B7 Radiation Flashcards
What are the two basic types of radiation
Electromagnetic- made up of energy waves
Particulate- made up of particles, these particles carry the energy in much the same way as the waves in electromagnetic radiation but these have a physical mass.
Difference between ironising and non ironising radiation
Ironising radiation causes ionisation in the material that absorbs it where as non ironising radiation does not cause ionisation of the material that absorbs it.
What is ionisation
Ionising radiation is radiation that carries enough energy to detach electrons from atoms or molecules, thereby changing the atomic structure of the material that is absorbing the radiation..
Electromagnetic spectrum
Gamma (ironising) X-ray (ironising) Ultraviolet (all below non ironising) Visible light Infrared Microwave Radio waves
Remember Randy, Men, In, Vans, Use, X-rated, Girls
Ironising electromagnetic radiation
Gamma-rays, naturally occurring, typical occupational source is cobalt 60 used for industrial radiography
X-Rays, artificiality generated by bombarding a metal target with electrons inside a vacuum tube, typical occupational source of X-rays would be a generator used for medical radiography
Both rays act like light and travel in straight lines at the speed of light, they are very penetrating.
Types of particulate radiation
Alpha = made up of two protons and two neutrons, emitted during radioactive decay. Poor penetration unlikely to penetrate the skin or be absorbed by living tissue as the horny layer of skin will block its entrance. Occupational source would be a smoke detector
Beta = more penetrating than Alpha particles can pass through skin but not thicker materials, typical occupational source would be a thickness gauge.
Neutrons = extremely penetrating, typical occupational source would be a nuclear reactor
Radiation protection agencies
International commission on radiological protection (ICRP)
International commission on non-ironising radiation protection (ICNIRP)
Sources of non ironising radiation
Natural = the sun
Artificial
- UV = welding equipment, sun lamps
- Visible = general lighting, cutting and welding equipment, lasers.
- IR = Metal furnaces, fire, heat lamps
- Microwaves = mobile phone masts, microwave oven.
- Radio waves = communication equipment
Effects of Ultraviolet on the body
Acute effects
- Skin = sunburn/ burns
- Arc eye = inflammation and temporary blindness
- Weaken immune system
Chronic effects
- Premature ageing of skin (Destruction of collagen)
- Skin cancer/ melanoma(damage to DNA molecules from free radicals)
- Cataracts (yellowing of lens to eye)
Indirect = photosensitisation and the formation of toxic contamination
Effects of visible light
Nuisance glare (difficulty in seeing difference)
Disability glare (temporary blindness)
Permanent blindness from lasers
Effects of radiation
Acute reddening of skin and surface layer of eyes
Chronic cataract from exposure to white hot surfaces over time
Effects of microwaves
Effects from internal heating
Effects of radio waves
Similar to microwaves = internal heating
Risk assessment criteria for non ironising radiation
- Source of non ironising radiation to which workers will be exposed to.
- The wavelength, intensity and duration of exposure
- Parts of body exposed (esp eyes for UV and visible light)
- Exposure to sunlight
- Exposure limit values (or guidance)
- Workers at increased risk
- Interactions between optical radiation and photosensitising chemicals
- Results of Health surveillance
- Multiple source of exposure
- information provided by manufacturers
Control measures for non ironising radiation
- Eliminate
- Choose Less radiation emitting Equipment
- Technical measures to reduce unwanted emissions (interlocking, shielding)
- Maintenance
- Design ie use of non reflective surfaces, control direction of source
- Limit duration and level or intensity of exposure, increase distance from source
- PPE
- Develop and implement safe systems of work
- Provide information, instruction and training
- Warning signage.
Quantify exposure to radiation
- Radioactivity Becquerel - an estimate of the likely amount of radiation being emitted (Bq)
- Absorbed dose Gray- Measure of energy deposited by the radiation
- Equivalent dose Sievert - Measure of the likely biological damage resulting from radiation exposure (Sv)
Effective dose and the Sieverts
This is the weighted sum of all the equivalent doses and relates to the whole body. The equivalent dose for each tissue is multiplied by the respective tissue weighting factor. These products are then added together to arrive at the effective dose for the whole body.
Penetrating power of the types of radiation
- Alpha particles have little penetrating power, can be stopped by a few centimetres of air, a sheet of paper or the horny layer of the skin.
- Beta particles more penetrating than alpha, can move through tens of centimetres of air and penetrate the horny layer of skin into the body.
- Neutrons, X-Rays and Gamma rays are extremely penetrating and can pass through kilometres of air, right through the body (longer wave X-Rays are less penetrating and absorbed by harder tissue such as bones and teeth.
Symptoms of acute radiation sickness
- Nausea
- Hair loss
- Diarrhoea
- Headache
- Fever
- Central nervous system impairment
- Skin burns and ulceration
- Death
Measurement of radiation and exposure
- Passive (doesn’t Provide a direct reading) dosimeters such as thermo luminescent dosimeters
- Active (gives a direct reading) dosimeters, such as personal alarm dosimeters
Control measures for ironising radiation
External exposure
- Reduce exposure time
- Increase distance from source (radiation follows the inverse square law so if the does at 1m is X the 2m it is 1/4X and 4m it is 1/16X
- Shielding
Internal exposure Prevention of *inhalation * Ingestion * Absorption * Injection
Legal requirement of Ionising radiation regulations
- Notification, registration or consent
- Risk Assessment
- Restriction of exposure
- Maintenance and testing
- Does limits
- Contingency plans
- Radiation protection advisors
- Information, instruction and training
- Controlled and supervised areas
- Demarcation and signs
- Local rules and radiation protection supervisors
- Radiation monitoring
- Classified persons
- Personal does assessment
- Medical surveillance
- Sealed sources
- Quantity accounting
- Receptacles and storage
Classified persons
Under the ironising radiation regulations a classified person is any employee who is likely to receive:
- An effective dose of more than 6mSv per year or
- An equivalent does of more than three tenths of the relevant does limits.
To be classified they must be:
- At least 18 years old
- Certified as fit for radiation work by an appointed doctor or employment medical advisor
Classified persons are permitted entry to controlled areas where they are likely to receive doses of radiation of sufficient magnitude, they will be:
- subject to does monitoring (by approved dosimetry service
- subject to medical surveillance by an appointed doctor
Records kept for 50 years or 75 years of age (which ever is sooner)
Controlled radiation area
Any area where a worker will receive:
- An effective dose of more than 6mSv per year or
- An equivalent dose of more than three tenths of the relevant does limit
In this area employers should
- Develop and communicate local rules
- Appoint one or more Radiation Protection Supervisor’s (RPSs)
- Denmark and sign area
- Restrict access to non classified persons
- Monitor Radiation levels
