Overview of CANDU Reactor Technology
and the CANDU 9 Simulator
Matthias Krause
Nuclear Power Technology Development Section (NPTDS)
May 2014
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International Atomic Energy Agency
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:
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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 subsystems 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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Heavy Water Reactors based on the CANDU design
in operation, under construction, or under refurbishment
- located on four continents
Romania
Cernavoda 2 units
Quebec, Canada
Gentilly 2 1 unit
Ontario, Canada
Darlington 4 units
Pickering 6 units
Bruce
8 units
Republic of Korea
Wolsong 4 units
China
Qinshan 2 units
India
13 units, 5 units under
construction, 2 in preproject phase
Pakistan
KANUPP 1 unit
New Brunswick,
Canada
Point Lepreau 1 unit
Argentina
Embalse 1 unit
Point Lepreau, Canada
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Pickering, Canada
Qinshan, China
The CANDU Design
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The CANDU Reactor Core - Components
Pressure tube
Calandria tube
Fuel
Calandria
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Fuel channels
Fueling
machine
CANDU Fuelling
Online refuelling at a rate of ~24 bundles or ~0.5% per FPD
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“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
Two capable, fast, independent lowpressure SDS’s
1. SDS-1: 28 Cd Rods
2. SDS-2: 6 Gd poison injection
nozzles
Three RRS or reactivity control
devices:
1. LZC – normally ~50%
2. Adjusters – normally fully IN
3. Absorbers – normally fully OUT
4. (SDR withdrawal only)
Diverse neutronic detectors
Huge heavy and light water inventories act a passive
heat sinks during prolonged accidents
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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
21 Adjusters
7
0.14
15
0.10
Control
Control
4 Mechanical
Control Absorbers
10
0.075(driving)
- 3.5 (dropping)
Control
Moderator Poison
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-0.01
(extracting)
Safety
28 Shutoff Units
-80
-50
Safety
6 PoisonInjection 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
Three RRS or reactivity
control devices:
1. LZC – normally ~50%
2. Adjusters – n. fully IN
3. Absorbers – n. fully OUT
4. (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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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
Primary-Side Panels
No control, parameter
display only - Control of
PHT sub-systems on
detailed panels:
• Feed & Bleed
• Inventory
• Pressure
• Pressurizer Bleed
Condenser
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The 480 channels are represented by four channels, two per loop with
opposite flow directions, in the “figure of eight” configuration
Secondary-Side Panels
No control, parameter
display only - Control of
secondary-side systems on
detailed panels:
• Feed pumps
• Man. Level control
• Extraction steam
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Detailed display of SG alarm, control, and trip points on separate panel
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
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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
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