Overview of CANDU Pressurized Heavy Water Reactor (PHWR)and the Canadian Nuclear Industry

Mikko I. Jyrkama and Mahesh D. PandeyDepartment of Civil Engineering, University of Waterloo, Waterloo, Ontario, N2L 3G1, Canada

Steam (light water)

SteamGenerator

PressurizerPump/MotorAssembly

Feedwater(light water)

Calandria

Fueling MachineFueling Machine

Moderator (heavy water)Fuel Channels

Feeders

From FuelChannels

High PresureTurbine

FeedwaterPump

Assembly

Condenser

ModeratorPump

ModeratorHeat Exchanger

Low Pressure Turbines

CoolingWater

Generator

Switchyard

Powerto Grid

To FuelChannels

Fuel

CANDU® - CANada Deuterium Uranium

CalandriaEnd Shield

Tubesheet

End Fitting

Feeder Pipe

ChannelClosure

Liner Tube

PositioningAssembly

Heavy Water Moderator

Fuel Bundles

Shield Plug

Fuel ChannelLattice Tube

Calandria Tube Pressure Tube

Annulus Gas (CO2)Fuel Bundle

Heavy Water CoolantAnnulus Spacer

2005

2007

2008

2009

2010

2006

2011

2012

2013

2014

2015

2016

2017

2018

2019

2020

2021

2022

2023

Pickering 2,3Restart

IMO Median Demand Growth ~0.9% p.a.

MW Dispatchable (after avg. Capacity Factors applied)36,000

34,000

32,000

30,000

28,000

26,000

24,000

22,000

20,000

18,000

16,000

14,000

12,000

10,000

Res

ou

rces

(M

W)

Coal (as shutdown)

New Hydro(incl. ~1,400 MW from Manitoba)

Existing Resources (2005)11,000 MW

7,700 MW7,600 MW5,100 MW

NuclearHydroCoalGas

Total Gas ~12,000 MW (~30% of Installed MW)New Gas Builds ~7,000 MW Installed

Nuclear RefurbishmentBruce & Darlington

(Pickering A&B run toend of current life)

New Nuclear (6,100 MW net)Six ACR-1000 units

Wind/Renewable ~10% of Installed MW

Reactor Assembly

AcknowledgementsThis work is part of the NSERC-UNENE Industrial Research Chair (IRC) program at the University of Waterloo. The Chair is one of the sixuniversity professorships established by UNENE in Ontario. The program is funded by UNENE in partnership with NSERC. Industrial sponsorship is provided by Ontario Power Generation, Bruce Power, and Atomic Energy of Canada Limited.

Regulation

1

2

3

4

5

6

7

Steam Outlet Nozzle

Shroud Cone

Tube Bundle

Tube Bundle Hot Leg

Tubesheet

D2O InletD2O Outlet

Feedwater Inlet Nozzle

Preheater Section

Tube Bundle Cold Leg

Grid Tube Support Plate

Shroud

U Bend

Primary Cyclone Separators

Secondary Cyclone Separators

Manway

CANDU Evolution

800

700

600

500

400

300

200

100

900

1950 1960 1970 1980 1990 2000 2010Years

Po

wer

(M

We)

900 MW ClassReactors

600 MW ClassReactors

Research & PrototypeReactors

ZEEPNRX NPD

NRU

RAPP 1,2

Douglas Point

KANUPP

Pickering A Pickering B

Gentilly 2

EmbalsePt. Lepreau

Wolsong 1 Cernavoda 1

Wolsong 2,3,4

Qinshan 1,2

Bruce A Bruce B

Darlington

CANDU 9

Demand for Electricity UNENE

NuclearNucléaire

Gross Capacity (per unit)Net Capacity (per unit)

Construction StartStart-up

Fuel:Elements in bundle/bundles per channelTotal number of fuel bundles in core

Fuel Channels:NumberCalandria tube materialCalandria tube ID/wall thickness (mm)Pressure tube materialPressure tube ID/wall thickness (mm)

Heat Transport SystemNumber of loopsReactor inlet/outlet temperature (°C)Number of heat transport pumpsNumber of steam generatorsNumber of SG tubes/material

791 MW740 MW

Operator

Reactor

Unit

Bruce A Bruce B

1-4

Dec 1970Jul 1976

37/136240

480a. Zircaloy-2129/1.37cw. Zr-2.5%Nb103.4/4.06

4250-265/30448*4200/Inconel 600

4250-265/30448*4200/Inconel 600

* Bruce A and B steam generators have separate preheaters

807 MW750 MW

5-8

Jan 1978May 1984

37/136240

480a. Zircaloy-2129/1.37cw. Zr-2.5%Nb103.4/4.11

Pickering A

2249/29312 plus 4 spare122600/Monel

542 MW508 MW

1-4

Jun 1966Feb 1971

28/124680

390a. Zircaloy-2130.8/1.55cw. Zr-2.5%Nb103.4/4.06

Pickering B

540 MW508 MW

5-8

Nov 1974Oct 1982

Darlington

4267/310444663/Incoloy 800

935 MW881 MW

1-4

Sep 1981Nov 1989

37/136240

480a. Zircaloy-2129/1.37cw. Zr-2.5%Nb103.4/4.19

Point Lepreau

2266/310443542/Incoloy 800

680 MW635 MW

N/A

May 1975Jul 1982

37/124560

380a. Zircaloy-2129/1.37cw. Zr-2.5%Nb103.4/4.19

Gentilly

2266/310443542/Inconel 600

675 MW640 MW

2

Apr 1974Sep 1982

37/124560

380a. Zircaloy-2129/1.37cw. Zr-2.5%Nb103.4/4.19

2249/29312 plus 4 spare122573/Monel

28/124560

380a. Zircaloy-2129/1.37cw. Zr-2.5%Nb103.4/4.01

Cross-Section

Steam Generator

Uses natural uranium as fuel and deuterium oxide (D2O) or "heavy water" as coolant and moderatorStarted as the Canadian contribution to the War effortDesigned by AECL (Atomic Energy of Canada Limited)All nuclear power reactors in Canada are CANDUsCan be refuelled at full powerMultiple shutdown systems for added safety

The steam turns tthe turbines and the turbines turn the generator to produce electricity.

Uranium atoms are split in the core under controlled conditions to produce a chain reaction, providing large amounts of energy in the form of heat.

Heavy water coolant circulates in the Primary Heat TransportSystem through the reactor core.

The hot heavy water coolant from the reactor istransferred to the steam generators to produce steam.

Feeders - inlet and outlet feeders connect each fuel channel individually to connectors (headers) above the core and then to the steam generators

Calandria - a horizontal, cylindrical, single-walled, 6 m long stepped shell enclosed at each end by tubesheets and spanned by calandria tubes and filled with the heavy water moderatorModerator - consists of heavy water at near atmospheric pressure and at a temperature of 70°C, used for moderating (slowing down) the high energy fission neutronsCalandria Tubes - provide access through the calandria for the fuel channel assemblies and also support the pressure tubes by means of four garter spring spacers per channelFuel Channels - the fuel channels contain the pressure tubes that hold the fuel bundles in the neutron flux of the reactor core

1. Calandria2. Calandria end shield3. Shut-off and control rods4. Poison injection5. Fuel channel assemblies6. Feeder pipes7. Vault

CANDU Nuclear PowerPlant Schematic

The condenser turns the steam back into water which is then returned to the steam generators through the feedwater system.

The heavy water coolant in the primary heat transport system removes heat from the reactor core by circulating in the pressure tubes and cooling the fuel bundlesThe HTS operating pressure is ~10 MPa and the typical variation of coolant temperature is from 266°C at the channel inlet to 312°C at the channel outletThe HT water has a pH above 10 and a very low oxidation potential in order to protect the HT piping such as pressure tubes, steam generator tubes, feeders, and fuel Steam Generators - transfer the heat from the hot heavy water (D2O) circulating in the primary heat transport system to ordinary "light" water in the steam generator

The CANDU fuel consists of natural uranium, which contains a fraction of 0.72 % (isotopic abundance) of isotope 235U, with the remaining fraction in the form of 238UThe fuel is fabricated into small UO2 pellets which are then placed inside 0.5 m long fuel rods (small Zircaloy tubes)The tubes are then arranged into fuel bundles consisting of an assembly of 37 elementsSpacer pads on the surface of the tubes prevent direct contact of the fuel rods with the pressure tube walls and allow space for coolant flow through the bundles

Heat Transport System

Fuel

Close-up

Fuel Bundle Zircaloy Fuel Rod(fuel sheath)

UO2 Fuel Pellet

End Plate

End Cap

Spacer Pad

(Sources: Atomic Energy of Canada Limited AECL and Canadian Nuclear Association CNA)

U N E N EUniversity Network of Excellence

in Nuclear Engineering

Point Lepreau Turbine-Generator

(image courtesy of AECL)

(image courtesy of AECL)

CANDU Reactor Assembly(during construction)

(image courtesy of AECL)

The Canadian Nuclear Safety Commission (CNSC), an independent agency of the Government of Canada operates and enforces regulations under the Nuclear Safety and Control Act (NSC Act)As the federal regulator, the CNSC

executes licensing decisions made by the Commission or its designatescontinually monitors licensees to ensure they comply with safety requirements that protect workers, the public, and the environmentuphold Canada’s international commitments on the peaceful use of nuclear energy

The CNSC functions as a tribunal, taking into account the views, concerns and opinions of interested parties and intervenors when establishing regulatory policy, making licensing decisions and implementing programs

In addition to the NSC Act, the CNSC also administers other nuclear related regulations and bylaws in the form of policies, standards, guides and notices

Current energy infrastructure in Ontario will be unable to meet futuresupply requirements

coal phase-out will place additional strains on supplyimports can only meet fluctuations in demand

Future demand can be met with a mix of sources, including Nuclear

(Source: Atomic Energy of Canada Limited)

(Sources: International Atomic Energy Agency IAEA and Canadian Nuclear Safety Commission CNSC)

(image courtesy of CANTEACH)

(image courtesy of CANTEACH)

(image courtesy of AECL)

(CANDU 6’s)

ACRAdvanced CANDU

Reactor

Gas Annulus - the gap between the fuel channel pressure tubes and the calandria tubes insulates the hot pressure tubes from the relatively cool moderator

University Network of Excellence in Nuclear Engineering

UNENE is an alliance of universities, nuclear power utilities, research and regulatory agencies for the support and development of nuclear education and R&D capability in Canadian universitiesThe main purpose of UNENE is to assure a sustainable supply of qualified nuclear engineers and scientists to meet the current and future needs of the Canadian nuclear industry

UNENE has created a fully accredited course-based Master's of Engineering (MEng) program in Nuclear Engineering which is offered jointly by the member universities

UNENE has established Industrial Research Chairs (professorships) in six Ontario universities through a partnership with NSERC and generous support from the Canadian nuclear industry

Nuclear Research and Development

Nuclear Engineering Education Program