Curie
Encyclopedia
The curie is a unit of radioactivity
, defined as
This 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
, the becquerel
(Bq), which equates to one decay per second. Therefore:
and
A radiotherapy machine may have roughly 1000 Ci of a radioisotope such as caesium-137
or cobalt-60
. This quantity of radioactivity can produce serious health effects with only a few minutes of close-range, un-shielded exposure.
Another commonly used measure of radioactivity is the microcurie:
The typical human body contains roughly 0.1 μCi of naturally occurring potassium-40
.
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...
, defined as
- 1 Ci = 3.7 × 1010 decaysRadioactive decayRadioactive 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 secondSecondThe second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....
.
This is roughly the activity of 1 gram
Gram
The gram is a metric system unit of mass....
of the radium
Radium
Radium is a chemical element with atomic number 88, represented by the symbol Ra. Radium is an almost pure-white alkaline earth metal, but it readily oxidizes on exposure to air, becoming black in color. All isotopes of radium are highly radioactive, with the most stable isotope being radium-226,...
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...
226Ra, a substance studied by the pioneers of radiology
Radiology
Radiology is a medical specialty that employs the use of imaging to both diagnose and treat disease visualized within the human body. Radiologists use an array of imaging technologies to diagnose or treat diseases...
, Marie
Marie Curie
Marie Skłodowska-Curie was a physicist and chemist famous for her pioneering research on radioactivity. She was the first person honored with two Nobel Prizes—in physics and chemistry...
and Pierre Curie
Pierre Curie
Pierre Curie was a French physicist, a pioneer in crystallography, magnetism, piezoelectricity and radioactivity, and Nobel laureate. He was the son of Dr. Eugène Curie and Sophie-Claire Depouilly Curie ...
, for whom the unit was named. In addition to the curie, activity can be measured using an SI derived unit
SI derived unit
The International System of Units specifies a set of seven base units from which all other units of measurement are formed, by products of the powers of base units. These other units are called SI derived units, for example, the SI derived unit of area is square metre , and of density is...
, the 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...
(Bq), which equates to one decay per second. Therefore:
- 1 Ci = 3.7 × 1010 Bq = 37 GBq
- (100 mCi = 3.7 GBq)
and
- 1 Bq = 2.703 × 10−11 Ci
A radiotherapy machine may have roughly 1000 Ci of a radioisotope such as 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...
or cobalt-60
Cobalt-60
Cobalt-60, , is a synthetic radioactive isotope of cobalt. Due to its half-life of 5.27 years, is not found in nature. It is produced artificially by neutron activation of . decays by beta decay to the stable isotope nickel-60...
. This quantity of radioactivity can produce serious health effects with only a few minutes of close-range, un-shielded exposure.
Another commonly used measure of radioactivity is the microcurie:
- 1 μCi = 3.7 × 104 disintegrations per second = 2.22 × 106 disintegrations per minute
The typical human body contains roughly 0.1 μCi of naturally occurring potassium-40
Potassium-40
Potassium-40 is a radioactive isotope of potassium which has a very long half-life of 1.248 years, or about 39.38 seconds.Potassium-40 is a rare example of an isotope which undergoes all three types of beta decay. About 89.28% of the time, it decays to calcium-40 with emission of a beta particle...
.
See also
- Ionizing radiationIonizing radiationIonizing 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...
- United Nations Scientific Committee on the Effects of Atomic RadiationUnited Nations Scientific Committee on the Effects of Atomic RadiationThe United Nations Scientific Committee on the Effects of Atomic Radiation was set up by resolution of the United Nations General Assembly in 1955. 21 countries are designated to provide scientists to serve as members of the committee which holds formal meetings annually and submits a report to...
- Radiation exposureRadiation exposureThe term radiation exposure commonly has several uses:* Absorption of high-energy ionizing radiation by an object. In living beings a high absorbed dose can lead to radiation poisoning.* Absorption by an object of non-ionizing radiation...
- Radiation poisoningRadiation poisoningAcute 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...
- 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...