Nuclear Power Plant Orientation

Browns Ferry Nuclear Plant

Nuclear Power Plant Orientation

Introduction to BWR Systems

TVAN Technical TrainingHealth Physics (RADCON) Initial Training Program

HPT001.014DRev. 0Page 2 of 34

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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Enabling Objectives

Identify the major components and flowpaths in the steam cycle.

Recognize the functions of water in a BWRRecognize the functions of the control rods in a

BWR

Recognize the capability and purpose of nuclear

instrumentation

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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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15

$

Tennessee River





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.

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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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BWR Internal Flow

Core

8


Recirculation System Flow Path

Recirc Pump Suction

Recirc Pump Motor

Ring Header

Risers

Jet Pump

9


Steam Dryer installed in Reactor Pressure Vessel

10


Steam Dryer stored in Equipment Pit

11


Fuel Transfer Canal

12




Plant Layout

• The entire Reactor Coolant System (RCS) and other primary support systems are located within containment (the drywell) and reactor buildings.

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Main Steam, Condensate and Feedwater (all radioactive) are housed within the turbine building.

The reactor is operated remotely from the control building.



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

To HP and LP Turbines

RPV

15




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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Makeup FromCST

RejectControl

To 9 Cond.Demins

MakeupControl

To29A & B

Reject toCST

To SealInjectionPumps

Condensate System Flow Path

A

B C

LP FW Heaters

B

C

A

A B C

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Feedwater System Flow Path

Reactor Feed Pumps

HP FW Heaters

Primary Containment

Reactor PressureVessel

RPV

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Fuel Cell

• Currently, Framatome is

the supplier of fuel for

BFN.

• Four fuel bundles per

cell.

• 764 bundles per

reactor.

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Fuel Cell

Control Rod Blade

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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

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Control Rod Blades

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Nuclear Instrumentation

• Source range - 0.1 to 106 cps

• Intermediate range - 104 cps to 40% power .

• Power range - 1 to 125% power.

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Three ranges of neutron monitoring; all in-core.

Nuclear Instrumentation

IN-CORE HOUSING GUIDE TUBE

CORE SUPPORT

REACTOR SUPPORT STRUCTURE

LENGTH OFACTIVE FUEL

DETECTOR CHAMBERSBOTTOM OF TOP GUIDE

REACTOR VESSEL

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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.TP-26



EMERGENCY CORE COOLINGSYSTEMS (ECCS)

• High Pressure Coolant Injection (HPCI)

• Low Pressure Coolant Injection (LPCI)

• Core Spray

• Automatic Depressurization System

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CondensateStorage Tanks

~2,000,000 gal

Torus~950,000 gal

Reactor

Tennessee River

Normal SystemsCONDENSATEFEEDWATERCONTROL ROD DRIVE

Emergency SystemsHIGH PRESSURE COOLANT INJECTIONCORE SPRAYLOW PRESSURE COOLANT INJECTION

RHR SVC WATERFIRE PROTECTION

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Emergency Core Cooling Water Sources



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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HPT001.014DRev. 0Page 30 of 34Containment 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.

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Primary and SecondaryContainment

Drywell

Torus31



HPT001.014DRev. 0Page 32 of 34Advantages 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.

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HPT001.014DRev. 0Page 33 of 34Disadvantages 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).

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HPT001.014DRev. 0Page 34 of 34Summary

• 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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Nuclear Power Plant Orientation