Introduction to BWR Systems
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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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Introduction to BWR Systems

ACADs (08-006) Covered

Keywords

Feedwater, recirculation, BWR, flowpath, instrumentation, emergency cooling, containment.

Description

Supporting Material

Augusta Technical College 2011


Nuclear power plant orientation

Nuclear Power Plant Orientation

Introduction to BWR Systems

Browns Ferry Nuclear Plant


Introduction
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.


Enabling objectives
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


Enabling objectives1
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


HPT001.014D

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HPT001.014D

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$

Tennessee River


Bwr design
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.


Bwr internal flow
BWR Internal Flow

  • Feedwater enters downcomer.

  • Recirculation loops provide forced circulation.

  • Moisture removed by separators and dryers.

  • Steam exits steam dome.


BWR Internal Flow

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Core

8


Recirculation System Flow Path

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Jet Pump

Risers

Recirc Pump Suction

Ring Header

Recirc Pump Motor

9


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Steam Dryer installed in Reactor Pressure Vessel

10


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Steam Dryer stored in

Equipment Pit

11


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Fuel Transfer Canal

12


Plant layout
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.


Main steam system
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.


Main Steam System

Flow Path

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RPV

To HP and LP Turbines

15


Condensate and feedwater systems
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.


Condensate System Flow Path

B

C

A

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LP FW Heaters

B

A

C

A

B

C

17


Feedwater System Flow Path

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HP FW Heaters

Reactor Pressure

Vessel

RPV

Primary Containment

Reactor Feed Pumps

18


Fuel cell
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

20


Control rods
Control Rods

  • Rods contain boron as the neutron absorber.

  • Tubes held in cruciform array by a stainless steel sheath.

  • 185 control rods per reactor.


Control Rod Blade

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22


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Control Rod Blades

23


Nuclear instrumentation
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.


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


Emergency core cooling systems eccs
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.


Emergency core cooling systems eccs1
EMERGENCY CORE COOLINGSYSTEMS (ECCS)

  • High Pressure Coolant Injection (HPCI)

  • Low Pressure Coolant Injection (LPCI)

  • Core Spray

  • Automatic Depressurization System


Emergency Core Cooling Water Sources

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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


Primary and secondary containment
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.


Containment design
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.


Torus

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Primary and Secondary

Containment

Drywell

31


Advantages of bwrs
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.


Disadvantages of bwrs
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).


Summary
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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