Nuclear Power Plant Orientation
Introduction to BWR Systems
Browns Ferry Nuclear Plant
HPT001.014D
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Introduction
• During this phase of the training we will
discuss the basic operation of a Boiling
Water Reactor (BWR) Plant, including:
– the major design concepts of the Browns Ferry
BWR-4 and its Mark I containment
– the importance of nuclear safety.
• We will also discuss several of the
systems associated with BFN’s operation.
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TP-2
HPT001.014D
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Page 3 of 34
Enabling Objectives
Identify the major components and flowpaths in
the steam cycle.
Recognize the functions of water in a BWR
Recognize the functions of the control rods in a
BWR
Recognize the capability and purpose of nuclear
instrumentation
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TP-3
HPT001.014D
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Page 4 of 34
Enabling Objectives
Identify alternate sources of emergency cooling
water to the reactor vessel
Relate major concepts employed in containment
design
Identify inherent safety features of a BWR
Compare advantages and disadvantages of a
BWR to that of a PWR
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TP-4
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BWR Design
• Selected by GE due to its inherent advantages
in control and design simplicity.
• Single loop system; steam and associated
secondary systems are radioactive.
• Operating pressure is approximately half that of
a PWR at 1,000 psi.
• Capacity of units two and three is ~1,100 Mwe
each.
TVAN Technical Training
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TP-6
HPT001.014D
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Page 7 of 34
BWR Internal Flow
• Feedwater enters downcomer.
• Recirculation loops provide forced
circulation.
• Moisture removed by separators and
dryers.
• Steam exits steam dome.
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TP-7
HPT001.014D
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Page 8 of 34
BWR Internal Flow
Core
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Recirculation System Flow Path
Jet Pump
Risers
Recirc Pump Suction
Ring Header
Recirc Pump Motor
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Steam Dryer installed in
Reactor Pressure Vessel
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Steam Dryer stored in
Equipment Pit
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Fuel Transfer Canal
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Plant Layout
• The entire Reactor Coolant System
(RCS) and other primary support
systems are located within containment
(the drywell) and reactor buildings.
Main Steam, Condensate and
Feedwater (all radioactive) are housed
within the turbine building.
 The reactor is operated remotely from
the control building.

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TP-13
HPT001.014D
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Page 14 of 34
Main Steam System
• Steam generated by the reactor is admitted to four main
steam lines.
• One high pressure and three low pressure turbines
convert thermody- namic energy into mechanical energy
to drive the main generator.
• Safety objective is to prevent overpressurization of the
nuclear system.
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Main Steam System
Flow Path
HPT001.014D
Rev. 0
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RPV
To HP and LP Turbines
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Condensate and Feedwater Systems
• Once the steam has passed through the
high and low pressure turbines, it must be
condensed and then pumped back to the
reactor so that the cycle can be repeated.
• These systems will collect, pre-heat, and
purify feedwater prior to its return to the
reactor plant.
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TP-16
HPT001.014D
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Page 17 of 34
Condensate System Flow Path
LP FW Heaters
To Seal
Injection
Pumps
A
BB
C
Makeup
Control
A
To 9 Cond.
Demins
B
C
Reject
Control
To
29A & B
Reject to
CST
Makeup From
CST
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Feedwater System Flow Path
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HP FW Heaters
Reactor Pressure
RPV
Vessel
Primary Containment
Reactor Feed Pumps
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Fuel Cell
• Currently, Framatome is
the supplier of fuel for
BFN.
• Four fuel bundles per
cell.
• 764 bundles per
reactor.
TP-19
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Fuel Cell
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Page 20 of 34
Control Rod Blade
20
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Control Rods
• Rods contain boron as the
neutron absorber.
• Tubes held in cruciform array by a
stainless steel sheath.
• 185 control rods per reactor.
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Control Rod Blade
HPT001.014D
Rev. 0
Page 22 of 34
Note:
(21) ABSORBER RODS 143" X
.188" OD IN EACH SHEATH OF
BLADE
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Control Rod Blades
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Nuclear Instrumentation
Three ranges of neutron monitoring; all
in-core.
• Source range - 0.1 to 106 cps
• Intermediate range - 104 cps to 40% power .
• Power range - 1 to 125% power.
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HPT001.014D
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Page 25 of 34
Nuclear Instrumentation
BOTTOM OF TOP GUIDE
DETECTOR CHAMBERS
LENGTH OF
ACTIVE FUEL
CORE SUPPORT
REACTOR VESSEL
IN-CORE HOUSING GUIDE TUBE
REACTOR SUPPORT STRUCTURE
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EMERGENCY CORE COOLING
SYSTEMS (ECCS)
• Prevent fuel cladding fragmentation for
any failure including a design basis
accident.
• Independent, automatically actuated
cooling systems.
• Function with or without off-site power.
• Protection provided for extended time
periods.
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HPT001.014D
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Page 27 of 34
EMERGENCY CORE COOLING
SYSTEMS (ECCS)
• High Pressure Coolant Injection (HPCI)
• Low Pressure Coolant Injection (LPCI)
• Core Spray
• Automatic Depressurization System
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Emergency Core
Cooling Water Sources
HPT001.014D
Rev. 0
Page 28 of 34
Condensate
Storage Tanks
~2,000,000 gal
Normal Systems
CONDENSATE
FEEDWATER
CONTROL ROD DRIVE
Reactor
Emergency Systems
HIGH PRESSURE COOLANT INJECTION
CORE SPRAY
LOW PRESSURE COOLANT INJECTION
Torus
~950,000 gal
RHR SVC WATER
FIRE PROTECTION
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Primary and Secondary Containment
• Primary Containment consists of the
Drywell and Suppression Pool (Torus).
• Secondary Containment consists of the
Reactor Building.
• Designed to contain the energy and
prevent significant fission product
release in the event of a loss of coolant
accident.
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Containment Design
HPT001.014D
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Page 30 of 34
• Structural Strength - steel structure with
reinforced concrete able to withstand internal
pressure.
• Pressure Suppression - large pool of water in
position to condense steam released from
LOCA.
• Designed to contain the energy and prevent
significant fission product release in the event
of a loss of coolant accident.
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TP-30
HPT001.014D
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Page 31 of 34
Primary and Secondary
Containment
Drywell
Torus
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Advantages of BWRs
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• Single loop eliminates steam generator
• Bottom entry control rods reduce
refueling outage time/cost; also provide
adequate shutdown margin during
refueling.
• Lower operating pressure lowers cost to
obtain safety margin against piping
rupture.
• Design simplifies accident response.
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Disadvantages of BWRs
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• More radiation/contamination areas;
increased cost associated with
radwaste.
• Piping susceptible to intergranular
stress corrosion cracking (IGSCC).
• Off-gas issues (e.g. - H2 gas presents
explosion potential, low levels of
radioactive noble gases are
continuously released).
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Summary
HPT001.014D
Rev. 0
Page 34 of 34
• A Boiling Water Reactor plant is comprised of
many different and complex systems, all of
which support the overall goal of safely
producing electricity.
• The design challenge of a BWR is to
incorporate all the criteria of power
generation and safety in non-conflicting ways
in order to meet the load demand of the
public and satisfy the requirements set forth
by the Nuclear Regulatory Commission
(NRC).
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