A synthetic radioisotope is a

radionuclide A radionuclide (radioactive nuclide, radioisotope or radioactive isotope) is a nuclide that has excess numbers of either neutrons or protons, giving it excess nuclear energy, and making it unstable. This excess energy can be used in one of three ...

that is not found in

nature Nature is an inherent character or constitution, particularly of the Ecosphere (planetary), ecosphere or the universe as a whole. In this general sense nature refers to the Scientific law, laws, elements and phenomenon, phenomena of the physic ...

: no natural process or mechanism exists which produces it, or it is so unstable that it decays away in a very short period of time. Frédéric Joliot-Curie and Irène Joliot-Curie were the first to produce a synthetic radioisotope in the 20th century. Examples include technetium-98 and promethium-146. Many of these are found in, and harvested from,

spent nuclear fuel Spent nuclear fuel, occasionally called used nuclear fuel, is nuclear fuel that has been irradiated in a nuclear reactor (usually at a nuclear power plant). It is no longer useful in sustaining a nuclear reaction in an ordinary thermal reactor and ...

assemblies. Some must be manufactured in

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

Production

Some synthetic radioisotopes are extracted from spent

nuclear reactor A nuclear reactor is a device used to initiate and control a Nuclear fission, fission nuclear chain reaction. They are used for Nuclear power, commercial electricity, nuclear marine propulsion, marine propulsion, Weapons-grade plutonium, weapons ...

fuel rods, which contain various

fission products Nuclear fission products are the atomic fragments left after a large atomic nucleus undergoes nuclear fission. Typically, a large nucleus like that of uranium fissions by splitting into two smaller nuclei, along with a few neutrons, the releas ...

. For example, it is estimated that up to 1994, about 49,000 terabecquerels (78

metric ton The tonne ( or ; symbol: t) is a unit of mass equal to 1,000 kilograms. It is a non-SI unit accepted for use with SI. It is also referred to as a metric ton in the United States to distinguish it from the non-metric units of the sh ...

s) of

technetium Technetium is a chemical element; it has Symbol (chemistry), symbol Tc and atomic number 43. It is the lightest element whose isotopes are all radioactive. Technetium and promethium are the only radioactive elements whose neighbours in the sense ...

were produced in nuclear reactors; as such, anthropogenic technetium is far more abundant than technetium from natural radioactivity. Some synthetic isotopes are produced in significant quantities by fission but are not yet being reclaimed. Other isotopes are manufactured by

neutron The neutron is a subatomic particle, symbol or , that has no electric charge, and a mass slightly greater than that of a proton. The Discovery of the neutron, neutron was discovered by James Chadwick in 1932, leading to the discovery of nucle ...

irradiation of parent isotopes in a nuclear reactor (for example, technetium-97 can be made by neutron irradiation of ruthenium-96) or by bombarding parent isotopes with high energy particles from a particle accelerator. Many isotopes, including

radiopharmaceutical Radiopharmaceuticals, or medicinal radiocompounds, are a group of pharmaceutical drugs containing radioactive isotopes. Radiopharmaceuticals can be used as diagnostic and therapeutic agents. Radiopharmaceuticals emit radiation themselves, which ...

s, are produced in

cyclotron A cyclotron is a type of particle accelerator invented by Ernest Lawrence in 1929–1930 at the University of California, Berkeley, and patented in 1932. Lawrence, Ernest O. ''Method and apparatus for the acceleration of ions'', filed: Januar ...

s. For example, the synthetic

fluorine-18 Fluorine-18 (18F, also called radiofluorine) is a fluorine radioisotope which is an important source of positrons. It has a mass of 18.0009380(6) u and its half-life is 109.771(20) minutes. It decays by positron emission 96.7% of the time and el ...

and

oxygen-15 There are three known stable isotopes of oxygen (8O): , , and . Radioactive isotopes ranging from to have also been characterized, all short-lived. The longest-lived radioisotope is with a half-life of , while the shortest-lived isotope is ...

are widely used in

positron emission tomography Positron emission tomography (PET) is a functional imaging technique that uses radioactive substances known as radiotracers to visualize and measure changes in metabolic processes, and in other physiological activities including blood flow, r ...

Uses

Most synthetic radioisotopes have a short

half-life Half-life is a mathematical and scientific description of exponential or gradual decay. Half-life, half life or halflife may also refer to: Film * Half-Life (film), ''Half-Life'' (film), a 2008 independent film by Jennifer Phang * ''Half Life: ...

. Though a health hazard, radioactive materials have many medical and industrial uses.

Nuclear medicine

The field of

nuclear medicine Nuclear medicine (nuclear radiology, nucleology), is a medical specialty involving the application of radioactivity, radioactive substances in the diagnosis and treatment of disease. Nuclear imaging is, in a sense, ''radiology done inside out'', ...

covers use of radioisotopes for diagnosis or treatment.

Diagnosis

Radioactive tracer compounds,

s, are used to observe the function of various organs and body systems. These compounds use a chemical tracer which is attracted to or concentrated by the activity which is being studied. That chemical tracer incorporates a short lived radioactive isotope, usually one which emits a

gamma ray A gamma ray, also known as gamma radiation (symbol ), is a penetrating form of electromagnetic radiation arising from high energy interactions like the radioactive decay of atomic nuclei or astronomical events like solar flares. It consists o ...

which is energetic enough to travel through the body and be captured outside by a

gamma camera A gamma camera (γ-camera), also called a scintillation camera or Anger camera, is a device used to image gamma radiation emitting radioisotopes, a technique known as scintigraphy. The applications of scintigraphy include early drug development ...

to map the concentrations.

Gamma camera A gamma camera (γ-camera), also called a scintillation camera or Anger camera, is a device used to image gamma radiation emitting radioisotopes, a technique known as scintigraphy. The applications of scintigraphy include early drug development ...

s and other similar detectors are highly efficient, and the tracer compounds are generally very effective at concentrating at the areas of interest, so the total amounts of radioactive material needed are very small. The metastable

nuclear isomer A nuclear isomer is a metastable state of an atomic nucleus, in which one or more nucleons (protons or neutrons) occupy excited state levels (higher energy levels). "Metastable" describes nuclei whose excited states have Half-life, half-lives of ...

technetium-99m Technetium-99m (99mTc) is a metastable nuclear isomer of technetium-99 (itself an isotope of technetium), symbolized as 99mTc, that is used in tens of millions of medical diagnostic procedures annually, making it the most commonly used Radiophar ...

is a gamma-ray emitter widely used for medical diagnostics because it has a short half-life of 6 hours, but can be easily made in the hospital using a

technetium-99m generator A 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 decaying sample of molybdenum-99. 99Mo has a half-life of 66 hours and can be easily tran ...

. Weekly global demand for the parent isotope

molybdenum-99 Molybdenum (42Mo) has 39 known isotopes, ranging in atomic mass from 81 to 119, as well as four metastable nuclear isomers. Seven isotopes occur naturally, with atomic masses of 92, 94, 95, 96, 97, 98, and 100. All unstable isotopes of molybdenum ...

was in 2010, overwhelmingly provided by fission of

uranium-235 Uranium-235 ( or U-235) is an isotope of uranium making up about 0.72% of natural uranium. Unlike the predominant isotope uranium-238, it is fissile, i.e., it can sustain a nuclear chain reaction. It is the only fissile isotope that exists in nat ...

Treatment

Several radioisotopes and compounds are used for

medical treatment A therapy or medical treatment is the attempted remediation of a health problem, usually following a medical diagnosis. Both words, ''treatment'' and ''therapy'', are often abbreviated tx, Tx, or Tx. As a rule, each therapy has indications an ...

, usually by bringing the radioactive isotope to a high concentration in the body near a particular organ. For example,

iodine-131 Iodine-131 (131I, I-131) is an important radioisotope of iodine discovered by Glenn Seaborg and John Livingood in 1938 at the University of California, Berkeley. It has a radioactive decay half-life of about eight days. It is associated with nu ...

is used for treating some disorders and tumors of the

thyroid The thyroid, or thyroid gland, is an endocrine gland in vertebrates. In humans, it is a butterfly-shaped gland located in the neck below the Adam's apple. It consists of two connected lobes. The lower two thirds of the lobes are connected by ...

gland.

Industrial radiation sources

Alpha particle Alpha particles, also called alpha rays or alpha radiation, consist of two protons and two neutrons bound together into a particle identical to a helium-4 nucleus. They are generally produced in the process of alpha decay but may also be produce ...

beta particle A beta particle, also called beta ray or beta radiation (symbol β), is a high-energy, high-speed electron or positron emitted by the radioactive decay of an atomic nucleus, known as beta decay. There are two forms of beta decay, β− decay and � ...

, and

radioactive emissions are industrially useful. Most sources of these are synthetic radioisotopes. Areas of use include the

petroleum industry The petroleum industry, also known as the oil industry, includes the global processes of hydrocarbon exploration, exploration, extraction of petroleum, extraction, oil refinery, refining, Petroleum transport, transportation (often by oil tankers ...

industrial radiography Industrial radiography is a modality of non-destructive testing that uses ionizing radiation to inspect materials and components with the objective of locating and quantifying defects and degradation in material properties that would lead to the ...

homeland security Homeland security is an American national security term for "the national effort to ensure a homeland that is safe, secure, and resilient against terrorism and other hazards where American interests, aspirations, and ways of life can thrive" to ...

process control Industrial process control (IPC) or simply process control is a system used in modern manufacturing which uses the principles of control theory and physical industrial control systems to monitor, control and optimize continuous Industrial processe ...

food irradiation Food irradiation (sometimes American English: radurization; British English: radurisation) is the process of exposing food and food packaging to ionizing radiation, such as from gamma rays, x-rays, or electron beams. Food irradiation improves ...

and underground detection.

Footnotes

External links

Map of the Nuclides at LANL T-2 Website
{{Webarchive, url=https://web.archive.org/web/20040404142354/http://t2.lanl.gov/data/map.html , date=2004-04-04 Radioactivity Radiopharmaceuticals af:Radio-aktiewe isotoop