Decay Calculation
The energy difference of the reactants is often written as Q:
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 dm 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 W is: or
Example: 60Co decays into 60Ni. The mass difference dm is 0.003u. The radiated energy is approximately 2.8 MeV. The molar weight is 59.93. The half life T of 5.7a corresponds to the activity A=(N*(-ln(2)))/T, where N is the number of atoms per mol. Taking care of the units the radiation power for 60Co is 17.9 W/g
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
Read more about this topic: Decay Energy
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