ML032090159
| ML032090159 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 08/08/2003 |
| From: | Thadani M NRC/NRR/DLPM/LPD4 |
| To: | |
| Thadani M, NRR/DLPM, 415-1476 | |
| Shared Package | |
| ML032090151 | List: |
| References | |
| TAC MB8435 | |
| Download: ML032090159 (8) | |
Text
August 8, 2003 LICENSEE:
South Texas Project Nuclear Operating Company FACILITY:
South Texas Project, Unit 1
SUBJECT:
SUMMARY
OF THIRD MEETING WITH SOUTH TEXAS PROJECT NUCLEAR OPERATING COMPANY REGARDING SOUTH TEXAS PROJECT, UNIT 1, REACTOR VESSEL AND BOTTOM-MOUNTED INSTRUMENTATION PENETRATION INTERFACE LEAKAGE (TAC NO. MB8435)
On July 17, 2003, STP Nuclear Operating Company (STPNOC), the licensee for South Texas Project (STP), Units 1 & 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 concluding 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.
At the outset, the NRC staff informed the audience that the NRC staff would not be making any decisions at this meeting. The purpose of the meeting was to gather information to facilitate the NRC staffs comprehensive evaluation of the issues raised.
The STPNOC stated that it has documented its commitments to take follow up actions as outlined in its letter dated July 11, 2003. The NRC staff commented that the letter does not specifically state that the described actions are in fact licensee commitments. The licensee stated that it will provide a follow up in response to the comment.
A list of meeting attendees is included as Enclosure 1 to this summary. Enclosure 2 contains the licensee's presentation view-graphs.
The STPNOC outlined its desired meeting outcomes: (1) to keep NRC fully informed and ensure that NRC has sufficient information to complete its comprehensive assessment; (2) to explain the results of comprehensive nondestructive examination (NDE); and (3) to describe remaining future activities, i.e., to collect boat samples, perform nozzle remnants analyses, and submit a licensee event report supplement. The licensee then summarized its root cause analysis process and planned monitoring and inspection activities. The STPNOC provided answers to NRC questions and understood the remaining NRC needs for information. The STPNOC summarized that the residue found at BMI penetration no. 1 and penetration no. 46 was very small. It indicated a very small leak from the reactor bottom.
NDE Campaign An extensive NDE campaign included ultrasonic testing (UT), enhanced visual examination of J-groove weld surface, volumetric interrogation of vessel base metal for wastage, eddy current testing (ET) of penetration tube inside diameter, ET of J-groove weld surface, profilometry, boroscope examination, Helium leak tests, metallurgical analysis of removed nozzle remnants, and future boat sample analysis.
The licensee stated that the results of the evaluation indicated that the observed leakage was caused by one axial crack in each of the two penetrations. Penetration no. 1 had three crack indications, with one leak path. Penetration no. 46 had two axial indications with one leak path.
Nozzle Repairs The condition was limited to two identified nozzles and the cracks identified were axial in orientation. Evaluation of stresses indicated that circumferential cracking was not likely to occur. The licensee selected the half-nozzle repair method. Repair of both of the leaking nozzles is complete.
Root Cause Process The licensee outlined that there were no circumferential indications, no cracks above or below the J-groove weld, and no material wastage was found. The STPNOC considered two possible causes of crack initiation: (1) The cracks were caused by primary water stress corrosion cracking (PWSCC), or (2) the cracks were caused by a fabrication flaw over-stress in the nozzle and/or weld. The cracks were either propagated by PWSCC or low-cycle fatigue. The licensee then deduced that the facts are not consistent with PWSCC. No cracks were identified in 56 out of 58 BMI nozzles. The cracks were about 4 years old, were about the same age, and did not initiate from the inside diameter of the tubes. The licensee concluded that for PWSCC to be the cause, the expectation would be to observe defects in approximately 20 percent of the penetrations. Hence, defects would be expected in 12 penetrations out of 58 examined, but only 2 penetrations with defects were found.
The residual stresses do not appear to show any correlation with the observed cracks.
Penetration no. 1 and penetration no. 46 differ in residual stresses, and still they are the only penetrations showing crack indications and leakage. Furthermore, some cracks did not appear to be in contact with primary water. Based on the above rationale, the licensee concluded that the root cause of the BMI cracks was fabrication flaws.
The NRC staff commented that the licensees hypothesis did not explain why the fabrication flaws occurred only in penetrations 1 and 46. The licensee responded that it would consider the NRC comment in further evaluation of the root cause.
Monitoring and Inspection Plan The licensee proposed that it will continue the bare metal inspections under its boric acid control program. It will perform UT and enhanced visual testing of the BMI instrumentation at the next Unit 1 vessel inservice inspection program inspection. It will also perform periodic UT of vessel base material around the repaired penetrations, and will perform volumetric examination of Unit 2 penetrations at the next refueling outage with the core barrel removed.
Conclusions The licensee concluded that: (1) the extent of the condition is known, (2) that STPNOC has identified the probable cause as understood at the time, (3) engineering work has been completed, (4) the condition has been corrected by the half-nozzle design repair, (5) the licensee has confidence in the effectiveness of the repair, and (6) the plant staff is trained and is prepared for start up of the plant.
The NRC staff informed the STPNOC that its boric acid inspection program has been proactive, and that its response to the conditions of leakage in BMI penetrations 1 and 46 has been thorough. The staff asked how is it that STPNOC can perform the operations at STP, Units 1&2, in such a proactive and thoroughly responsive manner. The licensee responded that it is the policy of the STPNOC management to ensure that, when challenges are identified, the company mobilizes the best internal resources and the worlds best contractors to support the resolution of the issues, and to eliminate the challenges.
The NRC staff then asked for public comments for the meeting attendees and the teleconference participants. No comments were offered. 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. List of Attendees
- 2. View-graphs (ADAMS Accession No.: ML032090144) cc: see next page
ML032090144) cc w/enclosure: See next page DISTRIBUTION: See Next Page Package No.: ML032090151 Handouts: ML032090144 ADAMS Accession No.: ML032090159
- via e-mail NRC-001 OFFICE PDIV-1/PM PDIV-1/LA RIV PDIV-1/SC NAME MThadani:sab MMcAllister WJohnson*
RGramm DATE 8/08/2003 8/08/2003 8/08/2003 8/08/2003
DISTRIBUTION FOR MEETING BETWEEN NRC AND STP NUCLEAR OPERATING COMPANY ON JULY 17, 2003.
Dated: August 8, 2003 DISTRIBUTION:
PUBLIC PDIV-1 RF RidsNrrAdpt (BSheron/MKotzalas)
RidsNrrDssa (SBlack/MJohnson)
RidsNrrDlpm (LMarsh/ELeeds)
RidsRgn4MailCenter (AHowell)
RidsNrrDlpmLpdiv (HBerkow)
RidsNrrDlpmLpdiv1 (RGramm)
RidsNrrPMMThadani RidsNrrLAMMcAllister RidsOgcRp RidsAcrsAcnwMailCenter BBateman MHartzman TMensah EDO Contact, RIV EReichelt TPruett, RIV ESullivan BCullen AHiser SCoffin SBurnell GCheruvenki WJohnson, RIV SBloom RBywater, RIV JFoster MEETING PARTICIPANTS FOR THIRD MEETING BETWEEN STPNOC AND NRC ON JULY 17, 2003 Licensee Participants Tom Jordan Mark McBurnett Tim Bowman Wayne Harrison Bill Humble Michael Lashley Ulhas Patil Steve Thomas NRC Participants Headquarters Region IV Brian Sheron William Johnson Richard Barrett Russell Bywater Robert Gramm Troy Pruett Stephanie Coffin Ganesh Cheruvenki Scott Burnell Mark Hartzman Other Edmund Sullivan Herb Berkow David Lochbaum, Union of Concerned Scientists Allen Hiser Al Gutterman, Morgan Lewis William Bateman Jim Riley, NEI Mel Fields Paul Gunter, NIRS Eric Reichelt Kazuhiko Kishioka, JAPC Mohan Thadani Altheia Wyche, SERCH Licensing/Bechtel William Cullen Randal Schmidt, PSEG Nuclear Joe Roarty, Def. Nuc. Fac. Safety Jim Osborn, Public Getachen Tesfaye, CEG Jon Kirkwood, CEG Robert Hermann, SIA
South Texas Project, 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 Project, 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