1. Nuclear Reactions

2. Balancing Nuclear Equations
Conservation of Atomic Number (subscript)
Conservation of Atomic Mass (superscript)

3. Balancing Nuclear Equations
16N  0e O -1 7 8
Conservation of mass number: 16 =
Conservation of atomic number: 7 =

4. Natural Transmutation
1 term on the reactant side
Original isotope
2 terms on the product side
Emitted Particle
New Isotope
Happens all by itself. Not affected by anything in the environment.

5. Natural Transmutation
16N  0e O 7 -1 8
1 term on reactant side
2 terms on product side

6. Artificial Transmutation
We cause it to happen by smashing particles into one another.
2 terms on the reactant side.
Original Isotope or Target
Particle that hit it or bullet: neutron, proton, or -particle
Product side usually has 2 terms.

7. Artificial Transmutation
27Al + 4He  30P + 1n 13 2 15
Original isotope or target nucleus
“Bullet”

8. Bombarding with Protons, 
Protons and -particles have positive charge and mass. They can do some damage when they hit the target nucleus.
Protons and -particles have to be accelerated to high speeds to overcome repulsive forces. (The nucleus they are aiming for is also positive.) Use magnetic and electric fields to accelerate them.

9. What is an accelerator?
An accelerator consists of a vacuum chamber, usually a long pipe, surrounded by vacuum pumps, magnets, radio-frequency cavities, high voltage instruments and electronic circuits.
Inside the pipe, particles are accelerated to very high speeds & smashed into each other.

10. FermiLab
4 miles in circumference!

11. CERN
27 kilometer ring.
Particles travel at just below the speed of light.
In 10 hrs, the particles make 400 million revolutions of the ring.

12. SLAC
LBL

14. Neutron Capture
Neutrons don’t have to be accelerated. They’re neutral so they aren’t repelled by a positive nucleus.
Don’t need high K.E. to overcome repulsive forces. So don’t need accelerators.
It’s a good thing – we can’t accelerate neutrons.

15. Artificial Transmutation
27Al + 4He  30P + 1n
All of these equations have 2 reactants! 13 2 15
14N + 4He  17O + 1H 1 2 8 7
75As + 4He  78Br + 1n 2 35 33
37Cl + 1n  38Cl 17 17

16. 2 more kinds of nuclear equations
Fission
Fusion
Both have 2 reactants
Equations have distinctive features, so easy to tell them from artificial transmutation

17. Fission Reaction
Involves splitting a heavy nucleus into 2 lighter nuclei.

18. Fission Involves splitting a heavy nucleus into 2 lighter nuclei.
Reactant side has 2 terms:
1 heavy isotope, U-235 or Pu-239
Bombarding particle – usually a neutron
Product side has at least 2 terms:
2 medium-weight isotopes
1 or more neutrons
Huge amount of energy is released.
Fission = Division

19. Fission 235U + 1n  91Kr + 142Ba + 31n + energy 56 92 3692 36
235U + 1n  72Zn + 160Sm + 41n + energy 62 92 30
More than 200 different product isotopes from the fission of U-235 have been identified.
A small amount of mass is converted to energy by E = mc2.

20. Fission Chain Reaction

21. Fission Chain Reaction
Requires a critical mass of fissionable isotope.
Controlled – nuclear reactor.
Uncontrolled – bomb.
Animation of nuclear reactor

22. Fusion Reactant side has 2 small nuclei – H + H or H + He or He + He.
Product side has 1 (still pretty small nucleus) and maybe a particle.
Source of sun’s energy.
2 nuclei unite.
2H + 3H  4He + 1n + energy 1 1 2

24. Inertial Confinement - Fusion

25. Magnetic Confinement - fusion