1. Nuclear Power Plant Orientation
Introduction to BWR Systems
Browns Ferry Nuclear Plant
Appendix 4 - EGT R4.ppt

2. 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.
Appendix 4 - EGT R4.ppt

3. 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

4. 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

5. $ Tennessee River HPT001.014D Rev. 0 HPT001.014D Page 5 of 34 Rev. 0
Appendix 4 - EGT R4.ppt

6. 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.
Appendix 4 - EGT R4.ppt

7. BWR Internal Flow Feedwater enters downcomer.
Recirculation loops provide forced circulation.
Moisture removed by separators and dryers.
Steam exits steam dome.
Appendix 4 - EGT R4.ppt

8. BWR Internal Flow
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Core 8

9. Recirculation System Flow Path
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Jet Pump
Risers
Recirc Pump Suction
Ring Header
Recirc Pump Motor 9
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10. Steam Dryer installed in Reactor Pressure Vessel
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Steam Dryer installed in Reactor Pressure Vessel 10

11. Steam Dryer stored in Equipment Pit 11 HPT001.014D Rev. 0
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Steam Dryer stored in
Equipment Pit 11

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Fuel Transfer Canal 12

13. 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.
There are many systems that connect to the RCS and thus could potentially contain radioactive water. All of these systems are located in the Auxiliary Building.
Appendix 4 - EGT R4.ppt

14. 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.
There are many systems that connect to the RCS and thus could potentially contain radioactive water. All of these systems are located in the Auxiliary Building.
Appendix 4 - EGT R4.ppt

15. Main Steam System Flow Path RPV To HP and LP Turbines 15 HPT001.014D
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RPV
To HP and LP Turbines 15
Appendix 4 - EGT R4.ppt

16. 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.
There are many systems that connect to the RCS and thus could potentially contain radioactive water. All of these systems are located in the Auxiliary Building.
Appendix 4 - EGT R4.ppt

17. Condensate System Flow Path
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LP FW Heaters A B C B C A A B C 17
Appendix 4 - EGT R4.ppt

18. Feedwater System Flow Path
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HP FW Heaters
Reactor Pressure
Vessel
RPV
Primary Containment
Reactor Feed Pumps 18
Appendix 4 - EGT R4.ppt

19. Fuel Cell Currently, Framatome is the supplier of fuel for BFN.
Four fuel bundles per cell.
764 bundles per reactor.
There are many systems that connect to the RCS and thus could potentially contain radioactive water. All of these systems are located in the Auxiliary Building.
Appendix 4 - EGT R4.ppt

20. Fuel Cell
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Control Rod Blade 20

21. Rods contain boron as the neutron absorber.
Control Rods
Rods contain boron as the neutron absorber.
Tubes held in cruciform array by a stainless steel sheath.
185 control rods per reactor.
There are many systems that connect to the RCS and thus could potentially contain radioactive water. All of these systems are located in the Auxiliary Building.
Appendix 4 - EGT R4.ppt

22. Control Rod Blade
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23. HPT D
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Control Rod Blades 23

24. Nuclear Instrumentation
Three ranges of neutron monitoring; all in-core.
Source range to 106 cps
Intermediate range cps to 40% power .
Power range - 1 to 125% power.
There are many systems that connect to the RCS and thus could potentially contain radioactive water. All of these systems are located in the Auxiliary Building.
Appendix 4 - EGT R4.ppt

25. Nuclear Instrumentation
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BOTTOM OF TOP GUIDE
DETECTOR CHAMBERS
LENGTH OF
ACTIVE FUEL
CORE SUPPORT
REACTOR VESSEL
IN-CORE HOUSING GUIDE TUBE
REACTOR SUPPORT STRUCTURE 25
Appendix 4 - EGT R4.ppt

26. 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.
Appendix 4 - EGT R4.ppt

27. EMERGENCY CORE COOLING SYSTEMS (ECCS)
High Pressure Coolant Injection (HPCI)
Low Pressure Coolant Injection (LPCI)
Core Spray
Automatic Depressurization System
Appendix 4 - EGT R4.ppt

28. Emergency Core Cooling Water Sources
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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
Tennessee River
RHR SVC WATER
FIRE PROTECTION 28

29. 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.
Appendix 4 - EGT R4.ppt

30. Containment Design
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.
Appendix 4 - EGT R4.ppt

31. Drywell Torus Primary and Secondary Containment 31 HPT001.014D Rev. 0
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Primary and Secondary
Containment
Drywell
Torus 31
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32. Advantages of BWRs 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.
Appendix 4 - EGT R4.ppt

33. Disadvantages of BWRs
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).
Appendix 4 - EGT R4.ppt

34. Summary
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).
Appendix 4 - EGT R4.ppt