Radiation - PowerPoint

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          Important characteristics of

•   Wavelength
•   Frequency
•   Intensity
•   Velocity
•   Straight line propagation
•   Spectrum
•   Inverse square law
      Ultraviolet radiation hazards
• Common sources: sun, UV lamps („black lights‟),
  welder‟s arc
• Some devices may emit only a small amount of
  visible light while emitting intense UV radiation
• Especially dangerous to the eyes since they do not
  dilate readily in response to UV -- retinal burns
• Photosensitization to UV can occur from certain
  dermal chemicals and oral drugs (e.g. antibiotics)
                       Types of UV Radiation

      Type               Wavelength       Effect

     UV-A                315-400 nm    Little effect
“Black light” Region

     UV-B                280-315 nm    Skin cancer
     UV-C                100-280 nm   Cornea damage
           Visible radiation hazards

• Common sources: sun, all visible lamps
• Major damage likely only if intense beam is
  focused on the retina
• Eye usually registers pain before serious
  damage occurs
                      Infrared Hazards

• Major effect is burns
• Eye is not very sensitive so can be damaged
  if IR is intense
• Skin burns possible but usually avoided
  due to pain from heat before serious injury
 Radio-frequency and Microwave
• Sources include analytical instruments (e.g.
  NMR), cathode ray tubes (including oscilloscopes,
  TVs, and computer monitors), microwave ovens,
  and communications devices (e.g. cell phones)
• Biological effects to man uncertain
• Suggestion of sterility problems, birth defects and
  cataracts from microwaves
• Pacemakers are effected by microwaves
                   LASER HAZARDS

• LASER = Light Amplified by Stimulated
  Emission of Radiation
• Especially hazardous due to very narrow
  beam which can be very intense
• Lens of eye may concentrate energy onto
  retina by another 100,000 times
         LASER HAZARDS (cont’d)
• Use minimum power laser possible for job
• Keep laser beam off or blocked when not in use
• Post warning signs when lasers are in use
• Never look directly at a laser beam or align it by
  sighting over it
• If possible, use laser in lighted room so that pupils
  will be constricted
• Do not depend on sunglasses for shielding.
• Make sure any goggles used are for the
  wavelength of the laser used and are of adequate
  optical density
               Ionizing Radiation
        Mass     Charge   Stopped by
Alpha   4        +2       4 cm air
Beta    0        -1       6-300 cm
                          10% by
X-ray   0        0        15-30 cm
Gamma   0        0        50 cm
            Ionizing Radiation Units

• Curie (Ci) = 37 billion disintegrations/sec
• Roentgen (R) = energy which will produce
  1 billion ion pairs/mL air
• Rad = 100 ergs absorbed energy/gm
• Rem = absorbed dose in rads multiplied by
  factor related to type of radiation (1 for
  beta, gamma, X-ray; 20 for alpha)
         Ionizing radiation damage

• Tissue burns, minor and/or destructive
• DNA breaks leading to cell death or
  mutation, potentially cancer
Human radiation dose-effect data

0-25            No noticeable effect
25-100          Slight blood changes
100-200         Vomiting, fatigue
                (recovery in weeks)
200-600         Vomiting, severe blood
                changes, hemmorhage
                (recovery in 1-12 mo.)
600-1000        Survival unlikely
                 Regulatory mandates
                 on ionizing radiation

• Nuclear Regulatory Commission
  occupational standard (10 CFR 20) is 5
  rems/yr for whole body radiation. [Note
  that a lifetime exposure to 5 rem total is
  thought to shorten life by 1-3 weeks.]
• Standard for nonwork environment is 170
                      Ionizing radiation
                    General precautions
• Confine radioactive chemicals to small areas
  which are posted
• Cover bench tops with plastic-backed absorbent
• Use trays to catch spills
• Wear gloves to protect hands and lab coat to catch
• Dispose of contaminated clothes appropriately
     Radiation monitoring devices

• Film badges – after the fact measurement,
  developed weekly or monthly
• Geiger counter – best for high energy beta,
• Scintillation counter – used for wipe