ML070820012

Extended Power Uprate (EPU) Meeting, Handouts from March 22, 2007, Meeting

ML070820012
Person / Time
Site:	Quad Cities
Issue date:	03/22/2007
From:	Gideon R Exelon Nuclear
To:	Office of Nuclear Reactor Regulation
References
Download: ML070820012 (40)

Text

Quad Cities Extended Power Uprate (EPU)

Meeting March 22, 2007

Introduction Randy Gideon Quad Cities (QC) Plant Manager 2

AGENDA 9 Introduction 9 Vibration Source Reduction 9 Steam Dryer Replacement 9 Electromatic Relief Valve (ERV) Actuator Modification 9 EPU Commitments 9 EPU Monitoring Plan 9 Summary 3

Introduction 9 Purpose

• Communicate the results and conclusions of the modifications and evaluations performed supporting EPU operation at QC

• Status EPU-related regulatory commitments

• Demonstrate QC can continue to operate safely at EPU power levels 4

Introduction 9 17% power uprate (2511 MWt to 2957 MWt)

• Approved in December 2001

• Initial EPU operation in 2002 9 Following initial EPU operation, both QC units experienced vibration related problems, resulting in several shutdowns and reactor power restrictions 5

Introduction 9 Initial actions focused on improving components ability to withstand EPU loading conditions

• ERV actuators

• Steam dryers 9 In parallel, actions included identifying and eliminating the vibration driving force

• Acoustic side branch (ASB) modification 9 Supporting analysis and evaluations previously reviewed with NRC technical staff

• QC technical issues resolved 6

Introduction 2 02 3 03 04 04 05 05 6 06 n0 ly n0 ly n ly n ly n0 ly Ja Ju Ja Ju Ja Ju Ja Ju Ja Ju ERV ASBs Restricted to Degradation Return to Initial EPU Pre-EPU Installed/ERV Steam Dryer Full-EPU ramp up Power Upgrade Dryer Failure Replaced Power QC1 Both Units Both Units ERV Restricted to Returned to Degradation Pre-EPU Full-EPU Power Power QC2 Initial EPU ASBs Steam Dryer ramp up Installed/ERV Replaced Dryer Failure Upgrade Dryer Failure Dryer Failure Target Rock Restricted to Return to S/RV Pre-EPU Full-EPU setpoint Power Power 7

Vibration Source Reduction Bruce Rash Corporate Design Engineering Director Roman Gesior Corporate Engineering Programs Director 8

Vibration Source Reduction 9 Following several EPU-related component problems, EGC determined that reduction of the vibration source should be pursued 9 Scale model testing and in-plant data provided positive results in our efforts to identify the vibration source 9 In early 2006, a thorough and comprehensive root cause evaluation (RCE) was performed

• RCE confirmed the need to address the source of main steam line (MSL) vibration

• Contributing factors related to ERVs also identified 9

Vibration Source Reduction 9 RCE also identified contributing organizational weaknesses

• A systematic approach was not used to evaluate decisions

• Over-reliance on contractor products and expertise

• Some decisions were based on the best information available; however, the collective conditions were not clearly understood 10

Vibration Source Reduction 9 Organizational contributing cause corrective actions are complete

• Revised operational and technical decision making (OTDM) process procedure

• Trained personnel on OTDM process requirements

• Revised process controls on review of complex vendor products 9 NRC 95001 Supplemental Inspection evaluated organizational weaknesses and corrective actions 11

Vibration Source Reduction 9 Testing confirmed the source of the pressure loads to be from the ERV and main steam safety valve (MSSV) standpipes 9 Vortex shedding at the branch opening resonated with the acoustic standing wave in the ERV and MSSV standpipes 9 Increased steam flow velocities at EPU conditions resulted in increased acoustic pressure loads 12

Vibration Source Reduction 9 ASB modification installed in Spring 2006 on standpipes of MSSVs and ERVs

• Reduced steam dryer loading increases stress margin for long-term operation of steam dryer

• Reduced overall MSL vibration impact on ERV actuators and other attached main steam components 13

Vibration Source Reduction 9 The addition of the ASB increases the effective length of the ERV/MSSV standpipe, thereby decreasing the frequency of the acoustic standing wave 9 When the acoustic and vortex shedding frequencies are no longer coupled, resonance does not occur 9 The addition of screen mesh material inside the ASB introduces a damping medium that absorbs the energy in the standpipe 14

Vibration Source Reduction 9 Rigorous pre-installation test plan confirmed ASB performance under service conditions 9 Further verification occurred during startup testing on both units

• MSL strain gage data at EPU are below original licensed thermal power (OLTP) levels Indication of MSL pressure oscillations and steam dryer load

• MSL accelerometer data at EPU are below OLTP levels Indication of MSL flow-induced vibration 15

Vibration Source Reduction Q2R18 TC18 2874 MWt - MSL A Lower 3.00E-01 2874 MWt with ASB QC2 pre-ASB EPU QC2 pre-ASB OLTP 2.50E-01 2.00E-01 uSTR-RMS 1.50E-01 1.00E-01 5.00E-02 0.00E+00 0 20 40 60 80 100 120 140 160 180 Frequency [Hz]

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Vibration Source Reduction 0.6 Inlet-Flange-ERV-3C-Y 2005 OLTP Inlet-Flange-ERV-3C-Y 2005 EPU 0.5 3C-ERV-Inlet-Flange-Y1 2006 EPU 0.4 Acceleration [g-RMS]

0.3 0.2 0.1 0

0 25 50 75 100 125 150 175 Frequency [Hz] 17

Vibration Source Reduction 9 Conclusions

• In-plant data demonstrates the ASB effectiveness in reducing MSL pressure oscillations to pre-EPU levels Reduces MSL component vibration related wear Reduces the steam dryer pressure oscillation load

• ASBs tested and demonstrated to be robust 18

Steam Dryer Replacement Roman Gesior Corporate Engineering Programs Director 19

Steam Dryer Replacement 9 Initial steam dryer damage identified on Unit 2 in July 2002 9 Subsequent EPU-related steam dryer damage identified on both units over following two years 9 Several repair and structural enhancements made to original steam dryers 9 In 2004, decision made to replace both QC steam dryers 20

Steam Dryer Replacement 9 New steam dryer design

• More structurally robust and vibration tolerant

• Minimizes number of welds in high-stress and high-fatigue areas

• Meets the ASME Code limits for all service levels (i.e.,

normal, upset, and faulted) 21

Steam Dryer Replacement 9 Unit 2 steam dryer instrumentation

• First fully instrumented steam dryer in US

• 96 sensors mounted on dryer and MSLs 9 New steam dryer testing

• Pressure and strain gage data collected at multiple power levels up to maximum achievable EPU power

• Collected data verified steam dryer structural integrity 22

Steam Dryer Replacement 9 Conclusions

• New steam dryer designed to meet pre-ASB, EPU loading conditions

• Robust steam dryer design, coupled with reduced vibration loading due to ASBs, results in significant structural margin 23

ERV Actuator Modification Bruce Rash Corporate Engineering Design Director 24

ERV Actuator Modification 9 ERV degradation

• Unit 1 ERV actuator failed in 2003 Both units ERV actuators were rebuilt with hardened materials

• Unit 2 ERV actuator inspections in December 2005 revealed internal damage, attributed to accelerated vibration-related wear

• ERV inspections performed on Unit 1 in January 2006 revealed similar wear 25

ERV Actuator Modification 9 2006 RCE identified contributing factors related to the ERVs

• Inadequate design test control for the ERV actuators rebuilds in 2003

• Inadequate ERV rebuild and inspection procedure 9 Corrective actions included:

• Development of comprehensive test control program

• Revisions to ERV actuator/pilot valve rebuild and inspection procedures to address preventive maintenance weaknesses 26

ERV Actuator Modification 9 2006 ERV actuator upgrade

• ERV actuators replaced with more robust design Several ERV actuator replacement options evaluated

• General Electric design selected Included several material improvements Significantly improved vibration resistance

• Actuator performance demonstrated through testing Timing tests Shaker table testing confirmed design robustness 27

ERV Actuator Modification New GE Design Original Design 28

ERV Actuator Modification 9 Conclusions

• Cause of the ERV degradation identified as MSL vibration

• Upgraded ERV design, coupled with reduced vibration loading due to ASBs, results in significantly improved vibration resistance 29

EPU Commitments Patrick Simpson Corporate Licensing Manager 30

EPU Commitments 9 In a January 26, 2006, letter to the NRC, EGC outlined 11 remaining regulatory commitments supporting long-term QC operation at EPU conditions 31

EPU Commitments 9 ERV and Unit 2 Spring 2006 Refueling Outage Inspections Commitment Status Inspect the 3E ERV turnbuckle tack welds and threads. Complete Inspect the currently (i.e., pre-Spring 2006 refueling outage) installed Complete ERV actuators.

General visual inspection of reactor pressure vessel internals, steam, Complete and feedwater systems, including inspection and disassembly, if necessary, of the most susceptible components.

Each QC unit will remain at pre-EPU power level until the ERV root Complete cause evaluation is complete, necessary corrective actions implemented, and meeting with NRC held to discuss these actions.

Inspect Unit 2 steam dryer to ensure no structurally significant cracking Complete that would limit operation.

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EPU Commitments 9 Meetings with NRC Commitment Status Present the planned QC Unit 2 Spring 2006 ERV Complete inspection scope and resultant extent of condition evaluations.

Following resolution of open technical issues, discuss Complete with NRC management the results and conclusions of (Today) evaluations performed supporting EPU operation at QC Units 1 and 2.

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EPU Commitments 9 Continuous monitoring and inspection activities Commitment Status Conduct daily monitoring of moisture carryover and Ongoing other key reactor and plant parameters. Future monitoring will conform to industry guidance.

Perform future steam dryer inspections using BWRVIP- Ongoing 139 guidance.

Where lessons learned from evaluations or inspections QC Unit 1 steam conducted pursuant to other commitments indicate dryer to be significant potential degradation of the steam dryer, inspected in May EGC will take appropriate actions up to and including 2007 refueling shutting down the applicable unit. outage 34

EPU Commitments 9 Following the meeting with NRC management, EGC will formally request NRC acceptance of continuous EPU operation of QC 35

EPU Monitoring Plan Steve Boline Quad Cities Engineering Senior Manager Design Engineering 36

EPU Monitoring Plan 9 On-line monitoring

• ASB performance confirmed by monthly trending against baseline vibration levels Trending includes vibration/strain/reactor pressure measurements until next refueling outage on each unit Subsequent monitoring to consist of quarterly trending of reactor pressure

• Steam dryer performance confirmed by daily monitoring of moisture carryover and other key reactor parameters Future monitoring will conform to BWRVIP-139 guidance 37

EPU Monitoring Plan 9 Refueling outage inspections

• ASBs 50% each outage until all ASBs inspected Subsequent outages will include one ASB inspection

• Steam dryer Inspections consistent with BWRVIP-139 guidance and vendor recommendations

• ERV inspections & PMs ERVs will be stroked three times Actuators and pilot valves will be replaced General area walkdowns of steam affected zones Frequency and sample size may be adjusted based on future performance 38

Summary Randy Gideon QC Plant Manager 39

Summary 9 Vibration-related concerns resolved

• ERV actuators and steam dryers redesigned to withstand pre-ASB, EPU loading conditions

• ASBs reduce vibration loads to below original licensed thermal power levels 9 Both QC units are operating safely at EPU power 40