RADIOACTIVITYDOE-HDBK-1019/1-93Atomic and Nuclear PhysicsRADIOACTIVITYThe rate at which a sample of radioactive material decays is not constant. Asindividual atoms of the material decay, there are fewer of those types of atomsremaining. Since the rate of decay is directly proportional to the number ofatoms, the rate of decay will decrease as the number of atoms decreases. EO 2.5DEFINE the following terms:a.Radioactivityd.Radioactive decay constantb.Curiee.Radioactive half-lifec.BecquerelEO 2.6Given the number of atoms and either the half-life or decayconstant of a nuclide, CALCULATE the activity.EO 2.7Given the initial activity and the decay constant of a nuclide,CALCULATE the activity at any later time.EO 2.8CONVERT between the half-life and decay constant for anuclide.EO 2.9Given the Chart of the Nuclides and the original activity, PLOTthe radioactive decay curve for a nuclide on either linear orsemi-log coordinates. EO 2.10DEFINE the following terms:a.Radioactive equilibriumb.Transient radioactive equilibriumRadioactiveDecayRatesRadioactivityis the property of certain nuclides of spontaneously emitting particles or gammaradiation. The decay of radioactive nuclides occurs in a random manner, and the precise timeat which a single nucleus will decay cannot be determined. However, the average behavior ofa very large sample can be predicted accurately by using statistical methods. These studies haverevealed that there is a certain probability that in a given time interval a certain fraction of thenuclei within a sample of a particular nuclide will decay. This probability per unit time that anatom of a nuclide will decay is known as the radioactivedecay constant, l. The units for thedecay constant are inverse time such as 1/second, 1/minute, 1/hour, or 1/year. These decayconstant units can also be expressed as second-1, minute-1, hour-1, and year-1.NP-01Page 30Rev. 0
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