Energy Production Systems Engineering

Transcription

1 Welcome to Energy Production Systems Engineering USF Polytechnic Engineering Session 4: Nuclear Energy & Prime Movers Spring 2011

2 Nuclear Energy Session 4: Nuclear Energy Prime Movers

3 Nuclear Energy

4 PWR Nuclear Energy 4

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6 Nuclear Energy PWR- Primary and secondary loops Primary loop liquid Pressurizer for pressure/temperature control Steam generators transfer heat between loops Reactivity control soluble poison & control rods Control rods top mounted gravity driven\ Three types of SG U tube Horizontal Once through vertical 6

7 Nuclear Energy Operational Function: Remove heat from reactor coolant system and transfer this heat to secondary fluid This creates the steam to drive the turbine 7

8 Nuclear Energy Safety Function: Cool down the reactor coolant system to the point where the Decay Heat Removal System can be placed in service Provides a fission product barrier from RCS to the public Loss of tube integrity creates a loss of two out of the three fission product barriers 8

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10 Nuclear Energy Steam Generator 10

11 Nuclear Energy Steam Generator 11

12 Nuclear Energy Tube integrity tester using eddy currents 12

13 Nuclear Energy Horizontal shell and tube heat exchanger 13

14 Nuclear Energy Vertical, single pass, counter flow, tube-and-shell heat exchangers The OTSGs produce superheated steam at a constant turbine-throttle pressure over the entire power range of the reactor (0-100%) For saturated vs. superheated steam - same energy transfer, less mass needed since enthalpy of SH steam > saturated steam at same pressure 14

15 Nuclear Energy Advantages single pass over U-Tube Steam Generator Produces superheated steam Minimizes turbine size Reduces steam flow Reduced reactor power requirements No steam drum RCS TAVE constant % Constant steam psig improves turbine efficiency Improves response of reactor to load changes 15

16 Nuclear Energy Tubes are monitored closely for wear or damage that could result in RCS to secondary leakage Damaged tubes are Plugged, or Sleeved 16

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18 Tom Blair, P.E. 18

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20 Feedwater Ring Nuclear Energy 20

21 Nuclear Energy Feedwater Nozzle 21

22 Nuclear Energy Emergency Feedwater Nozzle 22

23 Nuclear Energy Emergency Feedwater Nozzle 23

24 Nuclear Energy Pressurized Heavy Water Reactor 24

25 Nuclear Energy PHWR Heavy water = Deuterium LW has more neutron absorption than HW Uses Tubes for flow Moderator & coolant form two loops Online fuel cell replacement Reactivity control online refueling, control rods, or dumping of moderator Name, symbol Neutrons Protons 2 deuterium, H or D

26 Nuclear Energy Pressure Tube Graphite Reactor 26

27 Nuclear Energy PTGR LW cooled, Graphite moderated Direct steam cycle Fuel replacement online Moderator control via control rods 27

28 Nuclear Energy High Temperature Gas Cooled Reactor 28

29 Nuclear Energy HTGCR Graphite moderator, natural circulation air cooled (other gases as well) Primary loop of air or gas No pressurizer needed Uranium carbide spheres Reactivity control via control rods 29

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31 Nuclear Energy Liquid Metal Fast breeder reactor 31

32 Nuclear Energy Fissile Plutonium and fertile Uranium 238U used with fast neutrons No moderator Liquid sodium coolant Reactivity control control rods two sets since breeder reactor 32

33 Nuclear Energy Typical BWR heat cycle 33

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35 Nuclear Energy Safety Barriers 1.Fuel pellets, 2.Cladding, 3.Vessel & primary system 4.Containment structure 35

36 Nuclear Energy Operation of reactor in thermal limits ensures fuel cladding integrity. Nuclear reactor fuel rods are charged with He gas to improve the heat transferred by conduction from the fuel pellets to the cladding 36

37 Nuclear Energy Types of accidents Reactive transients neutron poison changes Overcooling LOCA / LOFA SG Rupture Fuel handling External 37

38 Nuclear Energy Safety systems Reactor trip (RT) Emergency core cooling (ECC) Post accident heat removal (PAHR) Post accident radioactivity removal (PARR) Containment integrity (CI) 38

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40 Nuclear Energy Advanced (next generation) design Passive safety features ECC borated source above reactor vessel gravity fed Natural circulation to remove heat Negative temperature reactivity Improvement in ceramic pellet design 40

41 Nuclear Energy Radiation Units: Quantify amount of radiation Quantify radiation absorbed In US, use Curie, Roentgen, Rad and Rem 41

42 Nuclear Energy CPM/Efficiency = DPM DPM/2.22 x 106 = uci Where CPM = Counts per min with Geiger-Mueller meter DPM = Decays per min uci = micro Curie Depend on geometry & radionuclide energy level Roentgen ionizing Xray / gamma radiation 42

43 Nuclear Energy Rad (radiation absorbed dose) = 100 ergs / gram absorber (SI Gray = 100 rads) Rem (radiation equivalent man) dose equivalent (SI Sievert = 100 rem) 43

44 Nuclear Energy Typical annual exposure levels in millirem: 5 statutory limit on radiation from operating a nuclear power plant 25 internal exposure from radioactive material ingested into the body 45 cosmic rays 75 diagnostic medical exposure (x-rays) 60 external radiation from radioactive ores, etc 44

45 Nuclear Energy Typical annual exposure levels in millirem: 120 natural radiation sources (combined) 200 average total exposure in the U.S. 500 average occupational dose for radiologists 1250 natural exposure in mountainous regions of Brazil 5000 maximum permissible occupational exposure (5 rem) 45

46 Nuclear Energy Consequences of radiation exposure in rem (not millirem!) rem Effect 0-25 No observable effect Slight blood changes Significant temporary reduction in blood platelets and white blood cells Severe blood damage, nausea, hair loss, hemorrhage, death in many cases >600 Death in less than two months for over 80% of people 46

47 Nuclear Energy Radiation damage to tissue not same quality factor (QF) rem dose = rad dose x QF x other modifying factors) Type of radiation X-, gamma, or beta Alpha particles Neutrons of unknown energy High-energy protons Quality factor (QF)

48 Nuclear Energy Other Multiplying factors Alpha = 2 P & 2N, Helium nucleus, very large, blocked by first layer of skin Beta = High energy e-, low mass (low tissue damage), blocked by clothing Gamma = electromagnetic radiation, high energy, low mass (low tissue damage), difficult to shield Neutron = high energy, high mass (high tissue damage) 48

49 The Nuclear Cookie Question You have 4 radioactive cookies -- one an alpha emitter cookie, one a beta emitter cookie, one a gamma emitter cookie, and one neutron emitter cookie. You must eat one, hold one in your hand, put one in your pocket, and the last one you throw away. Which cookie do you eat, which cookie do you hold in your hand, which cookie do you put in your pocket and which cookie do you throw away to minimize your radiation exposure? 49

50 The Nuclear Cookie Question Eat the gamma Cookie little tissue damage, and hard to shield Hold the alpha Cookie in your hand blocked by first layer of skin Put the beta Cookie in your pocket shielded by clothing Throw away the neutron Cookie away high energy, high mass, most tissue damage 50

51 Nuclear Energy Thermo luminescent Dosimeters (TLDs) Modern TLD Dosimeters measure Skin Dose, Eye Dose and Deep Dose, and the dose due to other nuclear particles. 4 TL detectors 51

52 Nuclear Energy Thermo luminescence (TL) - ability of materials convert the energy from radiation to a radiation of a different wavelength. Irradiation stores electronic in higher valence subsequent heating returns electron and releases energy in light form 52

53 Nuclear Energy After readout, TLD annealed to zero Advantages (compared to film dosimeter badges) includes: - Greater range of doses - Easily obtained doses - TLD read on site - Quick turnaround for readout - Reusable Disadvantages - Each dose cannot be read out more than once - The readout process effectively "zeroes" the TLD 53

54 End of Nuclear Energy

55 Prime Movers

56 Prime Movers Steam turbines Gas turbines Hydraulic turbines Reciprocating engine 56

57 Prime Movers Steam Turbine Fundamentals Steam expansion Impulse stage Pressure and volume constant in rotating buckets Velocity compounded stage several rotating buckets in series Pressure compounded stage several impulse stages in series Reaction stage Pressure drops and volume increases in rotating nozzles 57

58 Prime Movers Simple Impulse stage v, & p verses position 58

59 Prime Movers Velocity Compounded stage vs... Pressure Compounded stage v, & p verses position 59

60 Prime Movers Simple Reaction stage v, & p verses position 60

61 Prime Movers 61

62 Prime Movers 62

63 Prime Movers 63

64 Prime Movers 64

65 Prime Movers Heat & Pressure -> KE -> Mechanical Energy 65

66 Prime Movers Fossil vs.. Nuclear Steam Turbines A=N(No RH) B=N(RH) C=F(NoRH) 66

67 Prime Movers Straight flow condensing 67

68 Prime Movers Straight flow, non condensing 68

69 Prime Movers Single extraction condensing 69

70 Prime Movers Two section condensing 70

71 Prime Movers Single reheat / double flow LP 71

72 Prime Movers Double reheat 72

73 Prime Movers Four flow LP 73

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75 Prime Movers Tandem-compound unit 75

76 Prime Movers Cross compound unit 76

77 Prime Movers Valves name and purpose: Main Steam Stop (Throttle) valve backup to governor valves for trip, also throttle during startup Main Steam Control (Governor) valves regulate steam flow to turbine HP section, primary trip shutoff Multiple governor valves degree of arc = 360o / number of valves 77

78 Prime Movers Reheat stop & intercept valve Reheat Steam Stop valve backup to governor valves for trip Reheat Steam Intercept valve regulate steam flow to turbine IP section during load swings, primary trip shutoff Ventilator valves bleed steam trapped in HP turbine after trip to prevent overheat 78

79 Typical Steam Flow Diagram 79

80 Prime Movers Typical physical arrangement - overhead view 80

81 Prime Movers Typical physical arrangement side view 81

82 Prime Movers HP / IP turbine section. Opposed flow balance axial thrust Hot to cold expansion up to 1 Governor pedestal or front standard contains LO pump, mechanical over speed trip, thrust and #1 radial bearing. 82

83 Prime Movers Governor Pedestal 83

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85 Prime Movers LP turbine section Overpressure diaphragms or rupture discs on top of shell Exhaust hood spray to cool last stage during low steam flow Turning gear turn rotor to prevent bowing due to uneven rotor heating 85

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88 Prime Movers 4 types of steam flow control 1. Throttling control 2. Governing control 3. Variable pressure control 4. Hybrid variable pressure / governing control 88

89 Prime Movers Throttling control (full arc admission) constant Psteam, simultaneous operation of all control valves at same time. Least efficient Governing control (partial arc admission) constant Psteam, sequential operation of MS control valves. More efficient 89

90 Prime Movers Variable Pressure control Vary SG pressure, control valves in fixed position. Limited load response but first stage temp const. Hybrid variable pressure / governing control Vary SG pressure, and control valve sequential operation (partial arc admission) Heat rate comparisons -> 90

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92 Prime Movers Turbine Auxiliary Systems Turbine seal system prevents steam leakage out and air leakage in. Labyrinth type rings Turbine Drains prevent water induction MS & Reheat low point drains MS stop valves before seat drains De-superheat spray (attemporation) Reheat intercept and stop valves before seat drains 92

93 Prime Movers Radial shaft seals 93

94 Prime Movers Turbine Auxiliary Systems Turbine LO system Hydraulic system may be part of LO system Main oil pump (in front standard) - fed from booster pump driven by main oil pump. Turning gear oil pump (AC) Emergency backup oil pump (DC) 94

95 Prime Movers Controls - Typical turbine trip events Over speed trip Manual trip Generator trip High differential expansion Bearing failure of high vibration Low LO or hydraulic pressure Low vacuum trip High exhaust temp trip 95

96 Prime Movers Controls - Typical turbine parameters monitored Shaft speed Control valve position Shaft eccentricity X-Y vibration Differential expansion Shell & valve chest temperature Bearing metal temps Steam pressure & temp from boiler and into condenser 96

97 Prime Movers Gas Turbine Fundamentals GAS refers to the working media (air in most cases) not to the fuel used Peaking unit < 2000 annual hours Base load unit > 5000 annual hours Three basic types 1. Simple cycle 2. Combined cycle 3. Cogeneration 97

98 Prime Movers Thermodynamic fundamentals - Brayton cycle 98

99 Prime Movers Compression Combustion Expansion Exhaust 99

100 Prime Movers Compression Combustion Expansion Exhaust 50-60% of work in turbine drives compressor Wnet = useful work available = Wgross Wcomp QH = heat added QL = heat rejected 100

101 Prime Movers Assuming Cp constant, nth is; If I maximize T2/T3 and/or minimize T1/T4, I maximize thermal efficiency Material limitations 101

102 Prime Movers nth can also be expressed in terms of compressor ratio as; Where k = ratio of Cp of air P2/P1 is pressure ratio of compressor 102

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104 Prime Movers As I increase P2/P1, thermal efficiency increases However, Wnet effected by pressure ratio (i.e. Wgross Wcomp = Wnet) Final design compromise 104

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106 Prime Movers Compressor and turbine efficiencies 106

107 Prime Movers Where; h1 = enthalpy at compressor inlet h2s = enthalpy at constant entropy at disch. Press. H2 = actual enthalpy at disch press. 107

108 Prime Movers Where; h3 = enthalpy at turbine inlet h4s = enthalpy at constant entropy at exit. Press. H4 = actual enthalpy at exit press. 108

109 Prime Movers EXAMPLE 1 Determine Compressor efficiency if; H1 = 150 BTU/lbm H2 = 1000 BTU/lbm H2S = 850 BTU/lbm hcomp = (H2S H1)/(H2 H1) = ( ) / ( ) = 0.82 or 82% 109

110 Prime Movers EXAMPLE 2 Determine Turbine efficiency if; H3 = 2500 BTU/lbm H4 = 1000 BTU/lbm H4S = 600 BTU/lbm hturb = (H3 H4)/(H3 H4S) = ( ) / ( ) = 0.79 or 79% 110

111 Prime Movers Simple Cycle vs. Combined Cycle 111

112 Prime Movers Continued Next Week

113 Energy Production Systems Engineering USF Polytechnic Engineering End of Session 4: Nuclear Energy & Prime Movers Spring 2011