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-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

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)

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

Detection Film badges (personal) Ionisation chamber (similar to geiger counter) Personal air samplers Analysis of faecal and urine samples

Protection 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

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

Does not have sufficient energy to cause ionisation in matter and can be classified into: Ultra Violet Infra Red Microwaves Radio waves Lasers

Ultraviolet Radiation Produced 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: Distance Eye protection Reflective 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 tissue Reflected laser radiation is as hazardous as direct rays Classed from Class 1 (safest) to 2, 3a, 3b and 4 (most harmful) Controls: Fixed shielding Eye 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)