ML20246L262

Summary of 880517 Meeting W/Util & Westinghouse Re Results of bottom-mounted Instrumentation Thimble Tube Insp. List of Meeting Attendees.Presentation Matl Handout Withheld

ML20246L262
Person / Time
Site:	South Texas
Issue date:	05/09/1989
From:	Dick G Office of Nuclear Reactor Regulation
To:	Office of Nuclear Reactor Regulation
References
NUDOCS 8905180280
Download: ML20246L262 (6)

Text

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UNITED STATES hph

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, ,[. g NUCLEAR REGULATORY COMMISSION 7, 'p ;j WASHINGTON, D. C. 20555 May 9, 1989 g;.%4

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! Do'cket No. 50-498 LICENSEE: Houston Lighting & Power Company FACILITY: South Texas Project, Unit 1

SUBJECT:

RESULTS OF BOTTOM-MOUNTED INSTRUMENTATION (BMI)

THIMBLE TUBE INSPECTION Enclosure 1 is a list of the meeting attendees. The presentation material handout is proprietary so it is not included with this meeting summary. A copy is retained in the projec.t manager's. files.

Wear of Bl'I thimble tubes has been observed in a number of plants, the most severe being in several European plants. In order to monitor wear, the licensce committed to inspect the tubes after 16 weeks of three or four reactor coolant pump (RCP) operation. The first inspection was performed during May 4-7, 1988. A non-proprietary copy of the tests results is enclosed (Enclosure 2). The inspections showed wear indications en 19 of the 58 thimbles with no cbvious correlation of wear with thimble location in the core. In the majority of cases, wear occurred at the location of the flow limiter.

Thimble wear data was available from Tihange (Belgium) which has characteristics similar to Scuth Texas and was analysed by Westinghouse. The analysis indicated that wear rates are high initially and then approach zero es.ymtiotically.

Also, repositioning the tubes to present a fresh surface resulted in the same wear-time histories as before repositioning. Westinghouse and the licensee believe that the South Texas thimble tubes will perform similarly to these at Tihange.

Immediate actions proposed for South Texas were to: 1) reposition and cap tubes showing 40% wear or greater; and 2) reposition those thimble tubes with greater than 20% wear. Long-term corrective actions proposed included, investi-gation of heavier wall thimble tubes, examination of thimbles and flow limiters from Tihange to determine wear mechanism, and installation of isolation valves at the seal table. The licensee indicated that the correction deemed appropriate for Unit I would be applied to Unit 2 prior to fuel load.

At the end of the meeting, the staff concluded that there was reasonable assurance that after the proposed short term actions were taken, South Texas, Unit I could operate for additional 16 weeks. At the end of the operating period, another inspection of the thimbles would be conducted. Following that i

890518o280 eposop 6 gDR ADOCK 05000498 \ g PDC

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-2 inspection, the staff requested that the licensee inform the staff of the inspection results as well as any new information regcrding thimble wear- that was available.

OriginalSigned Gy

' George F. Dick, Jr.

George F. Dick, Jr., Project Manager Project Directorate - IV Division of Reactor Projects - III, IV, V and Special. Projects Office of Nuclear Reactor Regulation

Enclosures:

As' stated cc w/ enclosures:

See next page DISTRIBUTION Docket File NRC PDR Local PDR J. Sniezek PD4 Reading.

J. Calvo F. Hebdon G. Dick-Jack Ramsey P. T. Kuo L. B. Marsh Dennis Crutchfield Kamal Bandyopadhyay Carl H. Berlinger Emmett Murphy N. Prasad Kadambi T. O. Martin Wayne D. Lanning J. P. Clausner OGC-Rockville E. Jordan B. Grimes ACRS T. Martin(10) (Region IV)

PD4 Plant File DOCUMENT NAME: MTG

SUMMARY

STP 02 PD4/L(r PNoonh

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9 D4/PM ick:bj PD4/D h JCalvo 05/9/89 05/gP/89 05/f/89 i

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inspectiorr, the staff requested that the licensee inform the staff of the inspt: tion results as well as any new information regarding thimble wear that was available.

Georg Dick, Jr., Project Manager Project' Directorate - IV Division of Reactor Projects - III, IV, V and Special Projects Office of Nuclear Reactor Regulation

Enclosures:

As stated cc w/ enclosures:

See next page i

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i Mr. J. H. Goldberg South Texas Project Houston Lighting and Power Company J cc: .

I Brian Berwick, Esq. Resident Inspector / South Texas j Assistant Attorney General Project 1 Environmental Protection Division c/o U.S. Nuclear Regulatory Commission P. O. Box 12548 P. O. Box 910 Capitol Station Bay City, Texas 77414 Austin, Texas 78711 Ms, Iris J. Jones Mr. J. T. Westermeier Acting City Attorney General Manager, South Texas Project City of Austin Houston Lighting and Power Company P. O. Box 1088 P. O. Box 289 Austin, Texas 78767 Houston, Texas 77483 Ms. Pat Coy Mr. R. J. Miner Citizens Concerned About Nuclear Chief Operating Officer Power City of Austin Electric Utility 10 Singleton 721 Barton Springs Road Eureka Springs, Arkansas 72632 Austin, Texas 78704 Mr. M. A. McBurnett Mr. R. J. Costello Manager, Operations Support Licensing Mr. M. T. Hardt Houston Lighting and Power Company City Public Service Board P. O. Box 289 P. O. Box 1771 Wadsworth, Texas 77483 San Antonio, Texas 78296 Mr. E. T. Holnar Jack R. Newman, Esq. Mr. L. W. Hurst Newman & Holtzinger, P. C. Bechtel Corporation 1615 L Street, NW P. O. Box 2166 Washington, D.C. 20036 Houston, Texas 77252-2166 Melbert Schwarts, Jr., Esq. Mr. R. P. Verret Baker & Botts Mr. R. L. Range One Shell Plaza Central Power and Light Company Houston, Texas 77002 P. O. Box 2121 Corpus Christi, Texas 78403 Mrs. Peggy Buchorn Executive Director Doub, Muntzing and Glasgow Citizens for Equitable Utilities, Inc. Attorneys at Law Route 1, Box 1684 Suite 400 Brazoria, Texas 77422 808 Seventeenth Street, N.W.

Washington, D.C. 20006 Mr. S. L. Rosen General Manager, Operations Support Houston Lighting and Power Company P. O. Box 289 Wadsworth, Texas 77483

Mr. J. H. Goldberg South Texas Project Houston Lighting & Power Company CC:

Regional Administrator, Region IV Bureau of Radiation Control U.S. Nuclear Regulatory Commission State of Texas Office of Executive Director 1101 West 49th Street for Operations Austin, Texas 78756 611 Pyan Plaza Drive, Suite 1000 Arlington, Texas 76011 Office of the Gobernor ATTN: Ms. Darla Parker Mr. Lanny Sinkin, Office of Intergovernmental Relations Counsel for Intervenor Post Office Box 13561 Citizens Concerned about Nuclear Austin, Texas 78711 Power, Inc.

Christic Institute Judge, Matagorda County

-. 1324 North Capitol Street Matagorda County Courthouse Washington, D.C. 20002 1700 Seventh Street Bay City, Texas 77414 >

Licensing Representative Houston Lighting and Power Company Suite 610 Three Metro Center Bethesda, Maryland 20814 Rufus S. Scott Associate General Counsel l Houston Lighting & Power Company P. O. Box 1700 Houston, Texas 77001 INP0 Records Center 1100 Circle 75 Parkway Atlanta, Georgia 30339-3064 Joseph M. Hendrie 50 Be11 port Lane Be11 port, New York 11713 Gerald E. Vaughn, Vice President  ;

Nuclear Operations  :

Houston Lighting & Power Company P. O. Box 289 Wadsworth, Texas 77483 R. W. Chewning, Chairman Nuclear Safety Review Board Houston Lighting & Power Company P. O. Box 289 Wadsworth, Texas 77483 l

, Enclosure 1 South Texas Project. Unit 1 Thimble Tube Meeting May 17. 1988 U.S. Nuclear Regulatory Commission Westinghouse George Dick '

Ed Rusnica Jose Calvo Dr.niel Merkovsky Jack Ramsey Frank Langford P. T. Kuo Kenneth G. Lunt L. B. Marsh Norman Singleton Dennis Crutchfield Caal Hirst

- Kamal Bandyopadhyay Richard Schwirian Carl H. Berlinger Warren Junker Emmett Murphy John Irons H. Prasad Kadambi Gene Glasbergun T. O. Martin L. E. Hochreiter Wayne D. Lanning J. P. Clausner Houston Lighting & Power Company S. M. Dew S. L. Rosen Tom Godsey Mark McBurnett Mike Bunner Warren Kinsey l

. Enclosure 2 The Light company n.,_,,, ugs,,g u,_ m 8., moo n.,-,,a mooi m-co May 12, 1988 l ST-HL-AE-2655 i~

PFN: G4.2 10CFR50 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 South Texas Project Electric Generating Station.

Units I and 2 Docket Nos. STN 50-498, STN 50-499 Bottom Mounted Instrumentation (BMI) Thimble Inspection

Reference:

(1) ST-HL-4E-2458 dated January 5, 1988 (2) ST-HL-AE-2490 dated February 3, 1988 On May 4-7, 1968, Houston Lighting & Power Company (HL&P) performed eddy current inspection of all 58 BMI thimbles at the South Texas Project (STP) Unit 1 following approximately 11 weeks of 4 pump operation at RCS normal operating temperature (above 560 degrees F.). The thimbles have been subjected to approximately 16 weeks total operating time including lower temperature reactor coolant pump (RCP) operation.

The eddy current inspection was performed with the thimbles inserted into the reactor vessel. The entire length of each thimble was inspected except for the top 40 inches which was the same as for the baseline inspection in December 1987. As previously discussed in Reference 1, this 40 in. spacing is the top portion of the thimble inserted in the fuel assembly and is in an area where thicble tube wear has not been experienced. Additienal inspection was done on four thimbles which were temporarily retracted about 2 ft. in order to better measure and confirm indications which had been partially masked by interference from metal structures adjacent to the ' thimble. The eddy current inspection utilized a multifrequency data acquisition system. The test frequencies used were 62, 140, and 300 KHZ. The sensitivity of the inspection process had a threshold of 10% wall loss which corresponds to 0.0052 in or 0.13 mm. Wear below th's i level is insignificant and indistinguishable from normal surface markings. A calibration standard was used for each data taking run. The data for each thimble was reviewed and compared with the results obtained from the baseline inspection.

302-l 1

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'fiog 'ADOCK m" 680512 05000498 DCD

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Houston Lighting & Power Company May 12, 1988 ST-HL-AE-2655

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' PFN: G4.2 l The following summarizes the results of eddy current testing, short term and long term corrective action, and how it compares to the European data and action plan.

A. _ Eddy Current Results Data obtained from eddy current testing is shown in Attachment 1. The wear was found to be primarily in the region of the flow limiter nozzle and to be approximately 3/4" in length. Some wear waa identified at locations other than the flow limiter (primarily in the vessel penetration region) on 7 thimbles, but was determined to be minimal and have no adverse affect on thimble integrity.

Attachment 2 provides a comparison of the eddy ec.rrent data at Tihange

3. STP, and Doel 4. Doel 4, unlike Tihange 3 and STP, had larger.

heavier walled .339 in. OD. thimbles and operated for' a full fuel cycle with no intermediate inspections. Consequently, the data is less meaningful when trying to provide a comparison. Tihange 3 experienced a thimble leak after approximately 16 weeks of operatior. STP thimbles were also exposed to the equivalent of 16 weeks of operation with the worst vall loss indicated at 60%. Inspeccion of the 49 intact thimbles at Tihange 3, after 16 weeks of operation, revealed that all but 7 thimbles had indicated wall loss. By comparison, STP Unit I had no indication of wall loss in the flow limiter region on 39 thimbles.

B. Short Term Corrective Action As discussed in References 1 and 2, HL&P will reposition and cap thimbles as necessary in order to operate for 20 weeks before the next eddy current inspection. The chimbles to be capped and/or repositioned and the basis for that disposition is shown in Attachments 3 and 4.

Thimbles to be capped will also be repositioned in order to preclude wear through thereby minimizing ALARA concerns when thimbles are removed during the first refueling outage. All thimbles requiring repositioning will be retracted 2 inches which will relocate the defect area of the thimble out of the wear region. After not more than 20 weeks of 3 or 4 pump operation, HL&P will again perform eddy current inspection and take action based on the results to reposition and/or cap as necessary to preclude thimble leakage during subsequent power operation.

Tihange 3 repositioned and/or capped thimbles in October 1987 when they performed their first eddy current inspection and then again in January 1988 after performing their second inspection. Their intention is to remove flow limiters and the .313 in. OD thimbles in their May outage and replace them with .339 in. OD thimbles. Doel 4 operated for a full cycle without eddy current inspection. As a result of the significant wear on their thimbles, they will be removing their flow limiters and replacing their existing thimbles with like .339 in. OD thimbles during their refueling outage. Flow limiters will not be reinstalled at either plant.

I 1

H' ou'ston Lighting & Power Company May 12, 1988 ST-HL-AE-2655 PFN: G4.2 C. Long Term Corrective Action HL&P intends to correct the existing thimble wear. problem in Unit 2 prior to fuel load and by the first refueling in Unit 1. Heavier thimbles'are still being investigated by HL&P and Westinghouse. Test results from Waltz Mill shows that a .385 in. OD thimble is very resistant to flow induced vibration. The. thimbles have been tested for insertion / retraction in Unit 2 using a dummy fuel assembly and performed satisfactorily. In late May at the hot cell in' Mons, Belgium, limiters and thimbles from Tihange 3 will be analyzed to determine the mechanism for wear. By July 3, 1988, Westinghouse will provide a recommendation to HL&P regarding the long term solution.

Doel 4 and Tihange 3 are also waiting for Westinghouse to provide a recommendation regarding the.long term solution.

If you should have any questions on this matter, please contact me or M. A.

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McBurnett at 512-972-8530. "

S. L. Rosen General Manager, Ooerations Support SLR/MKB/jg Attachments: Summary of Thimble Wear Comparison of Tihange.3/STP/Doel 4 Eddy Current Results Thimble Recommendations BMI Thimble Wear Recommended Action Plan

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Houston Lighting & Power Company ST-HL-AE-2655 PFN: G4.2 Page 4 CC:

Regional Administrator, Region IV INP0 Nuclear Regulatory Commission Records Center 611 Ryan Plaza Drive, Suite 2000 1100 Circle 75 Parkway Arlington, TX 76011 Atlanta, GA 30339-3064 George Dick, Project Manager Dr. Joseph M. Hendrie U. S. Nuclear Regulatory Commission 50 Bellport Lane 1 White Flint Pike . Bellport, NY 11713 11555 Rockville Pike Rockville, MD 20859 Dan R. Carpenter Senior Resident Inspector / Operations c/o U. S. Nuclear Regulatory Commission P. O. Box 910 Bay City. TX 77414 Don L. Garrison Resident Inspector / Construction c/o U.. S. Nuclear Regulatory Commission P. O. Box 910 Bay City, TX 77414 J. R. Newman. Esquire Newman & Holtringer, P.C.

1615 L Street, W.W.

Washington, DC 20036 R. L. Range /R. P. Verret Central Power & Light Company P. O. Box 2121 Corpus Christi, TX 78403 R. John Miner (2 copies)

Chief Operating Officer City of Austin Electric Utility 721 Barton Springs Road Austin, TX 78704 R. J. Costello/M. T. Hardt City Public Service Board P. O. Box 1771 San Antonio, TX 78296 Rufus S. Scott Associated General Counsel Houston Lighting & Power Company P. O. Box 1700 Houston, TX 77001

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SUMMARY

OF THlMBLE WEAR

SOUTH TEXAS 1 - 5/9/88 OUANTITY '

PERCENT WALL LOSS '

(FLOW LIMITER) CORE LOCATION 1EACH 60 %

B8 2 EACH 40 X K-6,C 1 EACH 36 %

C-7 1 EACH 28 X F-14

. 1 EACH 25 X E-11 5 EACH 20 X  !

J-7, D-8, G-12, K-2. N-4 1 EACH 16 %

D-3 2 EACH 15 X H-15, N-8 5 EACH 12 X L-13, H-11, J-1, J-8, L-15 WEAR AT' LOCATION OTHER THAN FLOW LIMITER (ALL BELOW L! MITER)

OUANTITY PERCENT WALL LOSS CORE LOCATION 1 EACH 20 X K-2=

1 EACH 16 X B-8=

1 EACH 15 X H-15= . _ _

1 EACH 12 X D-3*

3 EACH 10 X D-12, F-1, P-4

= INDICATES THIMBLES THAT HAVE WEAR AT THE FLOW LIMITER AND A SECOND ELEVATION ATTACHMENT 1 SHT 1 OF 2 1

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. 1 BMITHIMBLE WEAR RECOMMENDED ACTION PLAN REPOSITION AND CAP: B-8 60%

K-6, C-8 40X REPOSITION:

C-7 = 36%

F 28%

E-11 -25% '

G-12 K-2, N-4. D-8, J 20%

O ATTACHMENT 4

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