ML19331C660

Interim Deficiency Rept Re Linear Indications in Gib Gusset Welds in Reactor Vessel Structural Support(Neutron Shield Tank).Metallographic Analysis of Weld Samples & Addl Insps Being Conducted.Next Rept Will Be Issued on 801101

ML19331C660
Person / Time
Site:	Beaver Valley
Issue date:	08/14/1980
From:	Woolever E DUQUESNE LIGHT CO.
To:
References
NUDOCS 8008190285
Download: ML19331C660 (4)

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(412) 456-6000 435 E'ath Avenue Pittsbu nh. Pennsylvania 15219 August 14, 1980 United States Nuclear Regulatory Commission Region I 631 Park Avenue King of Prussia, PA 19406 ATTENTION: MR. BOYCE H. GRIER, DIRECTOR

SUBJECT:

Beaver Valley Power Station - Unit No. 2 Docket No. 50-412 Linear Indications in Gib Gusset Welds in Reactor Vessel Structural Support (Neutron Shield Tank)

Significant Deficiency 80-03 Gentlemen:

Enclosed is the " Interim Report on Linear Indications in Gib Gusset Welds in Reactor Vessel Structural Support (Neutron Shield Tank) at Beaver Valley Power Station - Unit No. 2". We plan to issue another interim report on November 1, 1980.

DUQUESNE LIGHT COMPANY u

By 8'. J. Woolever VICE PRESIDENT Enclosure cc: Dr. V. Stello (15) 8 0 0819 0 2 T6 O

Interim Report Qn, Linear Indications In Gib Gusset Welds in Reactor Vessel Structural Support (Neutron Shield Tank)

O Beaver Valley Power Station - Unit No. 2 1.0 Summary A linear indication was found by magnetic particle (MP) examination of r.

weld connecting a gib gusset to the reactor vessel support structure top plate. The indication was partially excavated and the defect found to be extensive in that weld. Additional linear indications were found through MP examination of other similar welds.

2.0 Immediate Action Taken Approximately 15 in. of the initial indication, which extended the entire length of the gib gusset weld, was partially excavated to clear the indication leaving approximately 6 in. of weld defect af ter excavation.

Approximately 6 in were left unexcavated. The results of this grinding effort were evaluated and notification of the potentially reportable deficiency was made to NRC Region 1 on July 1.7, 1980, under the provisions of 10CFR50.55(e).

i 3.0 Description of Deficiency In the process of performing magnetic particle (MP examination of the reactor vessel structural support (RVSS) top plate, subsequent to removal of two (2) temporary lif ting lugs, a linear indication was found to exist on a nearby gib gusset weld. Fut ther MP examination of the gib gusset weld, after paint removal, revealed that the indication extended the entire

length of the weld attaching the inner gib gusset to the top surface of the RVSS. Additional MP inspection was performed at the remaining eleven (11) inner gib gusset locations. The additional inspection revealed one additional gib gusset weld where a linear indication extended the entire length (approximately 21 in.). Of the remaining ten (10) inner gussets, two welds contained no indications and eight welds contained intermittent indications, ranging in length from fractions of an inch to several inches. Finally, magnetic particle examination on twelve (12) outer gusset welds resulted in all the gusset welds exhibiting intermittent indications of various lengths.

The initial linear indication appeared to be confined to the base metal heat affected zone of the 7 in. thick top plate beneath the weld joining the

, 21/2 in. thick gib gusset to the top surface of the top plate. Excavation to a depth of ap; roximately 1 in, as measured along the heat affected zone cleared all excyt a 6 in. length of the indicat. ion. Since it was difficult to establish the cause of the weld defect, based on grinding and subsequent surface examination, a sample of the defective weld will be removed for metallurgical evaluation to characterize the defect.

4.0 Analysis of Safety Implications Analysis of safety implications will be provided in the final report.

5.0 Corrective Action to Remedy Deficiency Pending the outcome of the metallographic analysis of the weld sample, additional inspections of the gib gussets will be performed to determine the extent of weld repair required.

All linear indications will be removed and all weld excavations will be rewelded and magnetic particle inspection in accordance with the original specification requirements. Repairs will not be started until metal-lographic examination is completed.

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6.0 Additional Reports An interim ' report will be issued on November 1, 1980. The date for submittal of the final report will be indicated at that time.

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