Radionuclide
Encyclopedia
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 ray
(s) and/or subatomic particles. These particles constitute ionizing radiation
. Radionuclides occur naturally, and can also be artificially produced.
The number of radionuclides is uncertain because the number of very short-lived radionuclides that have yet to be characterized is extremely large and potentially unquantifiable. Even the number of long-lived radionuclides is uncertain (to a smaller degree), because many "stable" nuclides are calculated to have half-lives so long that their decay has not been experimentally measured. The total list of nuclides contains 90 nuclides that are theoretically stable, and 255 total stable nuclides that have not been observed to decay. In addition, there exist about 650 radionuclides that have been experimentally observed to decay, with half-lives longer than 60 minutes (see list of nuclides for this list). Of these, about 339 are known from nature (they have been observed on Earth, and not as a consequence of man-made activities).
Including artificially produced nuclides, more than 3300 nuclides are known (including ~3000 radionuclides), including many more (> ~2400) that have decay half-lives shorter than 60 minutes. This list expands as new radionuclides with very short half-lives are characterized.
Radionuclides are often referred to by chemists and physicists as radioactive isotope
s or radioisotopes. Radioisotopes with suitable half-lives play an important part in a number of constructive technologies (for example, nuclear medicine
). Radionuclides can also present both real and perceived dangers to health.
s and, like uranium
and thorium
, are still present because their half-lives
are so long that they have not yet completely decayed. Secondary radionuclides are radiogenic isotopes derived from the decay of primordial radionuclides. They have shorter half-lives than primordial radionuclides. Cosmogenic isotopes, such as carbon-14
, are present because they are continually being formed in the atmosphere due to cosmic ray
s.
Artificially produced radionuclides can be produced by nuclear reactor
s, particle accelerators or by radionuclide generators:
Trace radionuclides are those that occur in tiny amounts in nature either due to inherent rarity, or to half-lives
that are significantly shorter than the age of the Earth. Synthetic isotopes are inherently not naturally occurring on Earth, but can be created by nuclear reaction
s.
.
Radionuclides of familiar elements such as carbon
can serve as tracers
because they are chemically very similar to the non-radioactive nuclides, so most chemical, biological, and ecological processes treat them in a near identical way. One can then examine the result with a radiation detector, such as a geiger counter
, to determine where the provided atoms ended up. For example, one might culture plants in an environment in which the carbon dioxide
contained radioactive carbon; then the parts of the plant that had laid down atmospheric carbon would be radioactive.
In nuclear medicine
, radioisotopes are used for diagnosis, treatment, and research. Radioactive chemical tracers emitting gamma rays or positrons can provide diagnostic information about a person's internal anatomy and the functioning of specific organs. This is used in some forms of tomography: single-photon emission computed tomography and positron emission tomography
scanning.
Radioisotopes are also a method of treatment in hemopoietic forms of tumors; the success for treatment of solid tumors has been limited. More powerful gamma sources sterilise syringes and other medical equipment.
In biochemistry
and genetics
, radionuclides label molecules and allow tracing chemical and physiological processes occurring in living organisms, such as DNA replication
or amino acid
transport.
In food preservation
, radiation is used
to stop the sprouting of root crops after harvesting, to kill parasites and pests, and to control the ripening of stored fruit and vegetables.
In industry
, and in mining
, radionuclides examine welds, to detect leaks, to study the rate of wear, erosion and corrosion of metals, and for on-stream analysis of a wide range of minerals and fuels.
Radionuclides are also used to trace and analyze pollutants, to study the movement of surface water, and to measure water runoffs from rain and snow, as well as the flow rates of streams and rivers. Natural radionuclides are used in geology
, archaeology
, and paleontology
to measure ages of rocks, minerals, and fossil materials.
s contain americium formed in nuclear reactor
s. The radioisotope used is americium-241.
The element americium is created by bombarding plutonium with neutrons in a nuclear reactor. Its isotope, Am-241 decays by emitting alpha particle
s and gamma radiation to become neptunium-237.
The most common household smoke detectors use a very small quantity of Am-241 (about 0.29 micrograms per smoke detector) in the form of americium dioxide. The smoke detectors use the Am-241 since the alpha particles it emits collide with oxygen and nitrogen particles in the air. This occurs in the detector's ionization chamber
where it produces charged particles or ion
s. Then, these charged particles are collected by a small electric voltage that will create an electric current that will pass between two electrodes. Then, the ions that are flowing between the electrodes will be neutralized when coming in contact with smoke, thereby decreasing the electric current between the electrodes, which will activate the detector's alarm.
Steps for creating americium-241
The plutonium-241
is formed in any nuclear reactor by neutron capture from uranium-238
.
This will decay both in the reactor and subsequently to form Am-241 (Half-life: 432.2 years)
screening. It is a gamma-emitter with an 8-month half-life, making it easier to use for medical purposes. In nuclear medicine
, it serves to calibrate the equipment needed like single-photon emission computed tomography systems (SPECT) to make x-ray
s. It ensures that the machines work correctly to produce images of radioisotope distribution inside the patient. This isotope is produced in a nuclear reactor from europium
or enriched
gadolinium. It can also detect the loss of calcium
in the hip and back bones, allowing the ability to diagnose osteoporosis.
. They can also cause damage if they are excessively used during treatment or in other ways applied to living beings, by radiation poisoning
.
The remaining 650 radionuclides have half-lives longer than 1 hour, and are well characterized (see list of nuclides for a complete tabulation). They include 27 nuclides with measured half-lives longer than the estimated age of the universe (13.7 billion years), and another 6 nuclides with half-lives long enough (> 80 million years) that they are radioactive primordial nuclide
s, and may be detected on Earth, having survived from their presence in interstellar dust since before the formation of the solar system, about 4.6 billion years ago. Another ~51 short-lived nuclides can be detected naturally as daughters of longer-lived nuclides or cosmic-ray products. The remaining known nuclides are known solely from artificial nuclear transmutation
.
Numbers are not exact, and may change slightly in the future, as "stable nuclides" are observed to be radioactive with very long half-lives.
This is a summary table for the 905 nuclides with half-lives longer than one hour (including those that are stable), given in list of nuclides.
Atom
The atom is a basic unit of matter that consists of a dense central nucleus surrounded by a cloud of negatively charged electrons. The atomic nucleus contains a mix of positively charged protons and electrically neutral neutrons...
with an unstable 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...
, 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
Internal conversion
Internal conversion is a radioactive decay process where an excited nucleus interacts with an electron in one of the lower atomic orbitals, causing the electron to be emitted from the atom. Thus, in an internal conversion process, a high-energy electron is emitted from the radioactive atom, but...
. The radionuclide, in this process, undergoes 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...
, and emits gamma ray
Gamma ray
Gamma radiation, also known as gamma rays or hyphenated as gamma-rays and denoted as γ, is electromagnetic radiation of high frequency . Gamma rays are usually naturally produced on Earth by decay of high energy states in atomic nuclei...
(s) and/or subatomic particles. These particles constitute ionizing radiation
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...
. Radionuclides occur naturally, and can also be artificially produced.
The number of radionuclides is uncertain because the number of very short-lived radionuclides that have yet to be characterized is extremely large and potentially unquantifiable. Even the number of long-lived radionuclides is uncertain (to a smaller degree), because many "stable" nuclides are calculated to have half-lives so long that their decay has not been experimentally measured. The total list of nuclides contains 90 nuclides that are theoretically stable, and 255 total stable nuclides that have not been observed to decay. In addition, there exist about 650 radionuclides that have been experimentally observed to decay, with half-lives longer than 60 minutes (see list of nuclides for this list). Of these, about 339 are known from nature (they have been observed on Earth, and not as a consequence of man-made activities).
Including artificially produced nuclides, more than 3300 nuclides are known (including ~3000 radionuclides), including many more (> ~2400) that have decay half-lives shorter than 60 minutes. This list expands as new radionuclides with very short half-lives are characterized.
Radionuclides are often referred to by chemists and physicists as radioactive isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
s or radioisotopes. Radioisotopes with suitable half-lives play an important part in a number of constructive technologies (for example, nuclear medicine
Nuclear medicine
In nuclear medicine procedures, elemental radionuclides are combined with other elements to form chemical compounds, or else combined with existing pharmaceutical compounds, to form radiopharmaceuticals. These radiopharmaceuticals, once administered to the patient, can localize to specific organs...
). Radionuclides can also present both real and perceived dangers to health.
Origin
Naturally occurring radionuclides fall into three categories: primordial radionuclides, secondary radionuclides and cosmogenic radionuclides. Primordial radionuclides originate mainly from the interiors of starStar
A star is a massive, luminous sphere of plasma held together by gravity. At the end of its lifetime, a star can also contain a proportion of degenerate matter. The nearest star to Earth is the Sun, which is the source of most of the energy on Earth...
s and, like uranium
Uranium
Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons...
and thorium
Thorium
Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder....
, are still present because their half-lives
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
are so long that they have not yet completely decayed. Secondary radionuclides are radiogenic isotopes derived from the decay of primordial radionuclides. They have shorter half-lives than primordial radionuclides. Cosmogenic isotopes, such as carbon-14
Carbon-14
Carbon-14, 14C, or radiocarbon, is a radioactive isotope of carbon with a nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues , to date archaeological, geological, and hydrogeological...
, are present because they are continually being formed in the atmosphere due to cosmic ray
Cosmic ray
Cosmic rays are energetic charged subatomic particles, originating from outer space. They may produce secondary particles that penetrate the Earth's atmosphere and surface. The term ray is historical as cosmic rays were thought to be electromagnetic radiation...
s.
Artificially produced radionuclides can be produced by nuclear reactor
Nuclear reactor
A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...
s, particle accelerators or by radionuclide generators:
- Radioisotopes produced with nuclear reactors exploit the high flux of neutronNeutronThe 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 present. The neutrons activate elements placed within the reactor. A typical product from a nuclear reactor is thallium-201Isotopes of thalliumThallium has 37 isotopes which have atomic masses that range from 176 to 212. 203Tl and 205Tl are the only stable isotopes and 204Tl is the most stable radioisotope with a half-life of 3.78 years...
and iridium-192. The elements that have a large propensity to take up the neutrons in the reactor are said to have a high neutron cross-sectionNeutron cross-sectionIn nuclear and particle physics, the concept of a neutron cross section is used to express the likelihood of interaction between an incident neutron and a target nucleus. In conjunction with the neutron flux, it enables the calculation of the reaction rate, for example to derive the thermal power...
. - Particle accelerators such as cyclotronCyclotronIn technology, a cyclotron is a type of particle accelerator. In physics, the cyclotron frequency or gyrofrequency is the frequency of a charged particle moving perpendicularly to the direction of a uniform magnetic field, i.e. a magnetic field of constant magnitude and direction...
s accelerate particles to bombard a target to produce radionuclides. Cyclotrons accelerate protons at a target to produce positron emitting radioisotopes, e.g., fluorine-18Fluorine-18Fluorine-18 is a fluorine radioisotope which is an important source of positrons. It has a mass of 18.0009380 u and its half-life is 109.771 minutes....
. - Radionuclide generators contain a parent isotope that decays to produce a radioisotope. The parent is usually produced in a nuclear reactor. A typical example is the technetium-99m generatorTechnetium-99m generatorA technetium-99m generator, or colloquially a technetium cow or moly cow, is a device used to extract the metastable isotope 99mTc of technetium from a source of decaying molybdenum-99...
used in nuclear medicineNuclear medicineIn nuclear medicine procedures, elemental radionuclides are combined with other elements to form chemical compounds, or else combined with existing pharmaceutical compounds, to form radiopharmaceuticals. These radiopharmaceuticals, once administered to the patient, can localize to specific organs...
. The parent produced in the reactor is molybdenum-99. - Radionuclides are produced as an unavoidable side effect of nuclear and thermonuclear explosions.
Trace radionuclides are those that occur in tiny amounts in nature either due to inherent rarity, or to half-lives
Half-life
Half-life, abbreviated t½, is the period of time it takes for the amount of a substance undergoing decay to decrease by half. The name was originally used to describe a characteristic of unstable atoms , but it may apply to any quantity which follows a set-rate decay.The original term, dating to...
that are significantly shorter than the age of the Earth. Synthetic isotopes are inherently not naturally occurring on Earth, but can be created 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.
Uses
Radionuclides are used in two major ways: for their chemical properties and as sources of radiationRadiation
In physics, radiation is a process in which energetic particles or energetic waves travel through a medium or space. There are two distinct types of radiation; ionizing and non-ionizing...
.
Radionuclides of familiar elements such as 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...
can serve as tracers
Radioactive tracer
A radioactive tracer, also called a radioactive label, is a substance containing a radioisotope that is used to measure the speed of chemical processes and to track the movement of a substance through a natural system such as a cell or tissue...
because they are chemically very similar to the non-radioactive nuclides, so most chemical, biological, and ecological processes treat them in a near identical way. One can then examine the result with a radiation detector, such as a geiger counter
Geiger counter
A Geiger counter, also called a Geiger–Müller counter, is a type of particle detector that measures ionizing radiation. They detect the emission of nuclear radiation: alpha particles, beta particles or gamma rays. A Geiger counter detects radiation by ionization produced in a low-pressure gas in a...
, to determine where the provided atoms ended up. For example, one might culture plants in an environment in which the carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...
contained radioactive carbon; then the parts of the plant that had laid down atmospheric carbon would be radioactive.
In nuclear medicine
Nuclear medicine
In nuclear medicine procedures, elemental radionuclides are combined with other elements to form chemical compounds, or else combined with existing pharmaceutical compounds, to form radiopharmaceuticals. These radiopharmaceuticals, once administered to the patient, can localize to specific organs...
, radioisotopes are used for diagnosis, treatment, and research. Radioactive chemical tracers emitting gamma rays or positrons can provide diagnostic information about a person's internal anatomy and the functioning of specific organs. This is used in some forms of tomography: single-photon emission computed tomography and positron emission tomography
Positron emission tomography
Positron emission tomography is nuclear medicine imaging technique that produces a three-dimensional image or picture of functional processes in the body. The system detects pairs of gamma rays emitted indirectly by a positron-emitting radionuclide , which is introduced into the body on a...
scanning.
Radioisotopes are also a method of treatment in hemopoietic forms of tumors; the success for treatment of solid tumors has been limited. More powerful gamma sources sterilise syringes and other medical equipment.
In biochemistry
Biochemistry
Biochemistry, sometimes called biological chemistry, is the study of chemical processes in living organisms, including, but not limited to, living matter. Biochemistry governs all living organisms and living processes...
and genetics
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....
, radionuclides label molecules and allow tracing chemical and physiological processes occurring in living organisms, such as DNA replication
DNA replication
DNA replication is a biological process that occurs in all living organisms and copies their DNA; it is the basis for biological inheritance. The process starts with one double-stranded DNA molecule and produces two identical copies of the molecule...
or amino acid
Amino acid
Amino acids are molecules containing an amine group, a carboxylic acid group and a side-chain that varies between different amino acids. The key elements of an amino acid are carbon, hydrogen, oxygen, and nitrogen...
transport.
In food preservation
Food preservation
Food preservation is the process of treating and handling food to stop or slow down spoilage and thus allow for longer storage....
, radiation is used
Food irradiation
Food irradiation is the process of exposing food to ionizing radiation to destroy microorganisms, bacteria, viruses, or insects that might be present in the food. Further applications include sprout inhibition, delay of ripening, increase of juice yield, and improvement of re-hydration...
to stop the sprouting of root crops after harvesting, to kill parasites and pests, and to control the ripening of stored fruit and vegetables.
In industry
Industry
Industry refers to the production of an economic good or service within an economy.-Industrial sectors:There are four key industrial economic sectors: the primary sector, largely raw material extraction industries such as mining and farming; the secondary sector, involving refining, construction,...
, and in mining
Mining
Mining is the extraction of valuable minerals or other geological materials from the earth, from an ore body, vein or seam. The term also includes the removal of soil. Materials recovered by mining include base metals, precious metals, iron, uranium, coal, diamonds, limestone, oil shale, rock...
, radionuclides examine welds, to detect leaks, to study the rate of wear, erosion and corrosion of metals, and for on-stream analysis of a wide range of minerals and fuels.
Radionuclides are also used to trace and analyze pollutants, to study the movement of surface water, and to measure water runoffs from rain and snow, as well as the flow rates of streams and rivers. Natural radionuclides are used in 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...
, archaeology
Archaeology
Archaeology, or archeology , is the study of human society, primarily through the recovery and analysis of the material culture and environmental data that they have left behind, which includes artifacts, architecture, biofacts and cultural landscapes...
, and paleontology
Paleontology
Paleontology "old, ancient", ὄν, ὀντ- "being, creature", and λόγος "speech, thought") is the study of prehistoric life. It includes the study of fossils to determine organisms' evolution and interactions with each other and their environments...
to measure ages of rocks, minerals, and fossil materials.
Americium-241
Most household smoke detectorSmoke detector
A smoke detector is a device that detects smoke, typically as an indicator of fire. Commercial, industrial, and mass residential devices issue a signal to a fire alarm system, while household detectors, known as smoke alarms, generally issue a local audible and/or visual alarm from the detector...
s contain americium formed in nuclear reactor
Nuclear reactor
A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...
s. The radioisotope used is americium-241.
The element americium is created by bombarding plutonium with neutrons in a nuclear reactor. Its isotope, Am-241 decays by emitting 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...
s and gamma radiation to become neptunium-237.
The most common household smoke detectors use a very small quantity of Am-241 (about 0.29 micrograms per smoke detector) in the form of americium dioxide. The smoke detectors use the Am-241 since the alpha particles it emits collide with oxygen and nitrogen particles in the air. This occurs in the detector's ionization chamber
Ionization chamber
The ionization chamber is the simplest of all gas-filled radiation detectors, and is used for the detection or measurement of ionizing radiation...
where it produces charged particles or ion
Ion
An ion is an atom or molecule in which the total number of electrons is not equal to the total number of protons, giving it a net positive or negative electrical charge. The name was given by physicist Michael Faraday for the substances that allow a current to pass between electrodes in a...
s. Then, these charged particles are collected by a small electric voltage that will create an electric current that will pass between two electrodes. Then, the ions that are flowing between the electrodes will be neutralized when coming in contact with smoke, thereby decreasing the electric current between the electrodes, which will activate the detector's alarm.
Steps for creating americium-241
The plutonium-241
Plutonium-241
Plutonium-241 is an isotope of plutonium formed when plutonium-240 captures a neutron. Like Pu-239 but unlike 240Pu, 241Pu is fissile, with a neutron absorption cross section about 1/3 greater than 239Pu, and a similar probability of fissioning on neutron absorption, around 73%. In the non-fission...
is formed in any nuclear reactor by neutron capture from uranium-238
Uranium-238
Uranium-238 is the most common isotope of uranium found in nature. It is not fissile, but is a fertile material: it can capture a slow neutron and after two beta decays become fissile plutonium-239...
.
- + neutron =>
- by beta decay =>
- by beta decay =>
- + neutron =>
- + neutron =>
This will decay both in the reactor and subsequently to form Am-241 (Half-life: 432.2 years)
Gadolinium-153
The Gd-153 isotope is used in X-ray fluorescence and osteoporosisOsteoporosis
Osteoporosis is a disease of bones that leads to an increased risk of fracture. In osteoporosis the bone mineral density is reduced, bone microarchitecture is deteriorating, and the amount and variety of proteins in bone is altered...
screening. It is a gamma-emitter with an 8-month half-life, making it easier to use for medical purposes. In nuclear medicine
Nuclear medicine
In nuclear medicine procedures, elemental radionuclides are combined with other elements to form chemical compounds, or else combined with existing pharmaceutical compounds, to form radiopharmaceuticals. These radiopharmaceuticals, once administered to the patient, can localize to specific organs...
, it serves to calibrate the equipment needed like single-photon emission computed tomography systems (SPECT) to make x-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
s. It ensures that the machines work correctly to produce images of radioisotope distribution inside the patient. This isotope is produced in a nuclear reactor from europium
Europium
Europium is a chemical element with the symbol Eu and atomic number 63. It is named after the continent of Europe. It is a moderately hard silvery metal which readily oxidizes in air and water...
or enriched
Isotope separation
Isotope separation is the process of concentrating specific isotopes of a chemical element by removing other isotopes, for example separating natural uranium into enriched uranium and depleted uranium. This is a crucial process in the manufacture of uranium fuel for nuclear power stations, and is...
gadolinium. It can also detect the loss of calcium
Calcium
Calcium is the chemical element with the symbol Ca and atomic number 20. It has an atomic mass of 40.078 amu. Calcium is a soft gray alkaline earth metal, and is the fifth-most-abundant element by mass in the Earth's crust...
in the hip and back bones, allowing the ability to diagnose osteoporosis.
Dangers
Radionuclides that find their way into the environment may cause harmful effects of radioactive contaminationRadioactive contamination
Radioactive contamination, also called radiological contamination, is radioactive substances on surfaces, or within solids, liquids or gases , where their presence is unintended or undesirable, or the process giving rise to their presence in such places...
. They can also cause damage if they are excessively used during treatment or in other ways applied to living beings, by radiation poisoning
Radiation poisoning
Acute radiation syndrome also known as radiation poisoning, radiation sickness or radiation toxicity, is a constellation of health effects which occur within several months of exposure to high amounts of ionizing radiation...
.
Summary table for classes of nuclides, "stable" and radioactive
Following is a summary table for the total list of nuclides with half-lives greater than one hour. Ninety of these 905 nuclides are theoretically stable, except to proton-decay (which has never been observed). About 255 nuclides have never been observed to decay, and are classically considered stable.The remaining 650 radionuclides have half-lives longer than 1 hour, and are well characterized (see list of nuclides for a complete tabulation). They include 27 nuclides with measured half-lives longer than the estimated age of the universe (13.7 billion years), and another 6 nuclides with half-lives long enough (> 80 million years) that they are radioactive primordial nuclide
Primordial nuclide
In geochemistry and geonuclear physics, primordial nuclides or primordial isotopes are nuclides found on the earth that have existed in their current form since before Earth was formed. Only 288 such nuclides are known...
s, and may be detected on Earth, having survived from their presence in interstellar dust since before the formation of the solar system, about 4.6 billion years ago. Another ~51 short-lived nuclides can be detected naturally as daughters of longer-lived nuclides or cosmic-ray products. The remaining known nuclides are known solely from artificial nuclear transmutation
Nuclear 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'...
.
Numbers are not exact, and may change slightly in the future, as "stable nuclides" are observed to be radioactive with very long half-lives.
This is a summary table for the 905 nuclides with half-lives longer than one hour (including those that are stable), given in list of nuclides.
| Stability class | Number of nuclides | Running total Running total A running total is the summation of a sequence of numbers which is updated each time a new number is added to the sequence, simply by adding the value of the new number to the running total.... |
Notes on running total |
|---|---|---|---|
| Theoretically stable to all but proton decay Proton decay In particle physics, proton decay is a hypothetical form of radioactive decay in which the proton decays into lighter subatomic particles, such as a neutral pion and a positron... |
90 | 90 | Includes first 40 elements. Proton decay yet to be observed. |
| Energetically unstable to one or more known decay modes, but no decay yet seen. Spontaneous fission Spontaneous fission Spontaneous fission is a form of radioactive decay characteristic of very heavy isotopes. Because the nuclear binding energy reaches a maximum at a nuclear mass greater than about 60 atomic mass units , spontaneous breakdown into smaller nuclei and single particles becomes possible at heavier masses... possible for "stable" nuclides > niobium-93; other mechanisms possible for heavier nuclides. All considered "stable" until decay detected. |
165 | 255 | Total of classically stable nuclides. |
| Radioactive primordial nuclide Primordial nuclide In geochemistry and geonuclear physics, primordial nuclides or primordial isotopes are nuclides found on the earth that have existed in their current form since before Earth was formed. Only 288 such nuclides are known... s. |
33 | 288 | Total primordial elements include bismuth Bismuth Bismuth is a chemical element with symbol Bi and atomic number 83. Bismuth, a trivalent poor metal, chemically resembles arsenic and antimony. Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores. The free element is 86% as dense as lead... , uranium Uranium Uranium is a silvery-white metallic chemical element in the actinide series of the periodic table, with atomic number 92. It is assigned the chemical symbol U. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons... , thorium Thorium Thorium is a natural radioactive chemical element with the symbol Th and atomic number 90. It was discovered in 1828 and named after Thor, the Norse god of thunder.... , plutonium Plutonium Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation... , plus all stable nuclides. |
| Radioactive non-primordial, but naturally occurring on Earth. | ~ 51 | ~ 339 | Carbon-14 Carbon-14 Carbon-14, 14C, or radiocarbon, is a radioactive isotope of carbon with a nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues , to date archaeological, geological, and hydrogeological... (and other isotopes generated by cosmic rays); daughters of radioactive primordials, such as francium Francium Francium is a chemical element with symbol Fr and atomic number 87. It was formerly known as eka-caesium and actinium K.Actually the least unstable isotope, francium-223 It has the lowest electronegativity of all known elements, and is the second rarest naturally occurring element... , etc. |
| Radioactive synthetic (half-life > 1 hour). Includes most useful radiotracers. | 556 | 905 | These 905 nuclides are listed in the article List of nuclides. |
| Radioactive synthetic (half-life < 1 hour). | >2400 | >3300 | Includes all well-characterized synthetic nuclides. |
Gamma only
| Isotope | Activity | Half-life | Energies (KeV) |
|---|---|---|---|
| Barium-133 | 1uCi | 10.7 years | 81.0, 356.0 |
| Cadmium-109 | 1uCi | 453 days | 88.0 |
| Cobalt 57 | 1uCi | 270 days | 122.1 |
| Cobalt 60 Cobalt 60 Cobalt 60 is a Front 242 side project featuring Front 242's Jean-Luc de Meyer and Dominique Lallement. They are an electro-industrial/EBM group, though they frequently use guitars, an uncommon feature among artists of the genre... |
1uCi | 5.27 years | 1173.2, 1332.5 |
| Europium-152 | 1uCi | 13.5 years | 121.8, 344.3, 1408.0 |
| Manganese-54 | 1uCi | 312 days | 834.8 |
| Sodium-22 | 1uCi | 2.6 years | 511.0, 1274.5 |
| Zinc-65 | 1uCi | 244 days | 511.0, 1115.5 |
| Technetium 99m | 1uCi | 6.01 hours | 140 |
Beta only
| Isotope | Activity | Half-life | Energies (KeV) |
|---|---|---|---|
| Strontium-90 Strontium-90 Strontium-90 is a radioactive isotope of strontium, with a half-life of 28.8 years.-Radioactivity:Natural strontium is nonradioactive and nontoxic, but 90Sr is a radioactivity hazard... |
0.1uCi | 28.5 years | 546.0 |
| Thallium-204 | 1uCi | 3.78 years | 763.4 |
| Carbon-14 Carbon-14 Carbon-14, 14C, or radiocarbon, is a radioactive isotope of carbon with a nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues , to date archaeological, geological, and hydrogeological... |
10uCi | 5730 years | 49.5 (average) |
Alpha only
| Isotope | Activity | Half-life | Energies (KeV) |
|---|---|---|---|
| Polonium 210 | 0.1uCi | 138 days | 5304.5 |
Multiple radiation emitters
| Isotope | Activity | Half-life | Radiation types | Energies (KeV) |
|---|---|---|---|---|
| Caesium-137 Caesium-137 Caesium-137 is a radioactive isotope of caesium which is formed as a fission product by nuclear fission.It has a half-life of about 30.17 years, and decays by beta emission to a metastable nuclear isomer of barium-137: barium-137m . Caesium-137 is a radioactive isotope of caesium which is formed... |
1, 5, 10 uCi | 30.1 years | Gamma & beta | G: 32, 661.6 B: 511.6, 1173.2 |
- http://www.uic.com.au/nip27.htm
See also
- List of nuclides shows all radionuclides with half-life > 1 hour
- Hyperaccumulators table – 3Hyperaccumulators table – 3This section covers radionuclides, hydrocarbons and organic solvents, and information on the plants used for their remediation.Links to the other sections:*Hyperaccumulators table – 1 : Al, Ag, As, Be, Cr, Cu, Mn, Hg, Mo, Naphtalene, Pb, Pd, Pt, Se, Zn...
- Radioactivity in biology
- Radiometric datingRadiometric datingRadiometric dating is a technique used to date materials such as rocks, usually based on a comparison between the observed abundance of a naturally occurring radioactive isotope and its decay products, using known decay rates...
- Radionuclide cisternogram
External links
- EPA – Radionuclides – EPA's Radiation Protection Program: Information.
- FDA – Radionuclides – FDA's Radiation Protection Program: Information.
- Interactive Chart of Nuclides – A chart of all nuclides
- National Isotope Development Center – U.S. Government source of radionuclides - production, research, development, distribution, and information
- The Live Chart of Nuclides – IAEA , in Java or HTML
- Willey Online Library: Book Article