BWRsbasics Vaalll

Boiling Water Reactor Basics

Larry Nelson

November 2008

GE Global Research

2GE Global Research

Big Picture - BWR PlantsMajor ComponentsBWR EvolutionBWR Features vs. PWR FeaturesElectrochemical Potential (ECP) ConceptECP Monitoring & NobleChemTM

Overview

3GE Global Research

The Big Picture

4GE Global Research

Primary Containment

5GE Global Research

BWR Power Cycle

ReactorVessel

Core

RecircPump

RecircPump

FeedPumps

DrainPumps

Heaters

Heaters

CondensatePumps

Demineralizers

Generator

Condenser

LP LPHPTurbine

Moisture Separatorand Reheater

Steam

Feedwater

Separatorsand Dryers

Extraction Steam

Extraction Steam

NUCLEAR STEAM SUPPLYSYSTEM (NSSS)

BALANCE OFPLANT (BOP)

6GE Global Research

ABWR Power Cycle

SuppressionPool

MainSteam

Feedwater

MoistureSeparatorReheater

LowPressureTurbine

Generator

Stack

OffgasSystem

Steam JetAir Ejector

High PressureFeedwater Heater

Feed-waterPump

HighPressureTurbine

Condenser

CP

CBP

Low PressureFeedwater Heaters

Gland SteamCondenser

CondensatePurificationSystem

ReactorVessel

Condenser

NUCLEAR STEAM SUPPLYSYSTEM (NSSS)

BALANCE OFPLANT (BOP)

BWR MajorComponents

8GE Global Research

BWR Jet Pump

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

9GE Global Research

Lower Plenum

CRD Guide TubesCRBsCRD housingsStub TubesIn-core HousingsGuide TubesFlux monitor dry tubes

10GE Global Research

BWR Core Shroud

Stainless Steel CylinderSurrounds the Core

– Separates upward flow through the core from downward flow in the downcomer annulus

– Provides a 2/3 core height floodable volume

Core SpraySpargers

EcentricAligner

EcentricAligner

Core Plate

CoreShroud

CorShro

TopGuide

Shroud and Sep

Stud(Typical)

hroudabilizeryp of 4)


Fuel Assembly & Control Blade


Steam Separator

Turning vanes impart rotation to the steam/water mixture causing the liquid to be thrown to the outside163 standpipes

WetSteam

RetW

S

Stan

ingr

Toecirc

T(


Steam Dryer

Provides Qsteam dryer = 99.9% to the Main TurbineWet 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 uprateplants experiences FIV – minimized by design improvements

BWR Evolution


BWR Reactor Evolution

Oyster Creek

KRBDresden 1

ABWRDresden 2

ESBWR


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


BWR Development

BWR1Introduced in 1955

1st commercial plant in 1960 (Dresden 1)8 plants

Characteristics:– External or Internal steam

separation– Low power density core


3 plantsCharacteristics:– Internal steam separation– Low power density core– 5 Recirculation loops– Flow control load following



First Jet Pump application

9 plantsCharacteristics:– Low power density core– Internal Jet Pumps– 2 Recirculation loops

BWR Development


Increased power density

25 Plants Characteristics:– High power density core– Mark I or II containment


BWR5Introduced in 1969Improved safeguards (ECCS)Recirculation flow control valves8 plants

Characteristics:– Valve flow control load

following– ECCS injects into core shroud

BWR Development

BWR6Introduced in 1972Added fuel bundles; increased output; Improved fuel safety marginsImproved Recirc system performance8 plants

Characteristics:– Valve flow control– 8 x 8 fuel bundle


ABWRIntroduced in 1991Blend of best features: operating BWRs, available new technologies, & modular construction techniques4 plantsCharacteristics:

– Safety improvements (reduced core damage frequency)

– Design life 60 years– No external Recirc Loops;

Reactor Internal Pumps

BWR Development

ESBWRCurrently in licensing and designCharacteristics:

– Passive Safety– Natural Circulation; No Recirc

Loops or Pumps– Safety improvements (reduced

core damage frequency)– Design life 60 years– Larger Main Generator (~1600

MWe)


Parameter BWR/4(Browns Ferry 3)

BWR/6(Grand Gulf 1)

ABWR ESBWR

Power (MWt / MWe) 3293/1098 3900/1360 3926/1350 4500/1590

Vessel height / diameter (m) 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

Operating Parameters for Selected BWRs


ESBWR Reactor Pressure Vessel


ESBWR Passive Safety


• Simple design• Simple analyses

• Extensive testing• Large safety margins

Gravity driven flow keeps core covered

ESBWR Gravity Driven Cooling System

Before

After

BWR vs. PWR


BWR and PWR… the main differencesPressurized Water Reactor

Condenser Condenser

Steam Generator

TurbineGenerator

ReactorPressureVessel

T/G

Pre

ssur

e/Te

mpe

ratu

re

2 loops heat balance/heat transfer

1 loop heat balance/heat transfer

Pressurizer

Chemical &Volume Control

ReactorPressureVessel

Boiling Water Reactor

T/G

TurbineGenerator


Principle of Steam Generation

BWRRPV Pressure ~7 MPa (1020 psig)RPV Temperature 288 oC (550 ºF)Steam Generated in RPV (with Separator & Dryer)Bulk Boiling Allowed in RPV

PWRRPV Pressure ~15 MPa (~2240 psig)RPV Temperature 326 oC (~618 ºF)Steam Generated in Steam Generator (via Second Loop)No Bulk Boiling in RPV

BWR has Lower RPV Pressure and Simplified Steam CycleBWR has Lower RPV Pressure and Simplified Steam Cycle


Major NSSS Components

BWRRPV (with Dryer & Separator)No Steam GeneratorNo PressurizerNatural Circulation (ESBWR)RPV mounted pumps (ABWR)Bottom Entry Control Rod Drives

PWRRPV2 - 4 Steam Generators1 PressurizerReactor Coolant Pumps outside of RPVTop Entry Control Rod Clusters

Electrochemical Potential(ECP) Concept


Stress Corrosion Cracking History• 1969 1st detected in sensitized SS• 1970s Stainless steel welded

piping• 1980s BWR internals• 1990s Low stress BWR internals

Stress Corrosion Cracking History in BWRs

# of BWRs

Operating BWRsN. America Europe Asia Total

GE 34 4 11 49Non-GE 0 16 21 3880,000 MWe installed

Repair costs>$1B / BWR


“Nuclear Chain Reactions on One Slide”

X,Yhigh energy

neutronlow energy

neutronRadioactiveby-products

e.g. Kr, Cs, I, Ba, Th, Np

235U

n

X

Y

U238

Pu239

HEAT

n

n

n

U235

E=mc2HEAT

Etc.

“Moderator”

Wateror

Graphite

235U

n

X

Y

U238

Pu239

HEAT

n

n

n

U235

E=mc2HEAT

Etc.

“Moderator”

Wateror

Graphite

H20 H+ + OH-n


H2O

n

γ

H* H2

OH* H2O2

H2O+O2

OH-

HO2-

HO2*

Water Radiolysis Generates Species Harmful to Materials

Oxidant (H2O2 and O2) Generation By Water Radiolysis

eN2

NO2-

NO3-

(n,p)

Commonly Observed species


Weld

Cr depletion occurs during welding of

stainless steels with high carbon levels

Stress Corrosion Cracking

Outside

0

5

10

15

20

25

30

-25 -20 -15 -10 -5 0 5 10 15 20 25

Relative Distance From Weld Fusion Line (mm)

Plas

tic S

trai

n (%

)

GE1 Scan B 600AGE1 Scan D 600AGE2 Scan C 600AGE2 Scan D 600AGE3 Scan D 600AGE3 Scan C 600AGE8 Scan C 400AGE8 Scan D 400AGE9 Scan D 300AGE9 Scan C 300AGE4 Scan C 600AGE4 Scan D 600A

1.E-09

1.E-08

1.E-07

1.E-06

1.E-05

-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

Cra

ck G

row

th R

ate,

mm

/s

Sensitized 304 Stainless Steel30 MPa√m, 288C Water0.06-0.4 μS/cm, 0-25 ppb SO4SKI Round Robin Datafilled triangle = constant loadopen squares = "gentle" cyclic

42.5

28.3

14.2μin/h

GE PLEDGE Predictions30 MPa√m 0.5Sens SS 0.25

0.1

0.06 μS/cm

← 2

00 p

pb O

2←

500

ppb

O2

←20

00 p

pb O

2

2000 ppb O2

Ann. 304SS 200 ppb O2

316L (A14128, square ) 304L (Grand Gulf, circle ) non-sensitized SS50%RA 140 C (black )10%RA 140C (grey )

CW A600

CW A600

GE PLEDGE Predictions for UnsensitizedStainless Steel (upper curve for 20% CW)

Plastic strain occurs during welding and leads to cracking in stainless steels with low carbon

(L-grade SS)

Environment Stress

Microstructure

Environment Stress

Microstructure


Stress Corrosion Cracking Prediction & Application

Complex phenomenon must beunderstood mechanistically as“crack tip system” processes

Lab understanding & data must be verifiedby plant data before use in BWR prediction

Insights yieldnovel technologylike NobleChem

LAB

PLANTPREDICTION


Crack Growth Response

NobleChem™ Basics

• 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

- 200

0

200

- 400

- 600

EC

P, m

V (S

HE

)

Hydrogen Injection Rate (ppm)2.01.0 1.50.5

NWC - Piping

NobleChemHWC

NWC – In-core

//

- 200

0

200

- 400

- 600

EC

P, m

V (S

HE

)


NWC - Piping

NobleChemHWC

NWC – In-core

//

- 200

0

200

- 400

- 600

EC

P, m

V (S

HE

)


NWC - Piping

NobleChemHWC

NWC – In-core

//

- 200

0

200

- 400

- 600

EC

P, m

V (S

HE

)


NWC - Piping

NobleChemHWC

NWC – In-core

//

• 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

Electro Chemical Potential (ECP) Response

Feedwater Hydrogen Concentration (PPM)

Normalized Main Steam Line Activity

LowHydrogen

ModerateHydrogen

HighHydrogen

Feedwater Hydrogen Concentration (PPM)

Normalized Main Steam Line Activity

LowHydrogen

ModerateHydrogen

HighHydrogen

Radiation Field Response

Mai

n S

team

Rad

iatio

n Fi

eld

Stress Corrosion Cracking Mitigation

ECP Monitoring &NobleChemTM


Modified LPRM Assemblyfor Bottom-of-Core ECP Monitoring(3 ECP Sensors)

Recirculation\Decon FlangeAssembly (4 ECP Sensors)

Full FunctionData AcquisitionSystem

Drain Line Flange Assembly(4 ECP Sensors)

Modified LPRM Assemblyfor Lower Plenum ECP Monitoring(2 or 3 ECP Sensors)

CorePlate

EDM one newhole in GuideTube

Inlet to LPRM(ECP sensors

inside and above)

Drywell

Personal ComputerAir Conditioner

Digital Multimeter

MultiplexerDeskjet Printer

AC Line Conditioner

SimplifiedData AcquisitionSystem

Multimeter/Multiplexer

PersonalComputer

BWR ECP Monitoring Locations


Core Plate

Local Power Range Monitor Assembly

1/2” diameter Inlet Cooling Hole in In Core Monitor Housing

Lower Cooling Holes in LPRM Cover Tube, ECP Sensors Inside and Above Holes

Lower Plenum ECP MonitoringFe/Fe3O4

Platinum

Inlet Cooling Holes in LPRM Cover Tube

2.75 in.(70 mm)

Noble Metal Treated SS Electrode

High Temperature Prefilm (in laboratory)


Bottom Plenum ECP Response

FEEDWATER HYDROGEN (ppm)

-500

-400

-300

-200

-100

0

100

200

0 0.5 1 1.5 2 2.5

ECP

(mV

SHE)

Middle

Bottom

IGSCC Mitigation Potential-230 mV(SHE)

Lower Plenum ECP

Core Plate ECP

HWC is EffectiveIn Mitigating IGSCCBut…Lower PlenumRequires More H2


1.0 2.0(ppm)

Basis for NobleChemTM Technology


BWR/4 Low ECP After NobleChemTM and Low Hydrogen

-600

-400

-200

0

200

0 0.4 0.8 1.2 1.6 2Feedwater H2 (ppm)

ECP

mV(

SHE)

Before NobleChemTM - 1994

After NobleChemTM - 1999 -230 mV(SHE)

IGSCC Mitigation

HWC vs. NobleChemTM Technology


-600

-500

-400

-300

-200

-100

0

100

200

300

0 0.5 1 1.5 2 2.5

Feedwater Hydrogen, ppm

ECP

mV(

SHE)

Upper Core - UC

Lower Core - LC

Lower Plenum - LP

RRSNobleChem Plant Data for UC, LC, LP, RRS

Non-NobleChem Plant Data

-230 mV(SHE)

Provides Low ECPs At All Internal Locations

ECP Reduction With NobleChemTM


Noble Metal Distribution After On-Line Application

100 nm

Pt PARTICLE SIZE DISTRIBUTION(based on number)

0%

5%

10%

15%

20%

25%

30%

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)

Rel

ativ

e N

umbe

r Fre

quen

cy

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

Cum

ulat

ive

Num

ber

STATISTICSM ean : 6.1 nm

Std . De v. : 2.3 nmMinim um : 2.1 nm

Maxim um : 21.8 nmObject Count : 17331

(b ased on num b er)

Nano-particle Pt Generation By On-Line NobleChemTM


Summary

Reactor operation at low ECP is essential for minimizing component degradation in all BWR designs including the ESBWRESBWR is GEH’s latest evolution in BWR design

– 4500 MWt/~1575MWe– Natural circulation– Passive safety features– Significant simplification

ESBWR is under licensing review by USNRCESBWR chosen by NuStart, Dominion and Exelon as reference design

Documents

BWRsbasics Vaalll