ML16134A530
| ML16134A530 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 05/21/1997 |
| From: | Labarge D NRC (Affiliation Not Assigned) |
| To: | NRC (Affiliation Not Assigned) |
| References | |
| TAC-M98454, NUDOCS 9705230278 | |
| Download: ML16134A530 (37) | |
Text
May 21,19
[ICESEE:
Du ower Company FACILIT'i:
Oconee Nuclear Station, Units 1, 2, and 3
SUBJECT:
SUMMARY
OF THE MAY 14, 1997 MEETING ON THE HIGH PRESSURE INJECTION SYSTEM (TAC NO. M98454)
On May 14, 1997, personnel from the Office for Analysis and Evaluation of Operational Data, Region II, Office of the Executive Director for Operations, and the Office of Nuclear Reactor Regulation met at NRC Headquarters in Rockville, Maryland, with representatives of the Duke Power Company (DPC) management and engineering staffs to discuss technical information related to the High Pressure Injection (HPI) System weld crack, thermal sleeves, Letdown Storage Tank level control and design, system operation, etc., that has been the subject of the recent shut down of Units 2 and 3, and evaluations for continued operation of Unit 1. Enclosure 1 is a list of the individuals who attended the meeting and Enclosure 2 is the handout material that was supplied by DPC.
The topics discussed included the current status of Units 1, 2, and 3; overview history and sequence of events; root cause; corrective actions; technical discussions on nozzles and HPI pumps; and restart issues related to the weld crack issue on Unit 2. Additional topics included a discussion of the loss of HPI pump suction on Unit 3, sequence of events, root cause, contributing factors and observations, and short and long-term corrective actions.
ORIGINAL SIGNED BY:
David E. LaBarge, Senior Project Manager Project Directorate 11-2 Division of Reactor Projects -
I/II Office of Nuclear Reactor Regulation Docket Nos. 50-269, 50-270, and 50-287
Enclosures:
- 1. Attendance List
- 2. DPC Handout cc w/encls:
See next page Hard Copy E-Mail Docket File SCollins/FMiraglia CCasto, RH SNewberry PUBLIC RZimmerman CHsu JLyons PD II-2 Rdg.
SVarga EGirard CJackson OGC HBerkow JStrosnider MShuaibi ACRS LBerry TMcLellan BSheron JJohnson, RI DRoss (SAM)
NFields DWessman DLaBarge GTracy, EDO GLainas KManoly KWichman BElliot IAhmed PAmbros LLund RHermann MHartzman EGoodwin DO'Neal SSheng 9
- --7 0 52 3 0 2 7 8 9 7 0 5 2 1 --
PDR ADOCK 05000269 SMheng P_
-PDR To receive a copy of this document, indicate in the box: "C" Copy without attachment/enclosure "E" = Copy with attachment/enclosure NNI= No copy OFFICE PM:PDII-LA:PDII 0 D:
NAME DLaBarge n LBerry
) Hew DATE 5/-o /97 2/-1,0 7
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G:\\OCONEE\\MTG514.SUM OFFICIAL RECORD COPY
o0 UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-001 May 21, 1997 LICENSEE:
Duke Power Company FACILITY:
Oconee Nuclear Station, Units 1, 2, and 3
SUBJECT:
SUMMARY
OF THE MAY 14, 1997 MEETING ON THE HIGH PRESSURE INJECTION SYSTEM (TAC NO. M98454)
On May 14, 1997, personnel from the Office for Analysis and Evaluation of Operational Data, Region II, Office of the Executive Director for Operations, and the Office of Nuclear Reactor Regulation met at NRC Headquarters in Rockville, Maryland, with representatives of the Duke Power Company (DPC) management and engineering staffs to discuss technical information related to the High Pressure Injection (HPI) System weld crack, thermal sleeves, Letdown Storage Tank level control and design, system operation, etc., that has been the subject of the recent shut down of Units 2 and 3, and evaluations for continued operation of Unit 1. Enclosure 1 is a list of the individuals who attended the meeting and Enclosure 2 is the handout material that was supplied by DPC.
The topics discussed included the current status of Units 1, 2, and 3; overview history and sequence of events; root cause; corrective actions; technical discussions on nozzles and HPI pumps; and restart issues related to the weld crack issue on Unit 2. Additional topics included a discussion of the loss of HPI pump suction on Unit 3, sequence of events, root cause, contributing factors and observations, and short and long-term corrective actions.
David E. LaBarge, Senior Project Manager Project Directorate 11-2 Division of Reactor Projects -
I/II Office of Nuclear Reactor Regulation Docket Nos. 50-269, 50-270, and 50-287
Enclosures:
- 1. Attendance List
- 2. DPC Handout cc w/encls: See next page
Oconee Nuclear Station Units 1, 2, and 3 cc:
Mr. Paul R. Newton Mr. Ed Burchfield Duke Power Company, PB05E Compliance 422 South Church Street Duke Power Company Charlotte, North Carolina 28242-0001 Oconee Nuclear Site P. 0. Box 1439 J. Michael McGarry, III, Esquire Seneca, South Carolina 29679 Winston and Strawn 1400 L Street, NW.
Ms. Karen E.Long Washington, DC 20005 Assistant Attorney General North Carolina Department of Mr. Robert B. Borsum Justice Framatome Technologies P. 0. Box 629 Suite 525 1700 Rockville Pike Rockville, Maryland 20852 Mr. G. A. Copp Licensing -
ECO50 Manager, LIS Duke Power Company NUS Corporation 526 South Church Street 2650 McCormick Drive, 3rd Floor Charlotte, North Carolina 28242-0001 Clearwater, Florida 34619-1035 Dayne H. Brown, Director Senior Resident Inspector Division of Radiation Protection U.S. Nuclear Regulatory Commission North Carolina Department of Route 2, Box 610 Environment, Health and Seneca, South Carolina 29678 Natural Resources P. 0. Box 27687 Regional Administrator, Region II Raleigh, North Carolina 27611-7687 U. S. Nuclear Regulatory Commission Atlanta Federal Center Mr. J. W. Hampton 61 Forsyth Street, S.W., Suite 23T85 Vice President, Oconee Site Atlanta, Georgia 30303 Duke Power Company P. 0. Box 1439 Max Batavia, Chief Seneca, South Carolina 27679 Bureau of Radiological Health South Carolina Department of Health and Environmental Control 2600 Bull Street Columbia, South Carolina 29201 County Supervisor of Oconee County Walhalla, South Carolina 29621
ATTENDEES MEETING WITH DUKE POWER COMPANY TO DISCUSS RECENT HPI PROBLEMS MAY 14, 1997 NAME ORGANIZATION Chuck Hsu Clay A. Little NRC/AEOD/SPD/RAB ClayA. LttleDuke/Oconee/Engr/E1 ect.
Bill McAlister Duke/Oconee/Malntenance
.Duncan Brewer EdwardH.Gr Duke/General Office/PRA Edwar H.
Grard'NRC/Region.II/Div. of Reactor Safety, C. B. Cheezem Duke/NDE Steve Nader Duke/Oconee/Mech Systems Engineering Tim Brown Duke/Oconee/Mechanical-Civi1 Engineering/Stress Analysis Tony McConnell Duke/Nuclear General Office Lanny Wilkie Craig Tompkins Duke/Oconee/Mod Engineering David B. Coyle Duke/Oconee/Mech. Systems Dave Nix Duke/Oconee/Reg Compliance Bill Foster Duke/Oconee/Safety Assurance Jack Strosnider NRC/NRR/DE/EMCB Tom McLellan NRC/NRR/DE/ECGB Nick Fields NRC/NRR/PECB Gus Lainas NRC/NRR/DE Scott Newberry NRC/NRR/DSSA Jim Lyons NRC/NRR/DSSA/SRXB Christopher Jackson NRC/NRR/DSSA/SRXB Mohammed Shuaibi NRR/DSSA/SRXB Glenn Tracy EDO Joe M. Davis Duke/Oconee/Engineering D. LaBarge NRC/NRR/DRPE Brian Sheron NRC/NRR/DE Dick Wessman NRC/NRR/DE Kamal Manoly Keith Wichman NRC/DE/EMEB Barry J. Elliot NRC/DE/EMCB I. AhmedNRDEEC
- 1. AhmedNRC/DRCH/HICB P. Ambros NRC/Events Assessment Ken Stuckey Framatome Technologies Kevin Redmond Duke/Met Lab Bret Boman Framatome Technologies Ken Yoon Framatome Technologies Ronnie Lingle Duke/Oconee/Operations Louise Lund Art DeardorffNRRE//MB DStructural Integrity Assoc. (w/Duke Power)
George 1.NLehmann GPU Nuclear
-2 NAME ORGANIZATION James J. McArdle Duke/NDE Robert Gill Duke/Nuclear General Office Robert Hermann NRC/DE/EMCB Paul Newton Duke/Nuclear General Office Mark Hartzman NRC/DE/EMEB Ed Goodwin NRC/DRPM/PECB Dan O'Neal NRC/DSSA/SPSB Simon Sheng NRC/NRR/EMCB B. L. Peele Duke/Oconee
DUKE POWER COMPANY HANDOUTS MAY 14, 1997
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Oconee Nuclear Station Technical Interface Meeting with NRR NRC/Duke Meeting May 14, 1997 2
Agenda
- Current Plant Status - Joe Davis
- RCS Leak - Joe Davis Overview, History, and Sequence of Events a Root Cause n Corrective Actions
- Loss of Suction to two HPI Pumps - Jack Peele
> Overview and Sequence of Events
) Root Cause
>> Corrective Actions
- Technical Discussion on Nozzles
- Technical Discussion on HPI Pumps
- Clarify Restart Issues - Jack Peele 1
1
3 Current Plant Status
- Unit 2:
> Progressing toward hot shutdown
>) 2Al RCS safe end, thermal sleeve, and pipe to 1st valve replaced
> Other HPI nozzle components examined and found acceptable
> Significant portions of root cause for RCS leak complete a Monitoring equipment on HPI lines installed
> LDST instrumentation modifications complete 4
Current Plant Status
- Unit 3:
>> Cold Shutdown
> 3Al RCS safe end, thermal sleeve, and pipe to Ist valve being replaced
> Examination of HPI nozzle components in complete
)> Repairs of HPI pumps in progress
> LDST modifications in progress a Significant portions of investigation of root cause of loss of suction to HPI pumps complete SEIT complete and AIT exited on 5/9
- Unit 1:
> Operating at 100% Full Power 2
2
5 RCS Leak
- System Overview
> HPI System serves as high pressure makeup system to RCS
>> HPI System has two normal and two emergency makeup paths
> HPI System interfaces with RCS piping via nozzle components
> Nozzle and safe end protected from thermal gradients by thermal sleeve 6
RCS Leak
- History of Nozzle Component Failures
>> Safe end to pipe weld and thermal sleeve failed resulting in RCS leak at Crystal River Plant in early 1982
'> BWOG issued report in late 1982 with recommendations to owners regarding HPI nozzle components
>> BWOG report generally recommended:
- Inspect and repair/re-roll/replace damaged nozzle components
- Implement an augmented ISI plan for nozzle components
- Perform analysis on improved designs
)> Oconee committed to recommendations of BWOG report
>> NRC endorsed recommendations of BWOG in GL 85-20 3
3
7 RCS Leak
- Oconee Actions per BWOG Report:
> Actions taken on HPI nozzle components for Units 2 and 3 prior to 1985:
- 2B2: Replaced existing thermal sleeve with new design
- 2Al, 3Al, 3B2: Left as originally installed
- 2B1, 3B1: Rerolled original thermal sleeve 8
RCS Leak
- Oconee Actions per BWOG Report:
> Placed general augmented examination requirements for HPI nozzle components in ASME Section XI ISI Plan per GL 85-20
>> Performed augmented examinations 1983-1996 4
4
9 RCS Leak
- Oconee Actions per BWOG Report:
> Performed augmented examinations:
- 1996 results on Unit 2:
- 2Al - thermal sleeve gap degrading
- 2A2, 2B1, 2B2 -no thermal sleeve gap degradation
- 1996 results on Unit 3:
- 3Al -thermal sleeve gap degrading
>> 1984-1985-observed gap degradation a 1989-1996-observed gap degradation
- 3A2, 3B1, 3B2 -no thermal sleeve gap degradation
- Failed to recognize indications of thermal sleeve gap degradation on Al nozzles 10 RCS Leak
- Sequence of Events Time Event 4/21/97 Reactor Operator (RO) receives indicationsof a Reactor 2245 Coolant System (RCS) leak. Calculated RCS leakage - Igpm 4/21/97 RCS leakage exceeded Technical Specification Limits for 2337 unidentified RCS leakage.
4/22/97 Calculated RCS leakage - 2.8 gpm 0200 4/22/97 Reactor Building entry to investigate leak source. Unable to 0215 determine exact source of RCS leak.
5 5
11 RCS Leak
- Sequence of Events Time Event 4/22/97 Commenced Reactor Shutdown due to RCS leakage.
0352 4/22/97 Initiated FIP investigation.
1300 4/22/97 Declared Unusual Event on Unit 2 due to RCS leakage in 1600 excess of 10 gpm. Unit shutdown/cooldown in progress.
4/23/97 Reactor Building entry determines source of leak from a crack 0547 in HPI 2A I injection line on safe end to pipe weld.
12 RCS Leak
- Findings:
>A leak occurred in the pipe to safe end connection weld at the 2Al HPI nozzle
> Crack in weld was circumferential, with a portion being through-wall Crack propagated slowly
>> Details of crack described in JCO for Unit 1 6
6
13 RCS Leak
- Root Cause(s)
> Ineffective examination program for HPI nozzle components
- Inadequate examination procedures
- Unclear acceptance criteria
>> Related finding:
- Examination commitments inadequately controlled by the ISI program 14 RCS Leak
- Failure Mechanisms
>> High cycle low / stress thermal fatigue initiated failure in weld
>> Flow induced vibration contributed to thermal sleeve failure after loosening 7
7
15 RCS Leak
- Completed Corrective Actions:
>> Replaced thermal sleeve and safe end with new design for 2Al HPI normal injection line
>> Examined other Unit 2 HPI nozzle components
>> Shut down Unit 3 to examine nozzle components Replacing thermal sleeve and safe end with new design for 3Al HPI normal injection line
>> Installed temporary instrumentation for monitoring of Unit 2 nozzles 16 RCS Leak
- Completed Corrective Actions (Continued)
> Heightened awareness to RCS leakage rate on Unit 1
>> All NRC commitments reviewed to identify all augmented inspection requirements
>) Verified adequacy of most recent NRC-required augmented inpsection 8
8
17 RCS Leak
- Long Term Corrective Actions
> Shut down Unit 1 and perform appropriate examinations
> Evaluate warming line flow to reduce effects of thermal stress
>> Review of Operations procedures to minimize HPI nozzle component thermal stress and fatigue 18 RCS Leak
- Long Term Corrective Actions
> Improve nozzle component examination program
- Adjust frequency of examination program
- Develop tracking system for augmented examinations
- Develop specific examination procedures for augmented examinations
- Improvements complete by September 1997 refueling outage 9
9
19 RCS Leak
- Summary
>> Unit 2 weld failed due to thermal fatigue
>> Thoroughly investigated the event
>> Reviewed augmented examinations
>> Augmented examination program improvements will assure integrity of the system is maintained
>> Instrumented injection lines will aid in understanding of thermal phenomena 20 RCS Leak
- Unit 1 JCO Summary
>> Makeup flow through thermal sleeves is higher than other units
>> Maintaining increased makeup flow rate
>> Thermal sleeve is of different design than other units
>> No indications of loose sleeves in exams completed 10 10
21 RCS Leak
- Unit 1 JCO Summary (continued)
>> Administrative measures in place to minimize thermal cycles introduced by variations in makeup flow Increased level of attention to RCS leakage monitoring has been established
> Leak before break analyses demonstrate that there is a high level of confidence that the plant can be safely shut down if a leak occurs 22 11 11
2 Loss of Suction to HPI Pumps
- Agenda
>> Brief System Description
>> Sequence of Events
>> Root Causes
>> Contributing Factors and Observations
>> Corrective Actions Complete
>> Corrective Actions prior to Restart
> Long Term Corrective Actions
> Summary 1
II
3 Loss of Suction to HPI Pumps
- Initial Conditions
>> Unit 3 being shut down to investigate HPI nozzle components
>> Decay Heat Removal (3C LPI Pump) in service
>> Approaching end of Unit 3 cooldown, lost suction to 3A and 3B HPI pumps 4
Loss of Suction to HPI Pumps
0 System Description
>> 3 HPI Pumps, 300 gpm at 3,100 psig
>) Provides normal makeup and seal injection from LDST x Provides emergency makeup from BWST
> Normal Operation is one pump on, one in standby a Standby pump auto starts on low seal injection flow or after some loss of power scenarios
> All three pumps start on ES signal
>> LDST level and pressure manually controlled in band
> LDST level instrumentation not used for accident mitigation 2
2
5 Loss of Suction to HPI Pumps
- Sequence of Events (Initial Unit 3 shut down, cool down in progress, 3B HPI pump in RUN, Conditi 3A HPI pump in STBY, RCS< 250 F / 300 psig.
ons) 5/3/97 RCS cooldown. Indicated LDST level decreases, indicated 0700-pressurizer level decreases 0745 5/3/97 RCS cooldown. Indicated LDST level constant, indicated 0745-pressurizer level decreases 0912 5/3/97 Low HPI pump discharge pressure alarm 0913 5/3/97 3A HPI pump auto starts (low seal injection flow) and runs 0915 intermittently for 17 minutes 6
Loss of Suction to HPI Pumps
- Sequence of Events Time Eventnt n
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perators n pt 0932 of 92". Letdown from RCS isolated. Entered AP for Loss of HPI Makeup.
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-1030 pump in decay heat removal mode, letdown isolated. Began development of procedure to use 3C HPI pump for RCS makeup.
3 3
7 Loss of Suction to HPI Pumps
-1030 5/3/97 Unusual Event declared.
1504 5/3/97 LDST level instrument reference leg discoveredto be empty by I&E.
1515 I&E entered procedure to recalibrate instrument and refill reference leg.
5/3/97 NRC notified of event.
1547 8
Loss of Suction to HPI Pumps
- Sequence of Events
- Trime, Event
/49 Contmngencyplan for Unit 3shutdownusmng 3
-I pump, and backup 1030 contingency plan for using no HPI pumps completed and approved.
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9 Loss of Suction to HPI Pumps
- Root Cause of Event:
> Design weakness of a common reference leg for LDST level instruments combined with a leaking instrument fitting that resulted in inaccurate LDST level indication
>> Failure of Control Room team to properly monitor and detect the inaccurate level indications given the existing plant conditions.
- Contributing Cause:
>> Failure to adequately apply available operating experience 10 Loss of Suction to HPI Pumps
- Cause of Fitting Leak:
>> Scratches on seating surfaces
>> Over torquing cap 5
5
11 Loss of Suction to HPI Pumps
- Other Issues:
>> Procedure Problems
- Usefulness of AP
- Inventory Guidance during Cooldown
- Coverage during Contingency Planning
- 3C HPI pump procedure omission
>> Modification Selection 12 Loss of Suction to HPI Pumps
- Other Issues continued:
>> Configuration and Labeling of Root Valves
>> Operator Training
>> Mixed Vendor Fittings / Calibration Practices
>> Philosophy on Abnormal Procedure Use /
Knowledge vs. Rule Based 6
6
13 Loss of Suction to HPI Pumps
- Completed Corrective Actions:
> Initiated Detailed (FIP) and General (SEIT) event investigation teams
>> Activated support organizations (OSC, TSC) as necessary to assist plant recovery
> Recalibrated and refilled reference leg on LDST level instrument
>> Re-established operable HPI makeup path
>> Completed Unit 3 cooldown and depressurization a Revised Unit 1 HP to include 1 HP-5 closure 14 Loss of Suction to HPI Pumps
- Completed Corrective Actions:
>> Completed FIP and SEIT investigations
>> Established heightened awareness of monitoring of Control Room instrumentation
> For Unit 1, verify LDST reference leg weekly; check reference leg tubing fittings for leaks each shift
>> Reported Unit 3 HPI system past inoperability 7
7
15 Loss of Suction to HPI Pumps
- Corrective Actions Prior to Restart:
> Perform Modifications on Units 2 and 3 to:
- add separate reference legs for LDST level transmitters
- add a redundant LDST pressure transmitter
>> Repair, inspect, flush, and test Unit 3 HPI system as required
>> Assess applicability of this event to other tank level instruments
>> Short-term Operations training on this event, and on LDST modifications
> Improve Abnormal Procedure on Loss of HPI makeup 16 Loss of Suction to HPI Pumps
- Long Term Corrective Actions:
> Perform modifications on Unit I to:
- add separate reference legs for LDST level transmitters
- add a redundant LDST pressure transmitter
> Review and benchmark applicable procedures and make necessary improvements
> Review modification selection process to assure proper prioritization in light of this event
> Operator simulator training on loss of LDST level 8
8
17 Loss of Suction to HPI Pumps
- Long Term Corrective Actions:
)> Improve foreign material and damage inspection work practices for tubing caps and fittings
>> Modify work practices and develop action plans for addressing "mixed" fittings
>> Expand our root valve position verification program to include critical root valves outside containment where position is not self-revealing
>> Examine removed 3A and 3B HPI pumps a Perform root cause of failure to adequately apply OE 18 Loss of Suction to HPI Pumps
- Operating Experience Program
>> Prior to 1986:
- OEP managed at each site
- NRC documents administered by NGO
>> 1986:
- OEP coordinators centralized at NGO to gather, assess, and disseminate operating experience 9
9
19 Loss of Suction to HPI Pumps
- Operating Experience Program
>> 1994 and later:
- Dedicated staffing with operational focus to provide daily screening of operating experience
- Significant item ownership and monitoring
- Corrective actions assigned where appropriate
- Significant items tracked to completion by owner
- OEP database available to site personnel by PC
- Corrective action program requires OE review of appropriate items
- Daily OE updates to NGD
- Daily OE reviews by sitemanagement 20 Loss of Suction to HPI Pumps
- Summary:
>> HPI pumps failed due to loss of suction
>> Thorough investigations completed, root cause well understood
>> Corrective actions are comprehensive:
- Address all three units
- Address other similar instrumentation
- Focused on prevention of recurrence 10 10
21 Schedule/ NRC Interface
- Unit 2
> Restart projected for third week of May
- Unit 3 n Restart projected for end of May
- Unit 1
> Continuing Operation under JCO until Units 2 and 3 return to steady state power operation a Maintenance outage to perform LDST level inst mod and HPI nozzle inspections
> Refueling outage scheduled for early September, 1997
- Coordinate closure of restart issues with Senior Resident Inspector prior to restart 22 11 11
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