ML19332D750

Application for Amends to Licenses NPF-76 & NPF-80,revising Tech Spec Surveillances 4.6.1.6.1,4.6.1.6.2 & 4.6.1.6.3 Following Guidance of Reg Guide 1.35 Proposed Rev 3 & Tech Spec 3.6.1.6 Re Tendon Surveillance

ML19332D750
Person / Time
Site:	South Texas
Issue date:	11/29/1989
From:	Chewning R HOUSTON LIGHTING & POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML19332D751	List: ML19332D750 ML19332D754
References
RTR-REGGD-01.035, RTR-REGGD-1.035 ST-HL-AE-3212, NUDOCS 8912050194
Download: ML19332D750 (13)

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P.O. Box 1700 Houston. Texas 77001 (713) 228 9211 HouWon Lighting ac Power _ ~ , - ~ ~ ~ - " ~ ~ ~ ~ ' ~ ~ ~

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l November 29, 1989 ST-HL-AE-3212 File No.: G2.06, G09.06 10CFR50.90 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 South Texas Prcject Electric Generating Station Units 1 & 2 Docket Nos. STN 50-498, STN 50-499 Proposed Amendment to the Unit 1 and Unit 2 Technical Specification on Tendon Surveillance Pursuant to 10CFR50.90, Houston Lighting & Power Company (HL&P) hereby proposes to amend Operating Licenses NPF-76 and NPF-80, by incorporating the attached proposed change to Technical Specifications, for the South Texas Project Electric Generating Station (STPEGS) Units 1 and 2. The proposed change revises Technical Specification surveillances 4.6.1.6.1, 4.6.1.6.2 and 4.6.1.6.3 following the guidance of Regulatory Guide 1.35 proposed Revision 3 and revises Technical Specification 3.6.1.6. The revision to Technical Specification 3.6.1.6 follows the text of the sample Technical Specification provided by the NRC on July 11, 1989. This submittal is in addition to the requested amendment dated June 28, 1989 regarding tendon surveillance.

HL&P has reviewed the attached proposed amendment pursuant to 10CFR50.92 and determined that it does not involve a significant hazards consideration.

The basis for this determination is provided in the Attachment. In addition, based on the information contained in this submittal and the NRC Final 2nvironmental Assessment for STPEGS Units 1 and 2, HL&P has concluded that pursuant to 10CFR51, there are no significant radiological or nonradiological impacts associated with the proposed action and that the proposed license amendment will not have a significant effect on the quality of the environment.

Attached is a mark-up of the Final Safety Analysis Report which will be incorporated in a future update, r

F 8912050194 891129 PDR ADOCK 05000498 P PDC NL.89.163.01 A Subsidiary of Houston Industries incorporated i

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ST-HL-AE-3212 File No.: G2.06. G09.06 Page 2 ,

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-Please find attached:

[ Attachment 1, Significant Hazards Evaluation for the Proposed Chande to {

! the Containment Structural Integrity Technical Specification '

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Attachment 2, Proposed Technical Specification (Sample Technical ..,

,1 Specification Mark-up)

! Attachment 3, Present Technical Specification j Attachment 4, Mark-up of the Final Safety Analysis Report I.

l The STPEGS Nuclear Safety Review Board has reviewed and approved the proposed changes.  ;

i l- In accordance with 10CFR50.91(b), HL&P is providing the State of Texas

[ with a copy of this proposed amendment.  ;

If the NRC should have any questions concerning this matter, please contact Mr. M. A. McBurnett at (512) 972-B530.

R. W. Chewning Vice. President Nuclear Operations RWC/GCS/sgs ,

l Attachments: 1. Significant Hazards Evaluation For the Proposed Change to the Containment Structural Integrity Technical ,

Specification

2. Proposed Technical Specification

3. Present Technical Specification

4. Mark-up of the Final Safety Analysis Report l

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d Houston Lighting & Power Company ST HL AE 3212 File No. :G2. 06, G09.06 South Texas Project Electric Genersting Station Page 3 Ec:

L Regional Administrator, Region IV Rufus S. Scott  ;

Nuclear Regulatory. Commission Associate General Counsel i 611 Ryan Plaza Drive, Suite 1000 Houston Lighting & Power Company Arlington, TX 76011 P. O. Box 1700 Houston, TX 77001 Coorge Dick, Project Manager ,

U.S. Nuclear Regulatory Commission INPO ,

Washington, DC 20555 Records Center '

1100 circle 75 Parkway J..I. Tapia Atlanta, CA 30339 3064  ;

Senior Resident Inspector -

c/o U. S. Nuclear Regulatory Dr. Joseph M. Hendrie Commission 50 Be11 port Lane P 0.' Box 910 Be11 port, NY 11713 Bay City TX 77414 D. K. Lacker J. R. Navuan, Esquire Bureau of Radiation Control i Newman & Holtzinger, P.C. Texas Department of Health  !

1615 L Street, N.W. 1100 West 49th Street Washington, DC 20036 Austin, TX .78704 R. L. Range /R. P.'Verret Central Power & Light Company ,

P. 0, Box 2121

. Corpus Christi, TX 78403 J. C. Lanier

' Director-of Generations

' 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 l

San Antonio, TX 78296 s-Revised 11/15/89 l

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-UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION q In the Matter ) [

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Docket Nos. 50-498 Houston Lighting & 2over )

Company, et al., ) 50-499

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South Texas Project ) >

- ' Unit 1 and Unit 2. )

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AFFIDAVIT 0

J-L R. W. Chewning being duly sworn, hereby deposes and says that he is

' i Vice President, Nuclear Operations, of Houston Lighting & Power Company that he is. duly authorized to sign and file with the Nuclear Regulatory Commission '

i is familiar with the content of the attached proposed changes to the South

• Texas Project Electric Generating Station Technical Specification 3.6.1.6 and ,

lt surveillances 4.6.1.6.1, 4.6.1.6.2 and 4.6.1.6.33 and that the matters set I > forth therein are true and correct to the best of his knowledge and belief. ,

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I R. W. Chewning Vice President, Nuclear Opera on Subscribed and sworn to byfore me, a Notary Public in and for The State of Texas this $lGF6 day of No venibt f , 1989.  !

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vv 4 maven b>n i n 91 h Notary Dublic 16 and for the 0 _. _ _ . - - _- - I State of Texas ,

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ATTACHMENT 1 I a  % g M, '

, ' SIGNIFICANT HAZARDS EVALUATION FOR THE-

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-PROPOSED CHANGE TO THE CONTAINMENT R. 1 w-s STRUCTURAL INTEGRITY TECHNICAL SPECIFICATION r ; . .,

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V- Attachment 1 ST-ML-AE-3212 Page 1 of 8 g ATTACHMENT 1 SIGNIFICANT !!AZARDS EVALUATION FOR THE PROPOSED CHANGE TO THE CONTAINMENT STRUCTURAL INTEGRITY TECHNICAL SPECIFICATION BACKGROUND

-Technical Specification (T.S.) 4.6.1.6.1-requires Reactor Containment Building o '(RCB) surveillances at regular intervals on.both RCB'o throughout the life of the project. Structural integrity of the RCB's is required to be demonstrated

'at the end of 1, 3, and 5 years following the initial structural integrity b test'(I.Si!.T.)-and at 5 year intervals thereafter.

p The South Texas Project has-two reactor containment buildings. The cylinder.

n walls and dome are post-tensioned with high strength tondons while the mat is

~ conventionally reinforced. The purpose of the' containment building is to mitigate-the consequences of an accident.

-The. surveillance assesses the condition of the containment post-tensioning-1r system. The post-tensioning system is comprised of 96 vertical and 133 hoop tendons. Each tendon has 186,;1/4" diameter wires bundled together. Each wire has a minimum' ultimate tensile strength of 240 kai. The tendons are

initially tensioned to approximately 70% cf their ultimate strength. Tha tendons are protected from corrosion by a filler material (grease).

The Unit-1 3.S.I.T. was completed on Harch 26, 1987 and the Unit-2 I.S.I.T.

. was completed on September 29. 1988.

This proposed change to Technical' Specifications will allow STPEGS to utilize criteria for surveillence and required action which reflects industry and NRC experience.with containment tendon systems.

PROPOSED CHANGE-iDeleteithe present Technical Specification 3.6.1.6 and surveillances

'4.6.1.6.1, 4.6.1.6.2 and 4.6.1.6.3 and replace with the proposed Technical Specification.

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i l,' r Attachment 1 i ST-HL-AE-3212 Page 2 of 8 SAFETY EVALUATION L Limiting Condition for Operation, 3.6.1.6 Action (a).

The proposed change will utilize the average of all measured prostressing forces for each group as abnormal degradation when found below the minimum stress for that group. This is more representative of abnormal containment structural integrity when compared to the present Technical Specification Action (a) of more than one tendon between the predicted lower limit and 90% of the predicted lower limit, or with one tendon below 90% of the predicted lower limit. Should the average prestress levol.of a group of tendons drop below the minimum required by -

j calculations, immediate steps (within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />) ate required to -

demonstrate containment integrity is maintained or initiate plant shutdown. This was previously covered by Action (b) (see Attachment 3 surveillance requirement 4.6.1.6.1 d.). The containment integrity is ,

most dependant upon the average prestress condition of the tendons.

• Therefore, this change assigns the more appropriate urgency to the most important attribute which is verified during the surveillance, r

Limiting Condition for Operation, 3.6.1.6 Action (b).

ll The proposed change will allow a longer time period to evaluate the indicated abnormal degradation of structural integrity before plant shutdown is required. This time period is appropriate to verify that containment integrity is maintained or to restore the containment to the required level of integrity.

The inspected items covered by this action statement are items which provide indications of possible abnormal degradation of the containment structure. Surveillance results which are outside the criteria, do not indicate that the containment structural integrity is inadequate and require subsequent emergency action. The proposed action statement recognizes that the acceptance criteria for the containment tendon surveillance are preliminary warning signs of possible structural integrity degradation such that further investigation is required. None of the criteria by themselves provides an indication that requires emergency action. Further testing, engineering evaluation and possibly analysis are required on a case by case basis. The inherent safety of the containment structure design assures that there is no immediate hazard associated with continued operation of the plant.

The Action of the T.S. is with reference to OVERALL containment structural integrity. Specifically, this means the implementation of the T.S. will allow for an Engineering evaluation of deviations from the criteria of 4.6.1.6 without entering the ACTION statement provided that a preliminary review confirms that there is no indication that the containment integrity may be in immediate jeopardy. This philosophy is applicable to 4.6.1.6 with the exception of 4.6.1.6.1 a.4.

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Attachment 1 ST-HL-AE-3212 Page 3 of 8 h l SAFETY EVALUATION - Continued Surveillance 4.6.1.6 n,

The proposed chenge allows for combined inspections of two similar

! containments such that the two containments will be subjected to prestress monitoring and tendon detensioning with associated inspections and or tests on an alternating basis. While full surveillance is ,

performed on one unit, which includes lift-off testing as well as visual i inspection, a visual only inspection will typically be performed on the other' unit (T.S. Figure 4.6-1). This is acceptable because the

[. containments at STPEGS are identical in all aspects such as rize, tendon L system design, materials of construction, and method of construction.

The two containments initial Structural Integrity Tests were performed j within two years of each other and there is not a unique situation that may subject either containment to a dif ferent potential for structural or tendon deterioration. Therefore, when there are two similar containmer.ts at a rite, the prestressing force can be monitored by performing the lift-off testing during alternate inspections. ASME Section XI.

Division 1 IWL includes similar requirements for alternating full surveillance with visual only surveillance.

Representative Sample The proposed chango will use a representative sample of 10 tendons (4 inverted U and 6 hoop). The present sample size uses an arbitrary number of 13 (4 inverted U and 9 hoop). The selection of tb3 proposed representative sample uses a percentage of the tendon population (4%) in each group with limitations on the minimum and maximum number of tendons to be inspected. After three inspections with the proposed change, a larger sample size will be utilized when compared to the present Technical Specification (i.e. 6 tendone vs. 5 tendons). ASME Section XI, Division 1, IWL recommends the same sample size.

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Attachment 1 ST-HL-AE-3212  ;

Page 4 of 8 SAFETY EVALUATION - Continued Percentage Elongation'  ;

The proposed change utilizes an elongation difference corresponding to a  ;

specific load of 10% from that recorded during ir.sta11ation. The present

. Technical Specification uses an elongation difference of 5%. The repeatability of elongation measurements requires a larger tolerance for .

various factors. One factor is attributed to the changing friction conditions between the construction tensioning without grease and subsequent surveillance conditions with the tendon immersed in grease.

Another factor is the relative movement of individual wires within a twisted tendon. This effect is similar to the stretching of new cables.

The industry is trending towards a 10% tolerance for elongation. This  ;

proposed change takes into account observations noted in field measurement. Should elongation in excess of 10% be observed a review will be made to ensure that the difference in elongation la not related to wire or anchorage failure.

A change in the r. ample T.S. was made to the elongation measurement to more clearly meet the intent of the sample T.S.. Measurements during the surveillance are taken at three equally spaced intervals in order to compare with the measurements at initial installation. The tendon installer sneasured elongation at initial tensioning which typically corresponds to about 16% of Guaranteed Ultimate Tensile Strength (GUTS) of the tendon and again measured at 80% GUTS before seating the tendon at l approximately 70% GUTS. Therefore, during the surveillance, measurements will be taken at 3 equally spaced intervals from initial tensioning to 80% GUTS to compare with the initially measured elongations at installation instead of between zero and the seating force as identified in the sample T.S.

i Lift-Off Stresses

-The proposed change deletes the specific reference to the average minimum design values for lift-off stresses. These design values will be controlled by the 10CFR50.59 process. The deletion of specific design values from Technical Specifications is an industry and NRC goal.

Should the measured prestressing force of any tendon be below 90% of the prescribed lower limit, an engineering evaluation should be performed to determine the cause and extent of the occurrence. The investigation may require analysis, additional tendon lift-off testing, and possibly tendon detensioning. However, the methods of investigation should be determined with full consideration of actual conditions at the time of discovery (See proposed T.S. 4.6.1.6.1 a.4).

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Attachment 1 p ST-HL-AE-3212 I Page 5 of 8 t

O SAFETY EVALUATION - Continued Grease Replacement When grease is pumped in the duct during the surveillance, typically a ,

maximum installation pressure is specified rather than a specific installation pressure in order to prevent damage or unnecessary grease '

leakage during the surveillance. Therefore, T.S. 4.6.1.6.1 d is revised to incorporate 10% maximum of the net duct volume when injected at a pressure not to exceed the designers specification. ,

1 Net Duct Volume The quantity of grease replaced in excess of the grease removed is revised f rom 5% to 10% of the net duct volume when injected. Ten percent 7 (10%) is more appropriate for the criteria since the duct is expected to  ;

have a preexisting condition with some amount of voids. Voids are ,

attributed to the following:

1) Initial shrinkage of grease is expected since the grease is injected  ;

at an elevated temperature. Grease is expected to shrink by  ;

approximately 4% due to cool down.

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2) Spaces exist between the wires in the tendon bundle. The tendon is ,

tightly wound made-up of 186 wires. This condition makes it very difficult to fill all spaces between the wires during initial installation. After some period of time the grease may work its way to the middle spaces of the tendon. These spaces make-up a minimum of 3% of the net duct volume for a giver. tendon. l

3) The installation process introduces some air into the duct during the initial pumping of the grease.

During installation, the grease is fully injected into the duct. This is evident since the grease exits from a vent on the end of the tendon. The ,

voids which exist in the tendon duct are not significant since each tendon wire was coated with storage grease prior to installation and the installed filler material adheres to the steel surfaces protecting the tendon.

The previous surveillance at STP as well as surveillances at other plants which have similar installations of tendons have shown that this i preexisting condition with voids in the duct have not had adverse effects on the tendons.

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.; ' Attachment i y y ST-HL-AE-3212 L Page 6 of 8-1F111er' Material Chemical Properties j u

. . i The revision improves the T'.S. by providing acceptable tolerance limits j

[ for chemical' properties of the filler material. The guidelines are- t j

, ~ consistent with.the ASME requirements in Section XI. .The acceptance criteria for Base Number and Water' Content are based on current. industry 4; standards .

$ 3 7, .End Anchorages ~ and Adj acent Concrete Surf aces n; i With-the proposed. change, a general inspection of the accessible surfaces of the containment building shall be performed prior to the Type A containment leakage rate test (ILRT) in accordance with 10CFR50 Appendix.J.'.The end anchorages will not be inspected during the. Type A

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t leakage rato test. The internal pressure of the ILRT will not j JE significantly af fect the condition at the end anchorages adj acent surfaces. 'Therefore, the~ additional cost of inspection on end anchorages

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~ and' surrounding surfaces during the ILRT is not warranted.

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- Endianchorages and ~ adj acent surf aces shall be specifically inspected  ;

during the containment surveillance. During combined inspection, for the l

~ containment not receiving a full inspection, a visual inspection of the- ]

adj acent concrete. and the tendon -end anchorages is performed to the D , ,.

4U extent practical without dismantling the load bearing components. For  !

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'the containment' receiving a full. inspection, the adj acent ' concrete of all .

'ij[ tendons selected for inspection are' visually examined as well as the end

,u anchorages >of the tendons being inspected. Furthermore, the grease cans 4 ., of all-the vertical tendons shall be inspected for evidence of excessive greas'e' leakage.and or damage to the grease can due 1.o tendon anchorage .j '

1 failure. These inspectior.s assure the structural integrity of the 3 adj acent concrete surf aces and' determine if there . is any abnormal

-degradation of the end anchorages.  ;

NUREG/CR-2719

-As discussed in NUREG/CR-2719 " Evaluation of Inservice Inspections of g< "

. Greased Prestressing Tendons" dated September 1902, page 11, the 1

incidence of prestressing tendon corrosion were very low. This result s indicaten that the proposed criteria of monitoring 4% of the population of each tendon family (minimum of 4 from each group) for the first three surveillances, followed by a drop to 2% in future surveillances if no H abnormal degradation was uncovered, are reasonable. The report further states that the performance of tendons has been so good that consideration should be given to a reduction in these levels.

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,21 Regulatory' Guide 1.35/ASME Section XI Thel proposed change follows the guidance of Regulatory Guide 1.35

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6 f proposed Revision 3. . The= proposed Revision 3 to Regulatory Guido 1.35 provides clarification, expansion, or additional guidance. _. Additionally, ASME Section XI,-Division 1,' Article.IWL-2000, 1986 Edition, 1988 Addenda

< provides similar requirements as those proposed in this requested change-to Technical ~ Specification.

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DETERMINATION OF SIGNIFICANT HAZARDS V  :

Pursuant to 10CFR50.91 this analysis provides a determination that the L- proposed change to.the Technical Specifications does not involve any significant hazards consideration as defined in 10CFR50.92.

1) The. proposed change does not involve a significant increase in the probability or consequences of an accident previously evaluated.

The proposed change has no effect on the probability of occurrence of an accident because no physical modifications are involved, the containment mitigates the consequences of an accident and cannot increase the probability of occurrence of an accident. The ,

consequences of an accident are not significantly increased because the containment is not modified and the proposed change will not impact the program to detect degradation of the containment, thus insuring-that the structural-integrity of containment is maintained.

R2) The' proposed change does not create the possibility of a new or different kind of accident from any accident previously evaluated.

This proposed change does not alter any safety related equipment or its safety function, it merely revises the surveillance program.

3)lThe proposed revision to the Technical Specification does not result in a significant reduction in the margin of safety.

The margin of safety is not affected by a revision to the post-tensioning system surveillance. The maximum internal structural design pressure of 56.5 psi is unaffected by this proposed revision to the Technical Specifications. The calculated maximum pressure is 37.5 psig (See Containment System Bases 3/4.6.1.6).

A revision to the surveillance for the containment tendons will not allow degradation of the tendons to go undetected, allowing a condition that could compromise the structural integrity of the containment.

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~G Vi I '- ' -Attachment 1 ST-HL-AE-3212 X' Page 8 of 8 CONCLUSIONS-p The conclusions presented in the FSAR and other licensing basis analyses

remain valid. The effects of this revision to the post-tensioning system surveillance do not result in exceeding any STPEGS or regulatory design

-limits. Therefore', HL&P concludes that the proposed change does not involve a significant hazards consideration.

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