Radiation Hazards

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Radiation Hazards
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Radiation. A definition

• Energy that is transferred by either high energy
  particles or waves.

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Electromagnetic Spectrum

• The range of wavelengths of radiation in which
  the energy is transmitted by photons.
• The spectrum ranges from low energy extra low
  frequency radiation and radio waves to high
  energy gamma radiation.

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Electromagnetic Spectrum
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Units

• frequency cycles per second (hertz)
• wavelength metres, micrometres (10-6) or
  nano-metres (10-9)
• E h?, E hc/?
• Plancks constant 6.63?10-34

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Non-ionising radiation

• Low energy radiation that is unable to remove
  electrons from atoms but may still have damaging
  effects on living tissue.

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Non-ionising radiation

• Radar
• Radio waves
• Microwaves
• Mobile telephone signals
• Infrared radiation
• Visible light

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Hazards of visible light

• Insufficient illumination
• Lack of contrast
• Reflection and glare
• Lasers

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Lasers

• Light Amplification by Stimulated Emitted
  Radiation

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Lasers

• High power especially when pulsed
• Monochromatic
• Low divergence
• High power density

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Class 1 laser products

• These are inherently safe and no specific safety
  controls need be considered
• Best to avoid direct beam exposure to the eyes
• Product labels are required

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Class 2 lasers

• In the building and construction industry laser
  operator must be certified
• Usually low power
• Blink reflex may afford protection
• Product labels required

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Class 3A, 3B class 4 lasers

• Product labels required
• Certified laser operators
• Area warning signs
• Beam terminated at useful length
• Interlocked doors and start up for access and
  control
• Risk assessments completed
• Laser equipment registered
• Eye clothing protection required

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Ionising radiation

• High energy radiation that has the ability to
  strip electrons from atoms in materials including
  living cells. Ionising radiation may be high
  energy electromagnetic radiation such as X-rays
  or ? radiation or particulate radiation from
  radioactive sources.

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Ultra-violet Radiation

• Between visible and X-rays
• Wavelength range 220 400 nm
• Both ionising and non-ionising
• UV-A 400 300 nm
• UV-B 320 280 nm
• UV-C 280 220 nm

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Some important terms

• Absorbed dose the amount of radiation energy
  that is absorbed by an individual upon exposure
  to a radiation source. Units for absorbed dose is
  the Gray (Gy) 1J/kg.
• Dose equivalent measured as Sieverts. This
  value takes into account the effects of different
  radiation types. 1Sv 1Gy x Q x N (N 1 in air)
• ALARA As Low As Reasonably Achievable.

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Quality factors
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X-rays and Gamma rays

• Electromagnetic light
• Not visible to human eye
• Great penetrating power
• Will pass through the human body.

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? - alpha particles

• Positive electrical charge
• Emitted from naturally occurring elements
• Emitted from synthetic materials
• Low penetration
• May be stopped by skin or piece of paper
• Very hazardous inside the body

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? - beta particles

• Fast moving electrons
• Ejected from the nucleus of atoms
• Much smaller than alpha particles
• Can penetrate up to 1-2cm human skin
• May be stopped by aluminium gt3mm

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neutrons

• High energy particles from the nucleus of atoms
• Emitted during the fission of of atoms in a
  nuclear reactor
• Water and concrete are the most common shields

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Uranium Information Centre
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Radiation penetration
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Effects of ionising radiation

• Somatic affects the exposed individual
• Genetic affects the descendants of the exposed
  person via changes to sperm and ova
• Stochastic likelihood of negative effect is
  dose dependent (no threshold)
• Non stochastic severity of effect depends on
  dose and there may be a threshold

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Examples

• Somatic/ stochastic effect skin cancer from UV
  exposure.
• Somatic/non-stochastic effect sun burn from UV
  exposure.
• Genetic/stochastic effect hereditary blood
  disorders ie. Leukaemia
• The chance of dying from cancer is doubled by a
  single dose of 1 5 Sv.

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Principles of control

• No practices should be adopted unless it produces
  a positive net benefit
• All exposures should be kept ALARA with economic
  and social factors considered
• The dose equivalent to individuals shall not
  exceed the appropriate limits

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Control of external sources

• Shielding lead and concrete for X and ? rays,
  aluminium and wood for ?s plastic and cardboard
  for ?s
• Time - limit the time of exposure, use
  dosimeters to monitor exposure
• Distance the intensity of radiation obeys the
  inverse square law

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Control of internal sources

• Containment use of glove boxes etc
• Cleanliness use of special /disposable
  clothing, washing of clothing and skin
• Cut reduce the level of radioactivity, use the
  least amount possible

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Disposal of radioactive substances

• Delay and decay (time)
• Dilute and dispense (distance)
• Concentrate and contain (shielding)