IAEA International 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, Canada Gentilly 2 1 unit Romania Cernavoda2 units Ontario, Canada Darlington4 units Pickering 6 units Bruce 8 units New Brunswick, Canada Point Lepreau1 unit Argentina Embalse1 unit Republic of Korea Wolsong4 units India 13 units, 5 units under construction, 2 in pre- project phase Pakistan KANUPP1 unit China Qinshan2 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 Fueling machine 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’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

IAEA REACTIVITY WORTHS OF CANDU-6 REACTIVITY DEVICES Function Device Total Reactivity Worth (mk) Maximum Reactivity Rate (mk/s) Control14 Liquid Zone Controllers 7  0.14 Control21 Adjusters15  0.10 Control 4 Mechanical Control Absorbers 10  0.075(driving) (dropping) Control Moderator Poison — (extracting) Safety28 Shutoff Units Safety6 Poison- Injection Nozzles >

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 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)

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