feedwater system reliability users group – 2012 meeting power uprates & feedwater heaters 1

Feedwater System Feedwater System Reliability Users Group – Reliability Users Group – 2012 Meeting 2012 Meeting

Power Uprates Power Uprates & Feedwater Heaters& Feedwater Heaters

1

Introduction:Introduction:True North Consulting, LLC

◦Phone (970) 252-1489

Frank Todd – Mgr. Thermal Perf. Group Phone (856) 391-3347 fdt@tnorthconsulting.com

Iver Jacobson—Sr. Consulting Engineer ◦ Phone (479) 967-5077 or (479) 280-9072

(cell)◦ ijj@tnorthconsulting.com

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.

3

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.

4

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)

5

Nuclear Power UpratesNuclear Power Uprates

0

500

1000

1500

2000

2500

3000

3500

4000

4500

Last 10 yrs Pending Expected Next 5 yrs

Mwe

6

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.

7

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.

8

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.

9

Power Uprates & FWHsPower Uprates & FWHsExample of partial and missing baffle

plate, which may not be addressed by uprate.

10

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.

11

Power Uprates & FWHsPower Uprates & FWHs

Tube vibration amplitude and associated damage exhibit a “knee” response to increased shell-side flow.

12

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.

13

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)

14

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

15

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)

16

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

17

FWH Condition FWH Condition AssessmentAssessmentInternals Condition – Shell CutsCan’t indirectly detect by ECT or other NDE:

DC shrouds, vents, impingement plates, etc.

18

FWH Condition FWH Condition AssessmentAssessmentFailed section of impingement

plate:

19

FWH Condition FWH Condition AssessmentAssessmentDrain Cooler Shroud Damage:

20

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)

21

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

22

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.

23

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.

24

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.

25

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

26

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.

27

Post - UpratePost - Uprate

Why reset HX PMs? – Hedge your bets!

We don’t plan to fail, but………..

28

Sometimes mistakes are Sometimes mistakes are made.made.

29

Power Uprates & FWHsPower Uprates & FWHs

Who needs another leak at their plant?

30

Power Uprates & FWHsPower Uprates & FWHs

No need to end up looking like this.

31

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.

32

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

ijj@tnorthconsulting.com fdt@tnorthconsulting.com

33

34

35