IAEAInternational Atomic Energy Agency

Overview of CANDU Reactor Technology and the CANDU 9 Simulator

Matthias Krause

Nuclear Power Technology Development Section (NPTDS)

May 2014

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Why Nuclear, and How?

Quality of Life needs sustainable, affordable energy/electricity.“Nuclear power is the only existing option for large scale power production that transcends the limitations of non-renewable alternatives (such as coal, oil and gas) and renewable alternatives (wind, solar and biomass).”

Basic functional requirements for a Nuclear Reactor:• Fuel such as U-235• A moderator to thermalize fast neutrons• Coolant to remove the heat• Control systems to control the number of

neutrons/fissions• Shielding to protect equipment and people• Safe engineered systems that work together

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Stylized Nuclear Power Reactor

Simulators model most systems and sub-systems in a stylized, but “tuned” manner.

Safety Analysis codes model individual systems with more physical detail and less tuning.

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Systems and Sub-systems

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Quebec, CanadaGentilly 2 1 unit

RomaniaCernavoda 2 units

Ontario, CanadaDarlington 4 unitsPickering 6 unitsBruce 8 units

New Brunswick, CanadaPoint Lepreau

1 unitArgentinaEmbalse 1 unit

Republic of KoreaWolsong 4 units

India13 units, 5 units under construction, 2 in pre-project phasePakistanKANUPP 1 unit

ChinaQinshan 2 units

Point Lepreau, Canada Pickering, Canada Qinshan, China

Heavy Water Reactors based on the CANDU design in operation, under construction, or under refurbishment

- located on four continents

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The CANDU Design

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Pressure tube

Fuel

Calandria tube

Fuel channels

Fuelingmachine

Calandria

The CANDU Reactor Core - Components

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CANDU Fuelling

Online refuelling at a rate of ~24 bundles or ~0.5% per FPD• “Equilibrium core” with a mix of fresh and “burned-up” fuel• Slight power shape changes• Refuelling is the full-time job of the reactor station physicist• Refuelling simulators are available, but refuelling is NOT part of the

“normal” plant simulators

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The CANDU Reactor Core – Reactivity Control

Huge heavy and light water inventories act a passive heat sinks during prolonged accidents

Two capable, fast, independent low-pressure SDS’s1. SDS-1: 28 Cd Rods2. SDS-2: 6 Gd poison injection

nozzlesThree RRS or reactivity control devices:3. LZC – normally ~50%4. Adjusters – normally fully IN5. Absorbers – normally fully OUT6. (SDR withdrawal only)Diverse neutronic detectors

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REACTIVITY WORTHS OF CANDU-6 REACTIVITY DEVICES

 

Function 

Device 

Total Reactivity Worth (mk)

Maximum Reactivity

Rate (mk/s)

Control 14 Liquid Zone Controllers

7 0.14

Control 21 Adjusters 15 0.10

Control 4 Mechanical Control Absorbers

10 0.075(driving)- 3.5

(dropping)

Control Moderator Poison — -0.01 (extracting)

Safety 28 Shutoff Units -80 -50

Safety 6 Poison-Injection Nozzles

>-300 -50

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New Generation PHWRs

Enhanced CANDU 6 (EC6)• 740 MWe• Evolution of CANDU 6 (NU, heavy water coolant and

moderator)• Improvements based on Qinshan feedback and current

customer requirements• Enhanced safety, improved containment

ACR-1000• ~1150 MWe, Generation III+ technology • Combines experience of CANDU 6 with new concepts

(LEU, light water coolant, heavy water moderator)• Enhanced safety, economics, operability

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The Simulator

1. Plant Overview

2. Shutdown Rods

3. Reactivity Control

4. PHT Main Circuit

5. PHT Feed & Bleed

6. PHT Inventory Control

7. PHT Pressure Control

8. Bleed Condenser Control

9. SG Feed Pumps

10. SG Level Control

11. SG Level Trends

12. SG Level Man. Control

13. Extraction Steam

14. Turbine Generator

15. RRS / DPR

16. UPR

17. Trends

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Plant Overview Panel

Alarm Panel (top - common)

A ‘line diagram’ of the main plant systems and parameters• Moderator not modelled• Core with PK model for

fission and decay• PHTS avg parameters• SG and steam header• Valves (red = OPEN)• Simplified feedwater syst• 6 realtime trend displays

Control (bottom – common)• Panel/Manual Trips• Main Reactor Parameters• Simulator Run Control Overall Unit Control: Normal (turbine leads reactor)

Alternate (reactor leads turbine)

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Reactivity Control Panels

the movement of the AD and AB rods is designed to return the operating point (the intersection of power error and average zone level) to the central region

Three RRS or reactivity control devices:1. LZC – normally ~50%2. Adjusters – n. fully IN3. Absorbers – n. fully

OUT4. (SDR withdrawal only)

Diagram shows “Operating Point”, which defines automatic actions of AD and AB rods

All devices can be under AUTO or MAN control (different panel)

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Primary-Side Panels

The 480 channels are represented by four channels, two per loop with opposite flow directions, in the “figure of eight” configuration

No control, parameter display only - Control of PHT sub-systems on detailed panels:• Feed & Bleed• Inventory• Pressure• Pressurizer Bleed

Condenser

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Secondary-Side Panels

Detailed display of SG alarm, control, and trip points on separate panel

No control, parameter display only - Control of secondary-side systems on detailed panels:• Feed pumps• Man. Level control• Extraction steam

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Custom Parameters Panel

Plot 8 out of 65 available parameters to view parameters from different systems on one display.• Control of x-axis (time)• Automatic y-axis scale

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Two Simulator Exercises

• 2.3 Reactor and RRS Response to Power Manoeuvre

• 6.6 Main Steam Header Break

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Limitations of CANDU Simulator

• Only equilibrium core • No refuelling transients• No fresh/depleted fuel operation (initial reactor startup)

• No moderator and containment systems• no moderator/containment trips (e.g. for LOCAs)

• No large LOCA or ECC system, no LOC4P(SBO)• no simulation of “power pulse”• Very limited DBA and no SA simulation

• Some of the above are included in ACR simulator

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ACR Simulator Example

• LOCA in Reactor Inlet Header RIH#1• Plant Overview – show main features• RCS/Trip Parameters – watch for ROH-LP trip• RRS – observe SD actions and Flux Map• ECC/Passive Cooling – observe ECC actions