Radioactivity

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Physics SPM Form 5
Chapter : Radioactivity

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Radioactivity

  1. 1. RADIOACTIVITY BY : AIN NADHIRAH BINTI MAZDI FAIZAL MUHAMMAD NURARIF BIN SULEIMAN MUHAMMAD ARIQ BIN ISMAIL 5 AL-BIRUNI
  2. 2. INTRODUCTIONIN 1896, BEQUEREL, A FRENCH PHYSICIST DISCOVERED THAT CRYSTALS OF URANIUM SALTS EMITTED PENETRATING RAYS SIMILAR TO X-RAYS WHICH COULD FOG PHOTOGRAPHIC PLATES. TWO YEARS AFTER THIS PIERRE AND MARIE CURRIE DISCOVERED OTHER ELEMENTS: POLONIUM AND RADIUM WHICH HAD THIS PROPERTY. THE EMISSION WAS KNOWN AS RADIOACTIVITY. The Stability of Nuclei Protons and Netrons are held together in the nucleus of an atom by the strong-force. This force acts over a very short distance of about ~1 fm, (10-15m) and over this short distance it can overcome the electromagnetic repulsion between the positively charged protons. Nuclei with radii that are within the range of the Strong force are stable. As atomic number increases the radius of the nucleus also increases and the element becomes unstable. This instablity manifests itself as the emission of particles or energy from the nucleus. The elements with atomic number greater than 82 are radioactive. Radioactivity is the spontaneous and randomemission of radioactive rays from unstable radioactive materials to become more stable material.
  3. 3. PROPERTIES OF RADIOISOTOPES • EMITS RADIOACTIVE RADIATION. • RADIOACTIVE RADIATIONS CAN KILL CELLS. • RADIOACTIVE RADIATIONS HAVE DIFFERENT PENETRATINGABILITY WITH MATERIALS OF DIFFERENT THICKNESS AND DENSITIES. • RADIOACTIVE RADIATIONS CAN CAUSE CELL MUTATION. • RADIOACTIVE RADIATIONS CAN IONISE MOLECULES. • ITS ACTIVITY DECREASES WITH TIME. • RADIOISOTOPES HAVE THE SAME CHEMICAL PROPERTIES AS NON-RADIOACTIVE ISOTOPES OF THE SAME ELEMENT.
  4. 4. APPLICATIONS OF RADIOISOTOPES
  5. 5. To diagnose of thyroid disease using iodine-123 To treat an overactive thyroid gland and certain kinds of thyroid cancer by using sodium iodide labelled with radioactive iodine To detect position of blood clots or thrombosis using Sodium-24 injected in the bloodstream
  6. 6. To detect and treat brain tumor using phosphorus-32 To study the circulation of iron in the blood using iron-59 To sterilise medical equipments and to destroy cancer cells in radiotherapy radioisotope cobalt- 60 is used
  7. 7. Pests can be killed using radioactive rays esp using gamma rays To stop pests from reproducing, induced mutation by using gamma rays can be employed. But this has the probability of producing GMO and resistant pests
  8. 8. To be used as tracers in the effectiveness of fertilisers using nitrogen- 15 and phosphorus -32 To induce genetic mutation in a plant in order to produce a better strain which has higher resistance against pest and diseases
  9. 9. C-14 is another radioactive isotope that decays to C-12. This isotope is found in all living organisms. Once an organism dies, the C-14 begins to decay. The half-life of C-14, however, is only 5,730 years. Because of its short half-life, the number of C- 14 isotopes in a sample is negligible after about 50,000 years, making it impossible to use for dating older samples. C-14 is used often in dating artifacts from humans. For determining age of fossils older than 60,000 years one uses a potassium-argon dating technique. Potassium dating has a half life of 1.3 billion years, thus allowing the age of rocks several billions years old to be determined. A more accurate "argon-argon" dating technique (determining the ratio between argon-39 and argon-40) has also been developed.
  10. 10. To measure geological time. During the formation of rocks, some radioisotopes such as uranium-238 are trapped. As the decay continues, the proportion of uranium-238 decreases slowly resulting in the equally slow growth of its product lead-206. An estimate of the age of the rock can be inferred from the relative proportions of lead and uranium in the rock.
  11. 11. 1. The thickness of paper, plastics, clothes and metal sheets need to be standardised and this is done by placing a raioactive source at one side of the material and a detector on the other side. 2. For sheets of metal, gamma ray is used. For plastics, clothes and paper, beta particles are used. 3. The detector will register a higher count if the material is too thin and lower register if too thick. The computer will make adjustments according to the thickness of the material.
  12. 12. This mechanism is also used to ensure that containers such as cans and food packages are filled to the specified amount. Radioisotope is added to engine oil so that its level of wear and tear can be determined. In order to kill germs that cause food to spoil quickly, gamma rays are used. If exposed to gamma ray, latex becomes harder without the need for adding sulphur.
  13. 13. Nuclear Fission -most commonly used form of NP -U235 is a special Isotope of the normal (inactive) U231 -Neutron collides with atom of U235 -atom splits into Krypton and Barium plus ENERGY 235U + 1 neutron →→ 2 neutrons + 92Kr + 142Ba + ENERGY -fission of one U235 atom yields Seven million times the energy of Exploding one TNT molecule -control rods absorb neutrons -controlling the reaction -Supercritical reaction- resulting # neutrons > 1 -the reaction builds up
  14. 14. Supercritical Reaction Additional Neutrons create a chain reaction, which is controlled by the control rods . Control Rods
  15. 15. Breeder Reactors -The Breeder Reaction produces fissionable (weapons grade) Plutonium239 from unfissionable U238 -U239 becomes Neptunium -Neptunium becomes Plutonium239 that is available for fission with Exposure to neutron -BR- also fission reaction, but using different fuel. Instead of fissioning U235, BR manipulates U238 into Pu239
  16. 16. How is nuclear fission turned into electrical energy? • Powered by fission (primarily uranium-235) • Fission heats water to steam • Steam spins turbine, using dynamo effect to generate electricity • Steam circulated through cooling container; waste water from cooling container exhausted into rivers A little more detail… • Fission rate controlled by (control) rods called moderators or nuclear poisons • Moderators absorb or slow neutrons and thus mediate reaction • Moderators can be used to stop all fission, if necessary (replace fuel or in case of danger) • Some reactors use either a liquid metal (sodium, potassium) or gas (carbon dioxide, helium) as heat exchange element.
  17. 17. DIAGRAM OF NUCLEAR PLANT
  18. 18. PROS AND CONS OF USING NUCLEAR FISSION TO GENERATE ELECTRICITY Pros: •Environmentally, nuclear power has very little impact: *does not depend on fossil fuels→ the carbon dioxide emission is minimal. *Coal and natural gas power plants emit large amounts of carbon dioxide into the atmosphere which contributes to ozone problems, acid rain, and global warming. • Relatively inexpensive: *Uranium is less expensive than oil, natural gas, or coal. *Leads to lower energy cost for the consumer •Because it does not depend on fossil fuels, fluctuations in oil and gas prices do not affect its supply. •Reliability: *Nuclear power plants produce large amount of power on a consistent basis
  19. 19. Cons: • Waste: *Each nuclear power plant generates, on average, 20 metric tons of high-level radioactive waste which takes tens of thousands of years to decay to safe radioactive levels. Plants also produce low level radioactive waste which still takes thousands of years to decay. • Costs: *Expensive to store, monitor, and guard the large amounts of waste so that it doesn’t fall into the wrong hands, as waste may be used in the production of nuclear weapons. •The more power plants that are built, the higher the probability that some sort of breakdown in security would occur somewhere in the world. •Nuclear power is not a renewable energy resource. The energy source of nuclear power is Uranium, which is scarce, as its supply is estimated to only last for the next 30-60 years depending on demand.
  20. 20. NEGATIVE EFFECTS OF RADIOACTIVE SUBSTANCES Radioactive substances emit radiations that are harmful to living things. This is due to the ionisation and penetrating properties of these radiations. As the radiations pass through living cells, they ionise the neighbouring atoms or molecules. The reactive ions that are produced will i. Interfere with the chemical processes in the cell. ii. Induce mutations in the genetic structure of the cell. At the same time, the radiations might kill the cell in body tissues. If there are far too many cells that were destroyed, the organism may die.
  21. 21. The amount of damage inflicted to humans depends on the types of radiation, dosage and exposure period, methods of insertion into the body and location of exposure. i. Types of radiation - Alpha particles outside the body are harmless because they can be stopped by the human skin. ii. Dosage and exposure - Exposure to high dosage of radiation in a short period of time results in immediate symptoms such as vomitting, increase in body temperature, blood composition change and many more. iii. Methods of insertion into the body - The internal part of human body can be damaged by alpha particle that were ingested through food or inhaled through air, this is due to the high ionising effect of Alpha particles. iv. Cells that are actively dividing are more vulnerable to radiations. Skin cells in general can withstand higher dosage of radiation compared to the other internal organ.
  22. 22. The harmful effects of radiation on humans can be divided into two categories which can be categorised as Somatic effect or Genetic effect. i. Somatic effect: includes damage to all parts of the body except the reproductive organs. Symptoms include: fatigue, vomiting, hair loss, infertility in male, severe skin burn and leukemia or cataracts (which may arise after a long period of time). ii. Genetic effect: includes damage to reproductive cells. Genetic defect can be passed down to the next generations. Examples of genetic defects include Down Syndrome, Klinefelter Syndrome, Turner Syndrome.
  23. 23. PRECAUTIONARY STEPS IN HANDLING RADIOACTIVE SUBSTANCES • Experiments that involves radioactive substances are conducted in a room surrounded by concrete walls. • Strong radioactive substances are handled using remote-controlled mechanical arms from a safe distance. • Weak radioactive substances could be handled by using tweezers. • Radioactive wastes must be disposed off by using suitable and safe methods. Rooms, buildings, containers and radioactive storage places must be labelled with the sign for radioactive substance. Radioactive substances are contained in thick lead containers. • Protective suits and gears such as gloves and eye glasses made of lead are used at all times when handling radioactive substances. These shields protect the workers from harmful radiations. • Workers handling radioactive substances must wear special badges which detect the amount of radiation they are exposed to. Food and drinks are not allowed in places where radioactive substances are handled. tweezers thick lead containers Protective suits
  24. 24. PROPER MANAGEMENT OF RADIOACTIVE WASTE Low level radioactive wastes Sources: Hospitals, nuclear power stations, industries, research laboratories. Examples: Contaminated equipments, shoes, biohazard suit, clothing, wrappers, air filters, gloves, etc. Half-life: 10-50 years Radioactivity level: low Management: Solid wastes are stored Intermediate level radioactive wastes Sources: Nuclear power stations, industries, research laboratories Examples: Component in nuclear reactors, chemical sediments Half life: long Radioactivity level: High Management: Radioactive wastes are placed in concrete block and then buried underground
  25. 25. High level radioactive wastes Sources: Nuclear power stations Examples: Fuel rods used in nuclear power stations Half life: 100 000 years or more Radioactivity level: High Management: Fuel rods are submerged in a pool of water to cool them down. The rods are then stored in a steel container which are buried underground at a depth of between 500m and 600m, dispose in ocean or mountain carvens Deep Ocean Disposal • The waste is placed in borosilicate glass containers • These containers are made to be unbreakable – dumped into the deepest and darkest places on earth Deep Geological Burial • Waste is buried in caverns • Away from water sources (under and above ground) • Far from people or other living organisms • Dry climate- not prone to harsh weather conditions • Yucca Mountain, Nevada
  26. 26. VIDEO OF APPLICATIONSSodium-24 - A Radioisotope Hero in Industry Radioisotopes in Medicine

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