The glossary story... Home    Author    Research    Methodology    Contact   Glossary terms... A    B    C    D    E    F    G    H    I    J    K    L    M    N    O    P    Q    R    S    T    U    V    W    XYZ    numbers   Collections... dose    elements    neutrons    nuclides    radiation    radioactive decay    reactions    reactors radiation safety    units    U.S.Regs      Further Reading... general    nuclear science    nuclear engineering    health physics

A Collection of Radiation Safety Terms... α A symbol for alpha particle. α particle A synonym for alpha particle. γ ray A synonym for gamma ray. absorbed dose The amount of energy of an ionizing radiation absorbed per unit mass of material. The standard unit for absorbed dose is the gray. Symbol: D. Synonym: imparted specific energy. Related to collective dose. Related to committed dose equivalent. Related to committed effective dose equivalent. Related to dose. Related to dose equivalent. Related to effective dose equivalent. Related to gray. Related to integral absorbed dose. Related to total effective dose equivalent. absorption nuclear reactions and particulate radiation    (1) The process of taking up kinetic energy of a particle.    (2) The process of combining a particle with an atom, a nucleus, or another particle.    (3) The decrease of the number of particles in a beam as it passes through matter. electromagnetic radiation    (1) The process of transferring the energy of electromagnetic radiation to matter.    (2) The decrease of the number of photons in a beam as it passes through matter. Related to Compton scattering. Related to photoelectric effect. activation Of or pertaining to the process of inducing radioactivity by bombarding a nuclide with radiation. accelerator A device that uses electrostatic or electromagnetic fields to increase the kinetic energy of a particle. Related to cyclotron. Related to linear accelerator. activity (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). Synonym: decay rate. Synonym: disintegration rate. acute dose 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. Related to acute radiation dose. acute exposure 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. Related to acute dose. Related to chronic exposure. agreement state 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. Acronym: AS. Related to nonagreement state. ALARA An acronym for as low as reasonably achievable. ALI An acronym for annual limit on intake. annual dose limit The maximum dose that may be received in a calendar year. as low as reasonably achievable 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. Acronym: ALARA. References: 10CFR20, 10CFR30, 10CFR70, 10CFR72. anion A negatively charged ion. Synonym: negative ion. Related to cation. Related to ion. atom 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. Related to exotic atom. Related to ion. AS An acronym for agreement state. attenuation Of or pertaining to the process of attenuating radiation. background radiation (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. becquerel The SI standard unit of radioactivity defined as 1.0 disintegrations per second. Symbol: Bq. Related to curie. Related to microcurie. Related to millicurie. Related to megacurie. Related to nanocurie. Related to picocurie. beta particle 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). Symbol: β. Symbol: β-. Symbol: β+. Synonym: beta. 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. bioassay 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. Synonym: radiobioassay. biological half-life 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. Synonym: biologic half-life. Related to effective half-life. Related to half-life. body burden The amount of a toxic substance in the body of a human or animal. Bq A symbol for becquerel. bremsstrahlung A synonym for bremsstrahlung radiation. bremsstrahlung radiation Electromagnetic radiation emitted when energetic charged particles are accelerated in the Coulomb fields of atomic nuclei. A continuous spectrum of x rays is produced. by-product A material produced by a process or system that is not the primary product. An example is uranium depleted in the nuclide 235U which is a by-product of the uranium enrichment process. by-product material Any radioactive material other than special nuclear material yielded in, or made radioactive by, exposure to the radiation incident to the process of producing or utilizing special nuclear material. Reference: 10CFR20.1003. calibration The process of determining the numerical relationship between the observed output of a measurement system and the value, based upon reference standards, of the characteristic being measured. Reference: 10CFR74.4. calibration factor 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. Reference: LA-UR-95-1911. cation A positively charged ion. Synonym: anode ray. Synonym: positive ion. Related to anion. Related to ion. CDE An acronym for committed dose equivalent. CEDE An acronym for committed effective dose equivalent. CF An acronym for calibration factor. charged particle A synonym for ion. chronic dose A dose delivered over a period of greater than one day. Related to acute dose. chronic exposure One or more exposures that occur over a period longer than one day. Related to acute exposure. Related to chronic dose. chronic radiation dose 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. Related to acute radiation dose. Related to radiation dose. Related to radiation dose rate. Related to radiation sickness. Ci A symbol for curie. collective dose The sum of individual doses received in a given period of time by a specified population from exposure to a specified source of radiation. Related to absorbed dose. Related to committed dose equivalent. Related to committed effective dose equivalent. Related to dose. Related to dose equivalent. Related to effective dose equivalent. Related to integral absorbed dose. Related to total effective dose equivalent. committed dose equivalent The dose equivalent to organs or tissues of reference (T) that will be received from an intake of radioactive material by an individual during the 50-year period following the intake. Symbol: HT,50. Symbol: H50. Acronym: CDE. Related to absorbed dose. Related to collective dose. Related to committed effective dose equivalent. Related to dose. Related to dose equivalent. Related to effective dose equivalent. Related to integral absorbed dose. Related to total effective dose equivalent. Reference: 10CFR20.1003. committed effective dose equivalent Acronym: CEDE. Related to absorbed dose. Related to collective dose. Related to committed dose equivalent. Related to dose. Related to dose equivalent. Related to effective dose equivalent. Related to integral absorbed dose. Related to total effective dose equivalent. Reference: NUREG-0544, Rev. 4. contamination A synonym for radioactive contamination. controlled area (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. References: 10CFR20, 10CFR60, 10CFR72. cosmic radiation Radiation from outer space. Cosmic rays. cosmic rays 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. coulomb The SI unit of electric charge defined as 1.0 A-s. Symbol: C. Related to abcoulomb. Related to ampere hour. Related to faraday. Related to statcoulomb. count (1) A single event recorded by radiation detection equipment. (2) The total number of events recorded over a period of time. critical organ The organ or part of a body most sensitive to radiation damage by an ingested radioactive nuclide or by an external radiation source. curie A unit of radioactivity defined as 3.7x1010 disintegrations per second. Originally it was defined as the radon emitted by 1 g of radium. An older symbol for the curie is c. Symbol: Ci. Related to becquerel. Related to microcurie. Related to millicurie. Related to megacurie. Related to nanocurie. Related to picocurie. DAC An acronym for derived air concentration. daughter product A synonym for daughter nuclide. decay A synonym for radioactive decay. declared pregnant woman A woman who has voluntarily informed her employer, in writing, of her pregnancy and the estimated date of conception. Reference: 10CFR20. decontamination 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. Related to immediate decontamination. Related to operational decontamination. Related to radioactive contamination. Related to thorough decontamination. deep dose A synonym for deep-dose equivalent. deep-dose equivalent The dose equivalent to tissue at a depth of one centimeter due to external radiation. Symbol: Hd. Synonym: deep dose. Related to total organ dose equivalent. delayed health effects Effects of radiation that appear long after the original exposure. Related to nonstochastic effects. Related to stochastic effects. depleted uranium Uranium in which 235U has an isotopic abundance of less than is found in nature. It is less than approximately 0.711%. Related to enriched uranium. Related to natural uranium. derived air concentration 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. Reference: 10CFR20. Acronym: DAC. Related to annual limit on intake. Related to light work. Related to reference man. deterministic effects A synonym for nonstochastic effects. disintegration A synonym for radioactive decay. disintegrations per minute The number of decays that occur per minute for a population of a nuclide or a sample containing radioactive material. disintegrations per second The number of decays that occur per second for a population of a nuclide or a sample containing radioactive material. dose The amount of energy of a radiation absorbed in matter. The SI standard unit of dose is the gray. Synonym: dosage. Synonym: radiation dose. Related to absorbed dose. Related to collective dose. Related to committed dose equivalent. Related to committed effective dose equivalent. Related to dose equivalent. Related to effective dose equivalent. Related to gray. Related to integral absorbed dose. Related to total effective dose equivalent. dose equivalent A synonym for equivalent dose. dose rate The radiation dose per unit time. Synonym: dosage rate. dosimeter A device that measures radiation dose. Synonym: dose meter. dosimetry Of or pertaining to the process of measuring radiation dose. dpm A symbol for the measurement unit decays per minute. dps A symbol for the measurement unit decays per second. EDE An acronym for effective dose equivalent. Reference: 10CFR20.1003; 10CFR30.4; 10CFR70.4; 10CFR76.4; DOE-EH-413-9713; DOE Order 6430.1A. effective dose A measure of dose in which the type of radiation and the sensitivity of tissues and organs to that radiation is taken into account. Related to effective dose equivalent. effective dose equivalent The sum of the dose equivalents to the organ or tissue (HT) and the weighting factors (WT) applicable to each of the body organs or tissues that are irradiated. Symbol: HE. Acronym: EDE. Related to absorbed dose. Related to collective dose. Related to committed dose equivalent. Related to committed effective dose equivalent. Related to dose. Related to dose equivalent. Related to effective dose. Related to integral absorbed dose. Related to total effective dose equivalent. Related to tissue weighting factor. effective half-life The time required for the concentration of a radionuclide in a biological system to be reduced by one half. An effective half-life includes all processes of elimination, including radioactive decay. Related to biological half-life. Related to half-life. efficiency 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. electromagnetic radiation Radiation consisting of interacting electric and magnetic waves. Examples include gamma rays, x-rays, ultraviolet and visible light. Acronym: EMR. Synonym: photon. Related to gamma ray. Related to ionizing radiation. Related to nonionizing radiation. Related to x-ray. electron 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. Symbol: e-. Synonym: corpuscle. Synonym: negative thermion. Synonym: negaton. Synonym: negatron. Related to positron. electron capture A synonym for electron capture decay. electron volt 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. Symbol:  eV. Symbol: (obsolete) ev. Related to joule. erg A unit of energy defined as exactly 1x10-7 J. Related to joule. exposure Of or pertaining to the process of being exposed to ionizing radiation or to radioactive material. Reference: 10CFR20. Related to ionizing radiation. Related to nonionizing radiation. external dose That portion of the dose equivalent received from radiation sources outside the body. external radiation Generally it is radiation from sources outside a body. extremity A hand, forearm, elbow, foot, ankle, lower leg, or knee. Extremities are often considered separately from the rest of the body because they are less susceptible to radiation. Reference: 10CFR20. eye dose equivalent The external exposure of the lens of the eye. It is taken as the dose equivalent at a tissue depth of 0.3 centimeters (300 mg/cm2). film badge 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. Related to dose. Related to film ring. fission 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. Synonym: atomic fission. Synonym: nuclear fission. Related to fission fragment. Related to fission neutron. Related to fission product. Related to neutron chain reaction. Related to neutron generation. Related to nuclear fusion. Related to photofission. Related to spontaneous fission. Related to ternary fission. Geiger-Müller counter A synonym for Geiger-Müller detector. GM counter A synonym for Geiger-Müller counter which is a synonym for Geiger-Müller detector. gray An SI unit of absorbed radiation dose. One gray is equivalent to an energy absorption of 1 J/kg. It has replaced the rad, an older standard. One gray is equivalent to 100 rad. Symbol: Gy. Related to absorbed dose. Related to roentgen absorbed dose. Related to sievert. Reference: 10CFR10; NUREG-0544, Rev. 4. Gy A symbol for gray. Reference: 10CFR20.1004; 10CFR34.3; DOD 3150.8-M; DOE-HDBK-1106-97; USACHPPM TG 204. half-value layer A synonym for half-value thickness. half-value thickness That amount of an absorber which is required to reduce the intensity of a radiation by one half. Symbol: D. Synonym: half-value layer. Hd A symbol for deep-dose equivalent. HE A symbol for effective dose equivalent. HE,50 A symbol for committed effective dose equivalent. health physics The study of the effects of radiation on humans, the monitoring of radiation exposure and the reduction of health risks associated with radiation exposure. Acronym: HP. high radiation area 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. Reference: 10CFR20. Related to radiation area. Related to very high radiation area. hot spot Location where the radioactivity or radiation is higher than expected. Part of a fuel element surface that has become overheated. Hs A symbol for shallow-dose equivalent. HT A symbol for committed equivalent dose. individual monitoring devices 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. Synonym: individual monitoring equipment. Reference: 10CFR20.1003. individual monitoring equipment A synonym for individual monitoring devices. intake Material ingested, inhaled, or absorbed through the skin or otherwise introduced into the body. Related to uptake. internal radiation Radiation produced by the decay of radioactive material in the body. inverse square law The intensity of a radiation field is inversely proportional to the square of the distance from the source. ion An atom or molecule that has a non-zero electric charge. Synonym: charged particle. Related to anion. Related to atom. Related to cation. ionization Of or pertaining to the process of ionizing an atom, ion or molecule. ionization chamber A volume that contains a detection gas and electrodes which is used to count radiations or monitor radiation fields. Related to ionization detector. ionizing radiation 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. Synonym: ionising radiation. Related to electromagnetic radiation. Related to nonionizing radiation. Related to radiation. isotopic tracer A synonym for tracer. isotope 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. Related to isobar. Related to isomer. Related to isotone. Related to nuclide. J A symbol for joule. joule An SI unit of energy defined as 1.0 kg m2/s2 or 1.0 N m. Symbol: J. kinetic energy Energy possessed by a particle, nucleon, nucleus, atom or other body by virtue of its motion. label (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. labeled compound A molecule that contains a specific stable or radioactive nuclide. Synonym: labeled molecule. LD-50/30 A symbol for median lethal dose 50/30. LD-50/60 A symbol for median lethal dose 50/60. mCi A symbol for millicurie. micro A unit prefix equivalent to 10-6. Symbol: μ. microcurie A unit of radioactivity equivalent to 1.0x10-6 curies. The becquerel has replaced the curie as a unit of radioactivity. Symbol: μCi. Related to becquerel. Related to curie. Related to megacurie. Related to millicurie. Related to nanocurie. Related to picocurie. milli A unit prefix equivalent to 10-3. Symbol: m. millicurie A unit of radioactivity equivalent to 0.001 curies. The becquerel has replaced the curie as a unit of radioactivity. Symbol: mCi. Related to becquerel. Related to curie. Related to megacurie. Related to microcurie. Related to nanocurie. milliroentgen A unit of radiation exposure equivalent to 0.001 roentgen. Symbol: mR. Related to roentgen. monitoring 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. Synonym: radiation monitoring. Synonym: radiation protection monitoring. mR A symbol for milliroentgen. nano A unit prefix equivalent to 10-9. Symbol: n. NARM An acronym for naturally occurring or accelerator-produced radioactive materials. neutron 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. Symbol: n. Related to Bragg neutron. Related to neutron. Related to proton. nonstochastic effects Health effects, the severity of which varies with the dose and for which a threshold is believed to exist. Radiation-induced cataract formation is an example of a nonstochastic effect. Reference: 10CFR20. Synonym: deterministic effects. Related to stochastic effects. NRC Acronym for Nuclear Regulatory Commission. natural background radiation Ionizing radiation produced by cosmic rays, the interaction of cosmic rays with matter, and from the decay of non-anthropogenic radioactive materials. natural radiation A synonym for natural background radiation. NORM An acronym for naturally-occurring radioactive material. Nuclear Regulatory Commission 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. Acronym: NRC. Web Site: NRC nucleus A synonym for atomic nucleus. nuclide 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. Related to isobar. Related to isomer. Related to isotone. Related to isotope. occupational dose 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. Reference: 10CFR835.2. particle accelerator A synonym for accelerator. photon A quantum of electromagnetic radiation such as a gamma ray or an x-ray. It is a boson and has a mass of 0, a charge of 0 and a spin of 1. Related to electromagnetic radiation. Related to gamma ray. Related to X-ray. pico A unit prefix equivalent to 10-12. Symbol: p. pig A heavily shielded container designed to safely store or transport radioactive materials. Related to cask. Related to cave. Related to coffin. pocket dosimeter A small ionization detector that is generally used to monitor whole body exposure. positron The antiparticle of the electron. Its mass and spin are identical to that of the electron but it has a charge of +1. Symbol: e+. Symbol: β+. Synonym: positive electron. Synonym: positon. Related to beta particle. Related to electron. Related to exotic atom. protective barrier