1. Basic of radiation Prof. Dr. Moustafa. M. Mohamed Vice Dean
Faculty of Allied Medical Science
Pharos University
Alexandria
Dr. Yasser khedr
Department of Medical Biophysics

2. Operating Engineers National Hazmat Program
The New Understanding
In 1913 several scientists published the theory that an atom is made of
a positively-charged central nucleus
orbited by negatively-charged particles
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Operating Engineers National Hazmat Program

3. Bohr Model
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4. Atomic Structure
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5. Nucleus Contains positively-charged protons Non-charged neutrons
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6. Electrons Orbit nucleus
An atom can have as many electrons as it has protons
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7. How big is an atom? An atom is the same size compared to a golf ball
As a golf ball is compared to the earth
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8. Radioactivity: Elements & Atoms
Atoms are composed of smaller particles referred to as:
Protons
Neutrons
Electrons

9. Basic Model of a Neutral Atom.
Electrons (-) orbiting nucleus is the same number of protons; net charge = 0.
Atomic number (number of protons) determines element. 
Mass number (protons + neutrons)

11. Definition of Radiation
“Radiation is an energy in the form of electro-magnetic waves or particulate matter, traveling in the air.”

12. What is Radiation? Form of energy
Emitted by nucleus of atom or orbital electron
Released in form of electromagnetic waves or particles

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Energy in motion
What is Radiation?
As either particles or rays
Two kinds: ionizing and non-ionizing
Operating Engineers National Hazmat Program
Operating Engineers National Hazmat Program

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Fission
Fission is the process by which a large, unstable nucleus splits into two nuclei
It rarely occurs naturally
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15. Fission
When the atom splits, “fission fragments” are released

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The Search for Stability
An atom is stable based on it’s proton to neutron ratio
If there are too many or too few neutrons or protons, the atom will give off excess energy as
rays
particles
This process is called radioactive decay
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Radioactive Decay
When an atom’s nucleus gives off excess energy, the process is called radioactive decay
Radioactive half-life is the time it takes half the radioactive atoms present to decay
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Operating Engineers National Hazmat Program

18. Half-Life
The time it takes half the radioactive atoms present to decay
Before
After one half-life
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Half-Life
The time it takes half the radioactive atoms present to decay
Before
After one half-life
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20. Types of Radiation Ionizing radiation Non-ionizing radiation
Radiation is classified into:
Ionizing radiation
Non-ionizing radiation

21. The Electromagnetic Spectrum Waveform of Radiation

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Ionizing Radiation
The energy given off by the nucleus is called ionizing radiation
It is strong enough to detach an electron from an atom
When an atom loses an electron, it has a positive charge and is called an ion
The ion and its lost electron are called an ion pair
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Operating Engineers National Hazmat Program

23. Ionization
Ionizing radiation is produced by unstable atoms. Unstable atoms differ from stable atoms because they have an excess of energy or mass or both.
Unstable atoms are said to be radioactive. In order to reach stability, these atoms give off, or emit, the excess energy or mass. These emissions are called radiation.

24. TYPES OF IONIZING RADIATION
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25. Alpha Particle Large mass Consists of 2 protons and 2 neutrons
Electrical charge of +2
Range in air 1 to 2 inches +1
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26. Alpha shielding A sheet of paper Outer layer of skin
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Biological Hazard
Alpha radiation is not an external hazard, because it can be stopped so easily
If inhaled or swallowed, the alphas emitted from an alpha emitter, can deposit large amount of energy in a small area of body tissue
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28. Sources of Alpha Radiation
Plutonium 238 and 239
Uranium 238 and 235
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Operating Engineers National Hazmat Program

29. Beta Particle - ß Small mass Electrical charge of -1
Emitted from nucleus
Range in air about 10 feet
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30. Beta Shielding
Beta has a limited penetrating ability because of its negative charge
Most beta particles can be shielded by plastic, glass, metal foil, or safety glasses
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Biological Hazard
If ingested or inhaled, a beta-emitter can be an internal hazard
Externally, beta particles are potentially hazardous to the eyes and skin
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Operating Engineers National Hazmat Program

32. Operating Engineers National Hazmat Program
Beta Sources
Uranium decay products
Decay of some radioactive substances (Tritium)
Products of the fission process
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Operating Engineers National Hazmat Program

33. Gamma and X-Rays
An electromagnetic wave or photon, which has no electrical charge
Great penetrating power
Range in air easily several hundred feet
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34. Gamma and X-Ray Shielding
Concrete
Lead
Steel
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35. Neutron A neutron is ejected from the nucleus No electrical charge
Range in air easily several hundred feet
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36. Neutron Radiation Shielding
Best shielded by material with a high hydrogen content
Water
Plastic
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Operating Engineers National Hazmat Program

37. Types or Products of Ionizing Radiation 
or X-ray
neutron

38. Radioactive Atom
Ionizing Radiation
alpha particle
beta particle
X-ray
gamma ray

39. Non-Ionizing Radiation
Energy in transit that is too weak to detach an electron from another atom
Examples
Light
Radio and television waves
Microwaves
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40. RADIATION MEASUREMENT
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Roentgen (R)
A unit for measuring exposure
Defined for effect in air only
Applies only to gamma and x-rays
Does not relate radiation to the effect on the human body
Operating Engineers National Hazmat Program
Operating Engineers National Hazmat Program

42. Operating Engineers National Hazmat Program
Roentgen (R)
A unit for measuring exposure
Defined for effect in air only
Applies only to gamma and x-rays
Does not relate radiation to the effect on the human body
1 R = 1000 milliRoentgen (mR)
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43. Operating Engineers National Hazmat Program
Radiation Absorbed Dose (rad)
is the absorption of one joule of ionizing radiation by one kilogram (1 J/kg) of matter
Unit for measuring the absorbed dose in any material
Applies to all types of radiation
1 rad = 1000 millirad (mrad)
1 rad= 1000 millirad (mrad)
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44. Roentgen Equivalent Man (rem)
equal to an effective dose of a joule of energy per kilogram of recipient mass
Unit for measuring radiation dose equivalence
Most commonly used unit
Takes into account the energy absorbed (dose) and effect on the body of different types of radiation
1 rem = 1000 millirem (mrem)