ML20086G694

Ro:On 831205,during Surveillance Testing,Four Tendons Had Lift Off Forces Not Exceeding 95% of Base Value.Caused by Redistribution of Force Along Curved Tendons Set Up During Original Stressing

ML20086G694
Person / Time
Site:	Summer
Issue date:	01/04/1984
From:	Dixon O SOUTH CAROLINA ELECTRIC & GAS CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
NUDOCS 8401120357
Download: ML20086G694 (3)

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< SOUTH CAROLINA ELECTRIC & GAS COMPANY POST OPPICE 794 COLuusiA. SouTM CAROUNA 29218

o. W. DixoN. JR.

wCep So.ar January 4, 1984 ,

NuCLsAn Op. RATIONS Mr. J. P. O'Reilly, '

Regional Administrator.

U. S. Nuclear Regulatory Commission Region II, Suite 2900 101 Marietta Street, N.W.

Atlanta, GA 30303

Subject:

Virgil C. Summer Nuclear Station Docket No. 50/395 Operating License No. NPF-12 Special Report

Dear Mr. O'Reilly:

Please find attached a Special Report for the Virgil C. Summer Nuclear Station. This Thirty Day Report is required by Technical 4

Specification'6.9.2 as a result of entry into Acti;n Statement b.

of Terahnical Specification 3.6.1.6, " Containment Structural Integrity," on December 5,-1983.

Should there be any questions, please call us at your convenience.

Very trul yours, O. . W Di on .

-AM:OWD/fjc

Attachment:

cc: V. C. Summer C. L. Ligon (NSRC)

,. T. C. Nichols, Jr./O. W. Dixon, Jr. G. J. Braddick E. H. Crews, Jr. D. J. Richards E. C. Roberts NRC Res. Inspector W. A. Williams, Jr. J. B. Knotts, Jr.

D._A. Nauman I&E (Washington)

Group _ Managers Document Management O. S. Bradham Branch C. A. Price INPO Records Center D. A. Lavigne NPCF J. F. Heilman File ORqc] AL COPY G401120357-840104 gl %

g i PDR ADDCK 05000395 ]

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F' Mr. J. P. O'Reilly

.Special Report January 4, 1984 Page #2 The Second Tendon Surveillance for the Virgil C. Summer Nuclear Station was completed on December 5, 1983. During the surveillance testing four tendons (hoop tendons 18CB, 13BA, 28BA, and dome tendon D-219) had lift off forces-which did not exceed 95% of their Base Value as required by Section 4.6.1.6.a. of the Technical Specifications. Lift off tests were performed on tendons immediately adjacent to these four tendons as required by Technical Specifications. Adjacent tendons to 18CB and D-219 were above 95% Base Value. CThe adjacent tendons to 13BA (12BA and 14BA) were found to be below 95% Base Value.7 Tendon 28BA had one adjacent tendon (29BA) below and one adjacent tendon (27BA) above Base Value. Tendons 14BA and 28BA were detensioned to check for wire breakage or signs of ahnormal tendon degradation, but both were found to be normal. All seven tendons that were below 95% Base Value were restored to their required level of integrity above 95% Base Value. Of the seven tendons that were below 95% Base Value, they were below by 1.3% on average with a maximum of 2.3% and a minimum-of 0.6% below 95% Base Value. All of'the tendons involved in the surveillance had lift off forces above the 90% Base Value acceptance limit.

A further evaluation of possible causes for the low lift off forces (below .95% Base) will be performed. However, based on field observations e wire breakage and abnormal tendon degradation can be ruled.out as causes. Done likely cause is that a redistribution of force along the length of hoop and dome tendons has occurredd @he redistribution is caused by dissipation -- in time -- of the friction forces along curved tendons that were set up during original stressingD Such a condition does not affect the average force in each of these tendons, but it does cause a reduction in force at the anchorage of the tendons, and lower-than-predicted lift off forces are consequently measured.

This condition explains why the tendons with the largest initial friction forces -- the hoop tendous -- generally have the lowest lift off forces relative to their predicted values.

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y LMr. J. P..O'Reilly Special Report January 4, 1984

-Page #3 Also, during the surveillance testing, hoop tendon 13BA was found to have a Normalized Lift Off Force of 1177 kips which was below

.the minimum required average force of 1181 kips. Section 4.6.1.6.1.b. of the Technical Specifications requires that adjacent tendons-be lift off tested if the Normalized Lift Off

= Force of'any surveillance tendon is less than the minimum required average tendon force._ The adjacent tendons were lift off tested and the average lift off force for the three tendons was 1189 kips. Therefore, because of acceptable average tendon lift off force, this region of containment was found to be acceptable..

All three groups of tendons (vertical, hoop, and dome) continue to meet their design requirement because the average of the Normalized Lift Off Forces for each tendon group exceeded the minimum required average force _for each group specified in Section 4.6.1.6.1.b of the Technical Specifications. The average Normalized. Lift Off Force for the doma tendons was 1211 kips, which exceeded the 1115 kip requirement by 8.6%. The average Normalized Lift _Off Force for the vertical tendons was 1265 kips, which exceeded the 1195 kip requirement by 5.9%. The average Normalized Lift Off Force for the hoop tendons was 1206 kips, which exceeded the 1181 kip requirement by 2.1%.

-Visual: inspection of tendon anchorage areas was required by Section 4.6.1.6.2 of the Technical Specifications. The concrete surface surrounding hmap tendon 41AC had cracks which exceeded

'the 0.010 inch limit on crack width that is specified in the surveillance procedures. The cracks were located adjacent to the

-corners of-the tendon bearing plate. The crack pattern was mapped-and found to be of limited extent and less than 0.015 inches at the widest point. No abncrmal material or structural behavior was evident.

The wire testing required in Section 4.6.1.6.1.c. has not yet been completed. lWe~will provide additional notification if any lof the Technical Specification requirements for the wire testing are not met.

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