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alpha (α) decay
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loss of an alpha particle during radioactive decay
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alpha particle
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(α or or high-energy helium nucleus; a helium atom that has lost two electrons and contains two protons and two neutrons
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antimatter
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particles with the same mass but opposite properties (such as charge) of ordinary particles
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band of stability
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(also, belt of stability, zone of stability, or valley of stability) region of graph of number of protons versus number of neutrons containing stable (nonradioactive) nuclides
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becquerel (Bq)
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SI unit for rate of radioactive decay; 1 Bq = 1 disintegration/s
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beta (β) decay
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breakdown of a neutron into a proton, which remains in the nucleus, and an electron, which is emitted as a beta particle
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beta particle
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or or high-energy electron
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binding energy per nucleon
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total binding energy for the nucleus divided by the number of nucleons in the nucleus
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chain reaction
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repeated fission caused when the neutrons released in fission bombard other atoms
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chemotherapy
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similar to internal radiation therapy, but chemical rather than radioactive substances are introduced into the body to kill cancer cells
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containment system
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(also, shield) a three-part structure of materials that protects the exterior of a nuclear fission reactor and operating personnel from the high temperatures, pressures, and radiation levels inside the reactor
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control rod
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material inserted into the fuel assembly that absorbs neutrons and can be raised or lowered to adjust the rate of a fission reaction
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critical mass
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amount of fissionable material that will support a self-sustaining (nuclear fission) chain reaction
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curie (Ci)
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larger unit for rate of radioactive decay frequently used in medicine; 1 Ci = 3.7 10
10
disintegrations/s
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daughter nuclide
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nuclide produced by the radioactive decay of another nuclide; may be stable or may decay further
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electron capture
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combination of a core electron with a proton to yield a neutron within the nucleus
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electron volt (eV)
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measurement unit of nuclear binding energies, with 1 eV equaling the amount energy due to the moving an electron across an electric potential difference of 1 volt
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external beam radiation therapy
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radiation delivered by a machine outside the body
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fissile (or fissionable)
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when a material is capable of sustaining a nuclear fission reaction
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fission
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splitting of a heavier nucleus into two or more lighter nuclei, usually accompanied by the conversion of mass into large amounts of energy
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fusion
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combination of very light nuclei into heavier nuclei, accompanied by the conversion of mass into large amounts of energy
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fusion reactor
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nuclear reactor in which fusion reactions of light nuclei are controlled
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gamma (γ) emission
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decay of an excited-state nuclide accompanied by emission of a gamma ray
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gamma ray
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(γ or short wavelength, high-energy electromagnetic radiation that exhibits wave-particle duality
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Geiger counter
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instrument that detects and measures radiation via the ionization produced in a Geiger-Müller tube
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gray (Gy)
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SI unit for measuring radiation dose; 1 Gy = 1 J absorbed/kg tissue
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half-life (
t
1/2
)
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time required for half of the atoms in a radioactive sample to decay
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internal radiation therapy
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(also, brachytherapy) radiation from a radioactive substance introduced into the body to kill cancer cells
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ionizing radiation
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radiation that can cause a molecule to lose an electron and form an ion
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magic number
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nuclei with specific numbers of nucleons that are within the band of stability
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mass defect
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difference between the mass of an atom and the summed mass of its constituent subatomic particles (or the mass “lost” when nucleons are brought together to form a nucleus)
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mass-energy equivalence equation
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Albert Einstein’s relationship showing that mass and energy are equivalent
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millicurie (mCi)
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larger unit for rate of radioactive decay frequently used in medicine; 1 Ci = 3.7 10
10
disintegrations/s
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nonionizing radiation
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radiation that speeds up the movement of atoms and molecules; it is equivalent to heating a sample, but is not energetic enough to cause the ionization of molecules
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nuclear binding energy
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energy lost when an atom’s nucleons are bound together (or the energy needed to break a nucleus into its constituent protons and neutrons)
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nuclear chemistry
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study of the structure of atomic nuclei and processes that change nuclear structure
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nuclear fuel
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fissionable isotope present in sufficient quantities to provide a self-sustaining chain reaction in a nuclear reactor
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nuclear moderator
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substance that slows neutrons to a speed low enough to cause fission
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nuclear reaction
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change to a nucleus resulting in changes in the atomic number, mass number, or energy state
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nuclear reactor
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environment that produces energy via nuclear fission in which the chain reaction is controlled and sustained without explosion
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nuclear transmutation
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conversion of one nuclide into another nuclide
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nucleon
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collective term for protons and neutrons in a nucleus
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nuclide
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nucleus of a particular isotope
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parent nuclide
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unstable nuclide that changes spontaneously into another (daughter) nuclide
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particle accelerator
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device that uses electric and magnetic fields to increase the kinetic energy of nuclei used in transmutation reactions
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positron or
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antiparticle to the electron; it has identical properties to an electron, except for having the opposite (positive) charge
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positron emission
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(also, β
+
decay) conversion of a proton into a neutron, which remains in the nucleus, and a positron, which is emitted
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radiation absorbed dose (rad)
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SI unit for measuring radiation dose, frequently used in medical applications; 1 rad = 0.01 Gy
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radiation dosimeter
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device that measures ionizing radiation and is used to determine personal radiation exposure
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radiation therapy
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use of high-energy radiation to damage the DNA of cancer cells, which kills them or keeps them from dividing
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radioactive decay
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spontaneous decay of an unstable nuclide into another nuclide
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radioactive decay series
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chains of successive disintegrations (radioactive decays) that ultimately lead to a stable end-product
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radioactive tracer
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(also, radioactive label) radioisotope used to track or follow a substance by monitoring its radioactive emissions
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radioactivity
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phenomenon exhibited by an unstable nucleon that spontaneously undergoes change into a nucleon that is more stable; an unstable nucleon is said to be radioactive
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radiocarbon dating
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highly accurate means of dating objects 30,000–50,000 years old that were derived from once-living matter; achieved by calculating the ratio of in the object vs. the ratio of in the present-day atmosphere
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radioisotope
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isotope that is unstable and undergoes conversion into a different, more stable isotope
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radiometric dating
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use of radioisotopes and their properties to date the formation of objects such as archeological artifacts, formerly living organisms, or geological formations
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reactor coolant
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assembly used to carry the heat produced by fission in a reactor to an external boiler and turbine where it is transformed into electricity
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relative biological effectiveness (RBE)
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measure of the relative damage done by radiation
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roentgen equivalent man (rem)
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unit for radiation damage, frequently used in medicine; 100 rem = 1 Sv
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scintillation counter
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instrument that uses a scintillator—a material that emits light when excited by ionizing radiation—to detect and measure radiation
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sievert (Sv)
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SI unit measuring tissue damage caused by radiation; takes into account energy and biological effects of radiation
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strong nuclear force
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force of attraction between nucleons that holds a nucleus together
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subcritical mass
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amount of fissionable material that cannot sustain a chain reaction; less than a critical mass
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supercritical mass
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amount of material in which there is an increasing rate of fission
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transmutation reaction
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bombardment of one type of nuclei with other nuclei or neutrons
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transuranium element
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element with an atomic number greater than 92; these elements do not occur in nature
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