ML17345A302

Special Rept:On 880721,discovered That Ultimate Strength of Vertical Tendom Wire Below Min Specified Value of 240,000 Psi by Approx 1%.Plant Entered Action Statement Requiring Restoration of Containment Vessel to Required Level

ML17345A302
Person / Time
Site:	Turkey Point
Issue date:	08/04/1988
From:	Conway W FLORIDA POWER & LIGHT CO.
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
L-88-335, NUDOCS 8808110035
Download: ML17345A302 (6)

Text

AC CEIZMTED Dl~ BUTION DEMONST TION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:8808110035 DOC.DATE: 88/08/04 NOTARIZED: NO DOCKET FACIL:50-251 Turkey Point Plant, Unit 4, Florida Power and Light C 05000251 AUTH. NAME AUTHOR AFFILIATION CONWAY,W.F. Florida Power & Light Co.

RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)

SUBJECT:

Special rept:on 880721,discovered that ultimate strength of vertical tendom wire below min specified value.

I Incident Rpt,Q etc.

DISTRIBDTION CODE: IE22D COPIES RECEIVED:LTR I . ENCL SIZE:

TITLE: 50.73 Licensee Event Report (LER),

NOTES RECIPIENT COPIES RECIPIENT 'COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD2-2 LA 1 1 PD2-2 PD 1 1 EDISON,G 1 1 A

INTERNAL: ACRS MICHELSON 1 1 ACRS MOELLER 2 2 AEOD/DOA 1 1 AEOD/DSP/NAS 1 1 AEOD/DS P/ROAB 2 2 AEOD/DSP/TPAB 1 1 ARM/DCTS/DAB 1 1 DEDRO 1 1 NRR/DEST/ADS 7E 1 0 NRR/DEST/CEB 8H 1 1 NRR/DEST/ESB 8D 1 1 NRR/DEST/ICSB 7 1 1 NRR/DEST/MEB 9H 1 1 NRR/DEST/MTB 9H 1 1 NRR/DEST/PSB 8D 1 1 NRR/DEST/RSB 8E 1 1 NRR/DEST/SGB 8D 1 1 NRR/DLPQ/HFB 10 1 1 NRR/DLPQ/QAB 10 1 1 NRR/DOEA/EAB 11 1 1 NRR/DREP/RAB 10 1 1 NRR/DREP/RPB 10 2 2 NRR DRIS/NIB 9A 1 1 NUDOCS-ABSTRACT 1 1 G M 02 1 1 RES TELFORD,J 1 1 S/DSIR DEPY 1 1 RES/DSIR/EIB 1 1 RES/DSR DEPY 1 1 RGN2 FILE 01 1 1 EXTERNAL EG&G WILLIAMSP S 4 4 FORD BLDG HOY,A 1 1 H ST LOBBY WARD 1 1 LPDR 1 1 NRC PDR 1 1 NSIC HARRIS,J 1 1 NSIC MAYS,G 1 1 A

TOTAL NUMBER OF COPIES REQUIRED: LTTR 46 ENCL 45

SPECIAL REPORT LOW SLTERIhL ULTIMATE STRENGTH FOR VERTICAL TENDON WIRE DESCRIPTION On July 21, 1988, during the performance of the fifteenth year tendon surveillance of the Turkey Point Unit 4 containment post-tensioning system, the results of the tensile tests for wire samples taken from surveillance tendon 12V29 of the vertical tendon group revealed that the ultimate strength of the wire was

.below the minimum specified value of 240,000 psi by approximately 1 percent.

As a result, the plant entered an action statement requiring restoration of the containment vessel to the required level of integrity within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />, performance of an engineering evaluation of the containment, and the submission of a Special Report to the Commission within 15 days . This action statement is part of procedure O-ADM-021, "Technical Specification Implementation Procedure," and not a part of the current Technical Specifications to which Turkey Point is licensed .

As this report is not required by Turkey Point s current Technical Specifications, it is being submitted as a voluntary Special Report in accordance with O-ADM-021.

The Turkey Point Unit 4 reactor containment structure consists of a flat reinforced concrete base mat, an upright prestressed concrete cylinder and a shallow prestressed concrete dome. The prestressing force is provided by an unbonded post-tensioning"system. The system consists of 180 vertical, 489 horizontal, and 16$ dome tendons. Each tendon consist of 90 1/4 inch diameter wires . The tendons are inserted inside sheathing ducts embedded in the concrete, and anchored on both ends by means of steel anchor blocks. The wires are anchored to the anchor blocks by cold formed button heads. The tendon ducts are filled with a corrosion inhibiting grease, and the end anchorages are covered with tightly bolted caps.

The post-tensioning system for the Turkey Point Unit 4 containment has been in service since 1972. Periodic inspections have been performed previously on the tendon system in accordance with Technical Specification requirements.

In order to perform the surveillance, one wire was removed from a designated surveillance tendon in each directional tendon group (dome, vertical, and hoop) for tensile testing. Tensile tests were performed on three samples cut from each removed wire, one at each end and one at mid-length. The results of these tests revealed that two samples cut from the wire removed from vertical tendon 12V29 did not conform to the minimum ultimate tensile strength value of 240,000 psi . The minimum ultimate tensile strength of the wire was reported as 238,000 psi which is approximately one percent below the minimum value established by specification ASTM A421.

nJ 3808110035 8808 04 XJ POR ADOCK 05000251 PDC

ANALYSIS This deficiency involves only the ultimate tensile strength of the wire . The results of the tensile testing provides evidence that the yield strength of the wire meets the specified minimum value of 192,000 psi in accordance with the requirements of the ASTM A421-65 specification. Although the original jacking force in the tendons is related to the material ultimate strength, the design of the post-tensioning system is based upon the stress in the wire not exceeding the yield strength. Since the actual yield strength values were higher than the required yield strength of 192,000 psi, the deficiency of 1% in the ultimate strength of one wire in tendon 12V29 will not have any detrimental effect on the load carrying capabilities of the tendon.

The results of the tensile testing also show that the total elongation at fracture conforms to the ASTM specified minimum value of four percent. In addition, the results of the wire inspection indicated no deterioration of the tendon wires, and the corrosion level was within acceptable limits .

The containment post-tensioning system is designed to provide additional margins beyond the design criteria requirements:

1) As described in the FSAR, three vertical tendons spaced approximately 120 degrees apart have been provided over and above the strucural requirements for the purpose of inspection and obtaining lift-off readings. In addition, as stated in the FSAR, any three adjacent vertical tendons can be lost without significantly affecting the strength of the containment structure. This design feature considers the load redistribution capabilities of the containment shell .

2) Recent evaluations and testing to assess the ultimate capacity of reactor building containment structures similar to the Turkey Point containment design have shown an ultimate capacity of 2.$ to 3.0 times the design pressure.

No abnormal conditions which could have resulted in this deviation were identified .

Based on the design margins incorporated in the post-tensioning system and the fact that the measured yield strength exceeds the required yield strength, concluded that the functional capability of the post-tensioning system and the it is structural integrity of the containment structure are not adversely affected by the low recorded value of ultimate strength in the wire taken from tendon 12V29.

CORRECTIVE ACTIONS Tendon 12V29 was retensioned to its initial lift-off value (minus zero percent, plus six percent).

FLORIDA POWER 8( LIGHT COMPANY AUGUST) 4 1988 L-88-335 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555 Gentlemen:

Re: Turkey Point Unit 4 Docket No. 50-251 Special Report Low Material Ultimate Stren th for Vertical Tendon Wire In accordance with Turkey Point Administrative Procedures the attached Special Report is provided for your information.

Should there be any questions on this information, please contact us.

Very truly yours, W. F. Co Senior Vice President Nuclear WFC/RG/gp Attachment cc: Dr. J. Nelson Grace, Regional Administrator, Region II, USNRC Senior Resident Inspector, USNRC, Turkey Point Plant RG. SR PEOPLE... SERVING PEOPLE

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