materials in crystallography
Crystallography
Crystallography is the experimental science of the arrangement of atoms in solids. The word "crystallography" derives from the Greek words crystallon = cold drop / frozen drop, with its meaning extending to all solids with some degree of transparency, and grapho = write.Before the development of...
, condensed matter physics
Condensed matter physics
Condensed matter physics deals with the physical properties of condensed phases of matter. These properties appear when a number of atoms at the supramolecular and macromolecular scale interact strongly and adhere to each other or are otherwise highly concentrated in a system. The most familiar...
, biology
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...
, solid state chemistry, materials science
Materials science
Materials science is an interdisciplinary field applying the properties of matter to various areas of science and engineering. This scientific field investigates the relationship between the structure of materials at atomic or molecular scales and their macroscopic properties. It incorporates...
, geology
Geology
Geology is the science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which it evolves. Geology gives insight into the history of the Earth, as it provides the primary evidence for plate tectonics, the evolutionary history of life, and past climates...
, mineralogy
Mineralogy
Mineralogy is the study of chemistry, crystal structure, and physical properties of minerals. Specific studies within mineralogy include the processes of mineral origin and formation, classification of minerals, their geographical distribution, as well as their utilization.-History:Early writing...
and related sciences. Neutron radiation is also used in select facilities to treat
Boron Neutron Capture Therapy
Boron neutron capture therapy is an experimental form of radiotherapy that uses a neutron beam that interacts with boron injected into a patient...
cancerous tumors due to its highly penetrating and damaging nature to cellular structure. Neutrons can also be used for imaging of industrial parts termed neutron radiography when using film, neutron radioscopy when taking a digital image, such as through image plates, and neutron tomography for three dimensional images. Neutron imaging is commonly used in the nuclear industry, the space and aerospace industry, as well as the high reliability explosives industry.
Ionization mechanisms and properties
Neutron radiation is often called indirectly ionizing radiationIonizing radiation
Ionizing radiation is radiation composed of particles that individually have sufficient energy to remove an electron from an atom or molecule. This ionization produces free radicals, which are atoms or molecules containing unpaired electrons...
. It does not ionize atoms in the same way that charged particles such as protons and electrons do (exciting an electron), because neutrons have no charge. However, neutron interactions are largely ionizing, for example when neutron absorption results in gamma emission and the gamma ray (photon) subsequently removes an electron from an atom, or a nucleus recoiling from a neutron interaction is ionized and causes more traditional subsequent ionization in other atoms. Because neutrons are uncharged, they are more penetrating than alpha radiation or beta radiation. In some cases they are more penetrating than gamma radiation, which is impeded in materials of high atomic number
Atomic number
In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...
. In materials of low atomic number
Atomic number
In chemistry and physics, the atomic number is the number of protons found in the nucleus of an atom and therefore identical to the charge number of the nucleus. It is conventionally represented by the symbol Z. The atomic number uniquely identifies a chemical element...
such as hydrogen, a low energy gamma ray may be more penetrating than a high energy neutron.
Health hazards and protection
In health physicsHealth physics
Health physics is a field of science concerned with radiation physics and radiation biology with the goal of providing technical information and proper techniques regarding the safe use of ionizing radiation...
neutron radiation is considered a fourth radiation hazard alongside the other types of radiation. Another, sometimes more severe hazard of neutron radiation, is neutron activation
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 often decays immediately by emitting particles such as neutrons, protons, or alpha...
, the ability of neutron radiation to induce radioactivity in most substances it encounters, including the body tissues of the workers themselves. This occurs through the capture of neutrons by atomic nuclei, which are transformed to another nuclide
Nuclide
A nuclide is an atomic species characterized by the specific constitution of its nucleus, i.e., by its number of protons Z, its number of neutrons N, and its nuclear energy state....
, frequently a radionuclide
Radionuclide
A radionuclide is an atom with an unstable nucleus, which is a nucleus characterized by excess energy available to be imparted either to a newly created radiation particle within the nucleus or to an atomic electron. The radionuclide, in this process, undergoes radioactive decay, and emits gamma...
. This process accounts for much of the radioactive material released by the detonation of a nuclear weapon
Nuclear weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. Both reactions release vast quantities of energy from relatively small amounts of matter. The first fission bomb test released the same amount...
. It is also a problem in nuclear fission
Nuclear fission
In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...
and nuclear fusion
Nuclear fusion
Nuclear fusion is the process by which two or more atomic nuclei join together, or "fuse", to form a single heavier nucleus. This is usually accompanied by the release or absorption of large quantities of energy...
installations, as it gradually renders the equipment radioactive; eventually the hardware must be replaced and disposed of as low-level radioactive waste
Radioactive waste
Radioactive wastes are wastes that contain radioactive material. Radioactive wastes are usually by-products of nuclear power generation and other applications of nuclear fission or nuclear technology, such as research and medicine...
.
Neutron radiation protection relies on radiation shielding. In comparison with conventional ionizing radiation based on photons or charged particles, neutrons are repeatedly bounced and slowed (absorbed) by light nuclei, so a large mass of hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...
-rich material is needed. Neutrons readily pass through most material, but interact enough to cause biological damage. Due to the high kinetic energy of neutrons, this radiation is considered to be the most severe and dangerous radiation available. The most effective materials are e.g. water
Water
Water is a chemical substance with the chemical formula H2O. A water molecule contains one oxygen and two hydrogen atoms connected by covalent bonds. Water is a liquid at ambient conditions, but it often co-exists on Earth with its solid state, ice, and gaseous state . Water also exists in a...
, polyethylene
Polyethylene
Polyethylene or polythene is the most widely used plastic, with an annual production of approximately 80 million metric tons...
, paraffin wax, or concrete
Concrete
Concrete is a composite construction material, composed of cement and other cementitious materials such as fly ash and slag cement, aggregate , water and chemical admixtures.The word concrete comes from the Latin word...
, where a considerable amount of water molecules are chemically bound to the cement. The light atoms serve to slow down the neutrons by elastic scattering
Elastic scattering
In scattering theory and in particular in particle physics, elastic scattering is one of the specific forms of scattering. In this process, the kinetic energy of the incident particles is conserved, only their direction of propagation is modified .-Electron elastic scattering:When an alpha particle...
, so they can then be absorbed by nuclear reaction
Nuclear reaction
In nuclear physics and nuclear chemistry, a nuclear reaction is semantically considered to be the process in which two nuclei, or else a nucleus of an atom and a subatomic particle from outside the atom, collide to produce products different from the initial particles...
s. However, gamma radiation is often produced in such reactions, so additional shielding has to be provided to absorb it.
Because the neutrons that strike the hydrogen nucleus (proton
Proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....
, or deuteron) impart energy to that nucleus, they in turn will break from their chemical bonds and travel a short distance, before stopping. Those protons and deuterons are high linear energy transfer
Linear energy transfer
Linear energy transfer is a measure of the energy transferred to material as an ionizing particle travels through it. Typically, this measure is used to quantify the effects of ionizing radiation on biological specimens or electronic devices....
particles, and are in turn stopped by ionization of the material through which they travel. Consequently, in living tissue, neutrons have a relatively high relative biological effectiveness
Relative biological effectiveness
In radiology, the relative biological effectiveness is a number that expresses the relative amount of damage that a fixed amount of ionizing radiation of a given type can inflict on biological tissues...
, and are roughly ten times more effective at causing cancers or LD-50s compared to photon or beta radiation of equivalent radiation exposure.
Effects on materials
Neutrons also degrade materials; bombardment of materials with neutrons createscollision cascade
Collision cascade
A collision cascade is a set of nearby adjacent energetic collisions of atoms induced by an energetic particle in a solid or liquid....
s that can produce point defects and
dislocation
Dislocation
In materials science, a dislocation is a crystallographic defect, or irregularity, within a crystal structure. The presence of dislocations strongly influences many of the properties of materials...
s in the materials. At high neutron fluences this can lead to embrittlement
Embrittlement
Embrittlement is a loss of ductility of a material, making it brittle. Various materials have different mechanisms of embrittlement.* Hydrogen embrittlement is the effect of hydrogen absorption on some metals and alloys....
of metals and other materials, and to swelling
Neutron-induced swelling
Neutron-induced swelling is the increase of volume and decrease of density of materials subjected to intense neutron radiation. Neutrons impacting the material's lattice rearrange its atoms, causing buildup of dislocations, voids, and Wigner energy...
of some of them. This poses a problem for nuclear reactor vessels, and significantly limits their lifetime (which can be somewhat prolonged by controlled annealing
Annealing (metallurgy)
Annealing, in metallurgy and materials science, is a heat treatment wherein a material is altered, causing changes in its properties such as strength and hardness. It is a process that produces conditions by heating to above the recrystallization temperature, maintaining a suitable temperature, and...
of the vessel, reducing the number of the built-up dislocations). Graphite moderator
Neutron moderator
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235....
blocks are especially susceptible to this effect, known as Wigner effect
Wigner effect
The Wigner effect , also known as the discomposition effect, is the displacement of atoms in a solid caused by neutron radiation....
, and have to be annealed periodically; the well-known Windscale fire
Windscale fire
The Windscale fire of 10 October 1957 was the worst nuclear accident in Great Britain's history, ranked in severity at level 5 on the 7-point International Nuclear Event Scale. The two piles had been hurriedly built as part of the British atomic bomb project. Windscale Pile No. 1 was operational in...
was caused by a mishap during such an annealing operation.
Neutron radiation and nuclear fission
The neutrons in reactors are generally categorized as slow (thermal) neutrons or fast neutrons depending on their energy. Thermal neutrons are similar to a gas in thermodynamic equilibrium but are easily captured by atomic nuclei and are the primary means by which elements undergo atomic transmutationNuclear transmutation
Nuclear transmutation is the conversion of one chemical element or isotope into another. In other words, atoms of one element can be changed into atoms of other element by 'transmutation'...
.
In order to achieve an effective fission chain reaction, the neutrons produced during fission must be captured by fissionable nuclei, which then split, releasing more neutrons. In most fission reactor designs, the nuclear fuel is not sufficiently refined to be able to absorb enough fast neutrons to carry on the fission chain reaction, due to the lower cross section
Cross section (physics)
A cross section is the effective area which governs the probability of some scattering or absorption event. Together with particle density and path length, it can be used to predict the total scattering probability via the Beer-Lambert law....
for higher-energy neutrons, so a neutron moderator
Neutron moderator
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235....
must be introduced to slow the fast neutrons down to thermal velocities to permit sufficient absorption. Common neutron moderators include graphite
Graphite
The mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek γράφω , "to draw/write", for its use in pencils, where it is commonly called lead . Unlike diamond , graphite is an electrical conductor, a semimetal...
, light water and heavy water
Heavy water
Heavy water is water highly enriched in the hydrogen isotope deuterium; e.g., heavy water used in CANDU reactors is 99.75% enriched by hydrogen atom-fraction...
. A few reactors (fast neutron reactor
Fast neutron reactor
A fast neutron reactor or simply a fast reactor is a category of nuclear reactor in which the fission chain reaction is sustained by fast neutrons...
s) and all nuclear weapons rely on fast neutrons. This requires certain changes in the design and in the required nuclear fuel. The element beryllium
Beryllium
Beryllium is the chemical element with the symbol Be and atomic number 4. It is a divalent element which occurs naturally only in combination with other elements in minerals. Notable gemstones which contain beryllium include beryl and chrysoberyl...
is particularly useful due to its ability to act as a neutron reflector or lens. This allows smaller quantities of fissile material to be used and is a primary technical development that led to the creation of neutron bomb
Neutron bomb
A neutron bomb or enhanced radiation weapon or weapon of reinforced radiation is a type of thermonuclear weapon designed specifically to release a large portion of its energy as energetic neutron radiation rather than explosive energy...
s.
Cosmogenic neutrons
Cosmogenic neutrons, neutrons produced from cosmic radiation in the Earth's atmosphere or surface, and those produced in particle accelerators can be significantly higher energy than those encountered in reactors. Most of them activate a nucleus before reaching the ground; a few react with nuclei in the air. The reactions with nitrogen 14 lead to the formation of carbon 14, widely used in radiocarbon datingRadiocarbon dating
Radiocarbon dating is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years. Raw, i.e. uncalibrated, radiocarbon ages are usually reported in radiocarbon years "Before Present" ,...
.
See also
- Neutron activationNeutron activationNeutron 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 often decays immediately by emitting particles such as neutrons, protons, or alpha...
- Neutron emissionNeutron emissionNeutron emission is a type of radioactive decay of atoms containing excess neutrons, in which a neutron is simply ejected from the nucleus. Two examples of isotopes which emit neutrons are helium-5 and beryllium-13...
- Neutron bombNeutron bombA neutron bomb or enhanced radiation weapon or weapon of reinforced radiation is a type of thermonuclear weapon designed specifically to release a large portion of its energy as energetic neutron radiation rather than explosive energy...
- Neutron fluxNeutron fluxThe neutron flux is a quantity used in reactor physics corresponding to the total length travelled by all neutrons per unit time and volume . The neutron fluence is defined as the neutron flux integrated over a certain time period....
- Neutron diffractionNeutron diffractionNeutron diffraction or elastic neutron scattering is the application of neutron scattering to the determination of the atomic and/or magnetic structure of a material: A sample to be examined is placed in a beam of thermal or cold neutrons to obtain a diffraction pattern that provides information of...
and Neutron scatteringNeutron scatteringNeutron scattering,the scattering of free neutrons by matter,is a physical processand an experimental technique using this processfor the investigation of materials.Neutron scattering as a physical process is of primordial importance... - Neutron RadiographyNeutron RadiographyNeutron Radiography is the process by which film is exposed by first passing neutrons through an object to produce a visible image of the materials that make up the object. Primarily used in scientific investigations.- Brief History of Neutron Imaging :...