ST-HL-AE-4037, Special Rept Re Evaluation of Unit 2 Third Yr Containment Tendon Surveillance.Refilling of Grease Accomplished Simultaneously W/Discoveries of Voids as Result of Insp Process Used

Special Rept Re Evaluation of Unit 2 Third Yr Containment Tendon Surveillance.Refilling of Grease Accomplished Simultaneously W/Discoveries of Voids as Result of Insp Process Used

ML20091C260
Person / Time
Site:	South Texas
Issue date:	03/30/1992
From:	Jump W HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
ST-HL-AE-4037, NUDOCS 9204030147
Download: ML20091C260 (6)

Text

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March 30, 1992 ST-llL- AE- 4 03 7 Filo No.: G02 10CFR50.36 U- S. Nuclear Regulatory Commiusion Attention: Docuw nt Contr** nosk We.shington, DC 20S55 South Texas Proje Electric Conorating Station Unit 2 Docket No. STH S0-499 Special Report Regarding An Evaluation of The Unit 2 Thirst Year containment _TenAOD Survoillanco Pursuant to the South Texas Project Electric Conorating Station Technical Specifications 3.6.1.6, llouston Lighting & Power submits the attached Special Report regarding an ovaluation of the Unit 2 third year containment tendon surveillance.

If you should have any questions on this matter, plesso contact Mr. C. A. Ayala at (512) 972-8628 or me at (512) 972-7205.

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William J. Junt-Manager Nuclear Licensing JMP/atnp

Attachment:

Special Report Regarding An Evaluation Of the Unit 2 Third Year Containment Tendon Surveillance osoosa /pk o,

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WNW# A Subsidiary of liouton Induqtin incorporated 9204030147 920330 PDR ADCCK 05000499 S PDR

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11ouston lighting k Power Company

, , South Texas Projett Elettric Generating Station liL-AE-4 g;

Paga 2 Cet Regional Administrator, Region IV Rufus S. Scott Nuclear Regulatory Commission Associate General Counsel.

611 Ryan-Plaza Drive, Suite 400 Houston Lighting & Power Company Arlington, TX 76011 P. 0. . Box 61867 Ifouston, TX 77208 George Dick, Project Manager

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U.S. Nuclear Regulatory Commission INPO j Washington, DC 20555 Records Contor 1100 Circle 75 Parkway  ;

J. I.'Tapia Atlanta, GA 30339-3064 .

- Senior Resident Innpector '

c/o U. S.-Nuclear Regulatory Dr.- Joseph M. }{ondrie i

' Commission 50 Bellport Lane  !

lP . O . . Box 910 Bellport, NY- 11713 t Bay City, TX 77414 D.RK. Lacker J..R. Newman, Esquire Bureau of Radiation Control Novman C.Holtzinger, P.C. Texas Department of }{calth 1615 L Street,-N.W. 1100 West 49th Street Washington, DC 20036 Austin, TX 78756-3189 .

- D. E._ Ward /T. M. Puckett ,

Contral Power.and Light Company  ;

P. - O . Box 2121 Corpus Christi,-TX 78403 J. C. Lanier/M. B. Leo City of Austin Electric Utility Department P.O. Box 1088-Austin, TX 78767 i K. J. Fiedler/M. T. Hardt City Public Servico Board ,

P. O. Box 1771 San Antonio,-TX 78296 Revised 10/11/91 -

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i Attachment ST-IIL-AE-4 03 7 -

pago 1 of 4 South Texas project Electric Gonorating Station  ;

Unit 2  ;

Docket No. STN 50-499  !

'pocial Report Regarding An Evaluation of 11ut 1 2, Third Year containment Tendon _ Surveillance Technical Spocification 4.6.1.6 requires that the structural integrity of the containment tendons bo demonstrated at the end of '

1, 3, and 5 Years following the initial containment structural integrity test and at 5 year intervals thoroaf ter. Daring the performanco of the year throo surveillanco it was discovered that i tendon fillor grease voids in excosa of the Surveillanco >

Haquiroment 4.6.1.6.1d.2 maximum of 5 porcent of not duct volumo l existed. Compliance with the associated action statomont required  !

rostoration of containment structural intogrity, which was not >

compromised by the voids, performance of an engineering ovaluation and submittal of this Special Report.- lloto that refilling of greano was accomplished simultaneously with the discoverlos of voids as a result of the inspection process used.

Ton Reactor Containment Building tendons woro inspected.

Eight had grease. voids excooding the 5 percent of not duct volume as described above. The two satisfactory tendons wore the control tendons.

which areControl inspected tendons during (211075 and each2V110)illanco.are surve designated The tendons tendon identification numbers and groaso void volumes which excooded the 5 porcent of not duct volumo were as follows: '

Void Volume Tendon f inercent of duct volume)  ;

1H007 5.7%

1H078 11.0%

3H002 6.7% 3 3H008 7.4%

3111 1 0 6.9%

2V113 6.0%

2V119 9.0%

2V227 8.2%

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$ RIP \92 072,001

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Attachment ST-HL-A'E-4 03 7 $

Page 2 of 4

-g South Texas Project Electric Generating Station Unit 2 Docket No. STN 50-499 g Gpecial Report Regarding An Evaluation of s . The Unit 2 Third Year Containment Tendon Surveillance l

The main purpose for the sheathing fille material grease is

,. ovide long term corrosion protection for rue tendon wires and t'

.. arage components. Initial installation of che sheathing filler _

39 acial involved pumping the beated grease into the tendon v~'

. ching (duct) f rom one end of the horizontal tendon and continue aping until the hot grease (temperature > congealing point) is ected from the opposite end of the horizonta) tendon with a c m inuous stream of hot grease flow, free of air bubbles and i algn substances. AC,ditionally, for horizontal tendons rouced akie discontinuities such as a penetration, the sheathing was vented to release entrapped air during grease injection. Filling the vertical tendons is basically the same, except pumping is performed frw both ends of the tendon until the hot grease is ejected f rom tue high point vent located at the ape >_ of the dome. G This installation procedure assured that the tendon had been tnoroughly coated with grease over its entire length including filling the grease caps, thus encasing the tendon-end anchorages.

In addition, the tendon wires were coated with a temporary corrosion preventative Visconorust, 1601-Amber after fabrication for stcrag" sW handling of the tendon coil. Furthermore, the cedon wires wro hand-coated with Visconorust 2090 P-4 (grease) durcing installation where :he temporary corrosion preventative -

caterial had toen scraped off and to lubricate the tendon for insertion into the duct. This insured that all of the tendon wires were coated with corrosion inhibitor at the time of inscallation and maintained corrosion-free through their entire service life.

Greuse voids are expected in the tendon ducts. The percent voids can be in excess of the 5% limit for several reasons which are explained below:

1) Shrinkage of grease occurs since the grease was initially 1 injected at a temperature between 150 and 250 degrees.

The grease (Visconorust 2090 P-4) has a coefficient of expansion which yields an expansion of about 1% per 20*F.

Initial installation temperatures are typically greater than 18 0'F . Depending on the ambient temperature, shrinkage can be in excess of 4%.

$ REP \92-072,001

-Attachment ST-Hb-AE-4037 Page 3 of 4 South Texas Project Electric Generating Station Unit 2 Docket No. STN 50-499 Special Report Regarding An Evaluation of The Unit 2 Third Yegr Containment Tendon Surveillance

2) Spaces exist between the wires in the tendon bundle. The tendon is made up of 186 tightly wound wires. This condition makes it very difficult to fill all spaces betwesn the wires during initial installation because the tendon is at ambient temperature. As the hot grease surrounded the tendon, it is possible that it worked its way into the middle spaces of the tendon bundle. These spaces make up a minimum of 3% of the net duct volume for a given tendon. In addition, this migration of grease may occur in areas where the tendon is in contact -

with the sheathing, which is not considered in the previous 3%.

3) The initial installation process took care to eliminate duct voids as much as possible; however, it does introduce air into the duct during the pumping of the greasa. The process of pumping grease into the duct entrains air inside the greese. This entrained air _can surface from suspension between the time the duct is filled and the surveill.ance is performed. Additionally, air becomes entrapped while the grease is pumped from one end of the sheathing to the other end, which can be as long as 600 feet. This introduction of entrained and entrapped air can account for a significant percentage

-of the additional- grease p' imped into the tendon duct during the surveillance.

Therefore, voids in the range of 5.7% to 11.0% discovered during this surveillance are reasonable. There was no evidence of grease leakage as determined by performing a visual inspection of the accessible containment surfaces and by holding the pressure for one hour after replacing the greasa. A visual examination of exposed - anchorage components wac performed at both ends of the 4

tendons.and there was no evidence of degradation.

l-4 SREP\92 072.001

Attachment ST-HL-AE-4037 Page ? of 4 South Texas Project Electric Generating Jtation Unit 2 Pocket No. STN 50-499 Special Report Regarding An Evaluation of

,The Unit 2 Third Year Containment Tendon Surveillance As previously stated, the tendon wires and anchorage system weAe coated with storage or fillor grease prior to installation and the ducts were completely filled with filler material from one end of the tendon to the other at initial installation. Special consideration was given to the formulation of the filler grease as the original specification required it to have a liquid vapor phase it.t.ibitor for the prevention of corrosion within the voids. The filler material was also required to contain additives to enhance 3 the corrosion-inhibiting and wetting properties, as well as to form a chemical bond with the tendon steel. Therefore, the corrosion protection for the tendons not included in this surveillance is naintained.

Previous surveillances at other plants which have similar installation of tendons have shown that the existence of grease voids in the ducts have not had adverse affects on the tendons.

Additionally, the v.mufacturer of the grease has suggested against eliminating

• olds Tom the tendon duct due to the coefficient of expansion of the grease discussed in item 1 above, when the grease is installed while containment ambient temperature is below the upper operating range. The duct needs some void area to allow the grease to expand in order not to be detrimental to the to.ndon cheathing.

In conclusion, grease was initially installed throughout the entire length ci the tendon ducts and grease coverage was assured.

The grease will adhere-to the tendon and protect the wires from corrosion. There is a vapor phase inhibitor in the Visconorust 2090 P-4 for the prevention of corrosion within voids as well as additives to enhance corrosion-inhibiting properties of the grease.

The tendons which had voids have been filled and there is no evidence of grease leakage from the sheathing. The remaining tendons in the containment structure are adequate in their existing condition since minimum grease coverage still exista do y: ovide corrosion protection for the post-tensioning system. Adequate grease coverage exists for the tendons to maintain corrosion e protection and no grease leakage is evident, therefore, containment

& integrity is assured.

ISREP\92072.00 _ _ _ _ _ _ _ _ _ - _ _ _ _ _ _ _ _ _ _ _ _ _ _ - _ -

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