Feedwater System Reliability Users Group – 2012 Meeting Power Uprates & Feedwater Heaters 1

Introduction: True North Consulting, LLC ◦ Phone (970) Frank Todd – Mgr. Thermal Perf. Group  Phone (856)  Iver Jacobson—Sr. Consulting Engineer ◦ Phone (479) or (479) (cell) ◦ Heat Exchanger Training2

Terminal Objective Familiarize the attendee with feedwater heater issues which have resulted from power uprates and the actions which can be taken to avoid, address, or detect the adverse impacts prior to a loss of heater reliability. 3

Enabling Objectives Understand the importance of FWH uprate evaluations of current vs. new condition. Review FWH condition assessment process. Review vibration damage knee response curve for increased drain cooler flow. Understand potential uprate impact on FWH operating level and overload limit. Review post-uprate actions for PM interval resets and increased monitoring. 4

Power Uprates Power uprates improve nuclear plant economic efficiency and viability. Only 6 units do not have any type of uprate approved or pending. Uprates of 15-20% have been completed at 17 units and are pending at 11 more. 20 of 35 US BWRs have uprates of 15-20% approved (14) or pending (6) 5

Nuclear Power Uprates 6

Power Uprates & Feedwater Heaters Uprates increase the tube and shell side flows through Feedwater Heaters. The added shell-side flow increases the potential for FWH degradation, and has resulted in multiple cases of reduced reliability and increased repair costs. 7

Power Uprates & Feedwater Heaters Uprate engineering evaluations assess FWH capability for handling increased flow. Typically the FWH OEM is contacted by the A/E firm supporting the uprate. Updated heat balance diagrams are used for normal and overload flows, tube-side dp, and similar conditions. 8

Power Uprates & FWHs So why the problems? 1. Uprate evaluations should address the current condition vs. a new FWH. ◦ Many evaluations ignore degraded condition. 2. Limited knowledge of internal condition. Most have shell FAC & tube ECT data. Tube ECT data often neglects to report partial, missing, or displaced plates. Absence of internal visual inspection data. 9

Power Uprates & FWHs Example of partial and missing baffle plate, which may not be addressed by uprate. 10

Power Uprates & FWHs FWH Condition Assessment – Importance is magnified by: 1.% flow increase 2.Tube leak history or >5% plugged. Post-uprate damage rates/progression should NOT be assumed as linear or simply proportional to the increase in flow. 11

Power Uprates & FWHs Tube vibration amplitude and associated damage exhibit a “knee” response to increased shell-side flow. 12

Power Uprates & FWHs Considerations for the tube vibration “knee” (prev. slide): A. Uprate increases flow, moves toward knee. B. Don’t know how close you already are. C. If past tube vibration damage, then you may already be in the knee periodically. D. Degraded plates loosen the tubes, moves the knee (left) E. Wrong/false/poor operating level impact F. Pre-80’s designs were less accurate. 13

FWH Condition Assessment Condition Assessment Emphasis: 1.Support/Baffle/End Plate damage - may not be noted in ECT report (even if present). 2.Tube Damage – locations, types, causes % Plugged Tube margin recovery options 3.Internals damage: impingement plate, drain cooler shroud, air removal pipe 4.DCA / TTD versus design and stability 5.Shell / Nozzle Erosion (FAC) 14

FWH Condition Assessment FWH Assessment in Stages/Phases – i.e. start simple and apply more resources (time/cost) according to adverse findings.  Initial based on available data  Request funding/support, as warranted, for more intensive review or intrusive checks: -Operating Level optimization test -Shell cut for repair, assessment, LCM -Tube recovery, expansion, stabilization 15

FWH Condition Assessment Industry Information Sources: EPRI papers & information on detecting / sizing support plate degradation with ECT data (e.g. 10 th EPRI BOP NDE conf., etc.) NDE vendors Industry OE (INPO) Industry peers (benchmark uprated plants) 16

FWH Condition Assessment Data / Information Sources: 1. ECT data  Reanalysis of existing data may be needed.  New data with probe or scope changes 2. FAC Inspection data 3. Repair / Failure History 4. Shell-side Inspection ◦ Limited access from existing openings ◦ Shell-cut - if significant degradation likely 17

FWH Condition Assessment Internals Condition – Shell Cuts Can’t indirectly detect by ECT or other NDE: DC shrouds, vents, impingement plates, etc. 18

FWH Condition Assessment Failed section of impingement plate: 19

FWH Condition Assessment Drain Cooler Shroud Damage: 20

FWH Condition Assessment Benefits include (pre-, post-, or no uprate):  Understand degradation & most likely causes  Actions to avoid/prevent damage  Repair options (& justification)  Long-range planning / LCM Potential Changes from Assessment:  Overload limits  Operating Level  PM Actions (scope, frequency, probe types, LCV)  Monitoring – freq., limits, actions, etc. (Ops & SYE) 21

Power Uprates & FWHs Uprate Evaluation Conclusions for FWHs: 1. Replace FWH – degraded; new FWH should address past degradation modes. 2. Repair / Modify FWH – tube expansion in end plates, sleeving, staking, drain cooler shroud or impingement plate repairs, etc. (See BOP NDE Conference Papers, past & present) 3. No FWH Modifications  Overload limits validated  Operating level verification post-uprate  PMs reset and increased monitoring 22

Power Uprates & FWHs Other potential FWH issues w/ uprates: Nozzle size and higher dp, thus lower T sat and T FWout. Drain cooler higher dp Drain valve sizing, normal and high-level dump FWH mods pre-uprate & control stability Venting capacity (or degraded vents) System impacts (pumps, turbine, MSRs) Should be addressed by A/E uprate eval., but could be missed, aggregate impact not recognized, or impact not communicated. 23

Power Uprates & FWHs FWH Operating Level: May not have been optimum pre-uprate. Consider post-uprate level tests; one train and any FWHs w/ drain cooler problems. Consider level test pre-uprate on FWHs w/ drain cooler problems to identify possible modification to raise instrument levels. 24

FWH Overload Limits Overload Limits should reflect FWH current condition: Degraded baffle or support plates Impingement plates (problem history ) Level control capacities and stability # tubes plugged & degraded operating tubes FWH high level dump flow increase - impact on spargers and condenser tubes. 25

Post-Uprate Actions PM Resets: ECT – FWHs (verify impact of higher flow) FAC Program: FWH shells (most susceptible) Increased Attention: FWH Monitoring (level, DCA, TTD, acoustic, etc.) Visual Inspections ( incl. opportunities on shell-side) Repair & Margin Recovery Industry Uprate Experience 26

Post - Uprate Reset FWH PM’s after an uprate. - Even if pre-uprate HX condition known - Even with a thorough uprate impact study Consider: ½ current PM interval until rebaselined. Problem FWHs, one train 1 st outage, other train in the 2 nd outage, then new intervals. 27

Post - Uprate Why reset HX PMs? – Hedge your bets! We don’t plan to fail, but……….. 28

Sometimes mistakes are made. 29

Power Uprates & FWHs Who needs another leak at their plant? 30

Power Uprates & FWHs No need to end up looking like this. 31

Power Uprates & FWHs Summary of Uprate Actions for FWHs: 1. Condition assessment for FWH with past leakage history or >5% plugged. 2. Uprate evaluation based on existing degradation, not new conditions. 3. Validate operating level & O/L limits. 4. Reset PM actions to confirm condition and avoid surprises. 5. Monitor closely. 32

Power Uprates & FWHs Questions / Comments? Contacts: Frank Todd Iver Jacobson Manager Thermal PerformanceSr. Consulting Engineer True North ConsultingHeat Exchanger Programs Office:

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