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Requests Relief from ASME Code Requirements to Permit Use of Temporary non-code Repair on Class 3 Piping,Per Requirements of Generic Ltr 90-05.On 911124,leak Discovered on 30-inch Diameter concrete-lined Pipe in Unit 1
	ML20086G289
Person / Time
Site:	Calvert Cliffs
Issue date:	11/27/1991
From:	Creel G; BALTIMORE GAS & ELECTRIC CO.
To:	; NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
	GL-90-05, GL-90-5, NUDOCS 9112050012
	Download: ML20086G289 (20)
	v • d • e

.

i; BALTIMORE GAS AND ELECTRIC 1650 CALVERT CUFFS PARKWAY + LllSBY, MARYLAND 20657-4702 oconoc c. cace' November 27,1991

- VICC PRESIDENT NUCLE AM ENEMQY (4 o)aeo.4 ass U. S. Nuclear Regulatory Commission Washingten, DC 20555 ATTENTION:

Document Control Desk

SUBJECT:

Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2; Docket Nos. 50-317 & 50-318 Temporaty Non-Code Renair of ASME Code Class 3 Piping Gentlemen:

Baltimore Gas and Electric Company requests relief from ASME Code requirement; as allowed by 10 CFR 50.55a(g)(6)(i). This relief will allow the use of a temporary non. Code repair on Calvert Cliffs Unit 1 Class 3 piping in accordance with the requirements of Generic letter (GL) 90-05.

DESCRIPTION Cn November 24,1991, a 3Sinch through. wall hole was discovered on a 30" diameter concrete-lined carbon steel pipe in the Unit 1 No.11 Saltwater IIcader. The leak occurred on the inside radins of a 900 cibow on the discharge of butterfly valve 1-CV-5150 and upstream of the inlet of the No.11 Service Water IIcat Exchanger. A one-line drawing of the Saltwater system showing the location of the leak is included as Attachment (1).

The leak was discovered by a plant operator during normal watch rounds. The leak rate was estimated as less than 20 gallons per minute. At the time the leak was discovered, Unit 1 was operating at full power. Upon discavery of the leak, a wooden plug was inserted into the hole as a temporary means to stop the leak.

FLAW CilARACTERlZATION The Daw size was determined using ultrasonic examination. A large scale (1 inch between measurements) ultrasonic examination was performed to determine the extent of the flaw. A finer mesh examination (1/16 inches between measurements) was performed to provide data for the analysis. Sketches of the profile of the Gaw are included as Attachment (2). A drawing depicting the location of the Gaw is included as Attachment (3).

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'4 Document Control Desk November 27,1991 Page 2 ROOT CAUSE DETERMINATION Based upon the limited available data and until the flaw can be removed and analyzed, the most probable cause of the leak is accelerated corrosion as a result of failure of the concrete liner. This failure is most likely attributed to stress fluctuations caused by flow instabilities immediately downstream of butterfly valve 1-CV-5150.

The Dow disturbances probably caused a lluctuating pressure profile on the surface of the concrete liner, At the inner radius 01 the elbow, this would result in cyclic forces which tend to lift and separate the concrete from the metal surface. Eventually, the concrete would crack due to fatigue and the crack would propagate to the surface of the metal.

The surveyed failure indicates a long axis which is neither perpendicular nor parallel with the direction of How. As indicated by the attached sketches, the failure is relatively k)calized. These observations lead to the conclusion that the failure in the concrete is relatively small, exposing a small area of metal to accelerated corrosion and subsequent failure.

Following the Code repair, the Dawed material will be examined and a more detailed root cause analysis will be performed.

IMPRACTICAlliY OF CODE REPAIR WITIIOtrl' PIANT SilUTDOWN A Code repair of the flaw will require removal and replacement of the flawed section. Replacement of the elbow would require removing No.11 Saltwater Header from service for an extended period of time to effect the repair. Technical Specification 3.7.5.1 requires that the plant be shutdown if a saltwater header is out of service for more than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. Therefore,it is not tx>ssible to perform a Code repair to the flaw without a forced shutdown of the plant.

PROPOSED MITilOD OF TEMPORARY REPAIR Our proposed temporary non-Code repair is to clamp a rubber lined patch over the hole. De clamp is not integrally attached to the pipe but rather relies upon the mechanical force of a U-bolt to hold it in place. The patch is Safety Related. The U-bolt has a channel steel strong-back with a pad and jacking screw that forces a r.bber patch (backed with a piece of steel plate) over the hole. A sketch of the temporary repair is included as Attachment (4). This patch is currently installed and it climinates allleakage from the Daw.

We have also examined the effects of flooding, spraying of water on equipment, and loss of flow if the temporary repair should fail and determined that it would not prevent safety related equipment from performing its function.

FL_ AW EVALUATION The structural integrity of the Dawed piping has been assessed using a "Through-Wall Flaw" evaluation approach as described in GL 90-05, Enclosure 1, paragraph C.3.a.

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Document Control Desk November 27,1991 Page 3 in order to perform the analysis, ultrasonic readings of the Gaw area were hken at eight radial k> cations from the flaw along four vectors. The first readings were taken at one inch spacing in order to bound the maximum area of the Daw. Upon determining the area of the flaw, the examination area was narrowed to two inches on either side of the Gaw and readings were taken at a 1/16-inch spacing. From this data, the maximum size of the Daw was determined. Of the four pro 0les c.tamined, none execeded the GL 90-05 criteria of three inches or 15% of the circumference.

All deadweight, pressure, thermal, and sarcahutdown carthquake loads were combined to determine the stress at the Daw k> cation. A conservative corrosion rate was used in the evaluation to envelope degradation of the Daw and arrive at a limiting minimum wall thickness requirement. A three month corrosion allowance was used to justify the use of the tempcrary repair until the next inspection (see Augmented Inspecuon, below). A summary of the calculation is included in Attachment (5).

A stress intensity was dete mined as required in GL WOS and the resultant values for each axis were within the acceptance criteria. Therefore, we determined that the structnral integrity of the pipe is maintained and that the Saltwater System remains capabb of paforming all safety functions in the event of Design Basis Accidents and anticipated transients.

AUGMENTED INSPECTION As per the guidance in GL E05, five locations believed to be most susceptible to the same degradation mechanism have been selected and ultrasonically evaluated.

These evaluations determined that the sampled locations have not experienced a degradation.

In accordance with GL E05, the temporary repair will be removed every three months and the flaw will be ultrasonically examined. The results of those examinations will be compared to the structural integrity calculations to affirm the continuing acceptability of the temporary repair.

Additionally, the temporary repair will be visually examined weekly and any leakage quantified. Any 1

substantial increase in leakage will be evaluated and the structural integrity of the piping will be reconfirmed.

CONCLUSIOli Based upo; the guidance provided in GL 90 05, we have determined that temporary non-Code repair of thu llaw to avoid a plant shutdown is justified and that the structuralintegrity of the Dawed piping is maintained. We will perform a '

repair of the Dawed piping during the next refueling outage, which is currently scheduled to bt. un March 6,1992.

We have determined that the requested reliefis:

Authorized by law.

Will not endanger life, propert, or the common defense and security, and, is in the public interest conddering the burden on BG&E if the requirement is imposed.

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j Document Control Desk -

November 27,1991 Page 4 should you have any questions regarding this matter, we will be pleased to discuss them with you.

Very truly yours,

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1 GCC/DDM/bdm/ dim 1

Attachment ec:

D. A. Brune, Esquire J. E. Silberg, Esquire R. A. Capra, NRC D. G. Mcdonald, Jr., NRC T. T. Martin, NRC L E. Nicholson, NRC R. I. McLean, DNR J. II. Walter, PSC e

Document Control Desk -

November 27,1991 Page5 bec:

M. J. Micrnicki W. R. Corcoran C II. Cruse /P. E. Katz R. C. DcYoung i

R. M. Douglass/R. F. Ash R. P. Heibel/I'. N. Pritchett j

C. P. Johnson C. C. Lawrence, III/A. R. Thornton R. B. Pond, Jr./S. R. Buxbaum, Jr.

L B. Russell /R. E. Denton/J. R. Lemons W. A. Thornton/E.1. Bauereis C.J. Antirews A. B. Anuje G. L Detter D. V. Graf B. S. Montgomery R. E. Nagel j

K. R. Neddenien i

R. C. L Olson P. A. Pieringer Technical Library L. O. Wenger B. D. Mann W. C Holston T. M. Delaney K. M. Hoffman F;te 13.02 NRC Chrono File

ATTACHMENT (1)

P&ID OF THE SALTWATER _ COOLING SYSTEM r

(DETAIL OF UFSAR DRAWING 9-8A)

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ATTACHMENT (3)

LOCATION OF THE SALTWATER HEADER LEAK

UNIT 1 SALTWATER HEAbER LEAK o WCATION -:

UNIT 1 SERVICE WATER ROOM o LEAK DESCRlFT10M :

INSIDE RAblUS OF.30" EL20W BOWN5TIEAIA OF 1-CV 5150. ( Vs" # HOLE 1 -

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ATTACHMENT (4)

DIAGRAM -0F THE TERPJRARY NOR-C.0_DE REPAIR

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item Description Quantity 1

3/4* A-108 Bar Sto:k 94" 2

C6 x 10.5 A-36 42" 3A 2" x 31/2" x 1/2" A-30 Plate 1

3B 2" x 31/2" x 1/2* Rubber 1

4 7/b" A-193 Grade B7 All Thread G"

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5 3/4" A-194 Grade 2H Nuts 4

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7/8" A-194 Grade 2H Nuts 2

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a)

Use safety related material.

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Washers to suit.

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Use 1/4" Fidet Weld to Weld 7/8" Nut to Backside of Channel

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A 7/8" nut shall be tack welded to the end of item No. 4 5

e)

Channel (Item 2) is actually in contact with the pipe. Note that the above expanded drawing is provided for clarity.

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ATTACHMENT (5)

SUMMARY

OF STRUCTURAL INTEGRITY CALCULATION 1-l l

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ANALYSIS OF SW THROUGH WALL FLAW UNIT 1-(CA OF.15"/ YEAR,.0587" MIN WALL M91-048)

(.005 TOL UT, Paint Removed) 0 - 180 45 - 225 90 - 270 135 - 315 ELB OD 30.000 ELB OD 30.000 ELB OD 30.000 ELB OD 30.000 R

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147.721 s

3.744 s

3.744 2a 0.836 2a 0.801 2a 0.732 2a 0.640-a 0.418 a

0.401 a

0.366 a

0.320 t(MIN)

O'.101 t(MIN) 0.101 t(MIN) 0.101 t(MIN) 0.101 t(ADJ) 0.101 t(ADJ) 0.101 t(ADJ) 0.101 t(ADJ) 0.101 t(NOM) 0.375 t(NOM) 0.375 t(NOM) 0.375 t(NOM) 0.375 A

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3797 A'

3797 B;

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0.009 c

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-F 4.117 F

3.926 F

3.563 F

3.100 K

24.7 K

23.1 K

20.0 K

16.3 NOTE: (1)'TO FULLY COMPLY WITH THE GENERIC LETTER, t(ADJ) IS EQUAL TO t(MIN).

(2) NOMENCLATURE MATCHES GENERIC LETTER 90-05.

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ML20086G289

Text

SUBJECT:

SUMMARY

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