Radiation Protection

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Radiation Protection
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Sources of ionizing radiation

• Naturally-occurring radioisotopes
• Man-made radioisotopes
• Cosmic radiation
• Particle accelerators
• X-ray generators

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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.

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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.

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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

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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

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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)

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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)

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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)

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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

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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

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Dose limits
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Organ/tissue limits
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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

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Dose limits ALARA

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

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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

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Ring dosimeter and body badge dosimeter
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Direct-reading dosimeter
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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

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Radiation warning trefoil
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Reducing exposure

• Time
• Exposure proportional to time
• Distance
• Inverse-square reduction of exposure with
  distance
• Shielding
• Exponential attenuation by shielding

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Lead shielding blocks, 5 cm thick, used to
protect against high energy photons. The blocks
are available in standard and interlocking styles.
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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.
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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.
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