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PSC 4010 Nuclear Technology: A matter of Energy
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PSC 4010: Chapter 5 Goals: _ SWBAT compare the A-bomb and the H-bomb (components, power, nuclear reaction, effects) _SWBAT compare nuclear power stations with thermal and hydroelectric ones _SWBAT describe the operation of a CANDU nuclear reactor _SWBAT compare the technology used in CANDU reactors with that used in other countries _SWBAT describe the use of radioactivity in medicine, food irradiation and C-14 dating _ SWBAT compare advantages and disadvantages (and difficulties) of using nuclear fission or fusion to produce electricity
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PSC 4010: Chapter 5 Introduction (p. 5.3): Uses for nuclear energy Medicine Electrical generation Military (bombs, submarines, spaceships)
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PSC 4010: Chapter 5 Atomic bomb (A-bomb) (p. 5.4 – 5.8): First tested, and then used (Hiroshima & Nagasaki) in 1945 Uses nuclear fission Easily fissionable isotopes (U-235 or Pu-239) as fuel for chain reaction Critical mass: minimum amount of radioactive matter which produces stable number of fissions over time Amount of fissionable material can be calculated (more than critical mass, uncontrollable chain reaction; less, chain reaction does not sustain itself in time)
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PSC 4010: Chapter 5 Atomic bomb (A-bomb) (p. 5.4 – 5.8): Fissionable material is separated into two blocks, each with mass < critical mass. These block are propelled against each other with the detonation of an explosive (dynamite). The mass of both blocks exceeds critical mass, so chain reaction is uncontrolled Power of A-bomb is equivalent to 20 000 tons of TNT
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PSC 4010: Chapter 5 Atomic bomb (A-bomb) (p. 5.4 – 5.8): Four aspects (consequences) of A-bomb explosion: 1.Direct radiation (billion of small bullets shot at you, made of all 3 types, alpha, beta, gamma) 2.Extremely high temperatures 3.Blast of air (can destroy buildings or dismember animals and human beings) 4.Contamination of dust
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PSC 4010: Chapter 5 Nuclear changes: Practice Exercise Page 5.6, Ex. 5.1 & 5.2 Page 5.8, Ex 5.4
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PSC 4010: Chapter 5 Hydrogen bomb (H-bomb) (p. 5.9 – 5.13): First tested in 1952 Uses nuclear fusion Temperature at center of explosion is 5 times that of center of Sun! (Fig. 5.3, p. 5.9) Thermonuclear bomb (high temperatures needed : millions of degrees) Using Deuterium and Tritium (H isotopes) can lower T needed Needs an atomic bomb (nuclear fission) to provide energy for detonation!
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PSC 4010: Chapter 5 Hydrogen bomb (H-bomb) (p. 5.9 – 5.13): Use dynamite to trigger nuclear fission (A-bomb) Then use temperature and energy from A-bomb to detonate H-bomb (Figure 5.4, p. 5.11) Fusion of uranium in A-bomb releases neutrons that collide with lithium, and transform it to tritium Tritium then fuses with deuterium to form helium, releasing SPECTACULARLY LARGE amounts of energy (and neutrons) No critical mass, therefore no limits of explosive power of H-bomb Energy produced (fusion) is 3 to 3.5 times that of A- bomb (fission)
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PSC 4010: Chapter 5 Nuclear changes: Practice Exercise Page 5.13, Ex. 5.8 & 5.9
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PSC 4010: Chapter 5 Use of Nuclear Fission to produce electricity: (p. 5.13 – 5.17): History 1945 Atomic Energy of Canada Limited (Ontario) 1955 Canada Energy Program selected principles for CANDU (nuclear reactor) 1962 first experimental reactor started producing electricity (Ontario) 1972 first Canadian nuclear station (Pickering One)
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PSC 4010: Chapter 5 Use of Nuclear Fission to produce electricity: (p. 5.13 – 5.17): Production Electrical generator (force into electricity) Turbine moved by pressurized steam Figs. 5.5 & 5.6 (pp. 5.14, 5.15) Diagrams of power stations Fig 5.8, p. 5.16: 0.5 kg coal, 1.5 kW/h 0.5 kg gas, 2.0 kW/h 0.5 kg uranium, 30 000 kW/h
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PSC 4010: Chapter 5 Use of Nuclear Fission to produce electricity: (p. 5.13 – 5.17): Operation Nuclear fission Uranium (natural or enriched) arranged in rods or bundles (mass below critical to avoid chain reaction) Cadmium rods are inserted in core of reactor (control rods: absorb neutrons produced which will slow down chain reaction) Coolant: heats water and turns it into steam (at boiler), which is latter used to move turbine
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PSC 4010: Chapter 5 Use of Nuclear Fission to produce electricity: (p. 5.13 – 5.17): Operation In Canada, coolant is heavy water (D 2 O, made of Deuterium instead of Hydrogen). It also has the ability to act as moderator, slowing neutrons ejected by core of reactor In other countries, coolant is ordinary water or gas Heat after being absorbed by coolant is transported to Boiler (big water reservoir) Boiler, produces pressurized steam (large T and P) that is sent to rotate the turbine, which is connected to a generator, thus producing the electricity
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PSC 4010: Chapter 5 Use of Nuclear Fission to produce electricity: (p. 5.13 – 5.17): Operation Steam is then cooled down back to water in a condenser, using cold water pumped from outside source Water is sent to reactor afterwards for new cycle (closed circuit, minimum environment contact) Fuel bundles are changed during operation, in order to work continuously
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PSC 4010: Chapter 5 Power plants comparison: HydroelectricThermalNuclear CondenserNAYes E producedPotential Energy (Water) Chemical Change *operates with coal *contributes to acid rain Nuclear Change Pollution / WasteNAYes TurbineYes BoilerNAYes CoolantNA Yes Steam to move turbine NAYes
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PSC 4010: Chapter 5 CANDU Reactor (p. 5.18 – 5.20): CANada, Deuterium, Uranium Use Cadmium control rods (slow chain reaction) Use Heavy Water (coolant and moderator / to slow neutrons) Use natural uranium (nuclear waste, as old ones are replaced by new ones) (*States use enriched uranium) Work continuously (no interruptions)
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PSC 4010: Chapter 5 *Enriched uranium due to higher capacity of ordinary water to absorb neutrons. Thus, higher proportion of U-235 improves fission probability *No containment shell (Cherbnobyl, Ukraine), Containment shell (Three Mile Islan, PA, USA) Reactor Component CanadaUSAUK (England) Russia FuelNatural Uranium Enriched Uranium* ModeratorHeavy WaterOrdinary Water Graphite CoolantHeavy WaterOrdinary Water Pressurized Gas Ordinary Water
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PSC 4010: Chapter 5 Nuclear changes: Practice Exercise Page 5.20, Ex. 5.14 - 5.16 Page 5.24, Ex 5.17 & 5.19
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PSC 4010: Chapter 5 Slowpoke reactor (p. 5.21): Miniature nuclear reactor (12 m high) Household of water with reactor inside Produces up to 12 MW and 9 liters of waste per year of use
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PSC 4010: Chapter 5 Medical applications (p. 5.25 – 5.28): Destruction of cancerous cells Co-60 destroys tumors ( γ rays), breaks down genetic material _rotate to minimize affectation _many treatments to minimize overdose
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PSC 4010: Chapter 5 Medical applications (p. 5.25 – 5.28): Tracers Detecting rate of absorption of radioactive tracers by an organ, can show proper functioning of said organ (Figure 5.11, p. 5.26) Must have short half-life to minimize body exposure
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PSC 4010: Chapter 5 Food irradiation (p. 5.29 – 5.30): Co-60 radiations kills microorganisms that can cause food decay Food does NOT become radioactive (advantage Changes chemical composition of food, therefore changes it nutritional value (disadvantage)
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PSC 4010: Chapter 5 Nuclear changes: Practice Exercise Page 5.30, Ex 5.24 & 5.25
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PSC 4010: Chapter 5 Other uses of Nuclear Energy (p. 5.30 – 5.32): Carbon-14 dating _While alive, beings absorb C-12 & C-14 in same ratio _Once dead, C-12 stays, C-14 decays (half life = 5730 years) _C-12/C-14 ratio tells us age of dead tissues
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PSC 4010: Chapter 5 Nuclear changes: Practice Exercise Page 5.31, Ex 5.27
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PSC 4010: Chapter 5 Other uses of Nuclear Energy (p. 5.30 – 5.32): Submarines _To produce electricity and move propels of submarines _To produce water (electrolysis)
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PSC 4010: Chapter 5 Other uses of Nuclear Energy (p. 5.30 – 5.32): Spaceships, cargo planes, boats _To power cargo planes and boats _To power spaceships
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PSC 4010: Chapter 5 Use of Nuclear Fusion to produce electricity (p. 5.33 – 5.38): Sun _Natural fusion reactor (hydrogen atoms fuse to deuterium, which fuses with hydrogen to turn into tritium, which fuses with deuterium to form helium) _Earths uses very little of sun’s energy produced, still enough for our needs _Nuclear fusion brings about “Plasma” (4 th state of matter)
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PSC 4010: Chapter 5 Use of Nuclear Fusion to produce electricity (p. 5.33 – 5.38): Energy associated with fusion (Advantages) _Fusion produces 3 times the energy of Fission for same amount of initial material _No risk of uncontrolled reaction for fusion requires constant heat _Cheap and abundant fuel (deuterium is easily found in sea water) _Process releases very little radiation Energy associated with fusion (Disadvantages) _Temperatures needed are too high (millions of degrees). No material can withstand heat without melting (use of magnetic fields to contained lab-generated nuclear fusion material)
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PSC 4010: Chapter 5 The Tokamak fusion reactor: 1.Very strong electric currents (heat up plasma in middle of contained magnetic field) 2.Fusion is forced as T and P rise inside reactor 3.Energy produced boils water into steam and this moves turbines to generate electricity *UK (1991) first ever experimental fusion reactor (two minutes, 1 million Watts worth of energy!)
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PSC 4010: Chapter 5 Practice Exercises for Chapter 5: Page 5.41 – 5.43 – Ex 5.34 – 5.45
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