ML20044B184

Requests Approval of Temporary non-code Repair & Augmented Insp of Svc Water Piping,Per 900626 Telcon

ML20044B184
Person / Time
Site:	Davis Besse
Issue date:	07/10/1990
From:	Shelton D TOLEDO EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GL-90-05, GL-90-5, TAC-M77037, NUDOCS 9007180057
Download: ML20044B184 (5)

Text

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-0  ;

e TOLEDO

'. %ms EDISON  ;

• A Catyw Energ, W y c-I i' DONALD C. SHELTt I. Vvm Pveulett-Nsier

1419] P49 P300 p

D9cket Number 50-346 i License Number NPF-3 f

Serial Number 1825 July 10, 1990 i i

United States Nuclear Regulatory Commission

' Document Contr01 Desk Vashington, D.C. 20555 ,

Subject . Relief Request to Allow Temporary Non-Code Repair of Service Vater Piping (TAC Number M77037)

Gentlemen: ,

t

-On June 26, 1990,- Toledo Edison'(TE) received Generic Letter 90-05, "Gu.idance for Performing Temporary Non-Code Repair of ASME Code Class 1, 2, and 3  ;

Piping" (dated June 15, 1990, Log Number 3258). A tt.lephone call was

-initiated on that date between TE and Nuclear Regulatory Commission (NRC)/ Office of Nuclear Reactor Regulation (NRR) perso.inel to discuss a small ,

-leak in a four inch service water system line at the Davis-Bess e Nucleat Povel Station (DDNPS). -This leak had been identified and docimented on June 9, 1990, during startup of DBNPS from the sixth refueling outage. Since piplig .!

1ntegrity and system function vere not af fected by the ;eck, Toledo Edimn ,

provided a use-as-is temporarily disposition until an outage of 30 days or greater during the fuel cycle or until the seventh refueling outage, whichever occurred first. Ilovever, for housekeeping reasons, a gasketed patch and clamp were utilized to repair the leak. It was TE's position that continued startup

' efforts were-vithin the guidance for " continued operation" as cited by the Generic Letter, and the plan for deferred final repair was justified on this basis. The NRC personnel agreed and stated relief pursuant to -

10CFR50.55a(g)(b)(i), and as further explained in Generic Letter 90-05, vould  ?

be' required.

.6 Y 9007i80057 900710 m ( dg PDR ADOCK 05000346 \

P PDC .

THE TOLEDO EOISON COMPANY COISON PLAZA 300 MADISON AVENUE TOLEOD, OHIO 43652

Dockat Number 50-346' .l

, License Number NPP-3 Serial Number 1825~

Page 2 i

l Pursuant to 10CFR50.55a(a)(3), Toledo Edison requests approval of a temporary non-Code repair and augmented inspection of the affected service vater piping j

' as an alternative to the requirements of ASME Code, Section XI, IVX-4000. 3 LDetailed justification for the requested relief is provided in the attachment. l The justification vas prepared pursuant to Generic Letter 90-05 and the NRC l staff's guidance on preparing the relief request (the latter was telecopied to l TE on June 26, 1990, by NRC). This request justifies continued operation of ,

DBNpS'vith the temporary non-Code repair of the service water line until the I next refueling outage (presently scheduled for September 1991) or until an I outage of 30 days or greater during the present operating cycle, whichever  ;

occurs first.- l Based on the justification provided, TE concludes that the proposed I alternative provides an acceptable level of quality and safety, and compliance with the specified Code requirements vould result in hardship .l vithout a compensatory' increase in the level of quality or safety. Granting of this telief by NRC is requested by July 17, 1990.

If you have any questions, please contact Mr. R. V. Schrauder, Manager -

Nuclear Licensing, at (419) 249-2366.

Very truly yours,

,  ! f)\

i RMC/mmb-cc P. H. Byron, DB-1 Senior Resident Inspector A. B. Davis, Regional Administrator, NRC Region III T. V. Vambach, DB-1 NRC Senior Project Manager f

l '

Docket Number 50-346 t* .- Licens] Number NPF-3 -

Serial Number 1825

. Attachment .

Page 1 RELIEF REQUEST TO ALLOV TEMPORARY NON-CODE ,

REPAIR OF SERVICE VATER SYSTEM PIPING LEAK

< Description of Flav Detection .

L On June 9,-1990, a leak in the service water system was identified and

~

documented in Potential Condition Adverse to Quality Report (PCAOR) 90-0503.  ;

The particular line affected is the service water piping to the Emergency Core i t

Cooling System (ECCS) Room Cooler coils and the flydrogen Dilution Blovers f or Train 2. The leak was. described as approximately one gallon per minute. This '

piping is four inch diameter, 150 pound rated, schedule 40 ASME (SA53, Gr. B)

S Section III, Class 3. Ultrasonic (UT) examination of the piping vas performed later the same day to determine piping vall thickness in the area of the flav. ,

This data was evaluated, and, on June 12, 1990, in response to the PCAOR, '

, Engineering provided a disposition that piping integrity and system function '

vere not affected and that the piping vos acceptable for use until plant conditions were catablished which vould aov sufficient time to effect veld repair of the flawed area. This disposition was accepted by the Authorized  : Nuclear Inservice Inspector (ANII) on June 12, 1990. A gasketed pa.*ch and. clamp vere _used to repair the leak in the interim. Determination of Impracticality of Repair 4 The flav was determined to be acceptable for use temporarily (i.e. until the ,

               - next refueling outage or until an outage of 30 days or greater, whichever occurred first) as described in the PCAOR disposition.      On June 26, 1990, upon receipt of Generic Letter (GL) 90-05 and discussion with the NRC Staff, TE         ,

determined relief from the Code was needed due to the impracticality of repair - during operational startup activities then underway. Repair vas estimated to require approximately 89 hours which is in excess of the allovable out-of-service time for systems required to be isolated to effect repair, e.g., the Containment Cooling Units (Technical Specification 3/4.6.2.2). The NRC Staff concurred that interruption of startup activities did not appear varranted. i Subsequent Flav Characterization + Following discussion with the NRC Staff personnel on June 26, 1990, TE began addressing the temporary non-Code repair (i.e. the gasketed patch and clamp) in accordance with the aspects of GL 90-05. On June 28, 1990, additional UT examination measurements were performed to further characterize the flav. The measurements were further supplemented by a Radiographic (RT) examination on July 1, 1990,.vhich shoved the flav to be a through-vall hole of approximately 3/16" diameter with a cavity of 5/8" x 7/16". It has been assumed the through-vall hole could grow to the dimensions of the cavity as the vall thickness in the cavity is approximately 1/32". Therefore, evaluations of the flav have been performed assuming a through-vall hole of 5/8" diameter. The apparent root cause of the flaw is localized corrosive attack as adjacent piping areas indicate a greater vall thickness than the minimum required by the Code.- Following final repair of the pipe, the piping vill be examined and a thorough root cause evaluation vill be performed.

O U

  ',          Docket Number 50-346                                                                   !

'* 4 Licen e Nu ber NPF-3 i Serial Number 1825  !

       . . . Attachment                                                                              [
             .Page 2                                                                                 $

Five additionr3 mas of the Service Vater System have been selected and

             ~ inspected bast i      eusceptibility to the same type of corrosion attack and         j accessibility q: 7:a piping for examination. These inspections, performed in           ,

accordance with GL 90-05 and presently being evaluated, vill aid in further  ; 4-characterizing the corrosion mechanism and any effects on overall system , degradation. Flav Evaluation Results  ! Analysis of the (law utilizing the "through-vall flaw" approach presented in ' GL 90-05 requires calculating a stress intensity f actor "K" to be less than - 35 ksi (in) 0.5 for ferritic steel. Applying the equations as presented in  : GL 90-05, results in a "K" value of approximately $3.6 kai (in) 0.5 It is noted that the GL 90-05 equations are based on NUREG/CR-4572, "NRC Leak- i Before-Break (LBB.NRC) Analysis Method for Circumferentially Through-Vall > Cracked Pipe Under Axial Plus Bending Loads" (May 1986). These equations incorporate a geometric assumption that R/t be less than or equal to 16 and greater than or equal to 4. NUREG/CR-4572 suggests the use of 4 or 16, as appropriate, for R/t when the calculated R/t falls outside the specified ' range. Since the calculated R/t value for the 4 inch Schedule 40 Service Vater piping under evaluation is approximately 95, the use of 16 for R/t is f more appropriate. . Thus, the estimated "K" value for this case is 0.5 which is much less than the maximum acceptance approximately 6.6 ksi criteria of 35 ksi (in) 0. (in)5, In addition, a confirmatory evaluation was performed utilizing alternate equations for circumfer .itial through-vall flav stability as cited in NUREG/ 1 CR-3464, "The Application of Fracture Proof Design Methods Using Tearing Instability Theory to Nuclear Piping Postulating Circumferential Through-Vall Cracks" (September 1983),-page 78. Use of these equations, in conjunction , with a safety factor of 1.4 as specified by the GL, yields a "K" value of 7.73 ksi (in) 0.5. This compares favorably with the "K" value stated in the  : preceding paragraph. Description and Evaluation'of Temporary Repair The temporary repair of the piping flav consists of a clamp-type arrangement -t with rubber gasketing. The clamp is not intended to serve any structural- l function for this application, and its effect on the piping system is negligible due to the very small additional loading involved (estimated to be approximately 5-10 pounds) and the very lov stress levels in the vicinity of the clamp. Systems interactions (such as flooding, spraying vater on  ;'

            . equipment and' loss of system flow) have been evaluated, assuming the absence of the clamp and considering the flav location and area sump capacity, and found to be negligible.                                                              >

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       ,>          DohketLNumber.50-346
                  -Licens3 Number NPF-3                                                                                i Serial Number 1825 l
          .c -Attachment Page13                                                                                              !

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                 . Augmented Inspections                                                                              !

1

                  . Toledo Edison, during plant valkdowns, vill implement a veekly qualitat!ve

[; . assessment of leakage through the temporary non-Code repair. r An assessment of the integrity of the temporary non-Code repair vill be made. f at least quarterly.by UT or RT.  ! t Toledo Edison vill notify the NRC if flaws which require evaluation in c' ' accordance-with the rules of ASME Section XI are detected in the augmented 'f L inspectionc or.the aforementioned inspections of the selected five susceptible  : locations. [ b L conclusion i f , q Based on the above, the Service Water System flav identified is acceptable , until an outage of 30 days or greater or until the next refueling outage,  ? whichever occurs first. Therefore, relief from ASME Code, Section XI, i n IWX-4000 in accordance with 10CFR50.55a(a)(3) is' justified.  ! r f a l E 5 f i i o ie _ _ . , , _ _ - , . , -}}