SC 8.3

• Radiation

  • Energy transfer process to a medium or space, that occurs in the form of waves or particle
  • The wave form electromagnet waves while particles are charged particles and non-charge particles
  • Electromagnetic radiation comprises of ionising rays and non-ionising rays
• Non-ionising radiation

  • Refers to any less energised electromagnet rays that cannot ionises atom or molecule
  • Does not have sufficient energy to break the molecule bond and ionise atoms
  • Generally, radiation and particle energy or photon energy that is less than 10 eV are categorised as non-ionising
  • Radiation frequency : 100 - 100^15 Hz
  • The radiation lies at the end of the electron spectrum
  • Example : radio waves, microwaves, lasers, visible light, infrared
• Non-ionising radiation

  • Penetration of non-ionising radiation into tissue is not deep but is able to cause hazard to skin and eyes
  • Depending on the energy and time of exposure, this radiaion can cause global warming or photochemical reaction that leaves permanent damage
  • For instance, skin that is overly exposed to sunlight for a long period of time will result in sunburn
  • Thus, exposure to non-ionising radiation should be reduced
• Ionising radiation

  • Electromagnetic rays that have enough energy to ionise atoms or molecules
  • The radiation has enough energy to break the electronic bonds of atom or molecule thus forming ions
  • Example
  • Alpha particles, beta particles, gamma rays, X-rays, neutrons, near and far ulraviolet rays
• Characteristic of alpha particles

  • Helium nucleus
  • Positively charge
  • high ionising power
  • Penetration power is low (can be block by paper)
  • Small deflection to negative plate in electric field
  • Small deflection to south in magnetic field
  • 10% speed of light
• Characteristic of beta particles

  • electron
  • Negatively charge
  • Moderate ionising power
  • Penetration power is moderate (can be block by 3 mm thick aluminium)
  • Big deflection to positive plate in electric field
  • Big deflection in magnetic field
  • 99% speed of light
• Characteristic of gamma ray

  • Electromagnetic wave
  • No charge (Neutral)
  • Low ionising power
  • Penetration power is high (can be block by 10 cm thick lead or a thick wall of concrete)
  • No deflection in electric field
  • No deflection in magnetic field
  • Speed of light
• Sources of ionising radiation in the environment

  1. Natural resources
  2. Galatic cosmic rays
  3. Background radaition
  4. Earth radiation
  5. radon
  6. sunlight
  7. internal ray
  8. Man-made resources
  9. Nuclear accidents
  10. Nuclear test
  11. Use of radioisotopes for medicine
  12. background radiation
  13. Consumer goods
• Cosmic ray (Natural)

  • a form of high-energy radiation mainly originating outside the Solar System and even from distant or other galaxies
  • Also known as galatic cosmic rays
  • Upon impact with the Earth's atmosphere, cosmic rays can produce showers of secondary particles that sometimes reach the surface
  • The dosage of cosmic ray on aeroplane is very high. Airline staff receives an average dosage that's higher tahn other staff including workers at nuclear plant
• Earth radiation (Natural)

  • Most thing on Earth have some radioactive atoms
  • These are rays that come from walls and floors of house, water, rock and soil
  • Some rays are absorbed or eaten by animals and plants
  • causing animals and plants to store ionising radiation
  • Main radionuclide for Earth rays - potassium, uranium, thorium
  • In Malaysia, content of uranium and natural thorium is in the range of 49 - 86 Bq
• Radon (Natural)

  • An odourless and colourless gas that escapes from soil, rock, well and structural objects like brick and concrete
  • It become saturated in a tightly-closed background ray dosage
  • Main contributor for background ray dosage
• Sunlight (Natural)

  • Sun produce infrared rays, visible light and ultraviolet rays
  • Only ultraviolet rays is harmful
  • Overexposure to this ray will cause premature skin aging and the sun rays are known to cause skin cancer
• Internal radiation (Natural)

  • Produced by the human body especially from potassium-40 that is already stored in body and obtained from food consumed
  • Dosage of radiation : very low compared to other ionising radiation
• Nuclear energy (Man-made)

  • Vastly used to generate electricity at nuclear plants
  • Radioactive waste from nuclear plants cause plant workers and surrounding residents to be affected by its ionising radiation
  • Whatever safety precaution is take, mishaps in nuclear plants are inescapable
  • Such accidents can happen because of human errors
  • Nuclear accidents in Fukushima, Japan that released a huge amount of radioactive waste into the environment
• Nuclear energy (Man-made)

  • Radioactive waste is absorbed by land and aquatic plants
  • harm humans who consume the polluted plants and animals
  • Nuclear energy experiments - released ionising radiation into the environment
• Medical procedure (Man-made)

  • Medical procedure like X-rays,CAT scan and radiation therapy release radioisotopes
  • Patients are directly exposed to radiation when they undergo procedures like diagnostics for broken / fracture bones, X-rays for dental check-ups, CAT scan and nuclear medication as well as radiation therapy
• Application of radioisotopes in medicine

  1. Cobalt-60
  2. Radiotherapy to prevent cancer
  3. Iodine-131
  4. locate brain tumors, monitor cardiac, liver and thyroid activity
  5. Carbon-14
  6. Study metabolism changes for patients with diabetes, gout and anemia
  7. Carbon-11
  8. Tagged onto glucose to monitor organs during a PET (Position Emission Tomography)
  9. Sodium-24
  10. study blood circulation
  11. Thallium-201
  12. Determine damage in heart tissue, detection of tumors
• Application of radioisotopes in medicine

  1. Technetium-99m
  2. Locates brain tumor and damaged heart cells, radiotracer in medical diagnostics (Imaging of organs and blood flow studies)
  3. Most widely used radioactive pharmaceutical for diagnostic studies in nuclear medicine. Different chemical forms are used for brain, bone, liver, spleen and kidney imaging
  4. Uranium-234
  5. Used in dental fixtures to provide a natural colour and brightness
  6. Xenon-133
  7. used in nuclear medicine for lung ventilation and blood flow studies
• Unit of dose rate measurement for background radiation

  • Ionising radiation that is absorbed into human body will damage body cell
  • The biological effect from ionising radiation on human body is measured in a quantity known as dose (measured by dosimeter / Geiger counter)
  • A dose of 1 Sievert (Sv) = 1 joule of ionising radiation energy that is absorbed by 1 kg of living tissue
  • Unit of background radiation that is commonly used is microSievert/Hour (µSv/h)
  • Safe dose in daily life : less than 0.2 µSv/h
• Consumer goods (Man-made)

  • Direct radiation is obtained from consumer goods like tobacco, construction items, fossil fuels, television, radio ophthalmic glass, moblie phones and lit watches
• Estimation dose of ionising radiation

  1. TV / computer : Ionising radiation 0.1 mSv/h
  2. X-ray : 5.5 mSv/ medical test
  3. Building : radioactive radiation 1.5 mSv/year
  4. Food : radioactive radiation 0.1-0.5 mSv/year
  5. environment : background radiation 0.4- 1.0 mSv/year
  6. Flight : cosmic rays 0.003 mSv/h
  7. High altitude : cosmic ray 0.3-0.5 mSv/year
  8. Outer space: cosmic rays 0.35mSv/year
• Risk of ionising ray

  • expose to high dose rays
  • functions of body cells can be affected
  • disrupt blood system by reducing the lymphocyte cell
  • results in illness of a person
  • nausea, vomit, loss of appetite and lethargic body
  • internal bleeding, infertility and malignant tumours
  • Low dose rays
  • headaches, vomit, diarrhoea
  • Kills healthy cell and cause cell mutation
  • negative effects can be inherited by the next generation
  • pregnant women must avoid radioactive exposure - cause disability or foetal death
• Risk of ionising ray

  1. Radioactive waste that pollutes rivers, soil and air cause death in aquatic organism and makes the soil unsuitable for living things to live
  2. these dangerous wastes are also transferred in many plants and animal through food chains
• Safety measure

  • Background radiation
  • Use appropriate protective equipment such as spectacles fitted with anti-ultraviolet film, anti-ultraviolet umbrellas and others
  • Taking X-ray
  • Taken with doctor's prescription
  • Television
  • Ensure the distance between the television and the viewer is at least 2 m
  • Food contaminated with radioactive substances
  • Do not eat food produced in areas contaminated with radioactive substances such as fish from the sea contaminated with radioactive substances
• Safety measure

  • Cosmic rays
  • Working hours of a pilot are limited to a certain period of time because the pilot is exposed to cosmic rays