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Radiation Protection

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High doses of radiation delivered at high dose rates, for example 5 Sv in a few ... Eyewear is available which offers the equivalent protection of 0.8 mm of lead. ... – PowerPoint PPT presentation

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Title: Radiation Protection


1
Radiation Protection
2
Sources of ionizing radiation
  • Naturally-occurring radioisotopes
  • Man-made radioisotopes
  • Cosmic radiation
  • Particle accelerators
  • X-ray generators

3
Early effects of high doses
  • High doses of radiation delivered at high dose
    rates, for example 5 Sv in a few minutes, can
    produce a variety of effects in humans, including
    death, within a few months.
  • High doses, in a short time, kill so many cells
    in certain tissues that the body cannot cope with
    this damage.

4
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5
Late effects of low doses
  • Although low doses of radiation do not produce
    any early effects, they may result in late
    effects which do not become evident until many
    years after exposure.
  • Late effects of primary concern are an increased
    incidence of cancer in exposed persons, and of
    genetic disorders in their children.

6
Basis for radiation dose limits
  • Increased incidence of life-shortening cancer
  • Survivors of the atomic bomb blasts
  • Patients treated for ankylosing spondylitis
  • Watch dial painters
  • Uranium miners
  • Patients in a tuberculosis sanitarium in Nova
    Scotia
  • Other high exposure cases

7
Survivors of the atomic bomb blasts
  • 24,000 people received an average of 1300 mSv
  • About 120 extra cancers developed among them up
    to 1974

8
Treatments of ankylosing spondylitis(arthritis
of the spine)
  • 15,000 British patients treated with x-rays
  • Doses averaging 3700 mSv
  • 115 extra cancers
  • 900 Germans treated with injections of radium
  • Average dose to bone of 44 Sv
  • 45 developed bone cancer (0.1 expected)

9
Watch dial painters
  • 1700 American women employed during the 1920s
    painting radium on watch and clock dial numerals
    used their tongues to put a fine tip on their
    brushes
  • Average bone dose was 170 Sv
  • 48 died of bone cancer (0.4 expected)

10
Uranium miners
  • 4,100 U.S. uranium miners exposed to excess
    levels of radon gas due to poor mine ventilation
  • Average exposure to bronchial surfaces was 47 Sv
  • 135 lung cancer deaths up to 1972 (with 16
    expected)

11
High exposures resulting in about 10 extra cancers
  • Women in a Nova Scotia tuberculosis sanitarium
    exposed to excessive x-rays in the course of
    fluoroscopic examinations
  • U.S. women treated with x-rays for inflammation
    of the breasts following childbirth
  • Various types of pelvic x-ray treatments
  • Children treated with x-rays for enlargement of
    the thymus gland
  • Marshall Islands natives exposed to fallout from
    a nuclear bomb test

12
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13
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14
Who establishes radiation dose limits?
  • Canadian Nuclear Safety Commission
  • former Atomic Energy Control Board
  • www.nuclearsafety.gc.ca
  • International Commission on Radiological
    Protection (ICRP)
  • www.icrp.org

15
Dose limits
16
Organ/tissue limits
17
Dose limits Emergencies
  • During control of emergency and consequent
    immediate and urgent remedial work
  • Effective dose lt 500 mSv
  • Equivalent dose to skin lt 5000 mSv
  • May be exceeded by a person who acts voluntarily
    to save or protect human life

18
Dose limits ALARA
  • As Low As Reasonably Achievable
  • economic and other factors taken into account
  • Any exposure must be justified

19
Compliance
  • Facilities which are licensed to possess and use
    radionuclides or radiation-producing equipment
    must demonstrate compliance with applicable
    regulatory dose limits
  • Area monitoring
  • Personnel monitoring

20
Ring dosimeter and body badge dosimeter
21
Direct-reading dosimeter
22
Warning signs
  • Required on containers or devices
  • Boundary of and every point of access to an area,
    room, enclosure or vehicle
  • containing more than 100 times the exempt
    quantity of a radioactive substance
  • exposure rate greater than 25 ?Sv/hr

23
Radiation warning trefoil
24
Reducing exposure
  • Time
  • Exposure proportional to time
  • Distance
  • Inverse-square reduction of exposure with
    distance
  • Shielding
  • Exponential attenuation by shielding

25
Lead shielding blocks, 5 cm thick, used to
protect against high energy photons. The blocks
are available in standard and interlocking styles.
26
Mobile transparent full-body radiation barrier.
These panels can provide the shielding equivalent
of 0.5 to 1 mm of lead. Casters allow the
barrier to be moved easily.
27
Lead-vinyl aprons are available in a variety of
different styles. They generally provide
protection equivalent to 0.5 mm of lead. In
addition, staff may wear thyroid and/or gonadal
shields. Eyewear is available which offers the
equivalent protection of 0.8 mm of lead.
28
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