1. Spontaneous Decay, Fission, & Fusion
Nuclear Reactions
Spontaneous Decay, Fission, & Fusion

2. The N-Z Graph Why do nuclei decay at all?
Provides a survey of nuclear stability
For light nuclei (Z<20) N=Z for stable isotopes
As Z increases, stable nuclei have increasing proportion of neutrons providing strong force “glue”
Away from the stability curve, unstable nuclei decay to move closer to the stability curve

3. Nuclear Decay
Occurs when an unstable nucleus breaks apart in some fashion and releases radiation.
This decay occurs at a steady, measurable rate and is described with the following formula:
ln (At/A0) = - kt
A0 = initial amount of substance
At = amount of substance after a certain time
k = rate constant
t = time

4. Nuclear Decay
Half-life (t1/2) is the time required for half the amount of a radioactive sample to decay, so we can also estimate how much of a radioactive sample remains after a given amount of time if we know the half-life
k * t1/2 = 0.693

5. Alpha Decay

6. Beta Decay

7. Decay Series
An unstable isotope will decay in a series of steps until it reaches a stable state.
Releases alpha, beta, and/or gamma radiation

8. Nuclear Reactions
Transmutation is the process of converting one element into another (using bombardment with high energy particles).
The target nucleus is the isotope which is bombarded
The projectile is the particle fired at the nucleus
The product is the new nucleus produced by the reaction
The ejected particle is the light nucleus or particle emitted in the reaction.

9. Nuclear Reactions For Example:
Au He > Tl n γ
Target
Projectile
Product
Ejected
Particle

10. Nuclear Reactions
This bombardment takes place in a particle accelerator (cyclotron, synchrotron, linac, etc.).
Many of the radioactive products of nuclear bombardment are useful in medicine and industry as tracers, radiation sources, etc.

11. Fission
The splitting apart of an atomic nucleus into two smaller nuclei accompanied by a release of energy.
Occurs in nuclear power plants and nuclear bombs

12. Fission in War
August 6 and 9, 1945

13. Fission in Peace

14. Fusion
The joining of two nuclei to form a larger nucleus accompanied by a release of energy.
Occurs in stars and certain nuclear bombs