B7 Ollie Flashcards
Radiation
Form of energy
Natural (minerals,radon gas,UV)
Man-made (x-rays , microwaves )
The amount of energy will determine if it is ionis ing or non-ionis ing radiation
Radio activity is the term us ually applied to ionis ing radiation emissions
Electromagnetic waves or particulate
Electromagnetic Spectrum
All move at same speed (3 x 108 ms -1)
Different wavelengths
Shorter the wavelength, higher the energy
Gamma Rays and X-rays:
Ionising
UV/Visible/InfraRed/Microwaves/Radio-waves :
Non-ionising
Ionising radiation also includes particulate forms
Ultra-Violet Radiation - Basic Information
UV- A - 400 t o 315 nm
UV- B ( most hazardous ) - 315 t o 280 nm
UV- C - 280 t o 100 nm Intensity(irradiance) also important:
Welding arc at 1m - 1700 W/m2
Summers un at noon - 170 W/m2
Ultra-Violet Radiation - Sources & Effects
Sources:
Arc-welding, sunlight, tanning studios , UV water treatment, curing of resins
Effects:
Burns , erythema (reddening of s kin), keratoconjunctivitis (arc-eye), premature ageing, cataract, skin cancer
Infra Red Radiation - Basic Information
Electromagnetic radiation 700nm to 1mm
Does not penetrate deeply, so skin and eyes at risk Sources:
Emitted by any hot body
Furnaces , foundries , glas s blowing, hotwork
Effects:
Cataract, burns , erythema, heat effects
(e.g. heat-stroke)
Microwaves - Basic Information
Electromagnetic radiation 1mm to 1m
Cause water molecules to rotate and vibrant: heating
Radiated power (irradiance) important
Sources:
Microwave ovens , drying and curing processes , radar, communication systems
Effects:
Burns , localised heating, cataract, links with cancer
Radio frequency - Basic Information
Wave lengths 1 mm to 10 Km
1 mm to 1 m referred to as microwaves
All have heating effect, but particularly microwaves
Strength of field depends on irradiance (radiated power) and distance from antenna/source
Sources:
Radio transmitters , radar
Effects: Heating, burns, potentially cancer
Controls for Non Ionising Radiation
Reduce source strength
Reduce time of exposure
Increas e distance (note: inverse square rule applies ) Shielding
PPE (including suncream)
Controls for Non Ionising Radiation -Specific Measured
Design Siting Direction control Reduction of s tray fields Screening Enclosures Distance Safe systems of work Instructions Training
Sunbeds (Regulation)Act 2010
Persons in control of sunbeds
Must ensure not used(or offered for use)to persons under 18
Enforced by Local Authority
Fine on conviction
Control of Artificial Optical Radiation at Work Regulations (CAORR) 2010
Light emitted from all artificial sources i.e. light in all its forms such as ultraviolet, infrared and laser beams , but excluding sunlight
CAORWR -No Action (List1)
Ceiling-mounted and task lighting Photocopiers Computers and PDAs Remote control devices Photographic flash lamps – when used singly Gas -fired overhead heaters Vehicle lights Class 1 lasers e.g. laser printers and bar code scanners
CAORWR - Action Required (List 2)
Welding (both arc and oxy-fuel) and plasma cutting
UV fluorescence and sterilisation systems
Furnaces
UV curing of inks , paints and welding
Laser surgery, blue light and
UV therapies
Class 3 Band Class 4 lasers
Search lights and professional projection systems
Risk Assessment to Consider
The level, wavelength and duration of exposure
Employees particularly at risk
Interactions between radiation and photos ensitising chemical substances , and from multiple sources of exposure Information from health surveillance
Manufacturers and published information
The availability of alternative equipment
The Exposure Limit Values
CAORWR -ELV
Exposure Limit Values (differ for different wavelengths )
If RA suggests levels to exceed these limits , employer must produce action plan
Demarcation, restrict access and signage
Information, instruction and training
Health surveillance
Ionising Radiation - Basic Information
Sufficient energy to cause ionisation
Ion:
Atom or molecule that has gained or lost an electron Cause production of ions in body tissues
Subsequently cause damage to biological molecules
Types of Ionis ing Radiation
Particulate: Alpha particles Beta particles Neutrons Electromagnetic radiation: X rays Gamma rays
Radionuclides
Chemicals that emit radiation Unstable
Electromagnetic or particulate Occurs spontaneously
Us ually identified by name and
mas s no. e.g. radon-222
An atom changes identity as it decays (e.g. radon-222/polonium-218) U n i t o f d e c a y ; t h e B e c q u e r e l (B q ) = 1 trans formation per s ec
Alpha Particles
2 neutrons + 2 protons Releas ed by radionuclides Alpha emitters: Americium-241, Plutonium-236, Uranium-238, Polonium-210 Uses: Smoke alarms , s tatic eliminators Penetration: L o w, a b s o r b e d b y p a p e r
Beta Particles
High s peed electrons Releas ed by radionuclides Beta emitters: Carbon-14, Tritium, Iodine-131 Uses: Thickness gauges,medical Penetration: Medium, abs orbed by pers pex/aluminium
Free Neutrons
Neutron:
Sub atomic particle with neutral charge
Emitted by radionuclides e.g. Californium-252 and by nuclear reactors Uses:
Crystallography
Caus es materials (e.g. containers ) to become radioactive and have ionising effects
Very penetrative
Abs orbed by hydrogen rich material e.g. water, concrete
Gamma Rays
Electromagnetic radiation: High energy Produced by radionuclides Gamma emitters: Cobalt-60, Caes ium-137 Uses: Cancer treatment, fill level, NDT, thicknes s gauges Penetration: Highly penetrative - s topped only by dens e metals e.g. Lead
X-Rays
Electromagnetic radiation:
High energy (les s than gamma)
Generated electronically us ing high voltage electricity High s peed electrons interact with s olid materials
Uses:
Radiography, crys tallography
Penetration:
Highly penetrative - s topped only by dens e metals e.g. Lead
Half-life
Time taken for an atom to
dis integrate to half of its original energy
Units of Radiation
Becquerel (Bq) - no. dis integrations per s econd (amount of radioactivity at source)
Gray (Gy) - unit of abs orbed dos e (dos e of 1 Gray when 1 Joule of energy is absorbed by 1 Kg of tissue)
Sievert (Sv) - dos e equivalent; gives relative harmful effects (Grays x Quality Factor) (biological ris k of expos ure)
Sieverts
Sievert (Sv) - dos e equivalent, gives relative harmful effects (Grays x Quality Factor)
Gamma, X-rays x1
Thermal neutrons x5
Beta x1
Fas t neutrons x20
Alpha particles x20
This means alpha particles are 20x more ionis ing/harmful than gamma and X-rays
Doserates -Sieverts perunittime
Ionis ing Radiation Regulations - dos erates in milis ieverts (mSv)per year
Biological Effects
Erythema, burns Naus ea, vomiting, fatigue Weight los s , haemorrhage, hair los s Radiation s icknes s Cancer Cataract
Stochas tic Effects
Probability of effect is proportional to the initiating caus e (dos e received)
Increas ing dos e will increas e likelihood but not s everity Cancer induction
Hereditary effects