ML19241A668

LER 79-014/01T-0 on 790618:special Radiographic Insp of Three Steam Generator nozzle-to-feedwater Piping Welds Showed Cracking in Three Inlet Elbows.Caused by Fatigue Failure Assisted by Corrosion.Elbows Replaced

ML19241A668
Person / Time
Site:	Beaver Valley
Issue date:	07/02/1979
From:	Werling J DUQUESNE LIGHT CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19241A667	List: ML19241A666 ML19241A668
References
LER-79-014-01T, LER-79-14-1T, NUDOCS 7907090265
Download: ML19241A668 (2)

Text

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U. S. NUCLEAR REGULATORY E OMMISSION NRC FORM 366 Will LICENSEE EVENT REPORT CONTROL 8 LOCK: l i

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l d tW 6 Doc .ET NUMB E R t.d EVENT DESCRIPTICN AND PRC8 ABLL CCNSECUENCES o 2 l A special radiocrachic insoection of the three stean eenerator nozzle-to-feedwater I o 3  ; inlet piping welds was conducted June 15, 16 and 18. The radiocraohs showed 1 Icrackine to be cresent in all three inlet elbows. The elbows are 00 decrem .

I o 4 o 5 16 inches in diameter with an 0.843 inch wall thickness. The cracks originated at I 1

o es ] the shoulder of the counterbcce in the oicinc. or acoroximatelv 9/16 inch from the I

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liii[] corrosion. The feedwater pipine elbows have been removed and are beine reolaced y,;,ylwith new elbows. Radiographic insocetion of feedwater pioine welds in containment [

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Attachment To LER 79-14/0lT Beaver Valley Power Station Duquesne Light Ccmpany Docket No. 50-334 On May 31, 1979 during a telephone conversation with Messrs. J. A. Werling, BVPS Unit 1 Superintendent, and A. C. Mazukna, Duquesne Light Company Quality Control Supervisor, Mr. D. Beckman, NRC Inspector, discussed the finding of cracks in feedwater piping adjacent to the steam generator nozzle to feedwater piping weld at another power plant. Mr. Beckman asked if Beaver Valley Power Station would voluntarily radiograph those welds during the station's current shutdown. The BVPS Superintendent agreed to do so and the work was scheduled.

The radiographs of the three steam generator nozzle-to-feedwater iniet piping welds were taken on June 15,16, and 18,1979.

The radiographs showed cracking to be present in all thre" inlet pipes.

Actually, the inlet piping at these locations are 90* elbows. The lines are 16 inches in diameter with an 0.843 inch wall thickness. In each instance, the cracks originated at the shoulder of the counterbore in the piping, or approximately 9/16 inch from the root of the weld.

Measuring in a circumferential and clockwise direction and facing with the flow, the specific locations and size of the cr cks are as follows. The measurements of 0 and 51 inches are at the top of the pipe; 13 at 909; 25-26 at the bottom; and 38 at 270*.

Steam Generator No. lA Steam Generator No. 1B Steam Generator No. 1C Cracks were present at: Cracks were present at: Cracks were present at:

49 1/2" through 0 to 2" 48" through 0 to 2" 48" through 0 te 5" 10 1/2" to 15" 9" to 13" 26" to 30" in a auck-up 39" to 41" 33" to 43" area of the root pass 35" to 43" A magnetic particle examination of the offected areas did not show any cracking to be present on the outside surface of the piping.

The three elbows have been removed and three new elbows are being installed.

Radiographic inspection of all feedwater piping welds is continuing. Thus far, with 70% of the feedwater piping welds f rom the steam ger.erators to the containment penetrations radiographed, only three unacceptable code discontinuities have been discovered. One additional a/S inch long crack indication in line weld number 12, and one and two inch long lack of penetration areas in line welds number 10 and 1: ,

respectively, in the lA feedwater pipe have been observed. Required repairs will be made prior to plant startup.

Based on preliminary analysis of the pipe cracks, the cause of failures located at the steam generator nozzles appears to be fatigue f ailure assisted by corrosion. The cause of the discontinuities in the lA feedwater line welds is still under investigation.

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