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| {{Adams
| | #REDIRECT [[05000498/LER-2003-003, Regarding Bottom Mounted Instrumentation Penetrations Indications]] |
| | number = ML032950483
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| | issue date = 10/15/2003
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| | title = Bottom Mounted Instrumentation Penetrations Indications - Supplement to LER Dated 06/11/2003
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| | author name = Halpin E
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| | author affiliation = South Texas Project Nuclear Operating Co
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| | addressee name =
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| | addressee affiliation = NRC/Document Control Desk, NRC/NRR
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| | docket = 05000498, 05000499
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| | license number = NPF-076, NPF-080
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| | contact person =
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| | case reference number = NOC-AE-03001610
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| | document report number = LER 03-003-01
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| | document type = Letter, Licensee Event Report (LER)
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| | page count = 9
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| }}
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| {{LER
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| | Title = Bottom Mounted Instrumentation Penetrations Indications - Supplement to LER Dated 06/11/2003
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| | Plant =
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| | Reporting criterion =
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| | Power level =
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| | Mode =
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| | Docket = 05000498
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| | LER year = 2003
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| | LER number = 3
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| | LER revision = 1
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| | Event date =
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| | Report date =
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| | ENS =
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| | abstract =
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| =text=
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| {{#Wiki_filter:N Nuclear Operating Company South Tcs Pro/ed Ekctilc GCncr3UngStabon PO. Box 289 WMdsidh. Ten 77483AAA October 15, 2003 NOC-AE-03001610 1 OCFR50.73 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852 South Texas Project Unit 1 Docket Nos. STN 50-498, STN 50-499 Supplement to Licensee Event Report 03-003 Bottom Mounted Instrumentation Penetration Indications Reference: STP Unit 1 Licensee Event Report (LER) 03-003, dated June 11, 2003 (NOC-AE-03001548)
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| Pursuant to 1 OCFR50.73, the South Texas Project submits the attached supplement to Unit 1 Licensee Event Report 03-003 regarding boric acid residue discovered on two bottom-mounted instrumentation nozzles of the Unit 1 reactor vessel on April 12, 2003. This event did not have an adverse effect on the health and safety of the public.
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| Commitments are listed in the Corrective Actions section of the attached report.
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| If there are any questions on this submittal, please contact S. M. Head at (361) 972-7136 or me at (361) 972-7849.
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| E. D. Halpin Plant General Manager awh Attachment: Supplement to LER 03-003 (South Texas, Unit 1)
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| LER 1-03-003 supplement (BMI) 0300161 0.doc STI: 31657263
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| NOC-AE-03001 610 Page 2 of 2 cc:
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| (paper copy)
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| (electronic copy)
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| Bruce S. Mallett Regional Administrator, Region IV U. S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, Texas 76011-8064 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852 Richard A. Ratliff Bureau of Radiation Control Texas Department of Health 1100 West 49th Street Austin, TX 78756-3189 Jeffrey Cruz U. S. Nuclear Regulatory Commission P. 0. Box 289, Mail Code: MN1 16 Wadsworth, TX 77483 A. H. Gutterman, Esquire Morgan, Lewis & Bockius LLP L. D. Blaylock City Public Service David H. Jaffe U. S. Nuclear Regulatory Commission R. L. Balcom Texas Genco, LP A. Ramirez City of Austin C. A. Johnson AEP Texas Central Company Jon C. Wood Matthews & Branscomb C. M. Canady City of Austin Electric Utility Department 721 Barton Springs Road Austin, TX 78704
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| =Abstract=
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| On April 12, 2003, with South Texas Project Unit 1 in a refueling outage, personnel discovered deposits at two Bottom Mounted Instrument (BMI) nozzles of the reactor vessel. This condition was identified during the station's regular bare metal inspection of the reactor vessel bottom penetrations, which is done as part of the RCS Pressure Boundary Inspection for Boric Acid Leaks Program. A small amount of residue was noted around the circumference of BMI nozzle Penetrations #1 and #46 where they enter the reactor vessel.
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| The residue consisted of approximately 150 milligrams of material from penetration number 1 and approximately 3 milligrams from penetration number 46. No wastage was observed on the outside of the bottom head, and samples of the residue were collected and analyzed. Both deposits contained boron and elevated levels of lithium consistent with reactor coolant system (RCS) leakage. Cesium isotopic analysis indicated an approximate age of 4 years for each sample.
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| Ultrasonic testing was performed on all of the 58 BMI penetrations. Cracks were found in Penetrations #1 and #46, however, no cracks were found in any other penetration. The root cause is the use of Alloy 600 combined with nozzle manufacturing and installation methods that further increased the susceptibility of the metal to stress corrosion cracking when in contact with primary water.
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| The nozzles at Penetrations #1 and #46 were repaired prior to restart of Unit 1.
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| This event resulted in no personnel injuries, no offsite radiological releases, and no damage to safety-related equipment other than the affected BMI penetrations. There were no challenges to plant safety.
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| NRC FORM 366 (7-2001)
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| 9 (If more space is required, use additional copies of (I more space is required, use additional copies of NRC Formn 366A) (17)
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| The UT examination also found anomalies at the nozzle/weld interface in all of the nozzles. Examination of a boat sample specimen from Penetration #1 identified the anomalies as areas of lack of fusion (LOF) between the nozzle and weld.
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| Eddy current testing was also performed on the surface of the J-groove welds for eight nozzles. No surface breaking cracks were identified.
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| Other Testing A helium leak test was performed on the two leaking penetrations by pressurizing the annulus between the nozzle and the vessel. No bubbles were observed in Penetration #46. In Penetration #1 a small helium bubble was observed about every two seconds rising from a location outside the nozzle in the J-groove weld fillet at the tube interface.
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| Sampling and Destructive Examination To facilitate metallurgical analysis of the actual cracks, boat samples were removed from Penetrations #1 and
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| #46 employing an Electric Discharge Machining (EDM) cutting technique. In the case of the BMI nozzles inside the reactor pressure vessel, the boat sample excavations could not be repaired. The desire for the largest possible boat sample was balanced against conservative structural limitations.
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| The boat sample from Penetration #46 was designed to capture as much tube material as possible in an attempt to harvest a portion of a crack not connected to the ID of the nozzle. The margins for error associated with positioning the EDM equipment through 70 feet of water resulted in a shallow cut in Penetration #46. The resulting undersized sample was either inadvertently discarded or completely consumed in the margins of the EDM cutting tool. The boat sample from Penetration #1 captured material and defects from the J-groove weld and J-groove/tube interface, as designed. A composite drawing showing the axial crack, weld flaw and weld crack is attached.
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| The boat sample from Penetration #1 contained a portion of the large through-wall axial crack in the tube, three "discontinuities" which were confirmed to be lack of fusion resulting from slag inclusions, and one crack at the helium bubble location which connects the surface of the J-groove weld to the largest area of lack of fusion.
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| The crack in the weld that connects the surface of the J-groove weld to the largest area of lack of fusion is singular and unique. The 0.2-inch long crack spans an 80 mil ligament separating the lack of fusion void from the surface of the J-groove weld in the ground fillet transition at the tube/J-groove weld interface. The length of the crack spans and is limited to the width of the lack of fusion void. The section of the boat sample containing this crack was broken in the laboratory to expose the crack face for examination. Tenacious deposits obscured the crack face, and gradually more aggressive attempts to remove the deposits also attacked and distressed the metal surface. The crack exhibits some intergranular characteristics. To some reviewers, the nature of the oxide deposits suggests hot cracking. Fatigue could also be a factor in the development of this crack. However, the precise mechanism responsible for initiating and propagating this crack could not be determined.
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| Earlier UT results identified an axial crack in Penetration #1 which penetrated the ID of the nozzle and extended from just above to just below the J-groove weld. The boat sample from Penetration #1 successfully captured a part of the upper portion of this crack in the region of the tube/J-groove weld interface. The intergranular nature of this crack exhibits classic primary water stress corrosion cracking (PWSCC) characteristics. The extent of the crack was examined by progressively grinding away thin layers of the section of the boat sample. The orientation of the around surface was such that more weld material and less
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| (If more space Is required, use additional copies of (If more space Is required, use additional copies of (if more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A) (17)
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| Photographs of First and Last Face Grind Nozzle
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| ,. : 4 Weld
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| }}
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