Decay energy
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Nuclear physics |
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The decay energy is the energy change of a nucleus having undergone a radioactive decay. Radioactive decay is the process in which an unstable atomic nucleus loses energy by emitting ionizing particles and radiation. This decay, or loss of energy, results in an atom of one type (called the parent nuclide) transforming to an atom of a different type (called the daughter nuclide).
Decay calculation
The energy difference of the
Decay energy is usually quoted in terms of the energy units MeV (million electronvolts) or keV (thousand electronvolts):
Types of radioactive decay include
- gamma ray
- beta decay (decay energy is divided between the emitted electron and the neutrino which is emitted at the same time)
- alpha decay
The decay energy is the mass difference Δm between the parent and the daughter atom and particles. It is equal to the energy of radiation E. If A is the radioactive activity, i.e. the number of transforming atoms per time, M the molar mass, then the radiation power P is:
or
or
Example:
Radiation power in W/g for several isotopes:
- 60Co: 17.9
- 238Pu: 0.57
- 137Cs: 0.6
- 241Am: 0.1
- 210Po: 140 (T = 136 d)
- 90Sr: 0.9
- 226Ra: 0.02
For use in
Pu with its roughly eighty year half life and low gamma emissions has become the RTG nuclide of choice. 90
Sr performs worse than 238
Pu on almost all measures, being shorter lived, a beta emitter rather than an easily shielded alpha emitter and releasing significant gamma radiation when its daughter nuclide 90
Y decays, but as it is a high yield product of nuclear fission and easy to chemically extract from other fission products, Strontium titanate based RTGs were in widespread use for remote locations during much of the 20th century. Cobalt-60 while widely used for purposes such as food irradiation
See also
References
- ^ "Alpha Decay" (PDF). Soton. Archived (PDF) from the original on 2016-05-08. Retrieved 31 March 2021.
- OCLC 182729523.