1. Radiation
Objectives
Understand the concepts of ½ life and ½ thickness in radiation
Differentiate between fusion and fission
Describe the processes involved in radioactive decays (alpha, beta, and gamma)

2. Elementary Particle Properties
Particle Symbol Charge Weight Weight Ratio (e-)
proton p amu heavy
electron e amu light
neutron n amu heavy
1 Atomic Mass Unit (amu) = 1.66 x grams
Atoms are electrically neutral with no net charge.
Ions are atoms that have been stripped of one
or more of their electrons and have a net charge.

3. Isotopes Identical Chemical Properties, Different Atomic Weight
Difference = presence of number of neutrons in the nucleus
Hydrogen = amu
ISOTOPE Constituents Atomic Mass Occurrence
H 1 proton 1 electron amu %
Deuterium 1 proton 1 electron amu %
1 neutron
Tritium 1 proton 1 electron amu %
2 neutrons

4. Isotope Designations Hydrogen 11H 1 proton, 0 neutrons
Helium He 2 protons, 2 neutrons
Uranium U 92 protons, 143 neutrons
neutron 10n
proton 11p
electron 0-1e

5. Radiation Three types of Nuclear Radiation.
Revealed by their deflection in a magnetic field as neutral, charged negative or charged positive.

6. Radioactive Particles
Alpha a
Ejection of 2 protons and 2 neutrons from an
unstable nucleus. 42He = a
Beta b
Ejection of an electron from an unstable nucleus
as part of the decay of a neutron e = b
Gamma g
Atomic nucleus transition, yielding high energy
photons.

7. AZX Nuclear Reactions 22688Ra 22286Rn + 42He
Note that the numbers all add-up (conservation of particles).
AZX
A nucleons Total particles in nucleus =
Z protons Number of protons =

8. Alpha Decay Alpha a = 42He 22688Ra 22256Rn + 42He
Parent Ra Radium
Daughter Rn Radon
Radiation 42He a
22688Ra Rn He
Most of the energy is with the lighter particle, in this case
the alpha particle.

9. Beta Decay Beta b = 0-1e 10n 11p + 0-1e
The decay of a neutron into a proton and electron.

10. Beta Decay Beta b = 0-1e 10n 11p + 0-1e
The decay of a neutron into a proton and electron.
146C 147N + 0-1e (Radioactive Carbon)
9038Sr Y + b

11. Gamma Radiation Gamma g E = h f 8738Sr* 8738Sr + g
Very high energy photons are emitted from the nucleus.
Excess radiation emitted from an excited nucleus….
8738Sr* Sr + g
Excess radiation emitted as part of another process….
6027Co Ni + b + g

12. Radioactive Decay If you start out with a sample of parent atoms (No),
after some time
there will be fewer
because of
radioactive decay
into the daughter
atoms.

13. Shielding We can detect the radiation from a radioactive source.
Say we get X counts/minute (cpm).
Geiger Counter

14. Shielding We can shield the source with various
materials to test their usefulness in
protecting against the radiation.
Geiger Counter

15. Half Thickness Half Thickness: The thickness of a material needed to
cut the count rate by 1/2.
If a 4 inch thickness of lead, drops a count rate
from 1000 cpm to 500 cpm, the half thickness must
be 4 inches.

16. Half Thickness Half Thickness: The thickness of a material needed to
cut the count rate by 1/2.
If 12 inches of wood, drops a count rate
from 2000 cpm to 125 cpm, the half thickness must
be 3 inches.

17. Shielding Efficiency a b g Cotton Fabric Wood Lead
g’s are the most penetrating type of radiation.

18. Nuclear Energy Generation
Hydrogen
Fusion
Binding Energy/nucleon
Fission
Uranium
Iron
Atomic Mass Number