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Energy resources, Nuclear Power and Radioactivity


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Energy resources, Nuclear Power and Radioactivity

  1. 1. Natural ResourcesAnything humans use from the Earth is a natural resource. A renewable resource is one which can be replaced at the same rate at which it is used. Most renewable energy comes from the sun. In this unit we will look first at how the sunproduces its energy, and then how it is recycledinto renewable energy sources and fossil fuels.
  2. 2. Where does the Sun Get Its Energy?
  3. 3. What is it?The sun has a power of 4*1026 Watts. -- what fraction of the suns energy is needed to meet Japans extra energy needs (to replace the nuclear power)?“The Earth receives more energy from the sun in one hour than the worlds population uses in a year.”Why is this misleading (but true)?
  4. 4. 1. Write nuclide + + +symbols for each atom. 2. How many different elements are + + + ++ ++ + + ++ + shown? + 3. How many + + + + + isotopes of carbon are there? ____
  5. 5. Isotopes of Hydrogen + + +Hydrogen Deuterium Tritium
  6. 6. What happened to the Electrons? These atoms usually have electrons, and inchemistry these electrons form and break bonds. + e- e- +
  7. 7. What happened to the Electrons? These atoms usually have electrons, and inchemistry these electrons form and break bonds. + e- e- +
  8. 8. e- + e- e- + e- + ++ ++ e- + + + e- e- - e e- e-
  9. 9. e- + e- e- + e- + ++ ++ e- + + + e - e- - e e- e-
  10. 10. Everything Reaction We See isAround Us is Chemistry (electrons) e- e-e- e- e-
  11. 11. Nuclear Physics Nuclear physics is the study of what happensinside atoms. Electrons orbiting the nuclei do not matter in nuclear physics. e- e- + e- ++ ++ ++ + e- e- - e e - e-
  12. 12. Nuclear FusionNuclear fusion is the joining of atoms together into larger atoms. It gives even more energy than nuclear fission (used in nuclear reactors). Nuclear fusion requires enormous heat and pressure to occur. Nuclear fusion powers the sun.Unfortunately, it requires so much heat it can not yet be controlled to produce useful energy onEarth, but it is being developed.“Nuclear fusion is 50 years away and always will be.”
  13. 13. Mass into Energy In nuclear reactions matter is converted into energy. E = energy m = mass lost c = the speed of light = 3 * 108m/sCalculate the energy which would be released if one kilogram was converted to energy.
  14. 14. Animation
  15. 15. Nuclear Fusion Start: Number species Mass (individual) Mass (total) proton 1.672621777 ×10−27 kg End: proton Helium-4 6.64465675 ×10−27 kg Total mass the percentage lost
  16. 16. Experimental Fusion ReactorIt is hoped that fusion will provide energy in the future. Itprovides much more power than fission, and (apart from the reactor itself) no nuclear waste. There is plenty of deuterium and tritium in seawater – enough for thousands of years. It does not cause environmental problems extracting it (unlike mining uranium).It is impossible to build up the pressure that exists in the sun, but scientists can suspend the gas in a Tokomakand heat it to extremely high temperatures, but it cannot be sustained for long enough (yet) to produce power. “Fusion power is 50 years away and always will be.”
  17. 17.
  18. 18. GEKKO XII laser (Osaka)
  19. 19. Nuclear Fusion in WarfareThe temperature and pressure required for nuclear fusion have been created momentarily by using a nuclear explosion to compress hydrogen. This is known as a hydrogen bomb.The first H-bomb test was “Ivy Mike”, soon followed by Castle Bravo on Bikini Atoll. This caused the largest nuclear fallout caused by the US, including the islands inhabitants and the Daiko Fukuryu Maru.When Bravo was detonated, it formed a fireball almost four and a half miles (roughly 7 km) across within a second. This fireball was visible on Kwajalein atoll over 250 miles (450 km) away. The explosion left a crater 6,500 feet (2,000 m) in diameter and 250 feet (75 m) in depth. The mushroom cloud reached a height of 47,000 feet (14 km) and a diameter of 7 miles (11 km) in about a minute; it then reached a height of 130,000 feet (40 km) and 62 miles (100 km) in diameter in less than 10 minutes and was expanding at more than 100 m/s (360 km/h, 224 mph). As a result of the blast, the cloud contaminated more than seven thousand square miles of the surrounding Pacific Ocean including some of the surrounding small islands like Rongerik, Rongelap and Utirik. - WIKIPEDIA
  20. 20. Daigo Fukuryū Maru
  21. 21. The Blast (from the DFM)The sky on the west lit up like a sunrise. Eight minutes later the sound of the explosion arrived, with fallout several hours later. The fallout, fine white flaky dust of calcined coral with absorbed highly radioactive fission products, fell on the ship for three hours. The fishermen scooped it into bags with their bare hands. The dust stuck to surfaces, bodies and hair; after the radiation sickness symptoms appeared, the fishermen called it shi no hai ( 死の灰 ?, death ash). The US government refused to disclose its composition due to "national security", as the isotopic ratios, namely percentage of uranium-237, could reveal the nature of the bomb. --Wikipedia
  22. 22. Wind Power Wind is small but growing source of electricity. Once installed, wind turbines do minimal environmental harm. They can kill or harm birds.Some people dislike them because they claim they are noisy or unpleasant to look at. Wind turbines can be placed onshore (on land) oroffshore. Offshore is more expensive, but produces more wind. Wind technology is growing rapidly.
  23. 23. Fukushima Wind Farm Wikipedia
  24. 24. Solar EnergyEnough energy reaches the sun to power our energy needs. However, converting it to electricity is difficult and expensive, but it is being developed.Photovoltaic solar panels means converting light energy to electricity. The Japanese government buys electricity from solar panels at a higher price than normal to encourage people to install them.Rooftop installations do not require more land, but space is limited and installation can be difficult and potentially dangerous.
  25. 25. Waldpolenz Solar Park, Germany - Wikipedia
  26. 26. Solar FarmsMost solar farms use large arrays of photovoltaic solar panels.They produce DC, which must be converted to AC for a national grid.The energy is free and renewable, however the production of solar panels is energy-intensive.The power output is low, and inconsistent.
  27. 27. Solar Trackers A solar tracker can be used to follow the sun through the sky, to minimise the angle of incidence. The extra power output covers more than the use of the motor (so the power per square meter increases) but the installation costs increase.
  28. 28. Concentrated Solar PowerConcentrated Solar Power uses mirrors to focus sunlight to produce heat.The heat usually boils water, and the steam turns a turbine just as in a thermal power station.The power output per square metre is lower, but it is much cheaper to produce.
  29. 29.
  30. 30. Solar Water Heating Solar water heating is more efficient than making electricity, and could be used much more widely in Japan, especially in the south. It is much more efficient to use sunlight to heat water directly than it is to use it to produce electricity and use that to heat water.
  31. 31. Biomass is growing fuel to be burned. BiomassIt is renewable, clean and safe,however it requires a lot of time to grow the fuel. Biofuel is like solar energy, assun is needed to grow the fuel,and the plants are like batteries. Increasing use of biomass is increasing the prices of food around the world, with devastating consequences for the third world – why?
  32. 32. Geothermal EnergyGeothermal energy uses heat from within the Earth to produce heat or electricity. It is a clean, renewable energy source, but is only available in some areas. If too much is used, it runs out of heat.Geothermal heat comes from heat generatedwhen the Earth formed and radioactive decay inside the Earth.
  33. 33. Hydroelectric Power
  34. 34. HydroelectricityHydroelectricity is clean and renewable, and very reliable if a good dam is built.Building a dam usually has disastrous effects on the local ecosystem.Dams can run out of water if there is not enoughrain. It is also possible for them to run in reverse and pump water uphill, making a ‘battery’.
  35. 35. Banqiao Dam Banqiao Dam is a huge dam in China. It was built to survive a ‘1000 year flood’.It’s power stations produced 18GW, as much electricity as 20 nuclear reactors, or over half of Japans loss due to closure of its nuclear power plants.
  36. 36. Dam Collapse In 1975 a ‘one in two thousand years’ floodoccurred, producing record levels of rain. Banqiao Dam collapsed. The flood waters were 10km wide and 3-7 high, and wiped out an area of 55km. Official reports say 26 000 died in the flood and 145 000 from resulting disease and famine, but unofficial reports claim up to 230 000.
  37. 37. Quick ReviewHow does the sun produce its energy? How is this different to combustion of hydrogen (eg the pop test. You should explain Einsteins famous equation and how it applies here.Could the power (from Q1) be used to produce energy on Earth? Explain.Explain the difference between solar photovoltaics and solar water heating.What are biofuels and why does their increasing use cause devastation in the third world?Explain how hydropower has caused more deaths than any other type of electricity production.
  38. 38. Wave PowerWave power uses energy from waves to produce electricity.The technology is still being developed, but has potential to generate a lot of electricity (6kW/m).It is very weather dependent.
  39. 39. Tidal PowerTides are caused by the orbit of the moon.Tidal power has much potential but is currently not used much.Tides are predictable, unlike other renewables.Tidal stream generators are like wind turbines under water, which are turned by flowing water.Tidal barrages dam an enclosed area of water (eg harbour) and capture energy of water flowing over the dam as the water level drops.
  40. 40.
  41. 41. Renewable Energy SourcesEnergy Source How does the Energy Advantages Disadvantages Come from the Sun? Solar (photovoltaic) Concentrated Solar PowerWind TurbinesHydroelectricity BiofuelWave generation Tidal power
  42. 42. Atom The word atom means indivisible.Indivisible means it cant be broken down into more things. Why not? Is this true for atoms?
  43. 43. John Dalton John Dalton was a British schoolteacher. He said that atoms: 1. Everything is made of atoms.2. Atoms of the same element are exactly alike, and atoms of different elements are different.3. Atoms join with different atoms to make new substances.
  44. 44. J .J . Thomson J. J. Thomson was another British scientist. In 1887 he discovered electrons.
  45. 45. Plum Pudding Model J J Thompson suggested that electrons were mixed up in theatoms like raisins in a plum pudding.
  46. 46. Earnest RutherfordEarnest Rutherford was from Christchurch. A good image to describe his experiment can be found here:
  47. 47. Rutherfords Conclusions 1. The atom is mostly empty space.2. There is a small, dense, nucleus at the centre of the atom.The illustration showed that if an atom was the size of a sports stadium, the nucleus (protons and neutrons) would be the size of a pinhead in the centre, and all the rest is empty space. The alpha particles which travelled throughundeflected showed that it is mostly empty space. The alpha particles which were deflected or bounced back showed that the nucleus must be dense and charged.
  48. 48. Bohrs ModelBohr (Danish) improved Rutherfords Model by discovering that there are energy levels for electrons. Electrons can only be at set energy levels. They are like rungs on a ladder. A good diagram can be found here:
  49. 49. RadioactivityMost small atoms are ‘stable’. They stay together. Sometimes forces inside large atoms ‘push eachother away’ or change their form very quickly. This is known as radioactivity. 241 95 Am
  50. 50. Beta RadiationSome atoms emit beta radiation. A beta particle is an electron which comes from the nucleus. Aneutron becomes a proton and emits an electron.
  51. 51. Beta Decay of Iodine 131 131 0 53 I −− Xe   54 −11. Copy and complete the equation to show what Carbon-14 decays to when it undergoes beta decay. 14 6 C
  52. 52. Bananas"Food is radioactive, Bananas more so than most foods due to their high Potassium content. About 0.01% of Potassium is K-40, which undergoes beta decay. Writean equation for potassium undergoing beta decay. What does it become and is this harmful?" 40 19 K
  53. 53. Gamma Rays Gama rays are electromagnetic radiation with a low wavelength/high frequency. They are usually emitted with alpha and beta particles.
  54. 54.
  55. 55. Ionising Radiation and DNAAlpha particles stop at paper (or skin) so are harmless outside the body. Beta and Gama radiation can be more harmful."If an alpha emitting radionuclide gets inside us (typically by breathing it in or consuming it) it is much more dangerous than if it is outside us because when it is inside us there is nothing to stop the alpha particles from colliding with our DNA""When an alpha particle (or any other ionising radiation) strikes an atom in our body, it knocks of some of its electrons. That atom then participates in a chemical reaction that normally wouldnt take place in order to get enough electrons to be in a stable chemical configuration. If these abnormal chemical reactions happen in DNA
  56. 56. Half Life After one half life: 1. Half the remaining atoms will have decayed.2. The activity (number decaying per second) will halve. Americium-241 has a half life of 432 years. Potassium-40 has a half life of 1.3 billion years. Iodine-131 has a half life of 8 days. http://www.avon-
  57. 57. Use the first two simulations Half Life and answer the following: 1.What percentage of theoriginal atoms of carbon-14 oruranium-238 are left after onehalf life? Two half lives? Three half lives? 2. “God does not play dice” -Albert Einstein.Was he correct?  3. Why is the computer game 10B*called “Half-life” and what does the term refer to in the game?
  58. 58. Penetration
  59. 59. PenetrationAlpha particles can only travel a few centimetres in air, then they ionise the air and stop. They can be stopped by a piece of paper or skin.Beta particles can travel through paper but are stopped by a thin sheet of aluminium.Gamma rays are very penetrating, but their intensity can be reduced by thick concrete or lead.
  60. 60. Background RadiationWe naturally receive a small amount of radiation. Air, water, soil and food all naturally contain radioactive isotopes. We also receive radiation from the sun.The level of background radiation is different for different parts of the world. More radiation is received closer to the north and south pole. Radiation in Tokyo is still much lower than in many other cities around the world. Why?
  61. 61. Detection of RadiationA Geiger-Muller tube can detect nuclear radiation. It can be connected to:A ratemeter, which tells the number of counts per second. This may be converted to more user-friendly units.An electronic counter, which counts the total number of particles detected by the tube.An amplifier and a loudspeaker, which makes a sound each time it detects a burst of radiation.The “Air counter - S” is a device for sale locally (~6000 Yen at Yodobashi and pharmacies). It gives counts in microsieverts per hour. 10B*
  62. 62. Air Counter - S
  63. 63. Contaminated Food & WaterSpinach, milk and other foods from around Fukushima were found tocontain 7.5 times the safety limit for Iodine-131. Iodine 131 has a half life of 8 days.1) How long will it take for the radiation levels to drop to the allowed limit? EITHER give an approximate answer, or use logs. 2) What does Iodine-131 decay to? Is this safe to eat/drink? 3) Is it possible to save the spinach? How about the milk? How?4) Cesium-137 has a half life of 30 years. Is it possible to save food contaminated with Cesium?5) Traces of Iodine were found in Tokyos drinking water, above thelimit for babies. Why was it not necessary for residents to buy many months worth of bottled water (assuming the nuclear plant stopped leaking Iiodine-131)?
  64. 64. BookworkPages 185, 187, 189, 193 and 195. For question 3 on page 193, draw it to the standards expected by IGCSE Paper 6 exams. 10B* We will do these during the first class after Spring Break.
  65. 65. Irradiation of FoodFood can be irradiated with gamma rays, though the process is controversial.The food is not radioactive.Microorganisms are killed, so the food lasts longer and is less likely to cause food poisoning.Seeds are killed, so they will not germinate during storage.It may change some complex chemicals in the food and destroy important vitamins in the it.
  66. 66. Radioactive TracersIf doctors need to measure how or how quickly a certain liquid passes through the body (eg how quickly iodine is moved to the thyroid gland) a gamma emitter is chosen (why?) and introduced into the body.Its movement in the body can be followed by measuring the number of gamma rays emitted from different parts of the body (eg the thyroid).Radioactive isotopes with short half-lives are used for these purposes – why?
  67. 67. Osteoperosis diagnosis using a radioactive tracer
  68. 68. RadiotherapyRadiotherapy is the use of gamma rays to penetrate into the body to kill cancer cells.The gamma rays can be focussed very precisely to target the cancer cells, however some other (healthy) tissue will also be affected, and this may cause further cancer in future. g
  69. 69. Nuclear FissionNuclear fission is breaking apart large atoms into small atoms. It occurs in nuclear reactors and nuclear bombs. The smaller atoms created are radioactive, meaning the give off radiation.Nuclear energy releases enormous amounts ofenergy: one kilogram of uranium yields as much energy as 2000 Tonnes of coal.
  70. 70. Nuclear FissionSome large atoms can be broken up into smalleratoms if a neutron hits them. This releases more neutrons which can cause more atoms to split, making a chain reaction.
  71. 71. Density Normally, the density of atoms is too small so theneutrons just escape and no nuclear reaction occurs.
  72. 72. Simulation
  73. 73.
  74. 74. In a nuclear power plant, a moderator is used to slow down the neutrons so that they can make more atomssplit. The more moderator there is, the faster the reaction. "Control rods absorb neutrons to slow or stop the nuclear reaction. If the control rods are in too far, more neutronsare absorbed than are released and the reaction slows. If the control rods are out too far, the reaction builds exponentially as more and more neutrons are released than are absorbed - in old reactors, this can cause thereactor to overheat which can lead to a "meltdown" and or a steam explosion.
  75. 75. Example Try This: And then play this: Try to get as much power generated as possible.
  76. 76. Chernobyl AccidentChernobyl is an abandoned cityin the Ukraine, formerly Russia. The Chernobyl nuclear power station suffered a steam explosion (which blew the top ofthe reactor and the roof off of the building) which was followed a few seconds later by a second explosion of approximately 40 GJ.
  77. 77. The Effects of Chernobyl"The Chernobyl nuclear accident resulted in under 100 direct deaths – mostly workers at the plant and "liquidators" – but about 4000 extra cancer deaths can be expected over time due to the radioactive contamination of the environment. Many of these could have been prevented if the government had given people stable iodine and promptly evacuated them from the contaminated area."
  78. 78. The Fukushima Nuclear Power PlantsModern nuclear power plants are designed to automatically shut down in an earthquake. Many fission products are still radioactive, so they give out heat even after the reactor has been shut down. This heat must be removed fromthe fuel rods with cooling water otherwise they will melt down. Electricity is required to pump the water. The power station was stuck by a tsunami stronger than designed for. This cut off external power and drowned the backup generators. The emergency battery power supply was able to keep the cooling waterpumps running for 8 hours but unfortunately another source of electricitywas not made available before the batteries were completely discharged. Some new nuclear reactors are designed to use passive means likeconvection, conduction and infra-red radiation to remove decay heat from fuel rods without the need for electricity to run cooling water pumps.
  79. 79. CNN Animation
  80. 80. Why Fukushima Isnt Chernobyl The Chernobyl reactor was being used at the time itexploded, so much more radiation was being produced and released during the explosion. The Chernobyl reactor exploded. The Fukushima reactor(like all in the developed world) has a “containment vessel” around it which should keep most of the dangerous radionuclides inside it. The Japanese government is testing food and tellingeveryone what has happened. The Russian didnt want to admit what had happened, so they didnt do necessary safety measures. Thousands of cases of thyroid cancer could have been prevented by giving out iodine.