B7-RADIATION Flashcards
State the two main categories of non-ionising radiation.
Optical radiation and electromagnetic fields (or radiofrequencies).
Suggest five broad regions of the electromagnetic spectrum that can be used to classify non ionising radiation.
Ultraviolet
Visable
Infrared
Microwave
Radiowave.
What is the source of beta radiation and what is it used for.
Its results from the radioactive decay of certain radioactive substances or radionuclides. Beta radiation is used in many applications, such as medical and biological research and in thickness gauges.
What is the difference between gamma radiation and x-rays.
Gamma radiation originates in the nucleus of am atom
Xrays originate in the atoms electron layers surrounding the nucleus. Gamma-rays are naturally produced during radioactive decay of radionuclides
Xrays are artificially produced by an xray generator (or set). (Historically, gamma rays and xrays were simply differentiated by wavelength. This can be a little misreading, however, so it is the way that they are produced that determines their radiation type.)
What are the hazards of exposure to ultraviolet radiation.
- Acute effects, such as sunburn and arc eye (photokeratitus).
- Chronic effects, such as premature ageing of the skin, skin cancer (melanoma) and cataracts.
- Indirect effects, such as photosensitisation and the formation of toxic contaminants
What are the hazards of microwave radiation and how can harmful exposure be controlled.
Biological harm is caused by the process of heating. Certain tissues, such as the lens of the eye, have poor or non existent blood supplies and a poor capacity for temperature control by heat transfer. It is such tissue which is most at risk from microwave exposure, since only a relatively small temperature increase is needed to damage call proteins.
To control exposure to microwave radiation, the system should be enclosed in a metal structure
Access doors should be introduced by fail safe means
Panels not interlocked should be secured by fasteners that require special tools for their release.
Alternatively, microvaves emitters, such as antennae, must be of low power or positioned so that people cannot come close enough to the emitter to recieve a significant dose of radiation (above the ELV). When close approach is required (such as during maintenance work on mobile phone masts), the antenna must be isolated and locked off to prevent accidental power up.
Describe the framework or approach for control of exposure to non ionising radiation.
The framework or approach for control of exposure to non ionising radiation:
- Eliminate as far as possible - explore alternative technology’s.
- Other working methods that reduce the risk - administrative controls for routine operation, maintenance, etc. (Also permits)
- Choose equipment emitting less radiation (depends on work).
- Technical measures to reduce the emission of radiation, e.g. interlocks, shielding, enclosures, screens etc.
- Maintenance.
- Design, siting and layout of workplaces and workstations - control over directions, stray fields/reflections (by painting surfaces matt black), etc.
- Limit duration and level/intensity of exposure, e.g. time, distance (except lasers where distance doesnt work)
- PPE, e.g. eye protection.
- Follow manufacturer instructions.
- Signs
Outline the general requirements of the control of artificial optical radiation at work regulations 2010 (AOR).
- Carry out a risk assessment where there is a reasonably foreseeable health risk to the eyes or skin of employees exposed to artificial option radiation (unless the risk had already been eliminated or reduce by other means).
- Eliminate or control exposure to artificial optical radiation to as low level as reasonably practicable and below any exposure limit value.
- Provide information and training to employees.
- Provide health surveillance and medical examinations by a doctor or occupational health professional.
Explain the following terms.
- Half Life
- Activity
- Absorbed dose
- Equivalent dose
Half-life is the time required for one of a quality of radionuclide to disintegrate.
The activity of a quantity of radionuclide is given by the rate at which it decays (measured in Becquerels (Bq) or disintegrations per second).
Absorbed dose is a measure of energy deposited by the radiation (expressed in a unit called the Gray (Gy)).
The equivalent dose (measured in Sieverts (Sv)) gives a measure of the likely biological damage damage resulting from radiation exposure, taking into account the type of radiation involved.
What is the difference between stochastic and non stochastic effects.
- Stochastic effects are those that can occur after any level of exposure and are essentially random and unpredictable.
- Non-stochastic effects are those that are dose-dependent and only occur if the dose recieved is above a certain level, they are therefore predictable.
For each type of ionising radiation, give an example of its use or application in the workplace.
Alpha radiation: in the nuclear industry, static eliminators and smoke detectors.
Beta particles: in medical research, thickness gauges.
X-rays: medical use, security scanning, in chemistry for crystallography.
Gamma-rays: in industrial radiography (as a form of non-destruction testing), radiotherapy treatment.
Neutrons: in the nuclear industry, research applications
What is the principal instrument used to detect and quantify radiation.
Thermo-luminescent dosimeters.
What is the difference between exposure to external radiation and exposure to internal radiation.
External radiation, which arises from outside the body, may irradiate skin, tissue or internal organs, depending on the type of radiation and the ability to penetrate the body.
Internal radiation stems from radioactive materials deposited in the body by inhalation, ingestion, injection or absorbion through the skin, which are continually irradiating internal organs and tissues from within.
Outline the three principles of radiation protection.
Time - by reducing the time for a particular dose rate, the accumulated dose is reduced.
Distance - the intensity of all radiation is reduced by the distance travelled.
Shielding - the absorbion of radiation energy by interaction with a dense medium.
Describe the classification system for lasers based on relative hazard potential.
The classification system for lasers:
- Class 1 is considered safe under reasonably foreseeable use.
- Class 1M is similar to Class 1, but the beam is not safe id viewed with the aid of magnifying optical instruments.
- Class 1C is for contact application to skin such as in cosmetic skin treatments.
Class 2 (for lasers emitting in the visable range) - low power devices - eye protection is normally afforded by the aversion response and the blink reflex of the eye.
Class 2M is similar to Class 2, but beam is not safe if viewed with the aid of magnifying optical instruments.
Class 3R laser products limited to maxium output power of 5mW - these can potentially cause eye injury.
Class 3B laser products limited to a maxium output power of 500mW - these are considered hazardous to the eye, both directly and reflections.
Class 4 high-powered devices (>500mW) - they are hazardous to eyes and skin and can cause fires.
