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Radiation
Ionising Radiation
Ionising Radiation
Alpha Radiation
Beta Radiation
Gamma Rays
X-Rays
Neutrons
Alpha Radiation
Very short range
Stooped by air, paper or skin
Not a hazard outside the body
A concern when inside the body – cause intense local ionisation and biological damage
Beta Radiation
Longer range than Alpha
Low energy beta radiation does not penetrate the skin, whereas 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
Gamma & X-RaysBoth electromagnetic radiationGamma radiation is emitted continuously by radioactive decayX-rays are generated in special electrical equipment by bombarding a target with electronsConsequently, an x-ray beam only exists when machine is on, whereas gamma rays are emitted continuouslyPenetrating power of electromagnetic radiation depends on its energy and the properties of the matter through which it passesX-rays are able to pass through the human body, but gamma and x-rays can be stopped by lead shielding
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
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)
MeasurementIonising radiation is measured in sieverts (Sv)Sv include a weighting factor to take into account differing biological effects of alpha, beta, gamma and neutron radiationExposure 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
Detection
Film badges (personal)
Ionisation chamber (similar to geiger counter)
Personal air samplers
Analysis of faecal and urine samples
ProtectionBased on 3 principles:ShieldingDistanceReduced time exposure
Shielding is best method as it reduces risk positively. Distance and reduced time exposure are administrative controls which require considerable supervisory control
Shielding
Use of a dense medium to intercept radiation e.g. lead
Particulate radiation can be completely stopped
Electromagnetic radiation can be sufficiently absorbed so that emergent radiation has a reduced risk level
Distance Protection
The intensity of all radiation is reduced by distance travelled
Reduction is inversely proportional to the square of the distance
Reduced Time Exposure
Reduces exposure time and therefore reduces the accumulated dose
Workplace Examples of Ionising Radiation
Hospital x-ray equipment
Gamma rays are used for non-destructive testing of welds
Nuclear power generation
Non-Ionising Radiation
Non-Ionising Radiation
Does not have sufficient energy to cause ionisation in matter and can be classified into:Ultra Violet Infra RedMicrowavesRadio wavesLasers
Ultraviolet RadiationProduced by electric discharge tubes, electric arc welding and the sun
Can produce reddening, ageing or cancer of the skin
Can produce arc eye which causes pain and an aversion to bright light
Controls: Protection for face and eyes Screens Non-reflective surfaces Interlocks
Infra-Red Radiation
Produced by hot bodies
Can cause reddening of skin, burns and cataracts
Controls:DistanceEye protectionReflective clothing
Microwave Radiation
Harm is caused by heating
Can cause burns
Controls:Enclosure in metal structure with
interlocked access doors
Radio Waves
Used for heating purposes
Severe burns can occur by contact
Lasers
Can destroy tissueReflected laser radiation is as hazardous as direct raysClassed from Class 1 (safest) to 2, 3a, 3b and 4 (most harmful)Controls:Fixed shieldingEye protection
Workplace Examples of Non-Ionising Radiation
Electric arc welding (UV)
High temperatures and hot surfaces in a furnace (Infra-red)
Telecommunication (microwaves)
Heating units for particular industrial purposes (Radio waves)
Precision cutting (Lasers)
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