核技術(shù)導(dǎo)論英文課件：Chapter 4 Nuclear Power

1、Chapter 4. Nuclear PowerIntroductionCharacteristics of Fission General Features Commercial Reactors Nuclear Reactor Safety Nuclear Reactor Accidents Uranium MiningKey elements: fuel, neutron moderator, control rod, neutron detector and radioactivity detectors, productsSource: IEA (2007)DeliveryConst

2、ruction times for nuclear plants Global average66 months in mid-1970s 116 months (nearly 10y) in late 1990s82 months (nearly 7y) during 2001-05EnergyEstimate the energy released by the fission of 1.0 kg of 235U. (3.15e-11 J) 1000 g = 8.06e13 J (per kg). DiscussionThis is a large amount of energy, an

3、d it is equivalent to the energy produced by burning tones of coal or oil. 1 mol235 g6.023e231 mol235U92 142Nd60 + 90Zr40 + 3 n + QQ = (235.043924 - 141.907719 - 89.904703 - 3x1.008665) = 0.205503 amu (931.4812 MeV/1 amu) = 191.4 MeV per fission(1.6022e-13 J / 1 MeV) = 3.15e-11 J This amount of ener

4、gy is equivalent to 2.21010 kilowatt-hour, or 22 giga-watt-hour. This amount of energy keeps a 100-watt light bulb lit for 25,000 years.2. Characteristics of Fission 7Fission Energy BudgetKinetic energy of fission fragmentsPrompt ( 106 s) gamma () ray energyKinetic energy of fission neutronsGamma ()

5、 ray energy from fission productsBeta () decay energy of fission productsEnergy as antineutrinos (ve)168 MeV757812Energy (MeV) distribution in fission reactionsThe total and fission cross section for 235U based on NJOY-processed ENDF/B (version V) data.Neutron interactionsThe fast fission cross sect

6、ion for three fissionable uranium isotopes based on NJOY processed ENDF/B (version V) data10The Cyclotron and Fission ResearchThreshold* Energy range (keV)Reactionenergy(keV) narrow-energy neutron51V (p, n) 51Cr2909 5.6-5245Sc (p, n) 45Ti1564 2.36-78657Fe (p, n) 57Co1648 2-1425_* The threshold energ

7、y is the minimum energy of proton required for the reaction.Neutrons of desirable energy is required for fission research.Nuclear Fission11The Cyclotron and Fission ResearchFor neutron sources from the cyclotron, energy can be varied.Energy dependence of neutron induced fission studied.The cross sec

8、tion data enabled nuclear reactor design. fast neutrons - 10 MeV to 10 KeV) slow neutrons - 0.03 to 0.001 eV for neutron induced fissionChapter 4. Power From FissionIntroductionCharacteristics of Fission General Features Commercial Reactors Nuclear Reactor Safety Nuclear Reactor Accidents Key elemen

9、ts: fuel, neutron moderator, control rod, neutron detector and radioactivity detectors, productsSimplified schematic layout of a typical reactor power plant.3.1 A nuclear power plantControl rods, containing neutron-absorbing elements (boron or cadmium)pressure vessels must be capable of withstanding

10、 internal pressures up to 160 bar.A biological shield, normally several feet of concrete, surrounds the entire system. Its purpose is to attenuate the intensity and neutron radiations to levels that are safe for humans outside the plantThe coolant is pumped through the core inside the pressure vesse

11、l and through heat exchangers outside, where steam is generated and used to drive turbines for generating electric power. Core: The melting point of uranium is 1403 K, The melting point of UO2 is 3138 KOptimizing the designf is a decreasing function and p an increasing function of moderator-to-fuel

12、ratio NM / NFUranium graphite assembliesDiffusion lengththe root-mean-square distance a neutron will diffuse in the medium before being absorbedDiffusion and slowing-down constants for moderators.R, The reaction probability per unit time for N nuclei; M is the mass of fissile materialif each fission

13、 liberates an amount E of recoverable energy, the power output isReactor power and fuel consumptionexamplecalculate the power output, rating and fuel consumption for athermal reactor containing 150 tonnes of natural uranium operating with a neutron flux of energy per fission E = 200 MeV3.4 MW/tFuel

14、consumption, leading to a loss of 235U, depends on the total 235U absorption cross section= 5.9 x 1026 /yearone-fifth of the initial amount of 235Urefueling Chapter 4. Power From FissionIntroductionCharacteristics of Fission General Features Commercial Reactors Nuclear Reactor Safety Nuclear Reactor

15、 Accidents Uranium Mining Key elements: fuel, neutron moderator, control rod, neutron detector and radioactivity detectors, productsKey Reactor Power TermsAvailability Fraction of time over a reporting period that the plant is operationalIf a reactor is down for maintenance 1 week and refueling(補(bǔ)給燃料

16、） 2 weeks every year, the availability factor of the reactor would be(365-3 * 7) / 365 = 0.94Key Reactor Power TermsCapacity Fraction of total electric power that could be producedIf reactor with a maximum thermal power rating of 1000 MWt only operates at 900 MWt, the capacity factor would be 0.90Ef

17、ficiency Electrical energy output per thermal energy output of the reactorEff=W/QR (MWe/MWt) 33%Carnot efficiency,A source of steam is used to produce electricityThe inlet temperature islimited by the water/steam pressure rating of the boiler or reactor vessel in a steam cycle, or by the temperature

18、 limitation of the turbine blades in a direct-fired gasturbine.The outlet temperature is usually limited by the ambient temperature ofthe cooling water used in the condenser of a steam cycle 4. Commercial Reactors Piecing Together a ReactorFuelModeratorControl RodsCoolantSteam GeneratorTurbine/Gener

19、atorPumpsHeat ExchangerSimplified schematic layout of a typical reactor power plantBasic Diagram of a PWR (Pressurized Water Reactor)/two water loops: The water in the primary loop is pumped through the reactor to remove the thermal energy. The loop 2,water is converted to high temperature and high

20、pressure steam that turns the turbo-generator unit. The great disadvantage of water as a coolant: must remain in liquid form, steam is a much poorer coolant than liquid water.must be pressurized to prevent boiling at high temperatures(15.5 MPa).For water, the critical temperature is 375 C, above whi

21、ch liquid water cannot exist. Typically, coolant temperatures are limited to about 340 C.Advantage: small(nature U?)The steam cycle of a pressurized water reactor. Westinghouse Electric Corp.It is about 13 meters tallwith a diameter of about 4 to 6 m. The vessel is built from low-alloy carbon steela

22、nd has a wall thickness of about 23 cmThe primary coolant enters the vessel throughtwo or more inlet nozzles, flows downward between the vessel and core barrelParameters for a typical 1000 MW(e) PWR sold in the early 1970s.Boiling-water reactora pressurized-water reactorwater is allowed to boilself-

23、stabilizing behavioura direct-cycle, boiling-water reactorBreeder Reactor增值反應(yīng)堆The uranium cycle breeder reactors require fast neutrons. Liquid metal and steam may be used as coolants for fast breedingCANDU reactorReactor GenerationsGen IPrototypes in 50s & 60sGen II70s & 80sTodays Operational Reacto

24、rsBWR, PWR, CANDU, Gen IIIABWR, APWRApproved 90sSome Built around the WorldGen III+Current Advanced Designs in the Approval ProcessPebble Bed ReactorGen IVDeploy in 2030EconomicalSafeMinimize WasteReduce ProliferationWorld Nuclear Power443 Nuclear Reactors in 30 Countries in Operation, January 2006P

25、rovided 16% World Production of Energy in 200324 Nuclear Power Plants under ConstructionAlternativesRenewable energyWindBioenergySolarHydroWaveTidalGeothermalEnergy efficiencyCombined heat & power (CHP)Building insulationEfficient lightingEfficient appliancesEfficient vehiclesControlling demandBehav

26、iour changeCarbon capture and storageburial of carbon from fossil fuelsSource: IEA (2001)AlternativesRenewable energyWindBioenergySolarHydroWaveTidalGeothermalEnergy efficiencyCombined heat & power (CHP)Building insulationEfficient lightingEfficient appliancesEfficient vehiclesControlling demandBeha

27、viour changeCarbon capture and storageburial of carbon from fossil fuelsChapter 4. Power From FissionIntroductionCharacteristics of Fission General features Commercial Reactors Nuclear Reactor Safety Nuclear Reactor Accidents Key elements: fuel, neutron moderator, control rod, neutron detector and r

28、adioactivity detectors, productsWhat is the Public Hazard?chemical?biological?physical?radiological?psychological?Chlorine for water treatmentNoneNuclear explosion impossibleSmall risk of delayed effects, very small risk of promptChernobyl, Fukushima, nuclear testsWhat Is the Goal of Reactor Safety?

29、To prevent prompt effects with a high degree of assurance and minimize the risk of delayed effectsTypicallyfrequency of a large release 10-6 per reactor-yearfrequency of a core melt (intact containment) 10-5 per yearCareful, cautious, scrupulous!8. Nuclear Reactor Accidents Safety Public remains war

30、y of nuclear power due to Chernobyl and three mile island accidentsNuclear plants vulnerable to terrorist attacksSafer, more efficient, and more secure plants planned for the futureChapter 4. Power From FissionIntroductionCharacteristics of Fission The Chain Reaction in a Thermal Fission The Finite

31、Reactor Reactor Operation Commercial Reactors Nuclear Reactor Safety Nuclear Reactor Accidents Key elements: fuel, neutron moderator, control rod, neutron detector and radioactivity detectors, productsThree Mile IsleMarch 28, 1979, 4:00 amSecondary cooling loop stops pumping. Rising temperatures cau

32、sed emergency valve to open to release pressure, but indicator light malfunctionedDue to loss of steam, water level drops, water overheats and burns out pumpReactor core overheats and begins to melt (a “meltdown”)March 28, 1979, 6:30 amOverheated water contains 350 times normal level of melted down

33、radioactive matterA worker sees the open valve and closes itTo prevent an explosion, he reopens it, releasing radioactive steam into the atmosphereMarch 28, 1979, 8:00 amNuclear Regulatory commission is notifiedWhite House is notifiedTMI is evacuatedAll small children and pregnant women within a fiv

34、e mile radius are evacuatedA fifteen-year clean up project awaitsNo Nukes Words: Pat DeCou, Music: Tex LaMountain, 1977, ASCAPLook across the sky from your home, Can you see the tower blinking while you sit a spell at home?Can you see the branches growing? Can you feel the awesome power?Can you sens

35、e its evil purpose and its doom?It grows in ways we all can understand, And its limbs are spreading all across the land.The leaves they look like dollars and the sap it aint so sweet.It rests upon the profits hungry people cannot eat.With promises of quiet, comfort, and peace, The hanging tree can l

36、ure to its side.But the darkness of its shadow gives us warning of the greedThat tries to sell us more electric power than we need.No nukes for me, cause I want my air to be Free from radiation poison falling over me.These reactors that theyre building are a giant hanging tree. Dont you build a hang

37、ing tree over me.People soon will stop this money tree, And well stop its hangin people, you and me.And as we struggle all together all the powers that be will go down with their own hanging tree.And out of this struggle we can plant a seedling tree, A tree that lets the sunlight share its space.A t

38、ree in tune with living, whose branches lift the soul, When youre watching from a distance and youre sitting all alone.Uranium MiningThere are three main methods:Underground miningOpen pit miningIn Situ Leaching (ISL)Underground MiningThe Case of the Olympic Dam MineOlympic Dam mine is located in South AustraliaMost of the mines profit actually comes from th