Boiling Water Reactor Basics

Transcription

1 Boiling Water Reactor Basics Larry Nelson November 2008

2 Overview Big Picture - BWR Plants Major Components BWR Evolution BWR Features vs. PWR Features Electrochemical Potential (ECP) Concept ECP Monitoring & NobleChem TM 2

3 The Big Picture 3

4 Primary Containment 4

5 BWR Power Cycle NUCLEAR STEAM SUPPLY SYSTEM (NSSS) Steam BALANCE OF PLANT (BOP) Moisture Separator and Reheater Reactor Vessel Separators and Dryers Feedwater Extraction Steam Turbine HP LP Condenser LP Generator Core Demineralizers Recirc Pump Recirc Pump Feed Pumps Extraction Steam Heaters Condensate Pumps Drain Pumps Heaters 5

6 ABWR Power Cycle NUCLEAR STEAM SUPPLY SYSTEM (NSSS) BALANCE OF PLANT (BOP) Reactor Vessel Main Steam Feedwater Moisture Separator Reheater Low Pressure Turbine Generator Suppression Pool High Pressure Turbine High Pressure Feedwater Heater Feedwater Pump CP Low Pressure Feedwater Heaters Condenser Offgas System Steam Jet Air Ejector Gland Steam Condenser Stack Condenser CBP Condensate Purification System 6

7 BWR Major Components

8 BWR Jet Pump Provide core flow to control reactor power which yields higher power level without increasing the Rx size Provide part of the boundary required to maintain 2/3 core height following a recirculation line break event 8

9 Lower Plenum CRD Guide Tubes CRBs CRD housings Stub Tubes In-core Housings Guide Tubes Flux monitor dry tubes 9

10 BWR Core Shroud Shroud and Sep Core Spray Spargers Ecentric Aligner Top Guide Cor Shro hroud abilizer yp of 4) Core Plate Stud (Typical) Ecentric Aligner Core Shroud Stainless Steel Cylinder Surrounds the Core Separates upward flow through the core from downward flow in the downcomer annulus Provides a 2/3 core height floodable volume 10

11 Fuel Assembly & Control Blade 11

12 Steam Separator ing r Wet Steam Ret W S Turning vanes impart rotation to the steam/water mixture causing the liquid to be thrown to the outside 163 standpipes T ( To ecirc Stan 12

13 Steam Dryer Provides Q steam dryer = 99.9% to the Main Turbine Wet steam is forced horizontally through dryer panels Forced to make a series of rapid changes in direction Moisture is thrown to the outside Initial power uprate plants experiences FIV minimized by design improvements 13

14 BWR Evolution

15 BWR Reactor Evolution Dresden 1 KRB Oyster Creek Dresden 2 ABWR ESBWR 15

16 BWR Development VBWR (Vallecitos Boiling Water Reactor) 1 st General Electric BWR power plant Built in 1957 (near San Jose, California) 1 st commercial BWR; 5 MWe supplied to Pacific Gas & Electric grid (through 1963) 1000 psig (66.7 atm) operating pressure 16

17 BWR Development BWR1 Introduced in st commercial plant in 1960 (Dresden 1) 8 plants Characteristics: External or Internal steam separation Low power density core BWR2 Introduced in plants Characteristics: Internal steam separation Low power density core 5 Recirculation loops Flow control load following 17

18 BWR Development BWR3 Introduced in 1965 First Jet Pump application 9 plants Characteristics: Low power density core Internal Jet Pumps 2 Recirculation loops BWR4 Introduced in 1966 Increased power density 25 Plants Characteristics: High power density core Mark I or II containment 18

19 BWR Development BWR5 Introduced in 1969 Improved safeguards (ECCS) Recirculation flow control valves 8 plants Characteristics: Valve flow control load following ECCS injects into core shroud BWR6 Introduced in 1972 Added fuel bundles; increased output; Improved fuel safety margins Improved Recirc system performance 8 plants Characteristics: Valve flow control 8 x 8 fuel bundle 19

20 BWR Development ABWR Introduced in 1991 Blend of best features: operating BWRs, available new technologies, & modular construction techniques 4 plants Characteristics: Safety improvements (reduced core damage frequency) Design life 60 years No external Recirc Loops; Reactor Internal Pumps ESBWR Currently in licensing and design Characteristics: Passive Safety Natural Circulation; No Recirc Loops or Pumps Safety improvements (reduced core damage frequency) Design life 60 years Larger Main Generator (~1600 MWe) 20

21 Operating Parameters for Selected BWRs Parameter BWR/4 (Browns Ferry 3) BWR/6 (Grand Gulf 1) ABWR ESBWR Power (MWt / MWe) 3293/ / / /1590 Vessel height / diameter (m) 21.9/ / / /7.1 Fuel Bundles (number) Active Fuel height (m) Power density (kw/l) Recirculation pumps 2 (large) 2 (large) 10 zero Number of CRDs / type 185/LP 193/LP 205/FM 269/FM Safety system pumps zero Safety Diesel Generator zero Core damage freq./yr 1E-5 1E-6 1E-7 1E-8 Safety Bldg Vol (m 3 /MWe)

22 ESBWR Reactor Pressure Vessel 22

23 ESBWR Passive Safety 23

24 ESBWR Gravity Driven Cooling System Simple design Simple analyses Extensive testing Large safety margins Before After Gravity driven flow keeps core covered 24

25 BWR vs. PWR

26 BWR and PWR the main differences Pressurized Water Reactor Boiling Water Reactor Pressurizer Chemical & Volume Control Pressure/Temperature Reactor Pressure Vessel Steam Generator T/G Turbine Generator Reactor Pressure Vessel T/G Turbine Generator 2 loops heat balance/ heat transfer Condenser 1 loop heat balance/ heat transfer Condenser 26

27 Principle of Steam Generation BWR RPV Pressure ~7 MPa (1020 psig) RPV Temperature 288 o C (550 ºF) Steam Generated in RPV (with Separator & Dryer) Bulk Boiling Allowed in RPV PWR RPV Pressure ~15 MPa (~2240 psig) RPV Temperature 326 o C (~618 ºF) Steam Generated in Steam Generator (via Second Loop) No Bulk Boiling in RPV BWR has Lower RPV Pressure and Simplified Steam Cycle 27

28 Major NSSS Components BWR RPV (with Dryer & Separator) No Steam Generator No Pressurizer Natural Circulation (ESBWR) RPV mounted pumps (ABWR) Bottom Entry Control Rod Drives PWR RPV 2-4 Steam Generators 1 Pressurizer Reactor Coolant Pumps outside of RPV Top Entry Control Rod Clusters 28

29 Electrochemical Potential (ECP) Concept

30 Stress Corrosion Cracking History in BWRs # of BWRs Repair costs >$1B / BWR Operating BWRs N. America Europe Asia Total GE Non-GE ,000 MWe installed Stress Corrosion Cracking History st detected in sensitized SS 1970s Stainless steel welded piping 1980s BWR internals 1990s Low stress BWR internals 30

31 Nuclear Chain Reactions on One Slide n 238 U 235 U n 239 Pu X Y n n HEAT E=mc 2 HEAT Moderator Water or Graphite n H 2 0 H + + OH U Etc. high energy neutron low energy neutron X,Y Radioactive by-products e.g. Kr, Cs, I, Ba, Th, Np 31

32 Water Radiolysis Generates Species Harmful to Materials n e H 2 O H * H 2 Commonly Observed species H 2 O OH* H 2 O 2 + O 2 OH - (n,p) γ HO 2 * HO 2 - N 2 NO 2 - NO 3 - Oxidant (H 2 O 2 and O 2 ) Generation By Water Radiolysis 32

33 Stress Corrosion Cracking Environment Stress Cr depletion occurs during welding of stainless steels with high carbon levels Microstructure Weld Plastic Strain (%) Outside Relative Distance From Weld Fusion Line (mm) GE1 Scan B 600A GE1 Scan D 600A GE2 Scan C 600A GE2 Scan D 600A GE3 Scan D 600A GE3 Scan C 600A GE8 Scan C 400A GE8 Scan D 400A GE9 Scan D 300A GE9 Scan C 300A GE4 Scan C 600A GE4 Scan D 600A Plastic strain occurs during welding and leads to cracking in stainless steels with low carbon (L-grade SS) Crack Growth Rate, mm/s 1.E-05 1.E-06 1.E-07 1.E-08 1.E-09 Sensitized 304 Stainless Steel 30 MPa m, 288C Water μs/cm, 0-25 ppb SO 4 SKI Round Robin Data filled triangle = constant load open squares = "gentle" cyclic 316L (A14128, square ) 304L (Grand Gulf, circle ) non-sensitized SS 50%RA 140 C (black ) 10%RA 140C (grey ) CW A600 GE PLEDGE Predictions 30 MPa m 0.5 Sens SS μs/cm Corrosion Potential, V she 200 ppb O ppb O ppb O 2 CW A μin/h 2000 ppb O 2 Ann. 304SS 200 ppb O 2 GE PLEDGE Predictions for Unsensitized Stainless Steel (upper curve for 20% CW) 33

34 Stress Corrosion Cracking Prediction & Application Complex phenomenon must be understood mechanistically as crack tip system processes LAB PREDICTION Lab understanding & data must be verified by plant data before use in BWR prediction PLANT Insights yield novel technology like NobleChem 34

35 Stress Corrosion Cracking Mitigation Crack Growth Response Radiation Field Response Normalized Main Steam Line Activity Main Steam Radiation Field Low Hydrogen Moderate Hydrogen High Hydrogen Feedwater Hydrogen Concentration (PPM) High crack growth rates at high corrosion potential (ECP) ECP is a dominant variable effecting SCC response Electro Chemical Potential (ECP) Response Hydrogen injection results in an increase in main steam line radiation fields NobleChem Basics 200 NWC In-core ECP, mv (SHE) NWC - Piping NobleChem HWC With excess H2, O2 is consumed & its level at the surface is zero Hydrogen Injection Rate (ppm) // 2.0 H 2 + O 2 reaction is catalyzed with NobleChem particles Hydrogen added is more effective lower radiation fields 35

36 ECP Monitoring & NobleChem TM

37 BWR ECP Monitoring Locations Modified LPRM Assembly for Bottom-of-Core ECP Monitoring (3 ECP Sensors) Full Function Data Acquisition System Air Conditioner Recirculation\Decon Flange Assembly (4 ECP Sensors) Personal Computer Digital Multimeter Multiplexer Deskjet Printer Modified LPRM Assembly for Lower Plenum ECP Monitoring (2 or 3 ECP Sensors) Drywell AC Line Conditioner Simplified Data Acquisition System Core Plate EDM one new hole in Guide Tube Inlet to LPRM (ECP sensors inside and above) Drain Line Flange Assembly (4 ECP Sensors) Multimeter/ Multiplexer Personal Computer 37

38 Lower Plenum ECP Monitoring High Temperature Prefilm (in laboratory) Fe/Fe 3 O 4 Platinum Core Plate Noble Metal Treated SS Electrode 2.75 in. (70 mm) Inlet Cooling Holes in LPRM Cover Tube Lower Cooling Holes in LPRM Cover Tube, ECP Sensors Inside and Above Holes Local Power Range Monitor Assembly 1/2 diameter Inlet Cooling Hole in In Core Monitor Housing 38

39 Bottom Plenum ECP Response 200 Lower Plenum ECP ECP (mv SHE) Core Plate ECP Middle Bottom IGSCC Mitigation Potential -230 mv(she) HWC is Effective In Mitigating IGSCC But Lower Plenum Requires More H FEEDWATER HYDROGEN (ppm) 39

40 Basis for NobleChem TM Technology (ppm) 40

41 HWC vs. NobleChem TM Technology 200 Before NobleChem TM ECP mv(she) -200 After NobleChem TM IGSCC Mitigation -230 mv(she) Feedwater H 2 (ppm) BWR/4 Low ECP After NobleChem TM and Low Hydrogen 41

42 ECP Reduction With NobleChem TM Non-NobleChem Plant Data ECP mv(she) mv(she) Upper Core - UC -300 Lower Core - LC NobleChem Plant Data for UC, LC, LP, RRS Lower Plenum - LP RRS Feedwater Hydrogen, ppm Provides Low ECPs At All Internal Locations 42

43 Noble Metal Distribution After On-Line Application 30% Pt PARTICLE SIZE DISTRIBUTION (based on number) 100% Relative Number Frequency 25% 20% 15% 10% 5% STATISTICS Mean: 6.1 nm Std. De v.: 2.3 nm Minimum: 2.1 nm Maximum: 21.8 nm Object Count: (based on number) 90% 80% 70% 60% 50% 40% 30% 20% 10% Cumulative Number 100 nm 0% Particle Diameter (nm) 0% Nano-particle Pt Generation By On-Line NobleChem TM 43

44 Summary Reactor operation at low ECP is essential for minimizing component degradation in all BWR designs including the ESBWR ESBWR is GEH s latest evolution in BWR design 4500 MWt/~1575MWe Natural circulation Passive safety features Significant simplification ESBWR is under licensing review by USNRC ESBWR chosen by NuStart, Dominion and Exelon as reference design 44