ML031920459
| ML031920459 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 07/15/2003 |
| From: | Thadani M NRC/NRR/DLPM/LPD4 |
| To: | |
| Thadani M, NRR/DLPM, 415-1476 | |
| Shared Package | |
| ML031920451 | List: |
| References | |
| Download: ML031920459 (10) | |
Text
July 15, 2003 LICENSEE:
South Texas Project Nuclear Operating Company FACILITY:
South Texas Project, Unit 1
SUBJECT:
SUMMARY
OF SECOND MEETING WITH STPNOC REGARDING SOUTH TEXAS PROJECT, UNIT 1 REACTOR VESSEL AND BOTTOM MOUNTED INSTRUMENTATION PENETRATION INTERFACE LEAKAGE On June 5, 2003, STP Nuclear Operating Company (STPNOC), the licensee for South Texas Project (STP), Units 1 and 2, met with the U.S. Nuclear Regulatory Commission (NRC) staff at the NRC Headquarters. The purpose of the meeting was for STPNOC to brief the NRC staff and management regarding STPNOCs continuing efforts to address the issues arising from the April 12, 2003, discoveries of indications of leakage from the STP, Unit 1, bottom mounted instrument (BMI) penetrations 1 and 46. There are 58 BMI penetrations at STP, Unit 1. contains the licensees presentation view-graphs. A list of meeting attendees is included as Enclosure 2.
The STPNOC outlined its desired meeting outcomes to keep NRC fully informed; and to explain the nondestructive examination (NDE) results, future NDE activities and testing, and supporting analyses and schedules. The STPNOC provided answers to NRC questions and understood the future NRC needs for information. The STPNOC summarized that the BMI penetration 1 had 150 mg of residue due to leakage. Penetration 46 had 3 mg of residue due to leakage.
The licensee stated that it had completed NDE inside the vessel, selected vendor, commenced design of and preparation for half nozzle repair. The licensee has also established a root cause investigation team using the Electric Power Research Institute (EPRI) Material Reliability Program (MRP) failure modes and effects analysis technique.
Ultrasonic Testing (UT) and Eddy Current Testing results showed small axial cracks in BMI penetrations 1 and 46, confirming the leakage pathway. The licensee did not find any cracks in other penetration tubes that were inspected. The licensee did not find any surface breaking indications in any J-groove welds.
Future planned activities will include additional inspections, design and repair activities, sample removal and analysis, NRC reviews of documents submitted for approval, and analyses of the root and probable cause(s).
The licensee stated that it was pursuing a deliberate and careful process, the NDE campaign has been successful, the condition and the scope of the needed repair are known, and the completion of repairs will enable return to safe operation. Close cooperation with industry and the NRC on cause analysis will continue.
NDE Activities The licensee stated that its approach to BMI leakage evaluation objectives follows the EPRI MRP control rod drive mechanism approach, consisting of identification of the relevant flaw mechanisms, defining inspection locations and volumes, and defining the range of flaws that need to be addressed. The licensee designed and procured a mockup to aid the examination process. The licensee will demonstrate that the protocol and schedule of activities will ensure that the NDE objectives of identifying relevant flaw mechanisms, defining inspection locations and volumes, and defining the range of flaws that need to be addressed, are met.
Based on the inspections performed thus far, the licensee listed the results of its findings as follows:
- Three axial indications, one leak path
- Flaw 1 is approximately 1-3/8" in length and extends 1/16" above the weld to 1/4" below the weld
- No crack-like indications on J-groove weld
- Visual Grinding marks on the sides of the tubes.
Penetration 46
-Two axial indications, one leak path
- No crack indications on the J-groove weld The licensee confirmed its findings by bobbin coil eddy current examination of penetration inside diameter (ID), and array coil eddy current examination of J-groove weld. Additional confirmatory inspections and tests will include phased array UT of wastage, rod test, helium bubble test, profilometry, visual of tube ID, metallurgical sample, and boat sample.
Cause Analysis and Status The licensee summarized the findings as follows:
Residue on two nozzles
Total of five flaws in two nozzles
One flaw in each nozzle provides a leak path
Three embedded flaws
Presence of discontinuities at the tube to weld interface for numerous penetrations
Grinding marks
No flaws in other 55 nozzles (penetration 31 has stuck thimble)
No evidence of circumferential cracks
No evidence of ID initiated cracks The licensee deduced the most likely causes to be
Residual fabrication stresses
Lack of J-groove weld fusion to nozzle outside diameter
Weld cracking; fabrication defects; contaminants
Combination of one or more causes with primary water stress corrosion cracking Repair Plans The licensee outlined its repair plans for the half-nozzle repair option, as shown in the schematic illustrations (pages 73-82) in Enclosure 1. This method consists of cutting the guide tube and deploying a plug. This is followed by inspection for any leaks. The nozzle is then cut flush with the bottom head surface. A weld pad is then placed on the vessel head and the nozzle tube is then machine bored and weld prepared. The new nozzle is then installed in the nozzle bore, ensuring adequate gap between it and the old tube, to allow for differential expansion during operation. The plug is then removed.
The licensee performed analyses of residual stresses and limiting flaw, crack growth rates, corrosion, and stress and fatigue.
Based on the evaluations so far, the licensee has concluded that repair and startup can be safely accomplished. Severe consequences such as a small break loss of coolant accident are not likely due to axial crack indications and no circumferential crack indications, and there is no evidence of vessel wastage. There is no significant likelihood of loose parts hazards because there are no flaws above the weld, no circumferential flaws, and residual stresses would favor axial crack orientation.
Corrosion Studies The licensee also discussed the results of its half-nozzle replacement corrosion studies for the small gap between alloy 600 remnant tube and the new alloy 690 nozzle, and carbon steel in the annulus region exposed to primary coolant. Based on those studies, the licensee concluded that the corrosion rates are generally acceptable for STP, Unit 1.
Concluding Remarks The licensee also summarized the schedule of deliverables. The licensee stated that it planned to continue its close cooperation with the industry and the NRC on cause analysis.
The licensee completed its presentation by concluding that the NDE effort was successful, condition and repair scope are known, and repairs will enable STP, Unit 1 to return to safe operation.
The public was offered an opportunity to ask questions or to provide comments. There were no questions or comments from the public. The meeting was then adjourned.
/RA/
Mohan C. Thadani, Senior Project Manager, Section 1 Project Directorate IV Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-498
Enclosures:
- 1. View-graphs (ADAMS Accession No.: ML031920229)
- 2. List of Attendees cc w/encls: See next page
- 2. List of Attendees cc w/encls: See next page DISTRIBUTION: See Next Page Package No.: ML031920451 Handouts: ML031920229 ADAMS Accession No.: ML031920459
- See previous concurrence NRC-001 OFFICE PDIV-1/PM PDIV-1/LA RIV PDIV-1/SC NAME MThadani:sab MMcAllister WJohnson via e-mail RGramm*
DATE 7/15/2003 7/15/2003 7/15/2003 7/15/2003
DISTRIBUTION FOR MEETING BETWEEN NRC AND STP NUCLEAR OPERATING COMPANY ON JUNE 5, 2003.
Dated: July 15, 2003 DISTRIBUTION:
PUBLIC PDIV-1 RF RidsNrrAdpt (BSheron/MKotzalas)
RidsNrrDssa (SBlack/MJohnson)
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RidsRgn4MailCenter (Ahowell) CMoyer RBywater, RIV RidsNrrDlpmLpdiv (HBerkow)
RidsNrrDlpmLpdiv1 (RGramm) MHartzman MFields, EDO RidsNrrPMMThadani RidsNrrLAMcAllister BCullen KNaidu RidsOgcRp RidsAcrsAcnwMailCenter BDavis TPruett, RIV RCroteau MBarillas RBarrett SMagruder MReinhart DNaujock RHoefling JCushing SBloom KKavanagh NSaltos AMendiola WScott RTjader DFischer DThatcher TMensah WSifre, RIV LWert EReichelt AHiser MMitchell ESullivan CGratton KWichman JCollins JFoster DTerao SMonarque EBrown BElliot FGrubelich SBurnell DHarrison MTschiltz DChamberlain, RIV VKlein JStrnisha GGood, RIV MHoncharik BFu BJohnson, RIV SLong JMinns CMarschall, RIV DDuvigneaud SUnikewicz LEllershaw, RIV BBateman EAndruszkiewicz TFarnholtz, RIV BReckley WGott VDricks, RIV MEETING PARTICIPANTS FOR SECOND MEETING BETWEEN STPNOC AND NRC ON JUNE 5, 2003 Licensee Participants Ron Baker Wayne Harrison Bill Humble T. J. Jordan Michael Lashley Mark McBurnett Ulhas Patil Steve Thomas NRC Participants Headquarters Region IV Robert Gramm Wayne Sifre Stephen Monarque Russell Bywater Richard Croteau Troy Pruett Scott Burnell Mark Hartzman Other Keith Wichman Brian Sheron Chapelier Francois, EDF Herb Berkow Dan Salter, HGP, Inc.
Martha Barillas Terry Pickens, Null Management Company Anthony Mendiola Larry Mathews, Southern Nuclear Veronica Klein Cheng Chu, PII Allen Hiser John Hall, Westinghouse William Bateman Ron Latanision, Exponent/MIT Jay Collins Steve Hunt, DEI Eric Reichelt Al Gutterman, Morgan Lewis Barry Elliot David Lounsbury, Westinghouse Owners Group Carol Moyer David Wholl, Natural Gas Jack Foster Bob Hermann, SI Ted Sullivan David Lochbaum, Union of Concerned Scientists Richard Barrett John Bloussand, DEI Ed Andruszkiewicz Jim Riley, NEI Kamalakar Naidu Paul Gunter, NIRS Donnie Harrison Kazuhiko Kishioka, JAPC Bart Fu Altheia Wyche, SERCH Licensing/Bechtel Mohan Thadani Tom Doggett, Rentess Matthew Mitchell Bud Auvil, WSI William Cullen Randal Schmidt, PSEG Nuclear Matt Wald, N.Y. Times Deann Raleigh, LIS, Scientech Charles Brinkman, Westinghouse
South Texas, Unit 1 cc:
Mr. Cornelius F. OKeefe Senior Resident Inspector U.S. Nuclear Regulatory Commission P. O. Box 910 Bay City, TX 77414 A. Ramirez/C. M. Canady City of Austin Electric Utility Department 721 Barton Springs Road Austin, TX 78704 Mr. L. K. Blaylock Mr. W. C. Gunst City Public Service Board P. O. Box 1771 San Antonio, TX 78296 Mr. C. A. Johnson/A. C. Bakken AEP Texas Central Company P. O. Box 289 Mail Code: N5022 Wadsworth, TX 77483 INPO Records Center 700 Galleria Parkway Atlanta, GA 30339-3064 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011 D. G. Tees/R. L. Balcom Texas Genco, LP P. O. Box 1700 Houston, TX 77251 Judge, Matagorda County Matagorda County Courthouse 1700 Seventh Street Bay City, TX 77414 A. H. Gutterman, Esq.
Morgan, Lewis & Bockius 1111 Pennsylvania Avenue, NW Washington, DC 20004 Mr. T. J. Jordan, Vice President Engineering & Technical Services STP Nuclear Operating Company P. O. Box 289 Wadsworth, TX 77483 S. M. Head, Manager, Licensing Nuclear Quality & Licensing Department STP Nuclear Operating Company P. O. Box 289, Mail Code: N5014 Wadsworth, TX 77483 Environmental and Natural Resources Policy Director P. O. Box 12428 Austin, TX 78711-3189 Jon C. Wood Matthews & Branscomb 112 East Pecan, Suite 1100 San Antonio, TX 78205 Arthur C. Tate, Director Division of Compliance & Inspection Bureau of Radiation Control Texas Department of Health 1100 West 49th Street Austin, TX 78756 Brian Almon Public Utility Commission William B. Travis Building P. O. Box 13326 1701 North Congress Avenue Austin, TX 78701-3326
South Texas, Unit 1 cc:
Susan M. Jablonski Office of Permitting, Remediation and Registration Texas Commission on Environmental Quality MC-122 P.O. Box 13087 Austin, TX 78711-3087 Mr. Terry Parks, Chief Inspector Texas Department of Licensing and Regulation Boiler Division P. O. Box 12157 Austin, TX 78711 Mr. Ted Enos 4200 South Hulen Suite 630 Ft. Worth, Texas 76109 Mr. James J. Sheppard President and Chief Executive Officer STP Nuclear Operating Company South Texas Project Electric Generating Station P. O. Box 289 Wadsworth, TX 77483