ML19259B325

Interim Deficiency Rept 78-03 Re Cracking of Wall Liner Plate Adjacent to Continuous Fillet Weld.Final Rept Will Be Forwarded on 790322

ML19259B325
Person / Time
Site:	Beaver Valley
Issue date:	01/19/1979
From:	DUQUESNE LIGHT CO.
To:
Shared Package
ML19259B324	List: ML19259B322 ML19259B325
References
NUDOCS 7901260169
Download: ML19259B325 (4)

Text

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INTERIM REPORT ON REACTOR CONTAINMENT LINER OVERLAY PAD FILLET WELD AT BEAVER VAT.TM POWER STATION - UNIT NO. 2 1.0

SUMMARY

A required visual examination of the reactor containment liner plate and associated equipment, following a sandblast operation required for prime paint substrate, revealed a crack along the toe of a bottom horizontal fillet weld which attaches an overlay pad to the reactor containment liner plate.- The overlay pad is located at elevation 719 '--4 " ,

fourteen feet west of the north containment centerline.. See the attached sketch for a typical overlay pad configuration.

The crack was approximately 18-0" in length at the toe of the weld adjacent to tie liner plate.

As a result of gra.nding necessary for repair, the-crack depth was found to be greater than half the thickness of the liner material.

2.0 IMMEDIATE ACTION TAKEN Upon discovery that the crack continued beyond the contractor's m wimum allowed excavation depth, further grinding was stopped and detailed evaluation commenced.

Currently there is no overlay pad installation in progress.

No additional overlay pads will be installed until this problem is resolved.

Since. this problem was construed to be a possible reportable significant deficiency pursuant to 10CFR50.55 (e) (1) , the U.S.

Nuclear Regulatory Commission (NRC) was notified orally on December 22, 1978. '

3.0 DEFICIENCY 3.1 Description The overlay pad was fit up on Dscember 15, 1977, tacked in place on December 19, 1977, and final welded on December 21, 1977. Visual and magnetic particle examinations were performed on January 16, 1978 and February 15, 1978, respectively, with acceptable results. The candblast operation and resultant visual observation of the crack was performed on October 23, 1978.

The Contractor's general procedures allow for repair of base metal linear defects which do not exceed 1/2 t 1.

79012sotVI

(t is base metal thickness) in depth or 1/2 t in width.

Linear defects which exceed the above require the Contractor's Project Engineer to be notified.

Based on this information, Nonconformance and Disposition -(NSD) Report No. 9167 was issued by the site personnel. ~The Engineers reviewed the problems and dispositioned NSD No. 9167. Further grinding invoked by NSD No. 9167 showed the crack to approximate a through-liner crack, thus a potential breach of the containment vapor tight boundary.

3.2 Analysis of Problem The crack has been observed in the toe of the fillet weld at the parent liner base material. 'Ihe cause of the crack is presently under investigation. The investigation will involve an historical review of documentation, metallurgical evaluation of a sample, nondestructive examination of similar welds, and r.evisw' .

of events during construction which .might have contributed to the cause of the crack.

Historical Review of documentation will result in the review of the following items as a minimum:

a. Material mill certifications for:

1) Liner plate

2) Overlay plate

3) Weld electrode

b. Weld rod storage oven records

c. Weld rod issuance records

d. Welding procedure specifications

e. Environmental records

f. Nondestructive examination procedures and records

g. Fabrication checklists

h. Construction activities The metallurgical evaluation will be performed on a sample removed from the cracked weld and will include

'some or all of the following, should the need be identified as the investigation progresses:

2.

a. Nondestructive examination; i.e., magnetic particle

b. Hardness surveys of weld and base metals

c. Chemical analysis of weld and base metals

d. Macro-etch and examination of weld and base metals

e. Meta 11ographic examination of weld and base metals

f. Electron microscopy of cracked surface

g. Mechanical tests of weld and base metals Fillet welds at all similar 1'-0" square overlay plates will be reexamined by visual and magnetic; particle methods.

An independent consultant, Dr. C.M. Adams, Jr., has been engaged to review the problem. Dr. Adams's report will be included with the final report. ,

The stresses resulting from thermal excursions and construction events (e.g., concrete placement loading and wind brace effects) will be evaluated.

4.0 ANALYSES OF SAFETY IMPLICATION A through thickness crack constitutes a breach of the primary containment. Under postulated accident conditions, it is possible that containment leak rate cx>uld exceed the design basis causing radiation exposure to off-site individuals to exceed the limits set forth in 10CFR100.

5.0 CORRECI'IVE ACTION TO REMEDY DEFICIENCY Corrective action wi13 be determined and will be reported in the final report.

6.0 FINAL REPORT . -

A final report on this matter will be forwarded to the NRC on March 22, 1979.

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