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Light
Water

Reactor
Light
Water
Reactor
- Concept -
July
27
Second
Period
July

27
,
Second

Period
YOSHIKAWA
Kazuhiro
YOSHIKAWA
Hitachi-GE Nuclear Energy, Ltd.
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
1
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Contents
Contents
1. Concept of Power Plant
2. Configuration of Nuclear Reactor
3. Feature of LWR (Light Water Reactor)
4. BWR and PWR
5. Plant Layout of LWR
6
Concept

of
Safety
Design
of
LWR
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
2
6
.
Concept
of
Safety
Design
of
LWR
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1
Gt
St
t
Bil
H
t
t
ltiit?
1
.
G
enera
t
e
St

eam a
t
B
o
il
e
r
and send it to Turbine.
H
ow
t
o genera
t
ee
l
ec
t
r
i
c
it
y
?
Steam
Turbine
2. Drive Turbine with the
Steam’s pressure, then
Electricity is generated by
the Generator connected
Generato

r
to the Turbine.
3. Condense the exhausted
Condenser
Water
Steam to Water and send it
back
to
the
Boiler.
Boiler
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
3
/>back
to
the
Boiler.
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H
y
droelectric Powe
r
Plant
水
の
落差
（
位置
エ
ネルギ
ー
）

を
利用
して
水車
／
発電機
を
回
す
y
Generate Electricity by the Potential Energy of the Water.
水
の
落差
（
位置
ネルギ
）
を
利用
して
水車
／
発電機
を
回
す
スクリーン
ダム
Screen

D
Pt til
E
ダム
屋外機器
取水
塔
D
am
Transformer
Intake
T
P
o
t
en
ti
a
l
E
nergy
鉄管弁
発電機
変圧器
制御室
スクリーン
塔
Ilt
Vl
Generator

Transformer
Main Control
Room
Discharge
Screen
T
ower
鉄管
入口弁
水車
放水路
Steel Pipe
I
n
l
e
t
V
a
l
ve
Hydraulic
Turbine
Discharge
Canal
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
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Each
type
Each
type

uses steam to
work Turbine
and Generator
Thermal
Boiler
Steam
Power
Plant
Water
Transformer
Coal, Oil, Gas
Turbine
Generato
r
Nuclear
Reacto
r
Steam
Cd
Nuclear
Power
Plant
Water
C
on
d
ense
r
Circulation
Sea

Water
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
5
Nuclear Fission
Feedwater Pump
Circulation
Pump
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y
Thermal Powe
r
&Nuclea
r
Powe
r
Thermal Power Plant Nuclear Power Plant
Fl
Cl
Oil
G
Ui
Pl t i
F
ue
l
C
oa
l
,
Oil
o
r
G

as.
U
ran
i
um,
Pl
u
t
on
i
um
Fuel
Supply
Continuously
supply
Refuel
once
in
1
-
2
years
Fuel
Supply
Continuously
supply
.
Refuel
once
in

1
2
years
.
Steam Condition at Su
p
e
r
critical
p
ressure Saturation
p
ressure
Turbine
p
p
above 22MPa.
p
around 7MPa.
Self-Regulating
Fti
f
P
No. Yes.
F
unc
ti
on o
f
P

owe
r
Residual Heat after
Shutdown
No. Yes.
(Decay
Heat
to be
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
6
Shutdown
(Decay
Heat
to

be

removed)
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Contents
Contents
1. Concept of Power Plant
2. Configuration of Nuclear Reactor
3. Feature of LWR (Light Water Reactor)
4. BWR and PWR
5. Plant Layout of LWR
6
Concept
of
Safety
Design
of

LWR
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
7
6
.
Concept
of
Safety
Design
of
LWR
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LWR uses Enriched Uranium as a Fuel
Natural Uranium
U-238
U-235
Enrich
Low Enriched Uranium
Enrich
U-238
U-235
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
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Nuclear
Fi i
Self
-
sustaining Chain Reaction
Fi
ss
i
on
Energy

Self
sustaining

Chain

Reaction
at Reactor Core : Critical
Nuclear
Fission
Fission
Product
U
-
235
Moderator
(Light Water)
Energy
U-235
Thermal Neutron
U
-
235
Thermal
Neutron
(Low
Energy)
Moderator(Light Water)
(Low Energy)
E
One Nuclear Fission

(Low
Energy)
E
nerg
y
Absorption
generates two or three
Neutrons.
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9
U-238
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How can we make the
1.
More Uranium.
Reactor Critical?
1.
More

Uranium.
a. Fuel with Enriched U-235.
b. Layout More Fuel in Reactor.
2. More Thermal Neutron.
a. Use Neutron Moderator.
3. Reduce Neutron Absorption of U-238.
a. Fuel with less U-238.
b
Md t M
Nt
b
.
M

o
d
era
t
e
M
ore
N
eu
t
rons.
4. Reduce Neutron Leakage to Outside of
Reactor.
a. Larger Reactor.
b. Use Neutron Moderator.
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
10
c. Locate Neutron Reflector around
Reactor.
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General Configuration
Fuel
of Nuclear Reactor
Clt
Fuel Bundles consist of Fuel Rods.
C
oo
l
an
t
Remove heat from Reactor CoreCoolant Outlet
Moderator

Reduce Energy of Fast Neutron to be Thermal.
Reflector
Bounce back Neutrons into Reacto
r
Core.
Control Material
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
11
Reduce the number of Neutrons by Absorption.
Coolant Inlet
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Reactor Configuration
Fuel
of Light Water Reactor.
Clt
Enriched U-235.
Fuel Bundles consist of Fuel Rods.
C
oo
l
an
t
Light Water.
Remove heat and generate steam.
Moderator
Light Water.
Reduce
energy
of
Fast
Neutron
to

be
Thermal
Reflector
Reduce
energy
of
Fast
Neutron
to
be
Thermal
.
Li
g
ht Water.
Control Material
g
Bounce back Neutrons into Reactor Core.
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
12
Control Rods consist of Boron.
Reduce the number of Neutrons by Absorption.
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Nuclear
Fi i
Enriched U-235 increase
Fi
ss
i
on
Energy
the potential of Nuclear

Fission.
Nuclear
Fission
Fission
Product
U
-
235
Moderator
(Light Water)
Energy
U-235
Thermal Neutron
U
-
235
Thermal
Neutron
(Low
Energy)
Moderator(Light Water)
(Low Energy)
E
Moderation of
Neutrons by Light
Water
makes
more
(Low
Energy)

E
nerg
y
Absorption
Control
Rods
absorb
Water
makes
more
Nuclear Fission of U-
235, and less
A
bsor
p
tion b
y
U-238.
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
13
U-238
Control
Rods
absorb
Neutrons.
p
y
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LWR
is
“
Light

Water
-
cooled,
&
Light
Water
-
moderated
Reactor
”
.
LWR
(Light
Water
Heavy Water
Reactor
Gas Cooled
Reactor
LWR
is
Light
Water
cooled,
&
Light
Water
moderated
Reactor .
(Light
Water


Reactor
Reactor
Reactor
Fuel Enriched U-235 Non enriched U-235
(Natural
U
235)
Enriched U-235
(Natural
U
-
235)
Coolant Light Water (H2O) Heavy Water (D2O) Helium Gas, Carbon
Dioxide Gas etc.
Moderator Light Water (H2O) Heavy Water (D2O) Graphite
Reflector
Light Water (H2O)
Heavy Water (D2O)
Graphite
Reflector
Light

Water

(H2O)
Heavy

Water


(D2O)
Graphite
Control Material Boron (B4C), Hf etc. Boron (B4C), Boron (B4C)
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
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Contents
Contents
1. Concept of Power Plant
2. Configuration of Nuclear Reactor
3. Feature of LWR (Light Water Reactor)
4. BWR and PWR
5. Plant Layout of LWR
6
Concept
of
Safety
Design
of
LWR
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
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6
.
Concept
of
Safety
Design
of
LWR
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Nuclear
Fi i
Self –Regulating Function

Fi
ss
i
on
Energy
Void Effect
ltd
thi
P
Nuclear
Fission
Fission
Product
U
-
235
Moderator
(Light Water)
Energy
re
l
a
t
e
d
thi
s
P
rocess.
U-235

Thermal Neutron
U
-
235
Thermal
Neutron
(Low
Energy)
Moderator(Light Water)
(Low Energy)
E
(Low
Energy)
E
nerg
y
Absorption
Doppler Effect
related
this
Process
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
16
U-238
related
this
Process
.
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Md t
Effi i
dd

it
Vid
Void Effect
•
M
o
d
era
t
o
r
Effi
c
i
ency
d
epen
d
son
it
s
V
o
id
Fraction.
•When Void Fraction is low
,
Reacto
r
Powe

r
R=
Ug
U
+
U
f
Void Fraction
,
will be reduced.
•Water Density has similar feature, but Void
Effect
has
larger
impact
on
Reactor
Power
U
g
+
U
f
Ug: VolumeofGas
Uf : Volume of Liquid
Moderator
Fast Neutron
(High
Energy)
Thermal Neutron

(L
E)
U-235
Effect
has
larger
impact
on
Reactor
Power
.
(High
Energy)
(L
ow
E
nergy
)
Void Fraction; Low
Nuclear Fission
U-235
Moderator
Fast Neutron
(High Energy)
Fast Neutron
(High Energy)
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
17
17
Void Fraction; High

No Interaction
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Doppler Effect
•U-238 absorbs high energy
Neutrons (Fast Neutrons).
•Distribution of U-238 Absorption
Possibility depends on its
Temperature.
ion(barn)
•When Fuel Temperature is high,
U-238 will absorb the Neutrons
with
wider
range
of
Energy
due
Cross Sect
with
wider
range
of
Energy
due
to Resonance.
•Then Reactor Power will be
dd
re
d
uce
d
.

U-238 Absorption Cross Section
Neutron Energy (eV)
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
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vers
it
y
Self Re
g
ulatin
g
gg
Process of LWR
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Power Control of
LWR
Power

Control

of
LWR
Control the number of
Neutron by Absorption.
Control Rod Position
Dissolve Boron in
Coolant
and
Control
Coolant
and
Control
its Density.

Control the number of
Thermal Neutron by
Vid
Eff t
Control Coolant Flow
Rate at Reactor Core
to Control the Void
V
o
id
Eff
ec
t
.
Fraction.
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
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Power Control using Void Effect
High Core Flow Low Core Flow
Increase Core Flow
Reduce Core Flow
More Voids in
Reactor Boosted to
U
Ri
Less Voids in
Reactor Boosted to
U
Ri
U
ppe

r
R
eg
i
on.
Void Fraction
U
ppe
r
R
eg
i
on.
Void Fraction
Reduced.
Nuclear
Fission
Increased.
Nuclear
Fission
Nuclear
Fission
Increased.
Rt
P
Nuclear
Fission
Reduced.
Rt
P

Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
21
R
eac
t
o
r
P
owe
r
increased.
R
eac
t
o
r
P
owe
r
Reduced.
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Contents
Contents
1. Concept of Power Plant
2. Configuration of Nuclear Reactor
3. Feature of LWR (Light Water Reactor)
4. BWR and PWR
5. Plant Layout of LWR
6
Concept
of
Safety

Design
of
LWR
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
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6
.
Concept
of
Safety
Design
of
LWR
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y
BWR
Generate
Steam
by
(Boiling Water Reactor)
Power Supply
Generate
Steam
by
Boiling Light Water at
Reactor and directly
send
it
to
Turbine
Primary Containment Vessel
Steam
send

it
to
Turbine
.
Reactor Pressure Vessel
Steam
Water
Turbine
Generator
Transformer
Condenser
Water
Sea Water
Circulation
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
23
Pressure Suppression Pool
Feedwater Pump
Pump
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y
PWR：PressurizedWaterReactor
PWR
Has
2
Loops
(Pressurized Water Reactor)
Power Supply
Has
2
Loops
.
Primary Loop

make Heated
Light
Water
and
Primary Containment Vessel
Pressurizer
S
Steam Generator
Light
Water
,
and
generates Steam
at Steam
Generator.
S
team
Water
Turbine
Generator
Transformer
Generator.
2ndary Loop
sends it to
Turbine.
Condenser
Reactor Pressure Vessel
Coolant Pump
Sea Water
Circulation

Water
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
24
Feedwater Pump
Pump
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it
y
Com
p
arison between BWR & PWR
p
Reactor Type Pros and Cons

Simple
Configuration (Direct
Cycle)

Simple
Configuration
.
(Direct
Cycle)
Small Pressure Containment Vessel.
Low Power Density in Reactor.

Easy
Power
Control
using
Void
Effect.

Easy

Power
Control
using
Void
Effect.
Need Radiation Shield in Turbine Island.
Complex Configuration.(In-direct Cycle)
Large Pressure Containment Vessel with Steam
Generators
and
Pressurizers
as
well
as
Reactor
Generators
and
Pressurizers
as
well
as
Reactor
Pressure Vessel.
High Power Density in Reactor.

No
Radiation
Shield
is
needed

in
Turbine
Island
Copyright © 2011 Hitachi-GE Nuclear Energy, Ltd. All Rights Reserved.
25

No
Radiation
Shield
is
needed
in
Turbine
Island
.