feedwater system reliability users group – 2012 meeting power uprates & feedwater heaters 1
TRANSCRIPT
Feedwater System Feedwater System Reliability Users Group – Reliability Users Group – 2012 Meeting 2012 Meeting
Power Uprates Power Uprates & Feedwater Heaters& Feedwater Heaters
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Introduction:Introduction:True North Consulting, LLC
◦Phone (970) 252-1489
Frank Todd – Mgr. Thermal Perf. Group Phone (856) 391-3347 [email protected]
Iver Jacobson—Sr. Consulting Engineer ◦ Phone (479) 967-5077 or (479) 280-9072
(cell)◦ [email protected]
Heat Exchanger Training 2
Terminal ObjectiveTerminal 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.
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Enabling ObjectivesEnabling ObjectivesUnderstand 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.
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Power Uprates 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)
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Nuclear Power UpratesNuclear Power Uprates
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Last 10 yrs Pending Expected Next 5 yrs
Mwe
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Power Uprates & Power Uprates & Feedwater HeatersFeedwater HeatersUprates 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.
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Power Uprates & Power Uprates & Feedwater HeatersFeedwater HeatersUprate 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.
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Power Uprates & FWHsPower 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.
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Power Uprates & FWHsPower Uprates & FWHsExample of partial and missing baffle
plate, which may not be addressed by uprate.
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Power Uprates & FWHsPower 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.
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Power Uprates & FWHsPower Uprates & FWHs
Tube vibration amplitude and associated damage exhibit a “knee” response to increased shell-side flow.
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Power Uprates & FWHsPower Uprates & FWHsConsiderations 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 impactF. Pre-80’s designs were less accurate.
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FWH Condition FWH Condition AssessmentAssessmentCondition 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)
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FWH Condition FWH Condition AssessmentAssessmentFWH 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
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FWH Condition AssessmentFWH Condition Assessment
Industry Information Sources:
EPRI papers & information on detecting / sizing support plate degradation with ECT data (e.g. 10th EPRI BOP NDE conf., etc.)
NDE vendors Industry OE (INPO)Industry peers (benchmark uprated plants)
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FWH Condition FWH Condition AssessmentAssessmentData / Information Sources:1.ECT data
Reanalysis of existing data may be needed.
New data with probe or scope changes
2.FAC Inspection data3.Repair / Failure History4.Shell-side Inspection
◦ Limited access from existing openings◦ Shell-cut - if significant degradation likely
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FWH Condition FWH Condition AssessmentAssessmentInternals Condition – Shell CutsCan’t indirectly detect by ECT or other NDE:
DC shrouds, vents, impingement plates, etc.
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FWH Condition FWH Condition AssessmentAssessmentFailed section of impingement
plate:
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FWH Condition FWH Condition AssessmentAssessmentDrain Cooler Shroud Damage:
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FWH Condition FWH Condition AssessmentAssessmentBenefits 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)
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Power Uprates & FWHsPower Uprates & FWHsUprate 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
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Power Uprates & FWHsPower Uprates & FWHs
Other potential FWH issues w/ uprates:
Nozzle size and higher dp, thus lower Tsat and TFWout. 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.
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Power Uprates & FWHsPower 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.
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FWH Overload LimitsFWH 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.
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Post-Uprate ActionsPost-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 RecoveryIndustry Uprate Experience
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Post - UpratePost - UprateReset 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 1st outage, other
train in the 2nd outage, then new intervals.
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Post - UpratePost - Uprate
Why reset HX PMs? – Hedge your bets!
We don’t plan to fail, but………..
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Sometimes mistakes are Sometimes mistakes are made.made.
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Power Uprates & FWHsPower Uprates & FWHs
Who needs another leak at their plant?
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Power Uprates & FWHsPower Uprates & FWHs
No need to end up looking like this.
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Power Uprates & FWHsPower 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.
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Power Uprates & FWHsPower Uprates & FWHs
Questions / Comments?
Contacts:Frank Todd Iver Jacobson
Manager Thermal Performance Sr. Consulting Engineer
True North Consulting Heat Exchanger Programs
Office:856-391-3347 479-280-9072 www.tnorthconsulting.com
[email protected] [email protected]
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