2E3: Radiation and the Thermal Environment

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2E3 Radiation and the Thermal Environment

• Ionising Radiation

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Ionising Radiation

• Particulate
• Alpha Radiation
• Beta Radiation
• Non-Particulate
• Gamma Rays
• X-Rays
• Neutrons

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Alpha Radiation

• Very short range
• Stopped by air, paper or skin
• Not a hazard outside the body
• A concern when inside the body cause intense
  local ionisation and biological damage

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Beta Radiation

• Longer range than Alpha
• Low energy beta radiation does not penetrate the
  skin, but high energy beta can penetrate soft
  tissue to a depth of over one cm.
• Beta inside the body is a concern, but less
  intense than alpha

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Gamma X-Rays

• Both electromagnetic radiation
• Gamma radiation is emitted continuously by
  radioactive decay
• X-rays are generated in special electrical
  equipment by bombarding a target with electrons
• Consequently, an x-ray beam only exists when
  machine is on, whereas gamma rays are emitted
  continuously
• Penetrating power of electromagnetic radiation
  depends on its energy and the properties of the
  matter through which it passes
• X-rays are able to pass through the human body,
  but gamma and x-rays can be stopped by lead
  shielding

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Neutrons

• Emitted during certain nuclear processes such as
  nuclear fission
• Great penetrating power
• Produce ionisation directly and can cause great
  harm as they pass through the body

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Workplace Examples of Ionising Radiation

• Industrial Radiography (e.g. for NDT)
• Medical, dental and veterinary x-ray equipment
• Nuclear power generation

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Measurement

• Ionising radiation is measured in sieverts (Sv)
• Sv include a weighting factor to take into
  account differing biological effects of alpha,
  beta, gamma and neutron radiation
• Exposure is controlled by dose limitation, which
  is based on the premise that for conditions
  having no safe threshold, exposure is reduced to
  a level where probability of harm is small

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Ionising Radiation Health Effects

• Nausea and vomiting
• Reduction in bodies defences
• Reddening of skin
• Loss of weight hair
• Blistering and ulceration of skin
• Cataracts
• Cancer
• Genetic defects (affects subsequent generations)

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Dose/Response Relationship

• Some effects of ionising radiation are dose
  dependent and only occur if dose received is
  above certain level
• Radiation sickness, skin burns or cataracts
• Other effects are not dose dependent. Any
  exposure to radiation may cause the effect.
  However, likelihood of harm increases at higher
  levels of exposure
• Cancer, Genetic defects

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Detection

• Film badges (personal)
• Ionisation chamber
• Geiger counter
• Personal air samplers
• Analysis of faecal and urine samples

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Control Measures

• Based on 3 principles
• Shielding
• Distance
• Reduced time exposure
• Shielding is best method as it reduces risk
  positively. Distance and reduced time exposure
  are administrative controls which require
  considerable supervisory control

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Engineering Controls

• Shielding
• Containment
• Ventilation
• Glove boxes or fume hoods
• Under negative pressure

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Procedural Controls

• Restricted access
• IRR99 require designation of
• Controlled areas (dose is likely to exceed three
  tenths of dose limit)
• Classified persons (personal exposure likely to
  exceed three tenths of dose limit)
• Supervised areas (dose likely to exceed one tenth
  of dose limit)
• Systems of work
• Permit to work reduces time exposure

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Procedural Controls

• PPE
• Gloves, overalls, eye protection, RPE etc.
• Local Rules
• Hazard assessment
• Contingency plans
• Radiation protection advisor
• Monitoring procedures etc. etc.

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Ionising Radiation Regs 1999

• Employer must ensure that employees (18 and
  above), trainees (less than 18), women of
  reproductive capacity and other persons are not
  exposed to ionising radiation to an extent that
  exceeds annual dose limits in Schedule to
  Regulations
• Requirement to restrict exposure sfairp includes
• Proper maintenance, examination and test of
  engineering controls, design features, safety
  features or warning devices
• Provision concerning pregnant or breast feeding
  women

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Classified Workers

• Definition
• Someone likely to receive radiation dose of more
  than 3/10ths of any relevant dose limit
• Someone likely to receive effective dose of more
  than 6mSv per year
• Must be over 18 years old
• Certified as fit for the work by appointed doctor
  or Employment Medical Advisor
• Someone who may enter a controlled area

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Classified Workers

• Specific Arrangements
• Dosimeters/film badges to measure exposure
• Assessment of significant doses
• Use of approved dosimetry service
• Provide health surveillance
• Keep records of doses/health checks etc.

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Previous Exam Questions

• In relation to the Ionising Radiation Regulations
  1999
• i.) Explain what is meant by the term classified
  worker
• ii.) Outline the specific arrangements that must
  be made by employers for employees who are
  designated as classified workers (10
  marks)