Feedwater System Overview IUFW PV340 (NO) Call up desktop display for BFPs and panel 5 bottom. Again, before we look at the simplified Feedwater flowsheets, let’s start with a really simplified one. This is taken from the Darlington Safety Analysis (S/R Part 3, Appendix 7). Discuss the main flowpath/components: 4 MBFPs (3 i/s at FP) 2 ABFPs – flowpath to Unit bypasses HP Feedheaters. Supply to IUFW. HP Feedheaters HX5A/5B (note there are two stages of HP Feedheaters at Pickering). Boiler LCV stations (2 large/1 small per boiler). Each SG has an NV in the feedwater supply – downstream pipework/boiler seismically qualified. Seismic Boundary

Feedwater System Elevation Don’t get hung up on all the lines or “x” marks on this one. Note the elevation of the D/A & Storage Tank (highest point).

Boiler level instruments are connected to the downcomer annulus. Day 1 May-15-18 Boiler Operation Main Steam Outlet Boiler level instruments are connected to the downcomer annulus. Reheat Returns Recall that natural circulation is set up in the boilers due to the buoyancy of bubbles in the riser section. Recirculation Ratio: Ratio of riser flow to steam flow. Typically about 6-10. Downcomer flow Riser flow Feedwater Supply Heat & Thermodynamics, course 61311, module 1

Swell & Shrink Day 1 May-15-18 Heat & Thermodynamics, course 61311, module 1

Steady State Swell Level after power increase Level at ZPH Day 1 May-15-18 Steady State Swell Level after power increase Level at ZPH Heat & Thermodynamics, course 61311, module 1

Steady State Shrink Ramped Level Setpoint for 100% FP Level at ZPH Day 1 May-15-18 Steady State Shrink Ramped Level Setpoint for 100% FP Level at ZPH Heat & Thermodynamics, course 61311, module 1

Transient Swell: Rapid Rx Power Increase (or drop in Feedwater Flow) Day 1 May-15-18 Transient Swell: Rapid Rx Power Increase (or drop in Feedwater Flow) A large and rapid increase in reactor power would cause the volume of steam within the boiling section to increase quickly. Heat & Thermodynamics, course 61311, module 1

Transient Swell: Drop in Boiler Pressure (or increased Steam Flow) Day 1 May-15-18 Transient Swell: Drop in Boiler Pressure (or increased Steam Flow) Heat & Thermodynamics, course 61311, module 1

Day 1 May-15-18 Transient Shrink: Rapid Rx Power Decrease (or quick increase in Feedwater Flow) Heat & Thermodynamics, course 61311, module 1

Transient Shrink: Increase in Boiler Pressure (or drop in Steam Flow) Day 1 May-15-18 Transient Shrink: Increase in Boiler Pressure (or drop in Steam Flow) Heat & Thermodynamics, course 61311, module 1

Boiler Level Control Day 1 May-15-18 Swell Margin Constant Level Full Power Level Swell Margin Shrink Shrink Margin Margin Zero Power Level Fixed Level Control Ramped Level Control Heat & Thermodynamics, course 61311, module 1

Consequences: Level Too High Day 1 May-15-18 Consequences: Level Too High CSDVs are also tripped CLOSED in case of Turbine Trip on High SG Level Heat & Thermodynamics, course 61311, module 1

Consequences: Level Too Low Day 1 May-15-18 Consequences: Level Too Low Tubes partially uncovered Heat transfer impaired PHT coolant temp increase Excessive boiling Fuel overheating Potential fuel and sheath damage Setback, trip required to protect fuel. Heat & Thermodynamics, course 61311, module 1

Transient Shrink and Swell result in SG Level changes that are contrary to the desired Feedwater response Swell caused by: Reactor Power UP SG Level UP Feedwater Flow DOWN Steam Flow UP SG Level UP Feedwater Flow DOWN SG Pressure DOWN SG Level UP Feedwater Flow DOWN Feedwater Flow DOWN SG Level UP Feedwater Flow DOWN Shrink caused by: Reactor Power DOWN SG Level DOWN Feedwater Flow UP Steam Flow DOWN SG Level DOWN Feedwater Flow UP SG Pressure UP SG Level DOWN Feedwater Flow UP Feedwater Flow UP SG Level DOWN Feedwater Flow UP