Boiling Water
Reactor Basics
Larry Nelson
November 2008
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Overview
z
z
z
z
z
z
Big Picture - BWR Plants
Major Components
BWR Evolution
BWR Features vs. PWR
Features
Electrochemical Potential
(ECP) Concept
ECP Monitoring &
NobleChemTM
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The Big Picture
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Primary Containment
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BWR Power Cycle
NUCLEAR STEAM SUPPLY
SYSTEM (NSSS)
BALANCE OF
PLANT (BOP)
Moisture Separator
and Reheater
Steam
Reactor
Vessel
Turbine
Generator
HP
LP
LP
Separators
and Dryers
Condenser
Feedwater
Extraction Steam
Core
Demineralizers
Recirc
Pump
Recirc
Pump
Extraction Steam
Feed
Pumps
Heaters
Condensate
Pumps
Drain
Pumps
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Heaters
5
ABWR Power Cycle
NUCLEAR STEAM SUPPLY
SYSTEM (NSSS)
BALANCE OF
PLANT (BOP)
Reactor
Vessel
Moisture
Separator
Reheater
Main
Steam
Low
Pressure
Turbine
Generator
Feedwater
Suppression
Pool
High
Pressure
Turbine
Condenser
Feedwater
Pump
Offgas
System
CP
High Pressure
Feedwater Heater
Stack
Low Pressure
Feedwater Heaters
Steam Jet
Air Ejector
Gland Steam
Condenser
CBP
Condenser
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Condensate
Purification
System
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BWR Major
Components
BWR Jet Pump
z
z
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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
Lower Plenum
z
z
z
z
z
z
z
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CRD Guide Tubes
CRBs
CRD housings
Stub Tubes
In-core Housings
Guide Tubes
Flux monitor dry tubes
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BWR Core Shroud
Shroud
and Sep
Core Spray
Spargers
hroud
abilizer
yp of 4)
Ecentric
Aligner
Top
Guide
Core Plate
Stud
(Typical)
Ecentric
Aligner
Cor
Shro
Core
Shroud
Stainless Steel Cylinder
z Surrounds the Core
z
– Separates upward flow through the core
from downward flow in the downcomer
annulus
– Provides a 2/3 core height floodable
volume
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Fuel Assembly & Control Blade
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Steam Separator
Wet
Steam
Ret
W
ing
r
S
Turning vanes
impart rotation to
the steam/water
mixture causing the
liquid to be thrown
to the outside
z 163 standpipes
z
T
(
To
ecirc
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Stan
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Steam Dryer
Provides Qsteam dryer =
99.9% to the Main
Turbine
z Wet steam is forced
horizontally through
dryer panels
– Forced to make a
series of rapid
changes in direction
– Moisture is thrown
to the outside
z
z
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Initial power uprate
plants experiences
FIV – minimized by
design improvements
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BWR Evolution
BWR Reactor Evolution
Dresden 1
KRB
Oyster Creek
Dresden 2
ABWR
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ESBWR
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BWR Development
VBWR (Vallecitos Boiling Water Reactor)
– 1st General Electric BWR power plant
– Built in 1957 (near San Jose, California)
– 1st commercial BWR; 5 MWe supplied to Pacific
Gas & Electric grid (through 1963)
– 1000 psig (66.7 atm) operating pressure
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BWR Development
BWR1
z
Introduced in 1955
BWR2
z
Introduced in 1963
1st commercial plant in 1960 z 3 plants
(Dresden 1)
z Characteristics:
z 8 plants
– Internal steam separation
– Low power density core
z Characteristics:
– 5 Recirculation loops
– External or Internal steam
– Flow control load following
separation
– Low power density core
z
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BWR Development
BWR3
BWR4
z
Introduced in 1965
z
Introduced in 1966
z
First Jet Pump application
z
Increased power density
z
9 plants
Characteristics:
– Low power density core
– Internal Jet Pumps
– 2 Recirculation loops
z
25 Plants
Characteristics:
– High power density core
– Mark I or II containment
z
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z
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BWR Development
BWR5
BWR6
Introduced in 1969
z Improved safeguards (ECCS)
z Recirculation flow control
valves
z 8 plants
z
z
z
Characteristics:
– Valve flow control load
Introduced in 1972
z Added fuel bundles; increased
output; Improved fuel safety
margins
z Improved Recirc system
performance
z 8 plants
z Characteristics:
following
– Valve flow control
– ECCS injects into core shroud
– 8 x 8 fuel bundle
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BWR Development
ABWR
ESBWR
Introduced in 1991
z Currently in licensing and design
z Blend of best features:
z Characteristics:
operating BWRs, available new
– Passive Safety
technologies, & modular
– Natural Circulation; No Recirc
construction techniques
Loops or Pumps
z 4 plants
– Safety improvements (reduced
z Characteristics:
core damage frequency)
– Safety improvements
– Design life 60 years
(reduced core damage
– Larger Main Generator (~1600
frequency)
MWe)
– Design life 60 years
– No external Recirc Loops;
Reactor Internal Pumps
z
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Operating Parameters for Selected BWRs
Parameter
BWR/4
(Browns Ferry 3)
BWR/6
(Grand Gulf 1)
ABWR
ESBWR
3293/1098
3900/1360
3926/1350
4500/1590
21.9/6.4
21.8/6.4
21.1/7.1
27.6/7.1
Fuel Bundles (number)
764
800
872
1132
Active Fuel height (m)
3.7
3.7
3.7
3.0
Power density (kW/l)
50
54.2
51
54
Recirculation pumps
2 (large)
2 (large)
10
zero
Number of CRDs / type
185/LP
193/LP
205/FM
269/FM
Safety system pumps
9
9
18
zero
Safety Diesel Generator
2
3
3
zero
Core damage freq./yr
1E-5
1E-6
1E-7
1E-8
Safety Bldg Vol (m3/MWe)
120
170
180
135
Power (MWt / MWe)
Vessel height / diameter (m)
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ESBWR Reactor Pressure Vessel
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ESBWR Passive Safety
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ESBWR Gravity Driven Cooling System
• Simple design
• Simple analyses
• Extensive testing
• Large safety margins
Before
After
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Gravity driven flow keeps core covered
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BWR vs. PWR
BWR and PWR… the main differences
Pressurized Water Reactor
Boiling Water Reactor
Pressurizer
Pressure/Temperature
Chemical &
Volume Control
Reactor
Pressure
Vessel
T/G
T/G
Turbine
Generator
Turbine
Generator
Steam Generator
Reactor
Pressure
Vessel
Condenser
Condenser
2 loops
heat balance/
heat transfer
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1 loop
heat balance/
heat transfer
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Principle of Steam Generation
BWR
PWR
z RPV Pressure ~7 MPa (1020
z RPV Pressure ~15 MPa (~2240
psig)
z RPV Temperature 288 oC
(550 ºF)
z Steam Generated in RPV
(with Separator & Dryer)
z Bulk Boiling Allowed in RPV
psig)
z RPV Temperature 326 oC (~618
ºF)
z Steam Generated in Steam
Generator (via Second Loop)
z No Bulk Boiling in RPV
BWR
BWRhas
hasLower
LowerRPV
RPVPressure
Pressureand
andSimplified
SimplifiedSteam
SteamCycle
Cycle
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Major NSSS Components
BWR
z RPV (with Dryer & Separator)
z No Steam Generator
z No
Pressurizer
z Natural Circulation (ESBWR)
z RPV mounted pumps (ABWR)
z Bottom Entry Control Rod Drives
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PWR
z RPV
z 2 - 4 Steam Generators
z 1 Pressurizer
z Reactor Coolant Pumps
outside of RPV
z Top Entry Control Rod
Clusters
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Electrochemical Potential
(ECP) Concept
Stress Corrosion Cracking History in BWRs
# of BWRs
Operating BWRs
N. America Europe Asia
GE
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4
11
Non-GE
0
16
21
80,000 MWe installed
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Total
49
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Repair costs
>$1B / BWR
Stress Corrosion Cracking History
• 1969
1st detected in sensitized SS
• 1970s Stainless steel welded
piping
• 1980s BWR internals
• 1990s Low stress BWR internals
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“Nuclear Chain Reactions on One Slide”
HEAT
X
E=mc2
n
235
U
Etc.
235
U
HEAT
n
n
“Moderator”
Y
Water
or
Graphite
n
238
U
high energy
neutron
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n
239
Pu
low energy
neutron
H20
X,Y
H+ + OH-
Radioactive
by-products
e.g. Kr, Cs, I, Ba, Th, Np
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Water Radiolysis Generates Species
Harmful to Materials
H2
H*
n
e
γ
OH*
H2 O
H2 O
+
O2
H2O2
OHHO2
HO2
Commonly
Observed
species
(n,p)
-
*
N2
NO2NO3-
Oxidant (H2O2 and O2) Generation By Water Radiolysis
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Stress Corrosion Cracking
Environment
Cr depletion occurs
during welding of
stainless steels with high
carbon levels
Stress
Microstructure
Plastic Strain (%)
20
15
1.E-05
Sensitized 304 Stainless Steel
30 MPa√m, 288C Water
0.06-0.4 μS/cm, 0-25 ppb SO4
SKI Round Robin Data
filled triangle = constant load
open squares = "gentle" cyclic
1.E-06
5
0
-25
-20
-15
-10
-5
0
5
10
15
20
25
Relative Distance From Weld Fusion Line (mm)
Crack Growth Rate, mm/s
10
316L (A14128, square )
304L (Grand Gulf, circle )
non-sensitized SS
50%RA 140 C (black )
10%RA 140C (grey )
1.E-07
CW A600
42.5
28.3
14.2
μin/h
CW A600
GE PLEDGE
Predictions
30 MPa√m
Sens SS
0.5
2000 ppb O2
Ann. 304SS
200 ppb O2
0.25
Weld
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←2000 ppb O2
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← 200 ppb O2
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
← 500 ppb O2
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Outside
Plastic strain occurs during
welding and leads to cracking in
stainless steels with low carbon
(L-grade SS)
1.E-08
0.1
0.06 μS/cm
GE PLEDGE Predictions for Unsensitized
Stainless Steel (upper curve for 20% CW)
1.E-09
-0.6
-0.5
-0.4
-0.3
-0.2
-0.1
0.0
0.1
0.2
0.3
0.4
Corrosion Potential, Vshe
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Stress Corrosion Cracking Prediction & Application
Complex phenomenon must be
understood mechanistically as
“crack tip system” processes
LAB
Lab understanding &
data must be verified
by plant data before
use in BWR prediction
PLANT
PREDICTION
Insights yield
novel technology
like NobleChem
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Stress Corrosion Cracking Mitigation
Radiation Field Response
Crack Growth Response
Main Steam Radiation Field
Normalized Main Steam Line Activity
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
Hydrogen injection results in an increase in main steam line
radiation fields
NobleChem™ Basics
Electro Chemical Potential (ECP)
Response
ECP, mV (SHE)
200
NWC – In-core
NWC - Piping
0
- 200
- 400
HWC
NobleChem
- 600
0.5
1.0
1.5
//
2.0
•
With excess H2, O2 is consumed & its level at the surface is zero
•
H2 + O2 reaction is catalyzed with NobleChem particles
•
Hydrogen added is more effective – lower radiation fields
Hydrogen Injection Rate (ppm)
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ECP Monitoring &
NobleChem
TM
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)
Multiplexer
Personal Computer
Digital Multimeter
Deskjet Printer
AC Line
Conditioner
Modified LPRM Assembly
for Lower Plenum
ECP Monitoring
(2 or 3 ECP Sensors)
Drywell
Multimeter/
Multiplexer
Core
Plate
EDM one new
hole in Guide
Tube
Simplified
Data Acquisition
System
Personal
Computer
Drain Line Flange Assembly
(4 ECP Sensors)
Inlet to LPRM
(ECP sensors
inside and
above)
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Lower Plenum ECP Monitoring
High
Temperature
Prefilm (in
laboratory)
Fe/Fe3O4
Platinum
Noble Metal
Treated SS
Electrode
Core
Plate
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
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1/2” diameter Inlet
Cooling Hole in In
Core Monitor
Housing
Local Power Range
Monitor Assembly
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Bottom Plenum ECP Response
Lower Plenum ECP
200
100
HWC is Effective
In Mitigating IGSCC
But…Lower Plenum
Requires More H2
Middle
ECP (mV SHE)
0
Bottom
-100
-200
IGSCC Mitigation Potential
-230 mV(SHE)
-300
Core Plate
ECP
-400
-500
0
0.5
1
1.5
2
2.5
FEEDWATER HYDROGEN (ppm)
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Basis for NobleChem Technology
TM
1.0
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2.0
(ppm)
40
HWC vs. NobleChem Technology
TM
200
TM
Before NobleChem - 1994
ECP mV(SHE)
0
TM
After NobleChem - 1999
-230 mV(SHE)
-200
IGSCC Mitigation
-400
-600
0
0.4
0.8
1.2
1.6
2
Feedwater H2 (ppm)
BWR/4 Low ECP After NobleChemTM and Low Hydrogen
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ECP Reduction With NobleChem
TM
300
200
100
Non-NobleChem Plant Data
ECP mV(SHE)
0
-100
Upper Core - UC
-200
-230 mV(SHE)
-300
Lower Core - LC
-400
Lower Plenum - LP
-500
NobleChem Plant Data
for UC, LC, LP, RRS
RRS
-600
0
0.5
1
1.5
2
2.5
Feedwater Hydrogen, ppm
Provides Low ECPs At All Internal Locations
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Noble Metal Distribution After On-Line
Application
Pt PARTICLE SIZE DISTRIBUTION
(based on number)
100%
S TATI STICS
M ean :
6.1
Std . De v. :
2.3
Minim um :
2.1
Ma xim um :
2 1.8
O bject Co unt : 17 331
(b ased on num b er)
25%
20%
90%
nm
nm
nm
nm
80%
70%
60%
50%
15%
40%
10%
30%
Cumulative Number
Relative Number Frequency
30%
20%
5%
10%
0%
100 nm
0%
0.5
1.5
2.5
3.5
4.5
5.5
6.5
7.5
8.5
9.5
10.5 11.5 12.5 13.5 14.5 15.5 16.5 17.5 18.5 19.5
Particle Diameter (nm)
Nano-particle Pt Generation By On-Line NobleChemTM
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Summary
Reactor operation at low ECP is essential for minimizing component
degradation in all BWR designs including the ESBWR
z ESBWR is GEH’s latest evolution in BWR design
– 4500 MWt/~1575MWe
– Natural circulation
– Passive safety features
– Significant simplification
z ESBWR is under licensing review by USNRC
z ESBWR chosen by NuStart, Dominion and Exelon as reference design
z
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