BWR Description

Jacopo BuongiornoAssociate Professor of Nuclear Science and Engineering

22.06: Engineering of Nuclear Systems

1

Boiling Water Reactor (BWR)

Public domain image by US NRC.

2

The BWR is a Direct Cycle PlantThe BWR is a Direct Cycle Plant

S t MP 7 136 System pressure, MPa 7.136 Core thermal power, MWth 3323 Electric power, MWe 1130 Thermal efficiency, % 34 Vessel ID / Thickness / Height, m 6.4 / 0.16 / 22g , Core shroud diameter, m 5.2 Number of fuel assemblies 764 Core mass flow rate, kg/s 13702 Core inlet temperature, ºC 278.3 Core outlet temperature, ºC 287.2 Core exit quality, % 13.1 Feedwater flow rate, kg/s 1820 Feedwater temperature, ºC 220 St fl t k / 1820Steam flow rate, kg/s 1820 Steam temperature, ºC 287.2 Core power density, kW/L 50.5 Core flow bypass 14 %

A.V. Nero, Jr., A Guidebook to Nuclear Reactors, 1979

Image by MIT OpenCourseWare.

Steam line

Reactor vessel

Feedwater

Core

Feedpumps

Demineralizer

Condensatepumps

Turbine generator

Separators &dryers

Heater

Recirculation pumps

3

[MPa]

Phase Diagram of WaterPhase Diagram of Water

Pressure

7 37.3

Vapor Vapor

278 288 Temperature [C]

Saturation line

BWR core

Liquid

4

BWR Core

5

BWR Core LayoutBWR Core Layout0°

Fuel Bundle Control Cell Bundle Peripheral Bundle Control BladeControl Blade

270° 90°

Typical Control Cell Core Layout 180°180

© source unknown All rights reserved. This content is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse.6

BWR Fuel AssemblyBWR Fuel Assembly

Upper Tie Plate

Channel Fastener

Assembly

Fuel Cladding

Fuel Claddding Expansion

Spring

Fuel Channel

Lower

Plenum Spring

Tie Plate

Nose Piece Fuel Rod

Fuel Pellet

F l bli h d t ll t P07.cvs

Single bundle 3D view uel assemblies have a duct wall to prevent vapor radial drifting

Image by MIT OpenCourseWare. © source unknown All rights reserved. This content is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse.

F

7

BWR Fuel AssembliesBWR Fuel Assemblies

Image by MIT OpenCourseWare.

8

Fuel Assembly Parameters for 9x9 Fuel AssemblyParameter Value Fuel Pellet OD (mm) 9.55 Fuel Pin OD (mm) 11.18 Clad Thickness (mm) 0.71 Fuel Pin Pitch (mm) 14.27 Active Fuel rod height (mm) 3707.9 Total Fuel Rod height (mm) 4178.7 Part Length Rod Height (mm) 2436 Fuel Pins / Water Rods per Fuel Assemblyp y 74/2 Number of Part Length Rods 8 Inner/Outer diameter of the water rods (mm) 23.37/24.89 Duct Thickness (mm) 2.54 Clearance between duct and peripheral fuel rods (mm) 3.53 Clearance between water rods and fuel rods (mm)( ) 1.79 Assembly Outer Dimension (mm) 137.54 Inter-Assembly Gap (mm) 14.86 Average Linear Power (kW/m) 16.46 Pressure Drop (kPa) 160 Average enrichment (wt%) Average enrichment (wt%) 4.314.31 Average Discharge Burnup (GWd/t) 56 Refueling scheme 4 batches Number of rods with gadolinia 8 Gadolinia concentration (wt%) 5 Hydrogen to Heavy Metal Ratio Hydrogen to Heavy Metal Ratio 4 53 4.53 Void Coefficient (pcm/% void) -144 Fuel Temperature Coefficient (pcm/K) -1.7 Approximate Assembly Weight (kg) 281

9

Control BladeControl Blade

Image removed due to copyright restrictions.

Image by MIT OpenCourseWare.

10

BWR Control Rod Drive SystemBWR Control Rod Drive System

Image by MIT OpenCourseWare.

11

BWR SPATIAL CORE PROPERTIES(WITH CONTROL RODS PARTIALLY INSERTED)

Relative power

Average void fractionCritical heat flux ratioin hot channel x0.1

1.5

1.0

0.5

00 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

Relative axial length

Rel

ativ

e pa

ram

eter

s

Bottom of core Top of core

Image by MIT OpenCourseWare.

12

POWER IN FRESH FUEL ASSEMBLY AS ADJACENTCOCONTROOL ROD ISS WITHDRAAWN TOOWARD BOOTTOMO A O

“BWR/6: General Description of a BWR,” GE, 1980.

Nodal power normalized to 1.0 over the core.

(Bottom).2

.4

.6

.8

1.0

1.2

1.4

1.6

1.8

(Top)Axial Length of Fuel

17 25 33 42 50 58 0Percent FullInsertion

67

Rel

ativ

e Po

wer

670

Image by MIT OpenCourseWare.

13

Connection of BWR Core Desiggn to Neutronics

Why are the fuel rods spaced out more in a BWR than in a PWR?Why are the fuel rods spaced out more in a BWR than in a PWR?

Why is the core power density lower in a BWR core than in a PWR?

What is the purpose of spatial fuel enrichment zoning throughout a BWR fuel assembly?

What function do the water rods perform?

h h l d i d f h b f hWhy are the BWR control rods inserted from the bottom of the core?

Can dissolved boron be used as a means to control reactivity in a BWR core?

14

BWR Bundle Design AdvancesBWR Bundle Design AdvancesExtended burnup features More fuel ppins ((1010)) for a lower

heat flux

Heavier fuel loadings

Improved mechanical performance “Barrier” cladding

Low growth, wear resistant materials

Improved operational performanceImproved operational performance Natural uranium blankets

Flow mixing grids to enhance margin to critical power

Part-Length Fuel Rods (Stability, SDM)

Large Central Water Channels (Stability,y, SDM ))(

Sophisticated poison & enrichment zoning

Control Rod

Fuel RodPart Length Fuel Rod

Image by MIT OpenCourseWare.

© source unknown All rights reserved. This content is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse.

15

BWR Vessel and VesselBWR Vessel and VesselInternals

16

BWR VesselBWR Vessel

Vessel bottom head accommodates CR penetrations

Large vessel made of ring forgings to avoid welds in the core region

ABWR RPV beltline forging, weight: 127 tons; dimensions: From: L.E. Fennern, ABWR Seminar – Reactor, 7.48 m outside diameter, 7.12 m inside diameter, 3.96 m high; Core & Neutronics. April 13, 2007. material: ASME SA 508, Class 3 EQ.

© source unknown. All rights reserved. This content is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse.17

BWR Vessel InternalsBWR Vessel Internals

From: V. Shah, P. MacDonald, Aging and Life Extension of Major LWR Components, 1993.

© Elsevier. All rights reserved. This content is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse.Source: Shah, V. N. and P. E. MacDonald. Aging and Life Extension of Major Light Water Reactor Components. Atlanta, GA: Elsevier Science, 1993. ISBN: 9780444894489. 18

Steam Separators

Steam Dome

Steam Dryer Height

Steam Dryers

Drain Pipes Steam + Droplets

From: V. Shah, P. MacDonald, Aging and Life Extension of Major LWR Components, 1993.

© Elsevier. All rights reserved. This content is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse.Source: Shah, V. N. and P. E. MacDonald. Aging and Life Extension of Major Light Water Reactor Components. Atlanta, GA: Elsevier Science, 1993. ISBN: 9780444894489. 19

BWR Recirculation System

20

BWR Recirculation SystemBWR Recirculation System BWR/6 ABWR ESBWR

Steam Dryers

Steam Flow to Turbine

Steam Separators Feed Flow

from Condenser g o

Jet Pump Core

Driving Flow

RecirculationPump

Ten internal Relies on natural External recirculation pumps + jet pumps recirculation pumps circulation

Courtesy of GE Hitachi Nuclear Systems. Used with permission.21

Traditional BWR vs ABWR and ESBWRTraditional BWR vs ABWR and ESBWRParameter

Power (MWt/MWe) 3293/1098

21.9/6.4

764

3.7

50

185/LP

9

2

1E-5

115 150

1E-6

3

9

193/LP

2(large)

54.2

3.7

800

21.8/6.4

3900/1360 3926/1350

21.1/7.1

872

3.7

51

10

205/FM

18

3

1E-7 1E-7

269/FM

3.0

54

1132

27.7/7.1

4500/1550

ESBWR

160 <100

Zero

Zero

Zero2(large)

BWR/4-Mk I(Browns Ferry 3)

BWR/6-Mk III(Grand Gulf) ABWR

Vessel height/dia. (m)

Fuel bundles (number)

Active fuel height (m)

Power density (kW/L)

Recirculation pumps

Number of CRDs/type

Safety system pumps

Safety diesel generator

Core damage freq./yr

Safety Bldg Vol (m3/MWe)

Image by MIT OpenCourseWare.

22

Suction Flow Drive Flow 2

BWR/6 Recirculation FlowBWR/6 Recirculation Flow1 unit

Steam Dryers

Steam Flow to Turbine 1 unit

Steam Separators

Driving Flow

Feed Flow from Turbine 1 unit

5 units

Jet Pump Core

4 units

Recirculation Pump

2 units 6 units

Jet Pump M-Ratio = Suction Flow / Drive Flow = 2/

Courtesy of GE Hitachi Nuclear Systems. Used with permission.

23

BWR Recirculation PumpsBWR Recirculation Pumps

Image removed due to copyright restrictions.

© Elsevier. All rights reserved. This content is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse.

24

BWR Jet PumpsBWR Jet PumpsHolddown Assembly

Inlet

Jet Pump Nozzle AssemblyRestrainers and S tSupportsCore ShroudMixer

Restrainers and Supports

Inlet Riser

pp

Reactor Vessel WallCore Support

Diffuser and Tail PipeRecirculation InletRecirculation Inlet Nozzle – 1 per Jet Pump Riser

© Elsevier. All rights reserved. This content is excluded from our Creative Commons license. For more information, see http://ocw.mit.edu/fairuse.25

BWR Balance Of Plant (BOP)

26

eate s

BWR Power Cyycle Moisture Separator

and Reheater Steam

Reactor Vessel Generator

LP LPHPTurbine

Separatorsand Dryers

Core

Feedwater Extraction Steam

Recirc Pump

Recirc Pump

Feed Pumps

Demineralizers Extraction Steam

p p

Drain

Heaters

Heaters

Condensate Pumps

Condenser

Pumps

“BWR/6, General Description of a BWR,” GE, 1980

Courtesy of GE Hitachi Nuclear Systems. Used with permission.

27

Radioactive SteamRadioactive Steam Entire Power Conversion System becomes Radioactive Shi ldi i N d dShielding is Needed

Reaction products from water: O16 + n N16 + H1, T1/2 = 7.2 s; , 1/2O17 + n N17 + H1, T1/2 = 4.2 s; , O18 + n O19 F19, T1/2 = 29 s; ,

Activation of corrosion pproducts: Fe54 + n Fe55, T1/2 = 2.7 y;

Fe58 + n Fe59, T1/2 = 44.6 d; , Co59 + nn CoCo60, T, T1/2 = 5.3 y; , Co 5.3 y; ,

Ni58 + n Ni59, T1/21/2= 8x104 y; ,

Ni62 + n Ni63, T1/2 = 100 y; ,

28

Air Ejjector

Removes Anyy Gases in Coolant Downstream of Condenser

They Must be Held Up and Stabilized

Nobel Gas Fission Products Escaped from Faulty Fuel Pins(Xe, Kr isotopes)

Xe135 Cs135 + b-Xe Cs b + g, T1/2 = 9.2 h g, T 9.2 h1/2Kr88 Rb88 + b- + g, T1/2 = 2.8 h

Kr85 Rb85 + b-1 + g, T1/2 = 10.7 y

H2 from Radiolysis of H2O N Isotopes Produced by (O + n) Reactions Gases Leaking into CondenserGases Leaking into Condenser

29

BWR safety systems andBWR safety systems andcontainment to be discussed

later in the course

30

MIT OpenCourseWarehttp://ocw.mit.edu

22.06 Engineering of Nuclear SystemsFall 2010

For information about citing these materials or our Terms of Use, visit: http://ocw.mit.edu/terms.