# Decay energy

﻿
Decay energy

The decay energy is the energy released by 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 reactants is often written as Q:

$Q = (\text{Kinetic energy})_{\text{after}} - (\text{Kinetic energy})_{\text{before}}\,\!$ $Q = ((\text{Rest mass})_{\text{before}} \times c^2) - ((\text{Rest mass})_{\text{after}} \times c^2)\,\!$

Decay energy is usually quoted in terms of the energy units MeV (million electronvolts) or KeV (thousand electronvolts).

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: $W = dm \times \left ( \frac{A}{M} \right )\,\!$ or $W = E \times \left ( \frac{A}{M} \right )\,\!$

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

## References

Wikimedia Foundation. 2010.

### Look at other dictionaries:

• decay energy — skilimo energija statusas T sritis fizika atitikmenys: angl. decay energy; disintegration energy vok. Aufspaltungsenergie, f; Zerfallsenergie, f rus. энергия распада, f; энергия расщепления, f pranc. énergie de désintégration, f …   Fizikos terminų žodynas

• alpha decay energy — alfa skilimo energija statusas T sritis fizika atitikmenys: angl. alpha decay energy; alpha disintegration energy vok. Alpha Umwandlungsenergie, f; Alpha Zerfallsenergie, f rus. энергия альфа распада, f pranc. énergie de désintégration alpha, f …   Fizikos terminų žodynas

• beta decay energy — beta skilimo energija statusas T sritis fizika atitikmenys: angl. beta decay energy; beta disintegration energy vok. Beta Zerfallsenergie, f rus. энергия бета распада, f pranc. énergie de désintégration bêta, f …   Fizikos terminų žodynas

• Decay chain — In nuclear science, the decay chain refers to the radioactive decay of different discrete radioactive decay products as a chained series of transformations. Most radioactive elements do not decay directly to a stable state, but rather undergo a… …   Wikipedia

• Decay heat — RTG pellet glowing red because of the heat generated by the radioactive decay of plutonium 238 dioxide, after a thermal isolation test. Decay heat is the heat released as a result of radioactive decay. This is when the radiation interacts with… …   Wikipedia

• Energy transfer upconversion — or ETU is a physical principle (most commonly encountered in solid state laser physics) that involves the excitation of a laser active ion to a level above that which would be achieved by simple absorption of a pump photon, the required… …   Wikipedia

• Decay correct — is a method of adjusting the measurements of radioactive decay obtained at two different time points so that they may be used as a single data set. If a chemical compound is tagged with a radioactive isotope then the amount of radiation released… …   Wikipedia

• Decay scheme — The Decay scheme of a radioactive substance is a graphical presentation of all the transitions occurring in a decay, and of their relationships. Decay schemes of radioactive isotopes Decay scheme of 60Co These relations can be quite complicated;… …   Wikipedia