(1) (Colloquial) Radioactivity; the dose rate of a sample.
(2) The rate of decay of a population of radioactive nuclides. Activity can also refer to the emission rate of a radiation from a sample, useful for samples with nuclides that emit multiple radiations per disintegration. The activity of a sample is given by -λN when it contains one dominant nuclide that has a single half life. In this expression, λ is the decay constant and N is the number of atoms of that particular nuclide. N is more specifically defined as the number of nuclei in a particular nuclear state, a definition that accounts for systems in which a particular nuclide can exist in a number of isomeric states and the ground state. When the total activity is defined by a two or more radioactive nuclides or isomers, it is given by the expression -λ1N1 + λ2N2 + ... λnNn, where the terms define the decay constant and number of atoms for each isomer and nuclide.
(3) (10CFR20) The rate of disintegration (transformation) or decay of radioactive material. The units for activity are further defined as the curie (Ci) and the becquerel (Bq).
The amount of a substance that produces an acute exposure to a biological system. For radiation it is the amount of energy deposited in the biological system or a specific tissue or component of that system.
A short, intense exposure to a microorganism, radiation or a toxic substance severe enough that the recovery of the biological system cannot readily occur. Acute exposures generally last less than one day.
A State of the U.S. that has entered into an agreement with the Nuclear Regulatory Commission under the Atomic Energy Act of 1954 (68 Stat 919), subsection 274b, allowing that State to regulate the use of by-product radioactive materials within its borders.
A goal for reducing radiation doses to levels far below the dose limits, taking into account the state of technology, the economics of improvements in relation to state of technology, the economics of improvements in relation to benefits to the public health and safety, and other societal and socioeconomic considerations, and in relation to utilization of nuclear energy and licensed materials in the public interest.
The smallest particle of a chemical element. An atom consists of a small, dense nucleus surrounded by a cloud of electrons. The nucleus contains protons and neutrons that account for much of the atomic mass. Chemical properties are defined largely by the number of protons in the nucleus. An atom is said to be ionized when the number of electrons is not equivalent to the number of protons; the resulting electrical charge is the number of protons minus the number of electrons.
(1) (general) Radiation that interferes with measurements. Cosmic rays and radioactivity in soil, water and air are forms of ambient radiation that often interferes with low count rate measurements. Other forms of background radiation include sources of radiation observable by the detector, contamination of samples, incomplete absorption of radiation in the detector or incomplete charge collection by the detector.
(2) (10CFR20) Ambient radiation. Radiation from cosmic sources; naturally occurring radioactive materials, including radon (except as a decay product of source material or special nuclear material); and global fallout as it exists in the environment from the testing of nuclear explosive devices. Background radiation does not include radiation from source material, by-product material, or special nuclear materials regulated by the Nuclear Regulatory Commission.
The electron or positron (the antiparticle of the electron) emitted by a nucleus during beta decay. The name beta was coined by Rutherford in 1897.
Reference: E. Rutherford. Phil. Mag. 47, 109 (1897).
Synonym: beta radiation.
Synonym: beta ray.
Synonym: decay electron.
Synonym: disintegration electron.
Related to alpha particle.
Related to beta decay.
Related to gamma ray.
Related to positron.
The determination of kinds, quantities or concentrations, and, in some cases, the locations of radioactive material in the human body, whether by direct measurement (in vivo counting) or by analysis and evaluation of materials excreted or removed from the human body.
The time required for the concentration of a particular substance in a biological system to be reduced by one half. A biological half-life includes only normal processes for eliminating substances, thereby excluding radioactive decay.
A normalization factor that converts between the value of a measured parameter and the actual value of that parameter in a system. The need for calibration factors arises because detectors and sensors do not directly sample a parameter but instead produce a response that scales with the value of the parameter. An example is the measurement of a gamma-ray energy by a radiation detector that produces an electrical pulse whose total charge is proportional to the energy deposited by a gamma ray.
A single or multiple doses delivered over a period of greater than one day. Chronic radiation doses can be low enough to cause few effects and to permit recovery, and they can be severe enough to cause radiation sickness and death.
(1) It is the area outside of a restricted area but within the area whose access is limited by the operator (licensee). Generally, it is the non-restricted area within the site boundary.
(2) A surface location, to be marked by suitable monuments, extending horizontally no more than 10 kilometers in any direction from the outer boundary of the underground facility, and the underlying subsurface, which area has been committed to use as a geologic repository and from which incompatible activities would be restricted following permanent closure.
(3) It is the area immediately surrounding the storage installation for which the licensee exercises authority over its use and within which spent fuel storage operations are performed.
Relativistic (very-high-energy) particles that enter the Earth's atmosphere and secondary radiations produced by the interaction of these particles with the atmosphere. Photons or particles from outer space. High-energy cosmic rays, with energies of 104-1010 GeV, originate from outside our solar system, while lower-energy cosmic rays (<104 GeV) from our sun. Solar cosmic rays are primarily protons and helium.
The process of removing unwanted contaminants from the surface of an object or from an area. Decontamination is designed to reduce the risks of exposure. Contaminants can be radioactive, chemical, or biological. This term applies to removal by washing, biological agents, chemical action, mechanical cleaning, or other techniques.
The concentration of a given radionuclide in air which, if breathed by the reference man for a working year of 2,000 hours under conditions of light work, results in an intake of 1 ALI. Derived air concentration values are given in Table 1, Column 3, of appendix B to 10CFR part 20.1001-20.2401.
The probability an incident radiation will interact with a detection medium forming a recordable event. Efficiency can also be defined as the probability an incident radiation will deposit all its energy inside the detection medium. This definition is especially appropriate for gamma-ray spectroscopy where Compton scattering and other photon-interaction processes result in a degraded electrical signal and thus a loss of detected energy.
A basic constituent of the atom. The electron is a fundamental particle that has a mass of 0.000548579903 ± 0.000000000013 atomic mass units (0.51099907 ± 0.00000015 MeV). A free, unbound electron is stable against radioactive decay. The electron is a lepton with a spin of 1/2 and a charge of -1. The positron is the antiparticle of the electron.
Synonym: negative thermion.
Related to positron.
A unit of energy defined as 1.60919x10-19 joules. It is the energy required to raise an electron through a potential difference of 1 volt. The electron volt is not an SI unit but its use is valid unit within the International System of units.
Related to joule.
A small badge containing photographic film that is worn by personnel to monitor radiation exposure. Gamma rays and beta particles that interact with the film cause a darkening whose intensity is a function of dose.
The process of splitting a heavy nucleus into two lighter nuclei. Spontaneous fission is a type of radioactive decay for some nuclides, such as 252Cf. In other nuclides fission is induced through the reaction of an incident radiation with the nucleus. Neutron-induced fission of 235U is a common example. Considerable energy is released during the fission reaction and this energy can be used to produce heat and electricity.
An area, accessible to individuals, in which radiation levels could result in an individual receiving a dose equivalent in excess of 0.1 rem (1 mSv) in 1 hour at 30 centimeters from the radiation source or from any surface that the radiation penetrates.
Devices designed to be worn by a single individual for the assessment of dose equivalent such as film badges, thermoluminescence dosimeters (TLDs), pocket ionization chambers, and personal (lapel) air sampling devices.
Any electromagnetic or particulate radiation capable of producing ionization in matter. Examples of ionizing radiation include alpha particles, beta particles, gamma rays x-rays, neutrons, high-speed electrons, high-speed protons, and other particles capable of producing ions. This definition excludes non-ionizing radiation, such as radio- or microwaves, or visible, infrared, or ultraviolet light.
Two or more nuclides with the same number of protons. Isotopes are the same chemical element. The nuclides 5Li, 6Li, 7Li, and 8Li, all have 3 protons and are thus isotopes. Isotope is often incorrectly used in place of the term nuclide.
(1) A synonym for labeled atom. (2) A specific nuclide, stable or radioactive, attached to a molecule. Labels are used to track chemical or other processes. For a stable nuclide to be considered a label, the presence of the nuclide must perturb the isotopic ratio normally present in the sample.
The measurement of radiation levels, concentrations, surface area concentrations or quantities of radioactive material and the use of the results of these measurements to evaluate potential exposures and doses.
A basic constituent of the atomic nucleus. The neutron is a fundamental particle, has a mass of 1.008664904 ± 0.000000014 atomic mass units (939.56563 ± 0.00028 MeV). Free, unbound neutrons are produced in fission and in some radioactive decay processes (especially beta decay). A free neutron is unstable, having a half life of 614.6±1.3 s and decaying by β- decay. The neutron is a hadron that is composed of three quarks, udd, and it has a spin-parity of 1/2+ and a magnetic moment of -1.91304275±0.00000045.
The U.S. Nuclear Regulatory Commission (NRC) is an independent agency established by the Energy Reorganization Act of 1974 to regulate civilian use of nuclear materials. NRC is headed by a five-member Commission.
The NRC's mission is to regulate the Nation's civilian use of byproduct, source, and special nuclear materials to ensure adequate protection of public health and safety, to promote the common defense and security, and to protect the environment.
The NRC's regulatory mission covers three main areas: (1) Reactors - Commercial reactors for generating electric power and nonpower reactors used for research, testing, and training; (2) Materials - Uses of nuclear materials in medical, industrial, and academic settings and facilities that produce nuclear fuel; (3) Waste - Transportation, storage, and disposal of nuclear materials and waste, and decommissioning of nuclear facilities from service.
An atom or a collection of atoms whose nuclei have a specified number of protons and neutrons. Isotope is often (incorrectly) used for the term nuclide. The term nuclide was originally proposed by T.P. Kohman in 1947.
An individual’s ionizing radiation dose (external and internal) as a result of that individual's work assignment. Occupational dose does not include doses received as a medical patient or doses resulting from background radiation or participation as a subject in medical research programs.
A basic constituent of the atomic nucleus. The proton is a fundamental particle, has a mass of 1.007276470 ± 0.000000012 atomic mass units (938.27231 ± 0.00028 MeV). Chemical elements are defined by the number of protons in the nucleus, which is equal to the atomic number of that element. Free, unbound protons are stable with respect to radioactive decay with the lower limit of their half life as 1.1x1025 yr. The proton is a hadron that is composed of three quarks, uud, and it has a spin-parity of 1/2+ and a magnetic moment of +2.792847386 ± 0.000000063.
The dose received by a member of the public from exposure to radiation or to radioactive material released by a licensee, or to any other source of radiation under the control of a licensee. Public dose does not include occupational dose or doses received from background radiation, from any medical administration the individual has received, from exposure to individuals administered radioactive material and released under section 35.75, or from voluntary participation in medical research programs.
A measure of the effectiveness of a radiation at producing injury in a biological system. It is dependent on the linear energy transfer of a radiation. The dose times the quality factor is known as an equivalent dose. The quality factor has been superceded by the radiation weighting factor in the definition of the equivalent dose, except for calculations.
x-rays: QF = 1
Gamma Rays: QF = 1
Beta Particles: QF = 1
Neutrons, Unknown Energy: QF = 10
High-Energy Protons: QF = 10
Alpha Particles: QF = 20
Multiple-Charged Particle: QF = 20
Heavy particles, unknown charge: QF = 20
Fission Fragments: QF = 20
Neutrons E less than 1x10-3 MeV: QF = 2
Neutrons E = 0.001 MeV: QF = 2.5
Neutrons E = 0.01 MeV: QF = 7.5
Neutrons E = 0.1 MeV: QF = 11
Neutrons E = 0.5 MeV: QF = 9
Neutrons E = 1 MeV: QF = 8
Neutrons E = 2.5 MeV: QF = 7
Neutrons E = 5 MeV: QF = 6.5
Neutrons E = 7 MeV: QF = 7.5
Neutrons E = 10 MeV: QF = 8
Neutrons E = 14 MeV: QF = 7
Neutrons E = 20 MeV: QF = 5.5
Neutrons E = 40 MeV: QF = 4
Neutrons E = 60 MeV: QF = 3.5
Neutrons E ≥100 MeV: QF = 3.5.
An area, accessible to individuals, in which radiation levels could result in an individual receiving a dose equivalent in excess of 0.005 rem (0.05 mSv) in 1 hour at 30 centimeters from the radiation source or from any surface that the radiation penetrates.
Spontaneous emission by a nucleus of photons or particles.
The spontaneous transformation of one nuclide into another by emission of particles, absorption of an orbital electron, or by fission. It also refers to gamma-ray and conversion electron emission that only reduces the excitation energy of the nucleus.
The examination of the structure of materials by nondestructive methods, utilizing sealed sources of byproduct materials. Radiations can be used to produce images of an object either by measuring their transmission through or their interaction with the object. Medical x-rays and x-ray baggage inspection are examples of transmission measurements. A neutron baggage inspection system images an object by measuring the spatial distribution of capture gamma rays produced by the reaction of neutrons with nitrogen in the object. Autoradiography describes the process of imaging an object using radiations produced by the radioactive decay of nuclides in the object. The radionuclides can be the result of radionuclide tagging, contamination by some source, or they can be produced by irradiating the object with neutrons or other radiations.
A hypothetical aggregation of human (male or female) physical and physiological characteristics arrived at by international consensus. These characteristics may be used by researchers and public health workers to standardize results of experiments and to relate biological insult from ionizing radiation to a common base.
An area, access to which is limited for the purpose of protecting individuals against undue risks from exposure to radiation and radioactive materials. Restricted area does not include areas used as residential quarters, but separate rooms in a residential building may be set apart as a restricted area.
A radioactive source specifically manufactured, obtained, or retained for the purpose of utilizing the emitted radiation. The sealed radioactive source consists of a known quantity of radioactive material contained within a sealed capsule, sealed between layers of non-radioactive material, or firmly fixed to a non-radioactive surface by electroplating or other means intended to prevent leakage or escape of the radioactive material.
Any special nuclear material that is encased in a capsule rod, element, etc. designed to prevent leakage or escape of the special nuclear material and that prevents removal of the special nuclear material without penetrating the casing.
Any by-product material that is encased in a capsule designed to prevent leakage or escape of the by-product material.
The radioactivity of an isotope per unit weight of the element in a sample. The number of radioactive decays per unit mass of a sample. Additional Note: 10CFR part 71 includes the note that the radioactivity is uniformly distributed through the material.
Health effects that occur randomly and for which the probability of the effect occurring, rather than its severity, is assumed to be a linear function of dose without threshold. Hereditary effects and cancer incidence are examples of stochastic effects.
A normalization factor applied to equivalent doses to account for different sensitivities of tissues and organs. Tissue weighting factors recommended in ICRP publication 60 are bladder: 0.05; bone surface: 0.01; breast: 0.05; colon: 0.12; esophagus: 0.05; gonads: 0.20; liver: 0.05; lung: 0.12; red bone marrow: 0.12; skin: 0.01; stomach: 0.12; thyroid: 0.05; and remainder: 0.05.
An isotope of hydrogen with a single proton and two neutrons. Tritium is radioactive with a half-life of 12.33 years. It is found in nature as a result of the interaction of cosmic rays in the upper atmosphere. A tritium nucleus is called a triton.
An area, accessible to individuals, in which radiation levels could result in an individual receiving an absorbed dose in excess of 500 rads (5 grays) in 1 hour at 1 meter from a radiation source or from any surface that the radiation penetrates. Note: At very high doses received at high dose rates, units of absorbed dose (e.g., rads and grays) are appropriate, rather than units of dose equivalent (e.g., rems and sieverts).
A measure of the effectiveness of a radiation at producing injury in a biological system. It is dependent on the linear energy transfer of a radiation. The dose times the quality factor is known as a dose equivalent. Gonads: wT = 0.25; Breast: wT = 0.15; Red Bone Marrow: wT = 0.12; Lung: wT = 0.12; Thyroid: wT = 0.03; Bone Surface: wT = 0.03; Remainder: wT = 0.30; Whole Body: wT = 1.00.
Photons or electromagnetic radiation produced by the de-excitation of bound atomic electrons. The energy of an x-ray is equivalent to the difference in energy of the initial and final atomic state minus the binding energy of the electron.