ML20235M365

Deficiency Rept 87-09 Re Linear Indication on Reactor Vessel Weld.Initially Reported on 870301. Boat Sample Removed by Westinghouse for Vertical Linear Indication.No Addl Repts Anticipated

ML20235M365
Person / Time
Site:	Beaver Valley
Issue date:	07/01/1987
From:	Carey J DUQUESNE LIGHT CO.
To:	Russell W NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
2NRC-7-169, 87-09, 87-9, NUDOCS 8707170168
Download: ML20235M365 (4)

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M 2NRC-7-169 Beaver Vall o. 2 Unit Project Organization Telecopy 1 E Ext.160 P.O. Box 328 July 1, 1987 Shippingport, PA 15077 United States Nuclear Regulatory Commission  ;

I Region I 631 Park Avenue f King of Prussia, PA 19406 ATTENTION: Mr. William T. Russell Administrator l

SUBJECT:

Beaver Valley Power Station - Unit No. 2 ,

Docket No. 50-412 l Linear Indication Identified on Reactor Vessel Weld During PSI Examination Potential Significant Deficiency Report 87-09, Final Report l

Gentlemen: l l

This Potentially Reportable Significant Deficiency Report is being submitted pursuant to the requirements of 10CFR50.55(e). It is anticipated t h at no additional reports will be required.

DUQUESNE LIGHT COMPANY By b ao

'J. J. Carey u Vice President DLC/ijr NRC/DLC/SDR/8709 Attachment AR/NAR cc: Mr. P. Tam, Project Manager (w/a)

Mr. J. M. Taylor, Director (3) (w/a)

Mr. J. Beall, Sr. Resident Inspector (w/a) l Mr. L. Prividy, NRC Resident Inspector (w/a) ^

INP0 Records Center (w/a)

NRC Document Control Desk (w/a) j l

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ATTACHMENT l

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1. Summary l During the performance of the Preservice Inspection (PSI) remote ultra-sonic test (UT) of the Reactor Vessel, an indication was found on the .

outside diameter (0D) on the longitudinal weld (weld #6) located above the J '

loop 1 inlet nozzle. Subsequent surface examination from the OD using '

magnetic particle testing (MT) confirmed the indication.

2. Immediate Action Taken An Inservice Inspection Department (ISID) Deficiency Report and a Noncon- {

formance and Dispositon Report (N&D) were written.

Mr. L. M. Rabenau, Lead Compliance Engineer, Beaver Valley Power Station i

Unit No. 2, notified Mr. D. Limrot h , NRC Region I, of this concern on j

l April 1, 1987. An In*.erim Report, 2NRC-7-103, was issued on May 1,1987.

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3. Description of Deficiency The PSI examination of the Reactor Vessel identified an approximately 2 inch vertical linear indication on the 0. D. of the vessel at Weld #6, which is located above the loop 1 inlet nozzle. Additionally, three (3) 3/8 inch curvilinears and four (4) curvilinears of various lengths were also identified as a result of the MT.

4. Analysis of Safety Implication The results of the UT appear to exceed ASME XI acceptance criteria, IWB Category B-A 1980 - Winter 1980.

5. Corrective /ction To Resolve the Deficiency, ,

i A " Boat" sample, approximately 4" long by 1" wide and .75 inches deep, was I removed by Westinghouse NSTD for the vertical linear indication. This area and the areas containing the curvilinear indications have been blend-ed to meet the acceptance criteria of ASME XI, IWB Category B-A 1980 -

Winter 1980. Ultrasonic and magnetic particle examinations confirmed removal of the indication.

The metallurgical evaluations conducted at the Westinghouse research j f acilities were centered around the boat sample containing the axial UT  !

indication, as well as several surf ace replicas taken from the shallow-curvilinear indications (with the surface prepared in the polished and etched condition). The evaluations on the boat sample included surf ace examinations by low power light optical microscopy, metallographic and fractographic examinations by light optical and scanning electron  :

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microscopy and chemistry evaluations by energy dispersive X-ray analysis techniques. The evaluation of the shallow curvilinear indications was restricted to the vanning electron microscopy examination of the surface j

' replicas from the indications, which were prepared by gold sputtering under vacuum for enhanced imaging characteristics.

The results of the surf ace examination of the boat sample suggested the presence of an approximately 1.85 inch long crack on the boat surf ace. No evidence of a crack could be confirmed on the cut faces of the boat. The examinations indicated no evidence of corrosive attack or deposits on the i boat surface. The results of the metallographic examinations conducted ,

I l (on the boat surf ace as well as on a series containing transverse sections to the crack) in the "as-polished" and " polished and etched" conditions J confirmed that the cracking consistently followed the weld heat affected zone of the top weld pass. The crack measured only 0.05 inches at its deepest location, corresponding to approximately the mid-section along the crack length. The metallography results also confirmed that the crack ,

I followed prior austenite grain boundarios. The crack faces were covered with a thick layer of oxide. The crack tips were rather rounded and Evidence of inadequately tempered martinsite was found near the blunt.

top surface of the boat. A secondary crack initiated at approximately one {

third way down from the top end of the crack was seen arrested approaching j the coarse grained region of the weld heat affected zone. j i

The results of the fractographic examination conducted on the freshly I opened cracks showed that the fracture faces are covered with thick oxide deposits. Light optical color fractography revealed that the oxide i appearance corresponded to a dark grey color suggesting that the cracking may have occurred at temperatures appreciably higher than 1000*F. The thickness of the oxide layer and its color in fact suggested that the cracking may have occurred during the fabrication process. Fractographic examinations of the "as-opened" fracture faces by scanning electron micro-scopy showed that the oxide morphology resembled that ' of iron oxide.

Chemistry evaluation of the crack deposits by energy dispersive X-ray analysis failed to confirm any evidence of detrimental element s. The oxide primarily consisted of iron. Fractographic examination of the "endoxed" (oxide cleaned) fracture faces revealed surface attack and pit-ting morphology characteristic of high temperature surface oxidation.

Scanning electron microscopy examinations conducted on the gold sputtered surface replicas taken from the surface polished curvilinear indications l l

on the vessel OD surface corresponded to surface cracking associated with {

i weld repair process in most cases. Evidence of dissimilar weld micro- i structures on either side of the cracks was seen. l l 3 The results of the metallurgical evaluation on the boat sample showed that the recorded UT indication is associated with a crack measuring approxi-mately 1.85 inches long and 0.05 inches deep at its deepest location. The i crack is located in the seam weld and is contained in the weld heat affected zone of the top weld pass. The results showed that the cracking '

was most likey induced at temperatures in excess of 1000*F.

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Evaluation of the surface replicas from the curvilinear indications k suggested that the indications are associated with surface cracking i induced most likely during a weld repair process in the region. MT exami-  !

nations of these indications during subsequent ~ blending showed that these  !

curvilinear indications were very shallow.

In summary, the boat sample has been extracted and proved' of no impact on BV-2. No other unacceptable indications have been observed and the R/V is available to be in operation.

6. Additional Reports No additional reports are expected, i

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