Ionizing radiation units
Encyclopedia
Ionizing radiation units are standards for measuring ionizing radiation
, including units for measuring the activity of radioactive sources, and for quantifying the amount of radiation striking other objects, particularly people. The current SI
units replaces older conventional ones.
Conventional unit: 1 curie
= 37 billion disintegrations
per second.
SI unit: 1 becquerel
= 1 disintegration per second
conversions
1 curie (Ci) = 37 gigabecquerel (GBq)
1 gigabecquerel (GBq) = 27 millicurie (mCi)
1 roentgen
(R) = 258 microcoulomb/kg (µC/kg)
1 millicoulomb/kg mC/kg = 3876 milliroentgen (mR)
Conventional units: A dose of 1 rad
means the absorption of 100 erg
s of radiation energy per gram of absorbing material
SI units: A dose of 1 gray
means the absorption of 1 joule
of radiation energy per kilogram of absorbing material
conversion
1 Gy = 100 rad
1 rad = 0.01 Gy
The Quality Factor (Q) depends on the type of radiation:
X-ray
, Gamma ray
, or beta radiation: Q = 1
alpha particle
s: Q = 20
neutrons of unknown energy
: Q = 10 (If the neutron energy is known, see more specific Q values at 10 CFR 20.1004 )
conventional units: dose equivalent (rems
) is the product of dose (rads) and Q
SI units: dose equivalent (sievert
s) is the product of dose (grays) and Q
Conversion
1 Sievert
(Sv) = 100 rem
1 rem
= 0.01 Sievert
(Sv)
is an aggregate measurement that detects all decay events at a particular point. This could be alpha particles, beta particles or mixed gamma/beta, gamma/alpha, alpha/beta actual decays. This can be used with a conversion factor, knowing the type and composition of materials to convert to Roentgen or Coulomb per kilogram. Counts per minute can be useful when detector efficiency is in question.
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...
, including units for measuring the activity of radioactive sources, and for quantifying the amount of radiation striking other objects, particularly people. The current SI
Si
Si, si, or SI may refer to :- Measurement, mathematics and science :* International System of Units , the modern international standard version of the metric system...
units replaces older conventional ones.
Activity of an isotope or material
This measurement applies directly to the source and represents decay product per time unit.Conventional unit: 1 curie
Curie
The curie is a unit of radioactivity, defined asThis is roughly the activity of 1 gram of the radium isotope 226Ra, a substance studied by the pioneers of radiology, Marie and Pierre Curie, for whom the unit was named. In addition to the curie, activity can be measured using an SI derived unit,...
= 37 billion disintegrations
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...
per second.
SI unit: 1 becquerel
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...
= 1 disintegration per second
conversions
1 curie (Ci) = 37 gigabecquerel (GBq)
1 gigabecquerel (GBq) = 27 millicurie (mCi)
Exposure
Exposure is a quantity that expresses the radiation delivered to a point at a certain distance.1 roentgen
Röntgen
The roentgen is a unit of measurement for exposure to ionizing radiation , and is named after the German physicist Wilhelm Röntgen...
(R) = 258 microcoulomb/kg (µC/kg)
1 millicoulomb/kg mC/kg = 3876 milliroentgen (mR)
Radiation absorbed dose (rad)
Under exposure a given material has an ability to absorb radiation. This differs with certain materials (think lead versus water) and some will absorb more or less as radiation passes through.Conventional units: A dose of 1 rad
Rad (unit)
The rad is a unit of absorbed radiation dose. The rad was first proposed in 1918 as "that quantity of X rays which when absorbed will cause the destruction of the malignant mammalian cells in question..." It was defined in CGS units in 1953 as the dose causing 100 ergs of energy to be absorbed by...
means the absorption of 100 erg
Erg
An erg is the unit of energy and mechanical work in the centimetre-gram-second system of units, symbol "erg". Its name is derived from the Greek ergon, meaning "work"....
s of radiation energy per gram of absorbing material
SI units: A dose of 1 gray
Gray (unit)
The gray is the SI unit of absorbed radiation dose of ionizing radiation , and is defined as the absorption of one joule of ionizing radiation by one kilogram of matter ....
means the absorption of 1 joule
Joule
The joule ; symbol J) is a derived unit of energy or work in the International System of Units. It is equal to the energy expended in applying a force of one newton through a distance of one metre , or in passing an electric current of one ampere through a resistance of one ohm for one second...
of radiation energy per kilogram of absorbing material
conversion
1 Gy = 100 rad
1 rad = 0.01 Gy
Dose equivalent
The dose equivalent is a measure of biological effect for whole body irradiation. The dose equivalent is equal to the product of the absorbed dose and the Quality Factor.The Quality Factor (Q) depends on the type of radiation:
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...
, 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...
, or beta radiation: Q = 1
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: Q = 20
neutrons of unknown energy
Neutron radiation
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...
: Q = 10 (If the neutron energy is known, see more specific Q values at 10 CFR 20.1004 )
conventional units: dose equivalent (rems
Röntgen equivalent man
Named after Wilhelm Röntgen , the roentgen equivalent in man or rem is a unit of radiation dose equivalent...
) is the product of dose (rads) and Q
SI units: dose equivalent (sievert
Sievert
The sievert is the International System of Units SI derived unit of dose equivalent radiation. It attempts to quantitatively evaluate the biological effects of ionizing radiation as opposed to just the absorbed dose of radiation energy, which is measured in gray...
s) is the product of dose (grays) and Q
Conversion
1 Sievert
Sievert
The sievert is the International System of Units SI derived unit of dose equivalent radiation. It attempts to quantitatively evaluate the biological effects of ionizing radiation as opposed to just the absorbed dose of radiation energy, which is measured in gray...
(Sv) = 100 rem
Röntgen equivalent man
Named after Wilhelm Röntgen , the roentgen equivalent in man or rem is a unit of radiation dose equivalent...
1 rem
Röntgen equivalent man
Named after Wilhelm Röntgen , the roentgen equivalent in man or rem is a unit of radiation dose equivalent...
= 0.01 Sievert
Sievert
The sievert is the International System of Units SI derived unit of dose equivalent radiation. It attempts to quantitatively evaluate the biological effects of ionizing radiation as opposed to just the absorbed dose of radiation energy, which is measured in gray...
(Sv)
Counts per minute (CPM)
The counts per minuteCounts per minute
Counts per minute is a measure of radioactivity. It is the number of atoms in a given quantity of radioactive material that are detected to have decayed in one minute. Disintegrations per minute is also a measure of radioactivity. It is the number of atoms in a given quantity of radioactive...
is an aggregate measurement that detects all decay events at a particular point. This could be alpha particles, beta particles or mixed gamma/beta, gamma/alpha, alpha/beta actual decays. This can be used with a conversion factor, knowing the type and composition of materials to convert to Roentgen or Coulomb per kilogram. Counts per minute can be useful when detector efficiency is in question.
Roentgen equivalent physical (rep)
Roentgen equivalent physical (rep) is an obsolete unit of absorbed dose of any ionizing radiation with a magnitude of 93 ergs per gram. It has been superseded by the rad.External links
- X-Ray Risk Radiation Risk Calculator. Calculate radiation dose and cancer risk for medical diagnostic X-rays. Designed to be usable for patients.
- Rad pro calculator More technical calculations for radiologists, physicists, and other health professionals.
- Nucleonica nuclear science portal for general calculations of radiation doses.
- Measurement section of the online brochure "Guidance for Radiation Accident Management" at the Radiation Emergency Assistance Center/Training Site (REAC/TS) at Oak Ridge Institute for Science and Education.
See also
- Scintillation counterScintillation counterA scintillation counter measures ionizing radiation. The sensor, called a scintillator, consists of a transparent crystal, usually phosphor, plastic , or organic liquid that fluoresces when struck by ionizing radiation. A sensitive photomultiplier tube measures the light from the crystal...
- Geiger counterGeiger counterA 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...
- Radon gas
- Lucas cell
- PhotomultiplierPhotomultiplierPhotomultiplier tubes , members of the class of vacuum tubes, and more specifically phototubes, are extremely sensitive detectors of light in the ultraviolet, visible, and near-infrared ranges of the electromagnetic spectrum...