BWR Description
Jacopo Buongiorno
Associate 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 Plant
Steam line
Reactor vessel
Separators &
dryers
Turbine generator
Feedwater
Core
Heater
Condensate
pumps
Feed
pumps
Recirculation pumps
Demineralizer
Image by MIT OpenCourseWare.
System
S
t pressure, MPa
MP
Core thermal power, MWth
Electric power, MWe
Thermal efficiency, %
Vessel ID / Thickness / Height,
g ,m
Core shroud diameter, m
Number of fuel assemblies
77.136
136
3323
1130
34
6.4 / 0.16 / 22
5.2
764
Core mass flow rate, kg/s
Core inlet temperature, ºC
Core outlet temperature, ºC
Core exit quality, %
Feedwater flow rate, kg/s
Feedwater temperature, ºC
13702
278.3
287.2
13.1
1820
220
Steam fl
St
flow rate,
t kg/s
k /
Steam temperature, ºC
Core power density, kW/L
Core flow bypass
1820
287.2
50.5
14 %
A.V. Nero, Jr., A Guidebook to Nuclear Reactors, 1979
3
Phase Diagram of Water
Pressure
[MPa]
Saturation line
BWR core
73
7.3
Liquid
Vapor
278
288
Temperature
[C]
4
BWR Core
5
BWR Core Layout
0°
Fuel Bundle
Control Cell Bundle
Peripheral Bundle
Control Blade
270°
90°
180
180°
Typical Control Cell Core Layout
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6
BWR Fuel Assembly
Upper
Tie Plate
Channel
Fastener
Assembly
Fuel
Cladding
Fuel Claddding
Fuel
Channel
Expansion
Spring
Plenum
Spring
Lower
Tie Plate
Fuel Pellet
Nose Piece
Image by MIT OpenCourseWare.
Fuel Rod
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Creative Commons license. For more information, see http://ocw.mit.edu/fairuse.
F
bli have
h
d t wall
ll to
t
Fuell assemblies
a duct
prevent vapor radial drifting
P07.cvs
Single bundle 3D view
7
BWR Fuel Assemblies
Image by MIT OpenCourseWare.
8
Fuel Assembly Parameters for 9x9 Fuel Assembly
Parameter
Fuel Pellet OD (mm)
Fuel Pin OD (mm)
Clad Thickness (mm)
Fuel Pin Pitch (mm)
Active Fuel rod height (mm)
Total Fuel Rod height (mm)
Part Length Rod Height (mm)
Fuel Pins / Water Rods p
per Fuel Assembly
y
Number of Part Length Rods
Inner/Outer diameter of the water rods (mm)
Duct Thickness (mm)
Clearance between duct and peripheral fuel rods (mm)
Clearance between water rods and fuel rods (mm)
(
)
Assembly Outer Dimension (mm)
Inter-Assembly Gap (mm)
Average Linear Power (kW/m)
Pressure Drop (kPa)
Average enrichment (wt%)
Average Discharge Burnup (GWd/t)
Refueling scheme
Number of rods with gadolinia
Gadolinia concentration (wt%)
Hydrogen to Heavy Metal Ratio
Void Coefficient (pcm/% void)
Fuel Temperature Coefficient (pcm/K)
Approximate Assembly Weight (kg)
Value
9.55
11.18
0.71
14.27
3707.9
4178.7
2436
74/2
8
23.37/24.89
2.54
3.53
1.79
137.54
14.86
16.46
160
4.31
56
4 batches
8
5
4 53
4.53
-144
-1.7
281
9
Control Blade
Image removed due to copyright restrictions.
Image by MIT OpenCourseWare.
10
BWR Control Rod Drive System
Image by MIT OpenCourseWare.
11
BWR SPATIAL CORE PROPERTIES
(WITH CONTROL RODS PARTIALLY INSERTED)
Relative power
1.5
Average void fraction
Relative parameters
Critical heat flux ratio
in hot channel x0.1
1.0
0.5
0
0
0.1
Bottom of core
0.2
0.3
0.4
0.5
0.6
Relative axial length
0.7
0.8
0.9
1.0
Top of core
Image by MIT OpenCourseWare.
12
POWER IN FRESH FUEL ASSEMBLY AS ADJACENT
CONTRO
CO
OL ROD
O IS
S WITHDRA
AWN TO
OWARD
A
BO
OTTOM
O
1.8
1.6
Relative Power
1.4
1.2
0
17
25
33
42
50
58
67
Percent Full
Insertion
0
67
1.0
.8
.6
.4
.2
Nodal power normalized to 1.0 over the core.
(Bottom)
Axial Length of Fuel
(Top)
Image by MIT OpenCourseWare.
“BWR/6: General Description of a BWR,” GE, 1980.
13
Connection of BWR Core Desig
gn to Neutronics
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?
Why
h are the
h BWR controll rods
d inserted
i
d ffrom the
h bbottom off the
h core?
Can dissolved boron be used as a means to control reactivity in a BWR core?
14
BWR Bundle Design Advances
Extended burnup features


More fuel pins (1010)) for a lower heat flux
Heavier fuel loadings
Control Rod
Improved mechanical performance


“Barrier” cladding
Low growth, wear resistant materials
Improved operational performance
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
Fuel Rod
Part Length Fuel Rod
Image by MIT OpenCourseWare.
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15
BWR Vessel and Vessel
Internals
16
BWR Vessel
Large vessel made of ring
forgings to avoid welds in
the core region
Vessel bottom head
accommodates CR penetrations
From: L.E. Fennern, ABWR Seminar – Reactor,
Core & Neutronics. April 13, 2007.
ABWR RPV beltline forging, weight: 127 tons; dimensions:
7.48 m outside diameter, 7.12 m inside diameter, 3.96 m high;
material: ASME SA 508, Class 3 EQ.
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17
BWR 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
Dryers
Dryer Height
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 System
ABWR
ESBWR
Ten internal
recirculation pumps
Relies on natural
circulation
BWR/6
Steam Flow
to Turbine
Steam Dryers
Steam Separators
Feed Flow
from Condenser
Driving
g Flow
o
Jet Pump
Core
Recirculation
Pump
External recirculation
pumps + jet pumps
Courtesy of GE Hitachi Nuclear Systems. Used with permission.
21
Traditional BWR vs ABWR and ESBWR
BWR/4-Mk I
(Browns Ferry 3)
BWR/6-Mk III
(Grand Gulf)
ABWR
ESBWR
3293/1098
3900/1360
3926/1350
4500/1550
Vessel height/dia. (m)
21.9/6.4
21.8/6.4
21.1/7.1
27.7/7.1
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-7
Safety Bldg Vol (m3/MWe)
115
150
160
<100
Parameter
Power (MWt/MWe)
Image by MIT OpenCourseWare.
22
BWR/6 Recirculation Flow
1 unit
Steam Flow
to Turbine 1 unit
Steam Dryers
Steam Separators
5 units
Feed Flow
from Turbine 1 unit
Driving Flow
4 units
Jet Pump
Core
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 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 Pumps
Holddown Assembly
Inlet
Jet Pump Nozzle
Assembly
Restrainers and
S
Supports
t
Core Shroud
Mixer
Restrainers and
pp
Supports
Inlet Riser
Reactor Vessel Wall
Core Support
Diffuser and Tail Pipe
Recirculation 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
BWR Power Cyycle
Moisture Separator
and Reheater
Steam
Reactor
Vessel
Turbine
Generator
HP
LP
LP
Separators
and Dryers
Condenser
Feedwater
Extraction Steam
Core
Demineralizers
Recirc
Pump
p
Recirc
Pump
p
Extraction Steam
Feed
Pumps
Heaters
Condensate
Pumps
Drain
Pumps
eate s
Heaters
Courtesy of GE Hitachi Nuclear Systems. Used with permission.
“BWR/6, General Description of a BWR,” GE, 1980
27
Radioactive Steam
Entire Power Conversion System becomes Radioactive 
Shi ldi is
Shielding
i Needed
N d d
Reaction products from water:
O16 + n  N16 + H1, T1/2 = 7.2 s; , 
O17 + n  N17 + H1, T1/2 = 4.2 s; , 
O18 + n  O19  F19, T1/2 = 29 s; , 
Activation of corrosion products:
Fe54 + n  Fe55, T1/2 = 2.7 y; 
Fe58 + n  Fe59, T1/2 = 44.6 d; , 
Co59 + n  Co60, T1/2 = 5.3 y; , 

Ni58 + n  Ni59, T1/2 = 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- + g, T1/2 = 9.2 h
Kr88  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 Condenser
29
BWR safety systems and
containment to be discussed later in the course
30
MIT OpenCourseWare
http://ocw.mit.edu
22.06 Engineering of Nuclear Systems
Fall 2010
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