1. Summer Co-op Experience: OPG Aditi Garg

2. Darlington Nuclear G.S Located in Bowmanville, ON

3. About the plant 4-unit station with a total output of 3,524 megawatts (MW) 20 per cent of Ontario’s electricity  Tritium Removal Facility  extracts tritium from heavy water

4. COMPONENTS AND EQUIPMENT Electrical and I&C Major Components Mech & Rotating Equipment Valves

5. Major Components Fans Compressors Pumps Steam Generators (Boilers) Feeders Reactor Maintenance

6. Inside the plant… Main Boiler Feed Pump Turbine Hall

7. Projects Critical equipment and Critical spares List Root cause analysis of the seal failure Transient monitoring for Feeders Plant walk-down

8. Transient monitoring for Feeders CNSC  Keep track of transient events that have occurred in each unit. – For all nuclear class system piping Plant Information System (PI) – Temperature, pressure, %Power, etc. for all planned and forced outages

9. Feeder thinning reduction in pipe wall thickness of the outlet feeders High pH  dissolves pipes; reduces thickness The cause of feeder thinning is flow accelerated corrosion (FAC). – poor design defects, poor chemistry controls and high temperature and pressure.

10. Face of the CANDU reactor The face of a CANDU reactor (under construction). Some feeder pipes can be seen to the right of the reactor face.

11. Flow Accelerated Corrosion (FAC) motion of a corrosive fluid and a metal surface. Outlet feeders – Dissolution of magnetite (Fe3O4) Affects carbon steel components – High flow and specific water chemistry conditions. – Resulted in excessive thinning and failure of feedwater lines

12. Reduce thinning Outlet feeders – Injected by Titanium Dioxide  Uniform coating inside pipe to reduce thickness  Fe3O4  Dissolves with high temperature and pressure (pH >10.6) Chemistry: pH 10.1- 10.4  rate of solubility is low

13. Feeder Integrity Project The Project is actively pursuing means to: – Extend the life of the feeders – Developing tooling for eventual feeder replacement – Further developing pipe inspection techniques

14. Root Cause Evaluation Second Stage Reheat Pumps – Seal temperature was high above the alarm set point Perform a failure modes analysis of the historical seal failures Review modification packages and make changes to design – Identify technical and human performance related root cause

15. Thank you!!