Glossary


AA-Atomic Absorption

—Spectroscopy utilizing the emission, absorption, or fluorescence of light at discrete wavelengths by atoms in a vaporized sample to determine the elemental composition of the sample.

absorbed dose

—When ionizing radiation passes through matter, some of its energy is imparted to the matter. The amount of energy absorbed/per unit mass of irradiated material is called the absorbed dose. It is measured in gray or rad.

activation

—The process of making a material radioactive by bombardment with neutrons, protons, or other nuclear particles.

AMS-Accelerator Mass Spectroscopy

—A method that employs two sophisticated methodologies—a particle accelerator and a mass spectrometer—to provide in this application an estimate of the number of neutrons that a sample was exposed to at the time of the bombing.

APRF

—Aberdeen Pulse Reactor Facility

ATB-At Time of Bomb

—A designation to indicate that a particular event occurred at the time that the bombs were detonated in Hiroshima and Nagasaki, i.e., a reference point in time.

ATM-At Time of Measurement

—A designation to indicate that a particular event occurred at the time that a specific measurement was made (usually later than ATB).

attenuation

—The process by which a beam of radiation is reduced in intensity when passing through some material. It is the combination of absorption and scattering processes that leads to a decrease in flux density of the beam when projected through matter.


background radiation (measurement/level)

—The level, often low, at which some substance, agent, or event is present or occurs at a particular location and time in the absence of the radiation source under study.



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Status of the Dosimetry for the Radiation Effects Research Foundation (DS86) Glossary AA-Atomic Absorption —Spectroscopy utilizing the emission, absorption, or fluorescence of light at discrete wavelengths by atoms in a vaporized sample to determine the elemental composition of the sample. absorbed dose —When ionizing radiation passes through matter, some of its energy is imparted to the matter. The amount of energy absorbed/per unit mass of irradiated material is called the absorbed dose. It is measured in gray or rad. activation —The process of making a material radioactive by bombardment with neutrons, protons, or other nuclear particles. AMS-Accelerator Mass Spectroscopy —A method that employs two sophisticated methodologies—a particle accelerator and a mass spectrometer—to provide in this application an estimate of the number of neutrons that a sample was exposed to at the time of the bombing. APRF —Aberdeen Pulse Reactor Facility ATB-At Time of Bomb —A designation to indicate that a particular event occurred at the time that the bombs were detonated in Hiroshima and Nagasaki, i.e., a reference point in time. ATM-At Time of Measurement —A designation to indicate that a particular event occurred at the time that a specific measurement was made (usually later than ATB). attenuation —The process by which a beam of radiation is reduced in intensity when passing through some material. It is the combination of absorption and scattering processes that leads to a decrease in flux density of the beam when projected through matter. background radiation (measurement/level) —The level, often low, at which some substance, agent, or event is present or occurs at a particular location and time in the absence of the radiation source under study.

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Status of the Dosimetry for the Radiation Effects Research Foundation (DS86) biological dosimetry —The use of measurements in biological samples to provide an estimate of radiation exposures; examples include measurement of chromosome aberrations in blood cells and measurement of thermoluminescence emitted from tooth enamel. chromosome aberrations —Alteration from normal structure or number of chromosomes, i.e. dicentrics, translocations, etc. Co-cobalt —Element number 27 of the periodic table. Isotopes such as 60Co can be formed by neutrons irradiating 59Co(n,γ) often found in steel. cross-section —A measure of the probability that a nuclear reaction will occur. Usually measured in barns. It is the apparent or effective area presented by a target nucleus, or particle, to an oncoming particle or other nuclear radiation, such as a neutron. CV-Coefficient of Variation —A measure of relative variation expressed by the standard deviation as a percentage of the mean. DDREF—Dose and Dose-rate Effectiveness Factor —A factor used to adjust for the different biological effect with different doses and dose rates of low-LET radiation from those at which the original data was obtained. Typically, the factor refers to the possible reduction in carcinogenesis at low doses and/or at low dose rates. delayed neutrons —During the fission process in the detonation of the atomic bomb, some neutrons are emitted immediately as “prompt” neutrons, while others are emitted after a very short time period and are referred to as “delayed neutrons.” dicentrics —A type of chromosome aberration visible through the light microscope in which two chromosomes with broken ends rejoin to form a chromosome with two centromeres. DNA-Defense Nuclear Agency —A division of the U.S. Department of Defense that currently has been replaced by the Defense Threat Reduction Agency (DTRA). dose —A term denoting the amount of energy absorbed from radiation. down-scattering —The loss of energy by neutrons undergoing elastic collisions with the nuclei of the atmosphere and other intervening material. DS86 —The designation of the dosimetry system that was adopted in 1986 and is currently used to express doses to A-bomb survivors. It is also used by the Radiation Effects Research Foundation in the assessment of risk following exposures to the radiation from the atomic bombs in Hiroshima and Nagasaki. EAR-Excess Absolute Risk —The excess risk attributed to irradiation and usually expressed as the numerical difference between irradiated and non-irradiated populations (e.g., 1 excess case of cancer/1 million people irradiated annually for each gray). Absolute risk may be given on an annual basis or lifetime (70-yr) basis. electron spin resonance (ESR) —The measurement of magnetic resonance arising from the magnetic movement of unpaired electrons in a paramagnetic substance or in a paramagnetic center in a diamagnetic substance. electron volt (eV) —a unit of particle energy.

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Status of the Dosimetry for the Radiation Effects Research Foundation (DS86) EML-DOE Environmental Measurements Laboratory —A laboratory responsible for measurements of radiation that is located in New York City and operated by the U.S. Department of Energy. energy bin —Radiation emitted from a source, such as an atomic bomb, can cover a broad energy spectrum. This spectrum can be divided into specific energy groupings called “energy bins.” epicenter —The point at which the detonation of the atomic bomb actually occurred. epidemiology —The study of diseases as they affect populations, including the distribution of disease, or other health-related states and events in human populations; the factors (e.g., age, sex, occupation, economic status) that influence this distribution; and the application of this study to assess and control health risk. epithermal neutrons —A neutron having an energy in the range immediately above the thermal range, roughly between 0.02 and 100,000 eV. equivalent dose —A unit of biologically effective dose, defined by the ICRP in 1990 as the absorbed dose in gray multiplied by the radiation weighting factor (Wr). For all x-rays, gamma rays, beta particles, and positrons the radiation weighting factor is 1; for alpha particles it is 20; for neutrons it depends on energy (see ICRP 1991) and dose level. ERR-Excess Relative Risk —A model that describes the risk imposed by exposures as a multiplicative increment of the excess disease risk above the background rate of disease. Eu-europium —One member of the rare earth elements in the cerium subgroup, element number 63. Formed when certain atoms are bombarded with neutrons from atomic bombs fast neutrons —Neutrons with energy greater than approximately 100,000 electron volts. FISH-Fluorescence In Situ Hybridization —The use of DNA libraries derived specifically from particular chromosomes and conjugated with fluorescent molecules to generate reagents that cause distinctive fluorescence on individual chromosomes. Chromosomal aberrations involving the transfer of DNA from one chromosome to another (such as reciprocal translocations) can be detected using this “chromosome painting.” fluence —The number of radioactive particles, neutrons, or photons per unit cross-sectional area. free-field value —Also sometimes called free-in-air value, is the fluence one would calculate at a given distance if there were no surrounding shielding material such as building walls, etc., to either attenuate or scatter radiation. FSD-Fractional Standard Deviation —The fractional standard deviation of a random variable is equal to its standard deviation σ divided by its mean μ. This ratio has also been called the “coefficient of variation.” In practice, σ and μ are replaced by estimators such as sample standard deviation and a sample mean, respectively. The FSD is often expressed as a percent. When a mea-

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Status of the Dosimetry for the Radiation Effects Research Foundation (DS86) surement is considered as a random variable with some associated probability distribution, the FSD quantifies the relative precision of the measurement. gamma ray —The most penetrating radiation produced by radioactive decay, or in some other nuclear process. Gamma rays can be blocked only by dense material such as lead. globe-data shielding —A shielding model in DS86 to calculate the radiation shielding for the approximately 4,500 survivors in Hiroshima and Nagasaki for whom nine parameter shielding was not appropriate because they were either heavily shielded by concrete buildings or in the open, but shielded by a house or terrain. gray (Gy) —A unit used to describe the amount of energy that radiation deposits or is absorbed in tissue; 1 gray=100 rad. ground range —The distance from the point on the ground immediately below the point where the bomb was detonated (i.e., the hypocenter) to a specific location; as opposed to a “slant range,” which is the direct distance from the actual point of detonation (i.e., the epicenter) above ground to the specific point of interest. half-life —The time it takes for a radioactive quantity to decrease by half; used to describe how long radioactive isotopes take to decay to half their original activity. height of burst (HOB) —The height above the Earth’s surface at which a bomb is detonated in the air. hypocenter (ground zero) —The point on the Earth’s surface vertically below or above the center of a burst of a nuclear (or atomic) weapon; frequently abbreviated to GZ. in situ —In the original location. Any test conducted in the field or in a material such as granite, tissue, or cells. ionizing radiation —Radiation that has sufficient energy to be capable of ionizing atoms or molecules. kerma —Kinetic energy released in material. A quantity that represents the kinetic energy transferred to charged particles by the uncharged particles per unit of mass of a material. La-lanthanum —Element number 57 of the periodic chart. LANL-Los Alamo National Laboratory —A national laboratory in Los Alamos, NM, that played an important role in the development and testing of the Hiroshima and Nagasaki bombs. late gamma rays —Gamma rays emitted in a delayed manner from the detonation of the atomic bomb. linear dose response —A description of the response of a particular effect that is linear with radiation dose. LLNL-Lawrence Livermore National Laboratory —A national laboratory in Livermore, CA, that played an important role in the development and testing of the Hiroshima and Nagasaki bombs. Lu-lutetium —Element number 71 of the periodic chart.

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Status of the Dosimetry for the Radiation Effects Research Foundation (DS86) MDA-Minimum Detectable Activity —The lowest radioactivity at which detection is possible and measurements above background can be obtained. MDC-Minimum Detectable Concentration —The lowest concentration at which detection is possible and measurements above background levels can be obtained. MHW-Ministry of Health and Welfare —The agency in the Japanese government that has been responsible for sharing the funding of the Radiation Effects Research Foundation with U.S. DOE and some of the work of the dosimetry working groups; currently called the Ministry of Health, Labour, and Welfare (MHLW). Monte Carlo analysis —The computation of a probability distribution of consequences by means of a random sampling method analogous to the game of roulette. Combinations of events and outcomes that yield possible consequences are randomly selected according to a specified probability distribution. The resulting consequences are counted and used to estimate other probability distributions. NAA-Neutron Activation Analysis —Activation analysis in which the specimen is bombarded with neutrons; identification is made by measuring the resulting radioisotopes. NCRP-National Council on Radiation Protection and Measurements —A body chartered by the U.S. government to provide advice and to help solve the nation’s radiation problems. It produces reports on selected aspects of radiation protection. nine-parameter shielding —A model that uses nine discrete physical parameters to describe the shielding from radiation provided to survivors by the houses in Hiroshima and Nagasaki NIST-National Institute of Standards and Technology —A federal laboratory institute charged with maintaining expertise relative to measurements and standards. ORELA-Oak Ridge Electron Linear Accelerator —An accelerator in Oak Ridge, TN, used to increase the energy of neutrons. ORNL-Oak Ridge National Laboratory —A national laboratory in Oak Ridge, TN, that has played a major role in the production of nuclear weapons and studying the biological and environmental effects of radiation. prompt gamma rays —Gamma rays emitted within a time too short for measurement. prompt neutrons —A neutron released coincident with the fission process, as opposed to neutrons subsequently released. radiation protection (shielding) —Reduction of radiation by interposing a shield of absorbing material between any radioactive source and a person, work area, or radiation-sensitive device. RBE-Relative Biological Effectiveness —Ratio of the biological effectiveness of one radiation, e.g., neutrons, to another, e.g., gamma rays. Strictly, RBE is not

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Status of the Dosimetry for the Radiation Effects Research Foundation (DS86) the ratio of effects but rather the ratio of absorbed doses to produce the same level of effect (NCRP 1990). RERF-Radiation Effects Research Foundation —A binational research foundation located in Hiroshima and Nagasaki, Japan, sponsored by Japan and the U.S., and studying the health effects of the atomic bombs on the survivors of the two bombs (formerly the Atomic Bomb Casualty Commission—ABCC). RL-Relaxation Length —The distance an exponentially decreasing function is reduced to 1/e of its original value, i.e., if A=A′exp(-x/RL), when x=RL, A=A′/e. risk —The probability that harm, such as a fatal cancer, will occur. SAIC-Science Applications International Corp. —A company that has been involved in complex calculations related to atomic-bomb dosimetry and DS86. sievert (Sv) —The SI unit of equivalent dose or effective dose equal to the dose in grays multiplied by the radiation weighting factor of the radiation. slant range —The distance from a given location, usually on the Earth’s surface, to the point at which the explosion occurred. Sn-basic discrete ordinates —Sn is the angular segmentation method used for writing the transport difference equations in a form suitable for computer calculations in the discrete-ordinates method of calculating radiation transport. (The n in Sn is the number of solid angle segments representing the polar angles in a cylindrical geometry or the total number of angles with nonzero weights in a spherical one-dimensional geometry.) A discrete representation of the spatial and energy variables in the discrete ordinates transport equation is obtained by dividing the geometry systems into a fine space mesh and by using a multigroup set of cross sections (Roesch 1987)). The principal feature in discrete-ordinates methods is the discrete representation of angular, energy, and spatial variables in the Boltzmann transport equation. source term —(a) The amount of radionuclides or chemicals released from a site to the environment over a specific period for use in dose reconstruction, (b) The nature, energies, and amounts of the radiation released from a nuclear weapon. spallation —Splitting of the nucleus of an atom by high-energy bombardment. thermal neutrons —Neutrons in thermal equilibrium with their surrounding medium. Thermal neutrons are those that have been slowed down by a moderator to an average speed of about 2200 m/sec at room temperature from the much higher initial speeds they had when expelled by fission. Their energies are less than 0.02 eV. thermoluminescence —One of two principle methods of solid-state dosimetry for the measurement of integrated dose in certain crystalline natural materials such as quartz. TLD-Thermoluminescent Dosimeter —Type of crystal used to monitor radiation exposure by emitting light, often used in a body, wrist, or ring badge. Must be processed in order to be “read.” translocation —A type of chromosome aberration involving the transfer of genetic material from one chromosome to another, nonhomologous chromosome. An

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Status of the Dosimetry for the Radiation Effects Research Foundation (DS86) exchange of genetic material between two chromosomes is referred to as reciprocal translocation. tumorigenic —Any external influence capable of stimulating an increased growth or proliferation of abnormal cells, to form a tumor. yield —The total effective energy released in a nuclear (or atomic) explosion. It is usually expressed in terms of the equivalent tonnage of TNT required to produce the same energy release in an explosion. The total energy yield is manifested as nuclear radiation, thermal radiation, and shock (blast) energy, the actual distribution being dependent upon the medium in which the explosion occurs.