Synthetic radioisotope
Encyclopedia
A synthetic radioisotope is a radionuclide
that is not found in nature: 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. Examples include technetium
-95 and promethium
-146. Many of these are found in, and harvested from, spent nuclear fuel assemblies. Some must be manufactured in particle accelerator
s.
fuel rods, which contain various fission products. For example, it is estimated that up to 1994, about 49,000 TBq
(78 metric ton
) of technetium
was produced in nuclear reactors, which is by far the dominant source of terrestrial technetium. However, only a fraction of the production is used commercially. Other synthetic isotopes are produced in significant quantities by fission but are not yet being reclaimed. Other isotopes are manufactured by neutron
irradiation of parent isotopes in a nuclear reactor (for example, Tc-97 can be made by neutron irradiation of Ru-96) or by bombarding parent isotopes with high energy particles from a particle accelerator.
. Though a health hazard, radioactive materials have many medical and industrial uses.
covers any use of radioisotopes for
diagnosis or treatment.
which is energetic enough to travel through
the body and be captured outside by a gamma camera
to map the concentrations. Gamma cameras 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
Tc-99m is a Gamma-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-cow
".
-131 is used for treating some disorders and tumors of the thyroid gland.
, beta particle
, and gamma ray
radioactive emissions are industrially useful. Most sources of these are synthetic radioisotopes.
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...
that is not found in nature: 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. Examples include technetium
Technetium
Technetium is the chemical element with atomic number 43 and symbol Tc. It is the lowest atomic number element without any stable isotopes; every form of it is radioactive. Nearly all technetium is produced synthetically and only minute amounts are found in nature...
-95 and promethium
Promethium
Promethium is a chemical element with the symbol Pm and atomic number 61. It is notable for being the only exclusively radioactive element besides technetium that is followed by chemical elements with stable isotopes.- Prediction :...
-146. Many of these are found in, and harvested from, spent nuclear fuel assemblies. Some must be manufactured in particle accelerator
Particle accelerator
A particle accelerator is a device that uses electromagnetic fields to propel charged particles to high speeds and to contain them in well-defined beams. An ordinary CRT television set is a simple form of accelerator. There are two basic types: electrostatic and oscillating field accelerators.In...
s.
Production
Some synthetic radioisotopes are extracted from spent nuclear reactorNuclear 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...
fuel rods, which contain various fission products. For example, it is estimated that up to 1994, about 49,000 TBq
Becquerel
The becquerel is the SI-derived unit of radioactivity. One Bq is defined as the activity of a quantity of radioactive material in which one nucleus decays per second. The Bq unit is therefore equivalent to an inverse second, s−1...
(78 metric ton
Tonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...
) of technetium
Technetium
Technetium is the chemical element with atomic number 43 and symbol Tc. It is the lowest atomic number element without any stable isotopes; every form of it is radioactive. Nearly all technetium is produced synthetically and only minute amounts are found in nature...
was produced in nuclear reactors, which is by far the dominant source of terrestrial technetium. However, only a fraction of the production is used commercially. Other synthetic isotopes are produced in significant quantities by fission but are not yet being reclaimed. Other isotopes are manufactured by 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...
irradiation of parent isotopes in a nuclear reactor (for example, Tc-97 can be made by neutron irradiation of Ru-96) or by bombarding parent isotopes with high energy particles from a particle accelerator.
Uses
Most synthetic radioisotopes are extremely radioactive and have a short half-lifeHalf-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...
. Though a health hazard, radioactive materials have many medical and industrial uses.
Nuclear medicine
The general field of nuclear medicineNuclear 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...
covers any use of radioisotopes for
diagnosis or treatment.
Diagnosis
Radioactive tracer compounds 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 rayGamma 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...
which is energetic enough to travel through
the body and be captured outside by a gamma camera
Gamma camera
A gamma camera, also called a scintillation camera or Anger camera, is a device used to image gamma radiation emitting radioisotopes, a technique known as scintigraphy...
to map the concentrations. Gamma cameras 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
Nuclear isomer
A nuclear isomer is a metastable state of an atomic nucleus caused by the excitation of one or more of its nucleons . "Metastable" refers to the fact that these excited states have half-lives more than 100 to 1000 times the half-lives of the other possible excited nuclear states...
Tc-99m is a Gamma-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-cow
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 source of decaying molybdenum-99...
".
Treatment
Radiopharmaceuticals are any of a number of compounds using a radioisotope for medical treatment, usually by bringing the radioactive isotope to a high concentration in the body near a particular organ. For example, iodineIodine
Iodine is a chemical element with the symbol I and atomic number 53. The name is pronounced , , or . The name is from the , meaning violet or purple, due to the color of elemental iodine vapor....
-131 is used for treating some disorders and tumors of the thyroid gland.
Industrial radiation sources
Alpha particleAlpha 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...
, beta particle
Beta particle
Beta particles are high-energy, high-speed electrons or positrons emitted by certain types of radioactive nuclei such as potassium-40. The beta particles emitted are a form of ionizing radiation also known as beta rays. The production of beta particles is termed beta decay...
, and 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...
radioactive emissions are industrially useful. Most sources of these are synthetic radioisotopes.