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ACADs (08-006) Covered Keywords

Introduction to BWR Systems. ACADs (08-006) Covered Keywords Feedwater , recirculation, BWR, flowpath , instrumentation, emergency cooling, containment. Description Supporting Material. Nuclear Power Plant Orientation. Introduction to BWR Systems. Browns Ferry Nuclear Plant.

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ACADs (08-006) Covered Keywords

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  1. Introduction to BWR Systems ACADs (08-006) Covered Keywords Feedwater, recirculation, BWR, flowpath, instrumentation, emergency cooling, containment. Description Supporting Material Augusta Technical College 2011

  2. Nuclear Power Plant Orientation Introduction to BWR Systems Browns Ferry Nuclear Plant

  3. 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.

  4. 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

  5. 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

  6. HPT001.014D Rev. 0 Page 6 of 34 HPT001.014D Rev. 0 Page 6 of 34 $ Tennessee River

  7. 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.

  8. BWR Internal Flow • Feedwater enters downcomer. • Recirculation loops provide forced circulation. • Moisture removed by separators and dryers. • Steam exits steam dome.

  9. BWR Internal Flow HPT001.014D Rev. 0 Page 9 of 34 Core 8

  10. Recirculation System Flow Path HPT001.014D Rev. 0 Page 10 of 34 Jet Pump Risers Recirc Pump Suction Ring Header Recirc Pump Motor 9

  11. HPT001.014D Rev. 0 Page 11 of 34 Steam Dryer installed in Reactor Pressure Vessel 10

  12. HPT001.014D Rev. 0 Page 12 of 34 Steam Dryer stored in Equipment Pit 11

  13. HPT001.014D Rev. 0 Page 13 of 34 Fuel Transfer Canal 12

  14. 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.

  15. 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.

  16. Main Steam System Flow Path HPT001.014D Rev. 0 Page 16 of 34 RPV To HP and LP Turbines 15

  17. 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.

  18. Condensate System Flow Path B C A HPT001.014D Rev. 0 Page 18 of 34 LP FW Heaters B A C A B C 17

  19. Feedwater System Flow Path HPT001.014D Rev. 0 Page 19 of 34 HP FW Heaters Reactor Pressure Vessel RPV Primary Containment Reactor Feed Pumps 18

  20. Fuel Cell • Currently, Framatome is the supplier of fuel for BFN. • Four fuel bundles per cell. • 764 bundles per reactor.

  21. HPT001.014D Rev. 0 Page 21 of 34 Fuel Cell Control Rod Blade 20

  22. Control Rods • Rods contain boron as the neutron absorber. • Tubes held in cruciform array by a stainless steel sheath. • 185 control rods per reactor.

  23. Control Rod Blade HPT001.014D Rev. 0 Page 23 of 34 22

  24. HPT001.014D Rev. 0 Page 24 of 34 Control Rod Blades 23

  25. Nuclear Instrumentation • Source range - 0.1 to 106 cps • Intermediate range - 104 cpsto 40% power . • Power range - 1 to 125% power. Three ranges of neutron monitoring; all in-core.

  26. Nuclear Instrumentation HPT001.014D Rev. 0 Page 26 of 34 BOTTOM OF TOP GUIDE DETECTOR CHAMBERS LENGTH OF ACTIVE FUEL CORE SUPPORT REACTOR VESSEL IN-CORE HOUSING GUIDE TUBE REACTOR SUPPORT STRUCTURE 25

  27. EMERGENCY CORE COOLINGSYSTEMS (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.

  28. EMERGENCY CORE COOLINGSYSTEMS (ECCS) • High Pressure Coolant Injection (HPCI) • Low Pressure Coolant Injection (LPCI) • Core Spray • Automatic Depressurization System

  29. Emergency Core Cooling Water Sources HPT001.014D Rev. 0 Page 29 of 34 Condensate Storage Tanks ~2,000,000 gal Normal Systems Reactor CONDENSATE FEEDWATER CONTROL ROD DRIVE Emergency Systems HIGH PRESSURE COOLANT INJECTIONCORE SPRAYLOW PRESSURE COOLANT INJECTION Torus ~950,000 gal Tennessee River RHR SVC WATER FIRE PROTECTION 28

  30. 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.

  31. 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.

  32. Torus HPT001.014D Rev. 0 Page 32 of 34 Primary and Secondary Containment Drywell 31

  33. 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.

  34. 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).

  35. 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).

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