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Meeting Presentation, Extended Power Uprate (EPU) Vibration Assessment and Vulnerability Review
	ML042730260
Person / Time
Site:	Dresden, Quad Cities
Issue date:	09/23/2004
From:	; Exelon Nuclear
To:	; Office of Nuclear Reactor Regulation
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	Download: ML042730260 (57)
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Nuclear Extended Power Uprate (EPU) Vibration Assessment and Vulnerability Review September 23, 2004 1

Agenda Exeknn.

Nuclear

Introduction

EPU Vibration Assessment

EPU Vulnerability Review

Status of Steam Dryer Load Analysis, Design, Fabrication and Instrumentation

Closing Remarks 2

ExekfnI Nuclear Introduction James Meister Vice President, Nuclear Services 3

,%ffos Iu Nuclear EPU Vibration Assessment Sharon Eldridge Corporate Engineering Projects 4

Topics ExekOn.

Nuclear

Vibration Evaluation

Background

Original EPU Monitoring Plan

Vibration Evaluation/Scope

Purpose, Scope, and Methodology

Results

Planned Actions

Independent Reviews

Summary 5

Vibration Evaluation Exekrns.

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The purpose of the vibration evaluations was to provide assurance that potentially effected components would perform acceptably for at least a full 24 month cycle at EPU full thermal power operation

- All evaluations and testing are completed except for the Target Rock Safety/Relief Valve (S/RV)

- Implementation of actions is either planned or complete to support return of Quad Cities (QC) Units 1 and 2 to full EPU power operation

- Dresden (DR) evaluations support continuation of full EPU power operation 6

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Background===

QC Indications LxeIon Nuclear

Main Steam (MS) low point drain line failed shortly after EPU ramp up (QC2)

Forced outage to repair Caused by vibration-induced fatigue

Electrohydraulic Control system accumulator small bore line cracking (QC2)

Audible noise due to resonance of reactor building components to MS acoustic frequency (QC1)

Limitorque limit switch degradation (QC1)

Rotor wear due to vibration of fingers

Electromatic Relief Valve (ERV) actuator degradation (QC1)

Caused by higher vibration levels with EPU

Target Rock S/RV as-found set point 6.8% high (QC2)

Other Target Rock S/RVs showed similar wear 7

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Background===

xekrnA Indications xln Nuclear

Multiple equipment problems challenged plant operations

- In some cases, outages were required to resolve/repair identified individual component problems

Consolidated efforts were established to ensure that no more failures occurred

- Teams were assembled to address steam dryer, EPU vulnerabilities, and vibration issues I

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Background===

Original EPU Monitoring Plan Nuclear

DR/QC EPU initial vibration monitoring plan was based on industry guidance for piping Utilized accelerometers on large bore piping supports Focused on piping, both large and small bore, to prevent failures

- Acceptance criteria for piping based on American Society of Mechanical Engineers (ASME) criteria (OM Part 3)

- Weakness in implementation contributed to failure of MS low point drain line at QC2

Industry guidance for components was also utilized Pump vibration monitoring conducted Relied on component surveillance testing to ensure acceptability 9

Vibration Evaluation/Scope Exekrn..

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During QC1 dryer repair outage in November 2003, the 3B ERV actuator was discovered with significant damage Root cause investigation was performed

- A detailed inspection scope was developed and implemented for both QC and DR to determine "extent of condition" and identify any other potentially vulnerable components EPU related vibration issues identified as a result of these walkdowns include Remaining 3 ERVs (QC)

Limitorque limit switch (QC)

- Various pipe support mechanical connections (DR/QC) 10 X

Vibration Evaluation/Scope (cont.)

Exekrn Nuclear Based on the walkdown results, accelerometers were installed on susceptible components for data collection and reevaluation MS Isolation Valves (MSIVs)

ERVs

- Various limit switches, including Namco-type on MSIVs

- SRVs and Target Rock S/RV

- Valve operators (Limitorques) 11

Purpose, Scope, and Methodology Exektn.

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The purpose of these evaluations was to provide assurance that full EPU thermal power operation would pose no threat to continued equipment operation throughout the remainder of the current fuel cycle or to make specific recommendations required prior to allowing full cycle operation 12

Purpose, Scope, and Methodology (cont.)

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Component evaluations used data obtained during ramp to 912 MWe adjusted for expected full thermal power impact The expected impact of future increases to full thermal power (2957 MWt) is a further increase in the measured vibration levels Predicted increase calculated by plotting the available data and extrapolating to full thermal power Each component evaluation included an assessment of any potential effects of increased vibration levels as the unit approaches full thermal power Actual vibration levels will be measured when the units stabilize at full power to confirm the assumptions made 13

Purpose, Scope, and Methodology (cont.)

xeltn, Nuclear Component/system responses for full EPU thermal power operation were assessed using:

- Vibration data collected throughout the available range of power operation

Vibration data obtained during ramp up to full EPU power level for each of three units (fourth unit was already at full EPU power)

Data was extrapolated and utilized in evaluations Industry operating experience Component failure/Preventive Maintenance (PM) history

- Analytical modeling Wyle lab testing 14

Results General Assessment ExeOn Nuclear

Evaluations concluded that all components are acceptable for full-cycle operation at full EPU thermal power with the following exceptions:

ERV susceptibility to vibration at QC requires upgrades of vulnerable parts DR ERVs determined to be acceptable based on two factors:

As-found inspections of Units 2 and 3 actuators Data evaluations which showed lower vibration levels for DR Target Rock S/RVs show vibration wear degradation at both QC and DR

Degradation may impact the lift setpoint

Evaluation and testing of the current configuration complete

Additional testing of a modified configuration is in progress

The team identified additional recommendations for enhancements in testing, monitoring, and refuel outage inspections

- An example is confirmatory vibration testing of Limitorque and Namco limit switches - completed successfully 15

Results ERV Components Exektn.

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ERV response for full EPU power operation was evaluated using:

- Vibration data throughout the range of power operation Component failure history

- Analytical modeling

- Vibration testing of original ERV and proposed modification

These evaluations validated proposed modifications to improve the ERV response to vibrations at full EPU thermal power and provided assurance of ERV operability for a full 24 month fuel cycle Modification consists of replacing internal actuator parts with hardened materials 16

Results ERV Components (cont.)

Lxe on..

Nuclear

The four ERVs have virtually identical assemblies, which consist of the main ERV valve body, pilot valve, and solenoid actuator

Detailed finite element models were completed for the ERVs

- Analytical natural frequencies and mode shapes were compared to frequency content of the measured vibration data Modal test results were also used to validate the model

- Analysis utilized in determination of root cause of the 3B ERV failure 17

Results ERV Components (cont.)

Exektn.

Nuclear

Testing performed at Wyle labs to determine/confirm failure mode and to test proposed modifications Modal test performed on QC1 as-built configuration to validate and adjust finite element model Over 50 individual tests performed to validate wear mechanism and proposed valve/actuator modifications

Wear mechanism is a result of a local structural mode of the solenoid plunger assembly Response due to assembly floating on spring 18

Results ERV Components - Actuator Internalsbe xe om.,Sf Nuclear Actuator plunger Supporting springs' 19

Results ERV Components - Worn Bushings Exek n.,

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Groove worn by spring point 20

Results ERV Components - Acceptability xe On..

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Mitigation strategies were limited by desire to minimize internal actuator design effects Vulnerable components within the actuator assembly are being modified

Material changes implemented for parts which have historically exhibited unacceptable wear

Inconel X750 bushings and guide rods being installed

Springs are being chamfered to remove hard edges which cause damage

Endurance testing designed to provide assurance of full cycle operation without unacceptable wear of the affected components Final configuration changes tested for equivalency to 12 months of operation

Testing included prolonged aging tests of approximately 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months at low frequency (20-70 Hz) and 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months at high frequency (70-200 Hz)

No measurable wear was observed, therefore it was concluded that a full 24-month cycle of EPU thermal power operation was assured 21

Results ERV Components - New Bushings/Guide Rods LxeE n5.

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_I.Nuclear Inconel busning after first test I..g Inconel bushing A

after final test n P. I niid Incoa 22

Results Target Rock S/RV LxeunA Nuclear

As-found testing on QC Target Rock S/RV resulted in

+6.8% lift point Disassembly and inspection determined that wear of the bellows cap caused spring resistance to increase

Additional force required = approximately 70 pounds

Groove worn in bellows cap caused spring to bind

Two DR valves tested at -3.6% and -1.4%, one with EPU operating history, one without

Shaker table testing has been performed to confirm wear phenomena driver

- Testing produced similar wear to the as-found condition

- Preliminary conclusion is that the wear is a function of the spring and cap combination and the materials installed

Enhanced tolerances and materials on first stage pilot spring and cap combination being evaluated and tested 23

Target Rock Pilot Bellows Cap and Spring Nuclear I -

I' I-In-service bellows cap and spring 24

Results Other Testing ExekOn Nuclear

Namco limit switches tested with plant level data for vibration endurance

- Results showed acceptable performance

- Matched previous analytical results

Limitorque limit switch vibration endurance testing with plant level data

- Results showed minimal wear for simulated one cycle operation that resulted in no impact to valve function 25

Results Other Testing - Limitorque Limit Switch Exek6nLs Nuclear 26

Planned Actions ExekOn Nuclear

Validate PM scope and frequency for all evaluated components ERV PM changes already implemented

Replace ERV actuator parts for both DR and QC during future rebuilds

Inspect ERV actuator internals each cycle until performance is validated

Perform focused walkdowns during each refuel outage

Inspect minimum of one MSIV internally each cycle until satisfactory performance is demonstrated 27

Independent Reviews ExekOn.

Nuclear

Each individual component evaluation was subjected to an independent review

- The purpose was to ensure that the analytical methods, assumptions, judgment, and conclusions were reasonable

- Reviews were performed by MPR Associates and Stevenson and Associates personnel

Conclusions were that the assessments, combined with the planned testing, would provide the desired assurance that evaluated components are capable of performing satisfactorily for a full cycle of EPU full thermal power operation 28

Summary Exekr'n,.

Nuclear The vibration evaluations performed provide assurance that potentially effected components will perform acceptably for at least a full 24 month cycle at EPU full thermal power operation

- All evaluations and testing are completed except for the Target Rock S/RV

- Implementation of actions is either planned or complete to support return of the QC units to full EPU power operation

- DR evaluations support continued full EPU power operation 29

Exe l5nsk Nuclear EPU Vulnerability Review Mohammad Molaei Dresden Engineering Programs Manager 30

Topics Exek¢n Nuclear

Mission and Goals

Process Used

Systems Reviewed

Summary Statistics

Potential Vulnerabilities and Actions

Outage Scope

Conclusions

Summary 31

Mission and Goals Exek nn Nuclear

Mission - identify potential EPU-related vulnerabilities for DR and QC, and actions to prevent failures induced by these vulnerabilities

Goals - reduce/eliminate operational challenges, as measured by:

Licensee Event Reports Engineered safety features actuations Reactor scrams Plant power derates Unplanned entries into Technical Specifications Operator work-around challenges (increases risk of one of the above events)

Unexpected accelerated degradations (that increases risk of one of the above events)

Significant loose/lost parts 32

Process Used Iower and Safety Systems Exekn Nuclear

Power Systems Phase I - Data Collection Phase 11 - System Level and Component Evaluation Phase Ill - Vulnerability Assessments and Recommendations

Safety Systems Event input verification

- Task report output implementation validation Effect of power operation at EPU condition on safety components

Both power systems and safety systems were selected based on EPU impact

Safety systems reviews were scenario-based

A total of 42 power systems and 1 0 safety systems were reviewed 33

Process Used Technical Rigor Exektn.

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Utilized multiple industry organizations

For the purpose of this review, every component in the plant was assumed to be susceptible to failure, unless proven otherwise

Evaluated changes in operating parameters-EPU for 4 units Flow rate, temperature, pressure, radiation level, vibration level, and wear rate

Utilized process of elimination at system and component levels

Identified potential vulnerabilities due to the changed parameters

Developed actions to address the potential vulnerabilities

Results were challenged in multiple stages, by various teams 34

Systems Reviewed Power Systems Exet 6n SM Nuclear Reactor Recirculation and Vessel Internals Main Steam Off Gas Feedwater Feedwater Level Control Condensate Condensate Booster Condensate Demineralizer Main Generator Generator Hydrogen Cooler Stator Cooling Isolated Phase Bus Duct Instrument Air Reactor Building Closed Cooling Water Turbine Building Closed Cooling Water Spent Fuel Pool Cooling Shutdown Cooling/Residual Heat Removal Radwaste Circulating Water Reactor Building Equipment Drain Turbine Building Equipment Drain Hydrogen Addition Zinc Injection Service Water Reactor Water Clean Up Nuclear Instrumentation Control Rod Drive Reactor Building Ventilation Turbine Building Ventilation Control Room HVAC Extraction Steam Heater Drain Misc. Heater Vents and Drains Turbine Oil Main Turbine EHC Main Condenser On-Site Power Off-Site Power Process Radiation Monitoring DC Power Main Generator Exciter 35

Systems Reviewed Safety Systems xe On.

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Automatic Depressurization System (ADS)

Containment

Core Spray (CS)

Emergency Diesel Generator (EDG)

High Pressure Coolant Injection (HPCI)

Isolation Condenser (IC)

Low Pressure Coolant Injection (LPCI)/Residual Heat Removal (RHR)

Reactor Core Isolation Cooling (RCIC)

Standby Gas Treatment

Standby Liquid Control 36

Summary Statistics ExektbnA Nuclear 1 01 total actions

- 60 outage physical work activities

- 9 non-outage physical work activities

- 32 analysis/study/PM reviews

Applicability

- 27 Exelon-specific actions

- 74 potential General Electric (GE) fleet lessons learned

Action categories

- 43 inspections

- 42 PM reviews 17 modifications

- 9 studies

- 28 analyses 37

Potential Vulnerabilities and Actions Exekrn,,

Nuclear

1. Increased FW flow has increased the fatigue loading on some vessel internals, which may require more frequent inspections of susceptible components Perform a one-time visual inspection of the shroud head bolt locking pin window for evidence of wear Perform a one-time visual inspection of a sample of separator stand pipe weld to the shroud head Perform a one-time visual inspection of the feedwater sparger end bracket pin 38