Diese Präsentation wurde erfolgreich gemeldet.
Die SlideShare-Präsentation wird heruntergeladen. ×

OHH 01 Radiation.pptx

Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Anzeige
Nächste SlideShare
injury prevention.ppt
injury prevention.ppt
Wird geladen in …3
×

Hier ansehen

1 von 56 Anzeige

OHH 01 Radiation.pptx

Herunterladen, um offline zu lesen

Radiations classified as ionizing and non-ionizing radiations. ionizing includes ultraviolet, alpha, gamma and x-ray radiations. non-ionizing consists of infrared, microwave, radio wave and power line electromagnetic radiations

Radiations classified as ionizing and non-ionizing radiations. ionizing includes ultraviolet, alpha, gamma and x-ray radiations. non-ionizing consists of infrared, microwave, radio wave and power line electromagnetic radiations

Anzeige
Anzeige

Weitere Verwandte Inhalte

Aktuellste (20)

Anzeige

OHH 01 Radiation.pptx

  1. 1. Radiation Unit-1(Cont.)
  2. 2. • Radiation is the emission or transmission of energy in the form of waves or particles through space or through a material medium. This includes: electromagnetic radiation, such as radio waves, microwaves, infrared, visible light, ultraviolet, x-rays, and gamma radiation (γ) • Forms are Sound, heat or light • Radiation ranges from Radio waves through visible light spectrum and up through to gamma waves. • Radiation hazards in the workplace fall into 2 categories 1. Ionizing 2. Non ionizing INTRODUCTION
  3. 3. I. Ionizing Radiation • Ion is an electrically charged atom • To ionize is to become electrically charged or to change into ions • Ionizing radiation is radiation that becomes electrically charged or changed in to ions • Ionizing radiation includes alpha particle, beta particle, neutrons, X- radiations, Gamma radiation, high speed electrons and high speed protons • Ionizing radiation which is caused by unstable atoms giving off energy to reach more stable state • Health threat to humans because it involves changing the basic makeup of atoms in cells more specifically the DNA molecules inside the cell
  4. 4. 2. Non ionizing Radiation • Non ionizing radiation is described as a series of energy waves composed of oscillating electric and magnetic fields travelling at the speed of light • It includes the spectrum of ultraviolet (UV), visible light, infrared(IR), microwave(MW), radio frequency (RF), and Extremely low frequency (ELF) • Non ionizing radiations are found in a wide range • Harmful to human ,may leads to cancer and damage DNA
  5. 5. Terms in Radiation 1. Radiation: Consist of energetic nuclear particles and includes alpha rays beta rays and gamma rays X-rays neutrons high speed electrons high-speed protons 2. Radio active materials: emits radiations as the result of spontaneous nuclear disintegration. 3. Restricted area: any area to which access is restricted in an attempt to protect employees from exposure to radiation or radioactive materials 4. Dose: is the amount of ionizing radiation absorbed per unit of mass by part of the body or whole body 5. Rad: is a measure of the dose of ionizing radiation absorbed by body tissue stated in terms of the amount of energy absorbed per unit of mass of tissue. 1 Rad equal the absorption of 100 ergs per gram of tissue
  6. 6. 6. Rem : is a measure of the dose of ionizing radiation to body tissue stated in terms of its estimated biological effects relative to a dose of one roentgen(r) 7. Air dose: an instrument measures the air at or near the surface of the body where the highest dosage occurs to determine the level of dose 8. Personal monitoring devices: devices worn or carried by an individual measure radiation doses received. Eg. Film badges, pocket chambers, pocket dosimeter, film rings 9. Radiation area: area in which radiation hazards exist that could deliver doses as follows 1. Within 1 hour- body receives more than 5 millirems 2. Within 5 consecutive days – body receives more than 100 millirems within one hour 10. High radiation area: area in which radiation hazards exist that could deliver in excess of 100 millirems within one hour.
  7. 7. RADIOACTIVITY • Due to nuclear instability, an atom’s nucleus exhibits the phenomenon of Radioactivity. Energy is lost due to radiation that is emitted out of the unstable nucleus of an atom. • Two forces, namely the force of repulsion that is electrostatic and the powerful forces of attraction of the nucleus keep the nucleus together. These two forces are considered extremely strong in the natural environment. • The chance of encountering instability increases as the size of the nucleus increases because the mass of the nucleus becomes a lot when concentrated. • That’s the reason why atoms of Plutonium, Uranium are extremely unstable and undergo the phenomenon of radioactivity. Laws of Radioactivity • Radioactivity is the result of the decay of the nucleus. • The rate of decay of the nucleus is independent of temperature and pressure. • Radioactivity is dependent on the law of conservation of charge. • The physical and chemical properties of the daughter nucleus are different from the mother nucleus. • The emission of energy from radioactivity is always accompanied by alpha, beta, and gamma particles. • The rate of decay of radioactive substances is dependent on the number of atoms that are present at the time.
  8. 8. HALF LIFE IN RADIOACTIVITY • half-life, in radioactivity, the interval of time required for one-half of the atomic nuclei of a radioactive sample to decay (change spontaneously into other nuclear species by emitting particles and energy), or, equivalently, the time interval required for the number of disintegrations per second of a radioactive material to decrease by one-half.
  9. 9. Effects of Long-term Radiation Exposure on the Human Body • The effects of radiation depend on the type, energy, and location of the radiation source, and the length of exposure. As shown in Figure, the average person is exposed to background radiation, including cosmic rays from the sun and radon from uranium in the ground • Radiation from medical exposure, including CAT scans, radioisotope tests, X-rays, and so on; and small amounts of radiation from other human activities, such as airplane flights (which are bombarded by increased numbers of cosmic rays in the upper atmosphere), radioactivity from consumer products, and a variety of radionuclides that enter our bodies when we breathe (for example, carbon-14) or through the food chain (for example, potassium-40, strontium-90, and iodine-131).
  10. 10. • A short-term, sudden dose of a large amount of radiation can cause a wide range of health effects, from changes in blood chemistry to death. Short-term exposure to tens of rems of radiation will likely cause very noticeable symptoms or illness; a dose of about 500 rems is estimated to have a 50% probability of causing the death of the victim within 30 days of exposure. • Exposure to radioactive emissions has a cumulative effect on the body during a person’s lifetime, which is another reason why it is important to avoid any unnecessary exposure to radiation. Health effects of short-term exposure to radiation are shown in Table.
  11. 11. Classification of radiation exposure • There are 2 types of radiation exposure 1. External radiation exposure • It is measured by personnel monitoring devices • Personnel monitoring provides a permanent, legal record of an individual's occupational exposure to radiation. • Types of monitoring devices in use today are pocket dosimeter, film badge, the thermo luminescent dosimeter (TLD), and the optically stimulated luminescent (OSL) dosimeter. 2. Internal radiation exposure • It results when the body is contaminated internally with a radionuclide. • When radioactive materials enter into the body, they are metabolized and distributed to the tissues according to the chemical properties of the elements and compounds in it. • Internally deposited radioactive material can be monitored by measuring the radiation emitted from the body or by measuring the amount of radioactive material contained in the urine or feces. Such monitoring techniques are called bioassays. • Bioassays are required whenever surveys or calculations indicate that an individual has been exposed to concentrations of radioactive material in excess of established limits .
  12. 12. Radiation Detection • There are several methods of detecting radiation, and they are based on physical and chemical effects produced by radiation exposure. • These methods are :- 1. Ionization 2. Photographic effect 3. Luminescence 4. Scintillation
  13. 13. 1. Ionization • The ability of radiation to produce ionization in air is the basis for radiation detection by the ionization chamber. • It consists of an electrode positioned in the middle of a cylinder that contains gas. • When x-rays enter the chamber, they ionize the gas to form negative ions (electrons) and positive ions (positrons). • The electrons are collected by the positively charged rod, while the positive ions are attracted to the negatively charged wall of the cylinder. • The resulting small current from the chamber is subsequently amplified and measured. • The strength of the current is proportional to the radiation intensity
  14. 14. 2. Photographic effect • The photographic effect, which refers to the ability of radiation to blacken photographic films, is the basis of detectors that use film.
  15. 15. 3. Luminescence • Luminescence describes the property by which certain materials emit light when stimulated by a physiological process, a chemical or electrical action, or by heat. • When radiation strikes these materials, the electrons are raised to higher orbital levels. • When they fall back to their original orbital level, light is emitted. • The amount of light emitted is proportional to the radiation intensity. • Lithium fluoride, for example, will emit light when stimulated by heat. • This is the fundamental basis of thermo luminescence dosimetry (TLD), a method used to measure exposure to patients and personnel.
  16. 16. 4. Scintillation • Scintillation refers to a flash of light. • It is a property of certain crystals such as sodium iodide and cesium iodide to absorb radiation and convert it to light. • This light is then directed to a photomultiplier tube, which then converts the light into an electrical pulse. • The size of the pulse is proportional to the light intensity, which is in turn proportional to the energy of the radiation.
  17. 17. Personal monitoring devices • Devices for the measurement of the radiation doses received by individuals working with radiation. • Individuals who regularly work in controlled areas should wear personal dosimeters to have their doses monitored on a regular basis. • Used to verify the effectiveness of radiation control practices in the workplace. • Also used for detecting changes in radiation levels in the workplace and to provide information in the event of accidental exposures. • Four major types of monitoring devices are 1. Film badge 2. Pocket dosimeter 3. Thermo luminescent dosimeter 4. OSL dosimeter
  18. 18. 1. Film badge • Most commonly used device for X and Gamma radiation • It composed of a piece of photographic film and a special film holder • The effect of radiation exposure is darkening the film • The amount of darkening is proportional to the dose absorbed by the film. • Film is placed in light right packet which is placed in the film holder
  19. 19. • Film holder contains various filters (e.g. lead, tin, aluminium, plastic) • Radiation passing through the filters will produce a density distribution on the film. • Based on that distribution energy range and type of radiation can be determined
  20. 20. 2. Pocket dosimeter • Small ion chamber that are read on site type • They are two types (a) Direct reading dosimeter (b) In direct reading dosimeter
  21. 21. (a) Direct reading dosimeter • It consist of a small capacitor in a pen type housing • It is charged before use with a dosimeter charger • Radiation results in a loss of charge and a corresponding deflection of fiber • It contains lens and scale by which the amount of fiber deflection (dose) can easily be determined • Using this personal dose can be determined immediately • Exposure is in milli roentgens or in roentgens
  22. 22. (b) Indirect reading dosimeter • It is also shaped like a pen, but must be read using a charger reader • Charger reader is a voltmeter which is calibrated in roentgens
  23. 23. 3. Thermo luminescent Dosimeters (TLD) • Used for monitoring beta, x-, and gamma radiations • Energy absorbed from the incident radiation excites and ionizes the molecules of the thermo luminescent material • Some of the energy is trapped by impurities or deformations in the material • Energy remains trapped until the material is heated to a high temperature • Once heated, the trapped energy is released as an emission of light • The amount of light emitted is proportional to the energy absorbed within the thermo luminescent material, which is proportional to the radiation dose absorbed • The emitted light is measured with a photomultiplier tube,
  24. 24. 4. OSL dosimeter • Optically stimulated luminescent (OSL) dosimeters are currently the most common type of personnel dosimeter • The basic principle of operation is similar to that of the TLD • Energy absorbed from incident radiation becomes trapped in the material. • However, green laser light, rather than heat, is used to stimulate release of the stored energy. • The trapped energy is emitted as a blue light when it is released, so it can be collected and distinguished from the green incident light. • As with the TLD, the amount of light emitted is proportional to the energy absorbed by the material, which is proportional to the radiation dose absorbed.
  25. 25. Hazards Associated with Particular Radiation 1. Infra Red Radiation Definition: • The Infra Red (IR) spectrum has been classified into the following sub-bands: • Near Infrared (NIR): 780 – 3000 nm • Middle Infrared (MIR): 3000 – 50 000 nm • Far Infrared (FIR): 50 000 – 106 nm. (ISO, 2007) • IR radiation is a by-product of processes involving lighting or heating. • A prime source of IR is the sun • Sources can include any combustion process, furnaces, glassmaking, welding, etc. • IR is used specifically in heating lamps, room heaters and heat sensors • Drying, baking, heating and dehydration of food products. • IR conveyor ovens are used for curing, preheating, drying, soldering, stress relieving and annealing.
  26. 26. • IR can also be used for welding of plastics. • IR is also used for thermal imaging cameras which allow, • fire fighters to make faster searches for victims in structures • find hidden fires in walls • find hot appliances • to identify liquid levels in containers.
  27. 27. Health Effects: • As absorption of IR radiation heats objects, it will clearly heat the human body. • The eye is the organ most vulnerable to excessive IR exposure • It damage the most vulnerable tissues being the cornea and aqueous humour • It raises the overall temperature of the anterior eye. • Long wavelength infrared rays also reach the retina and can cause permanent damage to the delicate photoreceptors – for instance, through sun gazing. • In general excessive exposure to the subcategories of IR can cause: • Erythema MIR and FIR • Pigmentation MIR and FIR • Photo keratitis MIR and FIR • Cataracts NIR (Highest energies) • Retinal burn NIR
  28. 28. Risk Management: • Control of IR is primarily at the design stage – to ensure that the design of IR apparatus minimizes the adventitious emission of IR. • It is achieved through engineering controls such as shielding and failsafe inter-locks. • Routine maintenance of the apparatus to ensure the barriers do not degrade. • Where there are high levels of adventitious IR emissions that cannot be controlled by barriers • There are appropriate personal protective such as reflecting face-shields, glasses or other protective clothing including aprons, gloves and silvered coveralls are required.
  29. 29. 2. Ultraviolet Radiation Definition: • Ultra violet (UV) light is EMR with a wavelength in the range of 100–400 nm and is invisible to the human eye. • While UV light is found naturally in sunlight • It also can be found in workplaces as adventitious emissions associated with electric arcs (eg: from arc welding) & high intensity discharge lights (eg: mercury vapour lamps) • The high energy nature of UV is also utilized in biosafety cabinets to sterilize materials, and in germicidal lamps to disinfect water. • UV can be broken into the following sub-bands: • Near UV : 400-315 nm (UV-A) • Middle UV : 315-280 nm (UV-B) • Far UV : 280-100 nm (UV-C)
  30. 30. • It can be argued that UV is the highest risk, with the highest number of workers exposed and with the highest potential consequence. • The largest category is outdoor workers, particularly the following industries: construction, parks and gardens, lifeguards and rural workers • Solar UV can reach the worker: • Directly from the sun • Scattered from the open sky • Reflected from the environment.
  31. 31. Health effects Acute and sub acute effects: • Acute inflammatory erythema(sunburn) • Pigment darkening and delayed tanning • Epidermal hyperplasia • Desquamation • Immunologic changes Chronic effects • Photo aging • Photocarcinogenesis
  32. 32. • The UV spectrum has many effects, both beneficial and damaging to human health. • Beneficial applications: • used for killing bacteria (useful in medical or dental practices) and it can be used in curing resins or inks. • Exposure to sunlight is necessary to naturally develop vitamin D which is required for healthy bones • Some specific health effects of the different UV bands are: • UV-A Sun tan and pigmentation • UV-B Skin erythema, eye effects of keratitis and cataracts • UV-C Skin cancer.
  33. 33. Risk Management: • Engineering Controls: physical changes to the workplace or work environment e.g. putting up shade‐cloth to protect workers from the sun. • Administrative Controls: actions or behaviors employers and employees can take to reduce to their exposure e.g. do outdoor jobs/tasks earlier in the morning or later in the afternoon (when levels of solar UV are less intense). • Personal Protective Equipment: equipment that employees wear to protect against UV from the sun e.g. sun‐protection clothing that covers as much skin as possible, hats, sunglasses, and sunscreen.
  34. 34. 3. Lasers Definition: • Laser (Light Amplification by Stimulated Emission of Radiation) • devices utilise collimated (low divergence) beams of intense monochromatic, coherent light in the UV, Visible or IR wavelengths. • Lasers are classified according to the wavelength of light generated at their maximum power output. • Lasers are classed according to their safety as follows: • Class 1 – Safe under reasonably foreseeable conditions (including use of optical instruments)(eye is exposed to the direct or specularly reflected laser beam). • Class 1M(Magnifier)- λ in range 302.5 – 4000nm, safe under foreseeable conditions, but may be hazardous if user employs optics within the beam.
  35. 35. • Class 2 – λ in range 400 – 700nm where normal aversion response (blinking) offers adequate protection. • Class 2M (Magnifier) – as for 2 but viewing of output may be more hazardous if user employs optics within the beam • Class 3R (Restricted) – λ in range 302.5 – 106 nm where direct intrabeam viewing is potentially hazardous but risk is lower than 3B • Class 3B – normally hazardous when intrabeam exposure occurs. Viewing diffuse reflections is normally safe • Class 4 – lasers that are capable of producing hazardous diffuse reflections. They may cause skin injuries and could also constitute a fire hazard. Use requires extreme precaution.
  36. 36. • In construction lasers are used in surveying, levelling and alignment activities. • Gas-assisted laser fusion cutting is performed by concentrating the light from a laser onto a surface so that the material melts. • Laser fusion cutting is also used for glass and ceramics, wood, cloth and plastics, and is suited for high speed automation • In surgery, a laser beam can cauterize a wound, repair damaged tissue, or destroy cells under the beam, allowing for cutting through tissue without damaging neighboring cells. • Lasers have been used in place of surgical cutting instruments in various surgeries, including eye surgery, gynecological procedures, and removal of skin marks and excising small tumors. • Lasers are also used in barcode readers, pointers, and a wide range of consumer and industrial applications including CD/DVD players and analytical devices.
  37. 37. Health Effects: • The risks from lasers vary with the wavelength, intensity and duration of the output or length of exposure. • Except for Class 4 lasers, laser radiation is essentially optical with relatively shallow penetration. • The principal risk is normally to the eyes, although body burns may also occur at high power. • The risk may be either by directly viewing the beam, or seeing a reflected beam off a mirrored (specular) surface.
  38. 38. Risk Management: • Laser control measures vary depending on the type of laser being used and the manner of its use with the specific precautions for each class being: • Class 1 – none – provided Class 1 level maintained • Class 2 - Avoid staring into the beam (ie: deliberate viewing), pointing the beam at other people, or directing the beam into areas where other people may be present • Class 3 - Prevent eye exposure to the beam. Guard against unexpected specular reflections (ie: those arising from shiny, mirror-like surfaces) • Class 4 - Prevent eye and skin exposure to the beam, and to diffuse reflections (scattering) of the beam. Protect against beam interaction on flammable or other materials that could cause fire or fume.
  39. 39. Control & prevention 1. Radiation Protection Program • Developing and implementing a radiation protection program is a best practice for protecting workers from ionizing radiation. • A radiation protection program is usually managed by a qualified expert (e.g., health physicist), who is often called a radiation safety officer (RSO) • ALARA stands for As Low As Reasonably Achievable (ALARA). It is a guiding principle in radiation protection used to eliminate radiation doses that have no direct benefit. • Worker training on radiation protection, including health effects associated with ionizing radiation dose, and radiation protection procedures and controls to minimize dose and prevent contamination.
  40. 40. 2. Engineering Controls: Some examples of engineering controls are discussed below, including shielding and interlock systems. • the need for shielding depends on the type and activity of the radiation source • In general, the floors, walls, ceilings, and doors should be built with materials that provide shielding for the desired radiation protection. • Lead shielding may be installed, if appropriate, including leaded glass, sheet lead (e.g., built into walls), pre-fabricated lead-lined drywall or lead-lined plywood, pre-fabricated lead-lined doors and door frames, lead plates, and lead bricks. • A radiation safety interlock system is a device that automatically shuts off or reduces the radiation emission rate from radiation-producing equipment (gamma or X-ray equipment or accelerator).
  41. 41. Radiation protection Principles When it comes to ionizing radiation, remember time, distance, and shielding:
  42. 42. The three basic methods used to reduce the external radiation hazard are time, distance, and shielding. Good radiation protection practices require optimization of these fundamental techniques. A. Time :The amount of radiation an individual accumulates will depend on how long the individual stays in the radiation field, because: Dose (mrem) = Dose Rate (mrem/hr) x Time (hr) Therefore, to limit a person’s dose, one can restrict the time spent in the area. How long a person can stay in an area without exceeding a prescribed limit is called the "stay time" and is calculated from the simple relationship: Stay Time = Dose Rate (mrem/hr)/ Limit (mrem) B. Distance :The amount of radiation an individual receives will also depend on how close the person is to the source
  43. 43. 1. The Inverse Square Law - Point sources of x- and gamma radiation follow the inverse square law, which states that the intensity of the radiation (I) decreases in proportion to the inverse of the distance from the source (d) squared: C. Shielding When reducing the time or increasing the distance may not be possible, one can choose shielding material to reduce the external radiation hazard. The proper material to use depends on the type of radiation and its energy.
  44. 44. 3. Administrative Controls: • Examples of administrative controls include signage, warning systems, and written operating procedures to prevent, reduce, or eliminate radiation exposure.
  45. 45. Personal Protective Equipment • Personal Protective Equipment (PPE) is used to prevent workers from becoming contaminated with radioactive material. • It can be used to prevent skin contamination with particulate radiation (alpha and beta particles) and prevent inhalation of radioactive materials. • Alpha Radiation : • Alpha particles have very low penetrating power, travel only a few centimeters in air, and will not penetrate the dead outer layer of skin. • Shielding is generally not required for alpha particles because external exposure to alpha particles delivers no radiation dose
  46. 46. • When working with liquid sources that contain alpha particles, additional PPE, such as gloves, a lab coat, and safety glasses, may be required to prevent contamination or contact with the eyes. • Beta Radiation • High-energy beta particles can travel several meters in air and can penetrate several millimeters into the skin • For high-energy beta particles, first select adequate shielding with an appropriate thickness of low atomic number (Z<14) materials, such as specialized plastics (e.g., Plexiglas®) or aluminum. • Using safety goggles as PPE can help protect workers' eyes against beta particles as well as provide splash protection for the eyes (preventing potential internal exposure). Gloves and a lab coat may be used to prevent skin contamination.

×