IAEAInternational Atomic Energy Agency
Overview of CANDU Reactor Technology and the CANDU 9 Simulator
Matthias Krause
Nuclear Power Technology Development Section (NPTDS)
May 2014
IAEA
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
IAEA
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.
IAEA
Systems and Sub-systems
IAEA
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
IAEA
The CANDU Design
IAEA
Pressure tube
Fuel
Calandria tube
Fuel channels
Fuelingmachine
Calandria
The CANDU Reactor Core - Components
IAEA
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
IAEA
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
IAEA
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
IAEA
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
IAEA
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
IAEA
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)
IAEA
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)
IAEA
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
IAEA
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
IAEA
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
IAEA
Two Simulator Exercises
• 2.3 Reactor and RRS Response to Power Manoeuvre
• 6.6 Main Steam Header Break
IAEA
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
IAEA
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