RADIOACTIVITY
DOE-HDBK-1019/1-93
Atomic and Nuclear Physics
RADIOACTIVITY
The rate at which a sample of radioactive material decays is not constant. As
individual atoms of the material decay, there are fewer of those types of atoms
remaining. Since the rate of decay is directly proportional to the number of
atoms, the rate of decay will decrease as the number of atoms decreases.
EO 2.5
DEFINE the following terms:
a.
Radioactivity
d.
Radioactive decay constant
b.
Curie
e.
Radioactive half-life
c.
Becquerel
EO 2.6
Given the number of atoms and either the half-life or decay
constant of a nuclide, CALCULATE the activity.
EO 2.7
Given the initial activity and the decay constant of a nuclide,
CALCULATE the activity at any later time.
EO 2.8
CONVERT between the half-life and decay constant for a
nuclide.
EO 2.9
Given the Chart of the Nuclides and the original activity, PLOT
the radioactive decay curve for a nuclide on either linear or
semi-log coordinates.
EO 2.10
DEFINE the following terms:
a.
Radioactive equilibrium
b.
Transient radioactive equilibrium
Radioactive Decay Rates
Radioactivity is the property of certain nuclides of spontaneously emitting particles or gamma
radiation. The decay of radioactive nuclides occurs in a random manner, and the precise time
at which a single nucleus will decay cannot be determined. However, the average behavior of
a very large sample can be predicted accurately by using statistical methods. These studies have
revealed that there is a certain probability that in a given time interval a certain fraction of the
nuclei within a sample of a particular nuclide will decay. This probability per unit time that an
atom of a nuclide will decay is known as the radioactive decay constant, l. The units for the
decay constant are inverse time such as 1/second, 1/minute, 1/hour, or 1/year. These decay
constant units can also be expressed as second-1, minute-1, hour-1, and year-1.
NP-01
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