ML15261A144
| ML15261A144 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 05/22/1997 |
| From: | Reyes L NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | Hampton J DUKE POWER CO. |
| References | |
| CAL-2-97-03, CAL-2-97-3, NUDOCS 9706040316 | |
| Download: ML15261A144 (34) | |
Text
May 22, 1997 CAL NO. 2-97-003 Duke Power Company ATTN:
Mr. J. W. Hampton Vice President Oconee Site P. 0. Box 1439 Seneca, SC 29679
SUBJECT:
CONFIRMATORY ACTION LETTER (CAL NO. 2-97-003) UPDATE - RESTART OF OCONEE UNITS 2 AND 3 Gentlemen:
This letter is in response to your letter dated May 20, 1997, and confirms in writing, the Regional Administrator's concurrence for restart of Units 2 and
- 3. Your letter of May 20, 1997, notified the NRC that you have completed th se items addressed in CAL NO. 2-97-003, dated May 5, 1997, necessary to r start Units 2 and 3. These items, which involved root cause determination gnd resultant corrective actions with respect to the High Pressure Injection (HPI) nozzle cracking concern and degradation of the Unit 3 HPI system, were discussed in a Management meeting at the Oconee Nuclear Station on May 16, 1997. At the conclusion of this meeting, the Regional Administrator's concurrence was given for the restart of Units 2 and 3 (pending final system readiness actions, including resolution of HPI pump minimum recirculation flow orifice degradation). This concurrence was based upon our review of the actions you had taken or committed to as discussed during the meeting and subsequently addressed in your May 20, 1997 letter. A list of meeting attendees and a copy of your presentation handout are enclosed.
In addition to addressing the restart readiness of Units 2 and 3, your May 20, 1997, letter also reiterated the related actions previously committed to in your letter dated May 16, 1997. Included in these committed actions are the shutdown of Unit 1 no later than June 14, 1997, in order to perform appropriate examinations of HPI nozzle components and make letdown storage tank level and pressure instrument modifications. Accordingly, as discussed during the aforementioned meeting, the Unit 1 compensatory actions addressed in actions (2) and (3) of the CAL will remain in effect until Unit 1 is shutdown.
In accordance with 10 CFR 2.790(a) of the NRC's "Rules of Practice", Part 2, Title 10, Code of Federal Regulations, a copy of this letter and its enclosures will be placed in the NRC Public Document Room.
9706040316 970522 PDR ADOCK 05000269
DPC 2
Should you have any questions concerning this matter, please contact us.
Sincerely, Original signed by:
Luis A. Reyes Regional Administrator Docket Nos. 50-269, 50-270, and 50-287 License Nos. DPR-38, DPR-47, and DPR-55
Enclosures:
- 1. List of Attendees
- 2. Licensee Presentation Handouts cc w/encls:
Mr. J. E. Burchfield Compliance Duke Power Company P. 0. Box 1439 Seneca, SC 29679 Mr. Paul R. Newton Legal Department (PB05E)
Duke Power Company 422 South Church Street Charlotte, NC 28242-0001 Mr. Robert P. Gruber Executive Director Public Staff - NCUC P. 0. Box 29520 Raleigh, NC 27626-0520 Mr. Robert B. Borsum Framatome Technologies 1700 Rockville Pike, Suite.525 Rockville, MD 20852 Mr. J. Michael McGarry, III, Esq.
Winston and Strawn 1400 L Street, NW Washington, D. C. 20005 cc w/encls cont'd:
(See page 3)
DPC 3
cc w/encls cont'd:
Distribution w/encls:
Dayne H. Brown, Director H. Thompson, DEDR Division of Radiation Protection E. Jordan, DEDO N. C. Department of Environmental J. Lieberman, OE Health & Natural Resources S. Collins, NRR P. 0. Box 27687 S. Varga, NRR Raleigh, NC 27611-7687 D. LaBarge, NRR B. Uryc, RII Mr. Max Batavia, Chief C. Evans, RII Bureau of Radiological Health G. Tracy, OEDO South Carolina Department of Health R. Carroll, RIl and Environmental Control H. Berkow, NRR 2600 Bull Street C. Casto, RII Columbia, SC 29201 J. Johnson, RII J. Jaudon, RII County Supervisor of PUBLIC Oconee County Walhalla, SC 29621 NRC Resident Inspector U.S. Nuclear Regulatory Commission Manager, LIS 78128 Rochester Highway NUS Corporation Seneca, SC 29672 2650 McCormick Drive Clearwater, FL 34619-1035 Mr. G. A. Copp Licensing - ECO50 Duke Power Company P. 0. Box 1006 Charlotte, NC 28201-1006 Ms. Karen E. Long Assistant Attorney General N. C. Department of Justice P. 0. Box 629 Raleigh, NC 27602 pffice RII:DRP RP NRR RP O
C44-I.ir :b-5 signature nam Ca'~~L B
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JJ HN SON Mlr name LL date 05-\\/97
/97 j 5/97 05/21/97 OFFICIAL C D COPY UMENT NAME:
CAL29700.3
LIST OF ATTENDEES NUCLEAR REGULATORY COMMISSION L. Reyes, Regional Administrator, Region II (RII)
C. Casto, Chief, Reactor Projects Branch 1, Division of Reactor Projects (DRP), RII W. Holland, Chief, Maintenance Branch, Division of Reactor Safety (DRS), RII E. Girard, Reactor Inspector, Special Inspection Branch, DRS, RII M. Scott, Senior Resident Inspector, Oconee, DRP, RII DUKE POWER COMPANY J. Hampton, Vice President, Oconee Nuclear Station (ONS)
B. Peele, Station Manager, ONS J. Davis, Engineering Manager, ONS T. McConnell, Station Support Manager, Nuclear General Office ENCLOSURE 1
Oconee Nuclear Station Restart Activities Meeting NRC/Duke Meeting May 16, 1997 2
Agenda
- Introduction - Jim Hampton
- Current Plant Statis - Joe Davis
- RCS Leak - Joe Davis Overview, History, and Sequence of Events n Root Cause n Corrective Actions
- Loss of Suction to two HPI Pumps - Jack Peele Overview and Sequence of Events n Root Cause
)> Corrective Actions
- Confirmation of Action Letter Summary - Jack Peele
- Schedule/NRC Interface - Jack Peele
- Summary - Jim Hampton ENCLOSURE 2 1
3 Current Plant Status 0 Unit 2:
>> Progressing toward hot shutdown
>> 2A1 RCS safe end, thermal sleeve, and pipe to Ist valve replaced
> Other HPI nozzle components examined and found acceptable
>> Significant portions of root cause for RCS leak complete
> Monitoring equipment on HPI lines installed
> LDST instrumentation modifications complete 4
Current Plant Status 0 Unit 3:
>> Cold Shutdown Replaced 3AI RCS safe end, thermal sleeve, and pipe to 1st valve Examination of HPI nozzle components complete a Repairs of HPI pumps in progress
> LDST modifications in progress 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 examination 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 a GL 88-08 requirements met 3
3
7 RCS Leak
- Oconee Actions per BWOG Report:
) Actions taken on HPI nozzle components for Units 2 and 3 prior to 1985:
- 2A2, 3A2: Installed new safe end and thermal sleeve e 2B2: Replaced existing thermal sleeve with new design
- 2Al, 3A1, 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 4
4
9 RCS Leak 0 Oconee Actions per BWOG Report:
>> Performed augmented examinations:
- 1996 results on Unit 2:
- 2A 1 - thermal sleeve gap increasing
- 2A2, 2B l, 2B2 - no thermal sleeve gap increase
- 1996 results on Unit 3:
- 3Al - thermal sleeve gap increasing 1984-1985-observed gap increase 1989-1996-observed gap increase
- 3A2, 311, 3B2 - no thermal sleeve gap increase
- Failed to recognize indications of thermal sleeve gap increase Al nozzles 10 RCS Leak
- Sequence of Events Time Event 4/21/97 Reactor Operator (RO) receives indications of a Reactor 2245 Coolant System (RCS) leak. Calculated RCS leakage - I gpm 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 0 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 2A1 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
I*
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
> Replaced thermal sleeve and safe end with new design for 3Al HPI normal injection line
> Installed temporary instrumentation for monitoring of Unit 2 nozzles
> Installing instrumentation on Unit 3 16 RCS Leak
- Completed Corrective Actions (Continued)
> Heightened awareness to RCS leakage rate on Unit 1
>> NRC commitments reviewed to identify all augmented inspection requirements
> Augmented examinations completed on Units 2 & 3 exceed GL 85-20 requirement 8
8
I*
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
- 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
- Other Corrective Actions
> Inspections during the upcoming Unit 1 maintenance outage will include UT and RT of nozzle components
>> Specific UT/RT plans and schedules will be submitted by 30 days prior to the U 1 EOC 17 Refueling Outage 20 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 10 10
21 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 22 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 11 11
23 Loss of Suction to HPI Pumps
- System Description
>> 3 HPI Pumps, 300 gpm at 3,100 psig
> Provides normal makeup and seal injection from LDST
> Provides emergency makeup from BWST
> Normal Operation is one pump on, one in standby
> 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 24 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 12 12
25 Loss of Suction to HPI Pumps
- Sequence of Events 053/97 "HI pump secure.
A P upcniues to run.
0917 13/97
-Opened HP24(BWS T-ipp-y).
0921 57379T ClisedHP-24.
0928 5397 3A HPIpump secured. Olrtfilieitto EDSTToliidic 0932 of 92". Letdown from RCS isolated. Entered AP for Loss of HPI Makeup.
7397~ ClpletdP foEassfHPTikeup. Gif istauICPiiiiinLPI
~1030 pump in decay heat removal mode, letdown isolated. Began development of procedure to use 3C HPI pump for RCS makeup.
26 Loss of Suction to HPI Pumps
-1030 5/3/97 Unusual Event declared.
1504 5/3/97 LDST level instrument reference leg discovered to 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 13 13
27 Loss of Suction to HPI Pumps
- Sequence of Events ontingency p an or it s ut own usmng 3 pump, an
- ac 'p 1030 contingency plan for using no HPI pumps completed and approved.
5T479T Ug 3 H pup fol ileup.
1124 575797 SUii316ldown esse illyiiid 1943 55/97 Secured Unusual Event.
1946 5759ITHPIHFsreaigned 2135 28 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 14 14
29 Loss of Suction to HPI Pumps
- Cause of Fitting Leak:
> Scratches on seating surfaces
>> Over torquing cap 30 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 15 15
31 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 32 Loss of Suction to HPI Pumps
- Completed Corrective Actions:
>> Initiated Detailed (FIP) and General (SEIT) event investigation teams x 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
>> Revised Unit 1 AP to include 1 HP-5 closure 16 16
33 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 34 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 17 17
35 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
> Perform reliability study of HPI System 36 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
> Perform root cause of failure to adequately apply OE 18 18
37 Loss of Suction to HPI Pumps
- Operator Tools to Respond to Events:
>> Commit-to-Memory Items
>> Stabilizing the Plant/Skill-of-Operator
>> Alarm Response Guides
> Abnormal Procedures
>> Emergency Operating Procedures 38 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 19 19
39 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 site management 40 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 20 20
- g 0
Confirmation of Action 41 Letter Summary
> HPI System degradation actions
- Weekly level accuracy checks
>> Impact on continued operation of Unit 1
- Enhanced leakage detection and make-up flow guidelines
- JCO
- working closely with NRC staff
- various commitments in place
- conclude safe to continue to operate
- will shut down NLT June 14th
> Conditions of CAL met 42 Schedule/ NRC Interface
- Unit 2
)> Restart projected for third week of May
- Unit 3
>> Restart projected for end of May
- Unit 1
> Continuing Operation under JCO until Units 2 and 3 return to steady state power operation
> 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 21 21
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COOLANT PIPEn CLADDING --7P SAFE END TO SAFE END
/CD PIPE WELD (S.S.)
--BLOCK VALVE LU FLOW THERMAL 2L SLEEVE WELD BUTTONS DEC 21/2"S.S.
1"6000#S.S.SW HALF COUPLING C0 PIPE C1S.S.
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0 (30% l'V Maphygrph 240.
60 2700 900 MMetallography (26.5% TW) 2400 1200 210.
150.
Metallography 10 (24% T"W Note View is looking in direction of MIU flow Warming Line Flow
Oconee 3 HPI Event HPI Total RCP Seal Injection 90 3A HPIP Start First Indi ation of degraded flow 3HP-24 Opened (BWST Suction) 70
.3A HPIP Fails ???
60 3A HPIP St p:
3B HPI Stop 40
0 03-May-97 09:10:00 03-May-97 09:12:00 03-May-97 09:14:00 03-May-97 09:16:00 03-May-97 09:18:00 03-May-97 09:20:00 03-May-97 09:22 00 03-May-97 09:24:00
130 Oconee 3 5/3/97 HPI Event 240 120 akeup source is essentially gone therefore 235 Pressurizer level begins to drop 110 230 90 G)_
160 gLa mau t
70 (Actual4LDSTLvoluLel 50 n220 PZR Lvl 0NRCST-Hot 016-
_________a___e 7 0 215 60 Actual LDST volume 21 205 40 7
LLST Level stopped changing when levelL r eaches lower instrument tap atO0 inches) 30 1
_200 6:00 7:00 8:00 9:00 10:00 11:00 12:00
LETDOWN FLOW IV0086 IV0085 LETDOWN STORAGE0 TANK IV0087 HPILT0033P1 HPILT0033P2 Non-QA QA D
D HP1lVO052 HPIIVO103 II I
I TO HPI PUMP SUCTION HEADER OCONEE NUCLEAR STATION - UNITS 1, 2, & 3 NOTE:
LETDOWN STORAGE TANK LEVEL SKETCH FOR INFORMATION ONLY INSTRUMENTATION SKETCH MAY 12, 1997 FILE: LDSTSKCH.VSD REV. 0 SHEET 1 OF 1