Text

Extended Power Uprate (EPU) Vibration Assessment and Vulnerability Review
	ML043010209
Person / Time
Site:	Dresden, Quad Cities
Issue date:	10/25/2004
From:	; Exelon Nuclear
To:	; Office of Nuclear Reactor Regulation
References
	Download: ML043010209 (53)
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Exekrbn.m Nuclear Extended Power Uprate (EPU) Vibration Assessment and Vulnerability Review October 25, 2004 1

I Agenda Exe kn M Nuclear

Introduction

EPU Vibration Assessment

EPU Vulnerability Review

Sample Probes

Planned Actions/Outage Scopes

Closing Remarks 2

Exekrbn.h Nuclear Introduction James Meister Vice President, Nuclear Services 3

, Quad Cities (QC) Steam Dryer Replacement Project Exek6n.m Nuclear 0)

Install and test dryer instrumentation 4

(II Exe k n.M Nuclear EPU Vibration Assessment Sharon Eldridge Corporate Engineering 5

'-I Top ics Exe krnSM Nuclear

Vibration Evaluation

Timeline

Exelon Actions

Original EPU Monitoring Plan

Vibration Evaluation/Scope

Purpose, Scope, and Methodology

Results

Independent Reviews

Summary 6

Vibration Evaluation Exe enSM Nuclear

The purpose of the vibration evaluations was to provide assurance that potentially affected 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 QC Units 1 and 2 to full EPU power operation

- DR evaluations support continuation of full EPU power operation 7

Timeline Exek!rnsm Nuclear Li reactor building Electromatic Relief Valve (ERV) B degraded I Nov 03 l 8

Exelon Actions Exe 15nSM Nuclear

Exelon established a comprehensive action plan which included three teams to identify actions to prevent future EPU failures

- Steam Dryer Team

- EPU Vulnerability Team

- Vibration Team 9

Original EPU Monitoring Plan ExekrnM.

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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 vibration limits based on American Society of Mechanical Engineers criteria (i.e., OM Part 3)

Approach to implementing the monitoring plan 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 10

Vibration Evaluation/Scope Exek nsm Nuclear

During QC1 dryer repair outage in November 2003, the 3B ERV actuator was identified to be damaged Root cause investigation was initiated 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

Exelon completed comprehensive walkdowns of plant systems and components at DR3 and both QC units to bound the extent of condition The DR2 refueling outage occurred prior to November 2003 discovery Evaluations for DR2 were based on surveillance feedback information and EPU power ascension vibration data

ERV actuator inspections

Main Steam Isolation Valve (MSIV) work during outage

Miscellaneous MSL support inspections 11

Vibration Evaluation/Scope (cont.)

Exekn.m Nuclear

A detailed list of potentially vulnerable components was developed for each evaluation Each component was dispositioned by evaluation, walkdown results or testing

EPU related vibration issues identified as a result of these walkdowns include:

Remaining three ERVs degraded (QC)

Limitorque operator limit switch degraded (QC)

Various pipe support mechanical connections with loose nuts and bolts (DR/QC)

Based on the walkdown results, accelerometers were installed on susceptible components for data collection and reevaluation MSIVs ERVs Various limit switches, including Namco-type on MSIVs SRVs and Target Rock S/RV Valve operators (Limitorques) 12

Purpose, Scope, and Methodology Exek6nm 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 to correspond to levels expected at full thermal power and utilized in evaluations

Actual vibration levels will be measured when the units stabilize at full power to confirm the assumptions made Industry operating experience Component failure/preventive maintenance (PM) history

- Analytical modeling

- Testing at Wyle Laboratories Inspection results 13

Results General Assessment Exek9n.m Nuclear

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

ERV susceptibility to vibration at QC required upgrades of vulnerable parts

- Target Rock S/RVs showed vibration wear degradation at both QC and DR

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

- An example is confirmatory vibration testing of Limitorque and Namco limit switches (completed successfully) 14

Results ERV Components Exek(5nm Nuclear

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

ERV response for full EPU power operation was evaluated Detailed finite element models were completed for the ERVs

- Testing performed at Wyle Laboratories to determine/confirm failure mode and to test proposed modifications Over 50 individual tests performed to validate wear mechanism and proposed valve/actuator modifications 15

Results ERV Components (cont.)

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The four ERVs have virtually identical assemblies, which consist of the main ERV valve body, pilot valve, and solenoid actuator 16

Results ERV Components (Actuator Internals)

Exe 1nSM Nuclear

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

.Actuator Plunger ii Supporting Springs 17

Results ERV Components (Worn Bushings)

Exe kn.M Nuclear Brass bushing

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Groove worn by spring point 18

Results ERV Components (Acceptability)

Exek)n.m Nuclear

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

Vibration endurance testing completed and provides assurance of full-cycle operation with only inconsequential wear of the affected components

PM revisions were made to ensure that inspections/rebuilds are performed every cycle until adequate performance is assured

- Standard PM feedback/revision process will be used 19

Results Target Rock S/RV xe (5nSM Nuclear

As-found testing on QC2 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

Groove worn in bellows cap caused spring to bind

Additional force required to open valve is approximately 70 pounds

Test results for two DR Target Rock S/RVs: -3.6%

(with EPU operating history) and -1.4% (without EPU operating history)

- Both valves exhibited wear patterns similar to QC valves 20

Results Target Rock S/RV Exek)nsm Nuclear Shaker table testing has been performed to confirm wear phenomena driver

- Testing produced similar wear to the as-found condition

- Conclusion is that the wear is a function of the spring and cap configuration combination and the materials installed

Phenomenon is not exclusive to EPU operation

Enhanced tolerances and materials on first stage pilot spring and cap combination being implemented

- The solution has been developed and tested, and will be installed in DR3 during the November 2004 refueling outage

An additional enhancement is being evaluated, including any necessary prototype testing 21

Target Rock Pilot Bellows Cap and Sprinq Exek6n.

Nuclear In-service bellows cap and spring 22

Results Other Testing Exel (n.m 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 23

Independent Reviews ExekrnS.

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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 (i.e., shaker table), would provide the desired assurance that evaluated components are capable of performing satisfactorily for a full cycle of EPU full thermal power operation 24

Summary Exekrn.m Nuclear The completed vibration evaluations provide assurance that potentially affected 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

Detailed walkdowns

Installations of upgraded ERVs and Target Rock S/RV

New steam dryer DR evaluations support continued full EPU power operation

Detailed walkdowns

Installation of Target Rock S/RV upgrade and enhancements to steam dryer 25

Exektin.

Nuclear EPU Vulnerability Review hi1 1

Mohammad Molaei Dresden Engineering Programs Manager i -

i i

I I I i i

26

Topics Exekrnsm Nuclear

Mission and Goals

Process Used

Systems Reviewed

Potential Vulnerabilities and Actions

Conclusions

Summary 27

Mission and Goals Exek¢5n.m Nuclear

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

Goal - 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-arounds or challenges (increases risk of one of the above events)

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

Loose/lost parts 28

Process Used Power and Safety Systems ExekrnS.

Nuclear Power Systems Phase I - Data Collection and interviews Phase 11 - System Level and Component Level Evaluations 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

A total of 42 power systems and 1 0 safety systems were reviewed 29

Process Used Technical Rigor Exekrnim Nuclear

For the purpose of this review, the components in the plant were assumed to be susceptible to failure, unless proven otherwise

Evaluated changes in operating parameters post-EPU for four 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 i* Utilized multiple industry organizations 30

I.

Systems Reviewed Power Systems Exek 6nM 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 Ventilation Extraction Steam Heater Drain Misc. Heater Vents and Drains Turbine Oil Main Turbine EHC Main Condenser Onsite Power Offsite Power Process Radiation Monitoring DC Power Main Generator Exciter 31

Systems Reviewed Safety Systems SM Nuclear

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 (SBGT)

Standby Liquid Control (SLC) 32

Potential Vulnerabilities and Actions Exen e!)n Nuclear 1.

Components susceptible to increased vibration due to increased FW flow Perform a visual inspection of a sample of separator stand pipe welds to the shroud head Perform a visual inspection of the FW sparger end bracket pin

2. Components susceptible to increased vibration due to increased core differential pressure (d/p)

Establish the value of core d/p at which slip joint bypass leakage initiates jet pump vibration Accelerate the Boiling Water Reactor Vessel Internals Project (BWRVIP)-41 required inspection of the restrainer gate wedges for evidence of wear 33

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