ML20071J320

Final Deficiency Rept Re Welding Cracks in Reactor Protection Plates (D/N 25).Defects Found in Weld Metal Completely Removed.Defects Found in Base Plate Removed by Excavating Into Plate

ML20071J320
Person / Time
Site:	Satsop
Issue date:	04/16/1982
From:	Leddick R WASHINGTON PUBLIC POWER SUPPLY SYSTEM, WISCONSIN POWER & LIGHT CO.
To:	Bishop T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
10CFR-050.55E, 10CFR-50.55E, G3-82-391, GO3-82-391, NUDOCS 8204270220
Download: ML20071J320 (7)

Text

Docket.Nos. 50-508/509

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50 55(e) Report Washington Public Power Supply System g Box 1223 Elma, Washington 98541 (206)482-4428 '-'

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Docket Numbers 50-508 and 50-509 @ ._. y April 16, 1982 k 1 G03-82-391 p g C co g' U. S. Nuclear Regulatory Commission, Region V e ,

Office of Inspection and Enforcement s Q 1450 Maria Lane, Suite 260 -

Walnut Creek, California 94596-5368 9

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~ M Attention: Mr. T. W. Bishop E ' O EN ---

Chief, Reactor Construction Projects Branc d "$E.5]l[fy $ y 3 /)

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Subject:

PROJECT N05. 3 AND 5 10CFR50.55(e) REPORTABLE CONDITION

% g , f , .,i \ J' WELDING DEFICIENCIES IN RP PLATES (D/N #25)

In accordance with the provisions of 10CFRSO.55(e), Region V was noti-fied that the subject condition was potentially reportable. Subsequent investigation has determined that the deficiency is significant and were it to have remained uncorrected could have adversely affected the safety of operations of the facility.

Attached is the Supply System approved final report for the subject con-dition detailing a description of the deficiency, safety analysis and corrective / preventive actions taken.

Should you have any questions or desire further informatian, please con-tact me directly. ,

c' R. S. Leddick, 760 Program Director, WNP-3 DRC/tt Attachment cc: J. Adams - NESCO D. Smithpeter - BPA Ebasco - New York WNP-3/5 Files - Richland 7677J

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ATTACHMENT 1 WASHINGTON PUBLIC POWER SUPPLY SYSTEM DOCKET NUMBERS 50-508 AND 50-509 FINAL 10CFR50.55(e) REPORT WELDING DEFICIENCIES IN RP PLATES (D/N #25)

INTRODUCTION Fought Steel, Portland, Oregon,'-fabricated the type RP enbed plates under Contract 3240-95 for WNP-3/5. The embed plates are designed for installation in concrete on the interior and exterior shear walls of the Reactor Auxiliary Buildings (RAB) to support the pipe rupture restraints and seismic interface restraints for main steam and feedwater piping.

RP is a designation given to identify these embed plates for the main steam and feedwater piping and is subdivided into a number of RP types. These embed plates are fabr.icated from ASTM A-36 steel to Quality Class I and the thickness of the plates varies from 1 inches to 3 inches. Most of the RP pl,ates have shear lugs welde8 on the back. In addition to these shear' lugs, some of the RP plates have shear bars welded on the face of the pla,tes . The thickness of these shear bars and shear lugs also varies from 1 inch to 3 inches.

Cracks were found in the welds placed at the corner joints where transverse and longitudinal shear lugs meet. These cracks were discovered during the course of the fabrication of the embed plates. The design does not require these two plates to be we'.ded together, but Fought Steel welded across the corner with a thin pass seld.

During the course of the Engineer $ng investigation of the cracks identified above, it was also found that the fabrication of these plates did not provide full penetration welds nor was post veld heat treatment performed as required by the design drawings and contract specifications. Failure to meet these requirements constitutes a significant breakdown in the Quality Assurance Program.

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DESCRIPTION OF DEFICIENCY The deficiencies can be categorized as follows:

Weld Crack: Welds were applied across the ends of the shear lugs and in corners formed at the intersection of the shear lugs. These welds were not shown on design drawings and cracks were found in these welds.

Partial Penetration Welds Instead of Full Penetration Welds: Shear lugs and bars were welded to the plate by partial penetration groove welds whereas design drawings required full penetration welds.

Lack of Post Weld Heat Treatment: The Project Specification required a post weld heat treatment of welds thicker than 1 1/2 inches; however this was not performed.

Breakdown in Quality Assurance Program: Failure to detect the material and fabrication deficiencies described above represents a breakdown in the Quality Assurance Program. This is evidenced by the following:

1. Vendor failure to adequately implement special process controls;

2. Vendor and Engineer failure to perform work in accordance with in-structions, procedures or drawings;

3. Vendor fa'ilure to perform inspections to verify conformance to draw-ings.

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SAFETY ANALYSIS The type RP plates are provided to attach pipe rupture and seismic interface restraints for main steam and feedwater piping to building structure and are installed in the Reactor Auxiliary Building exterior and interior shear walls and on the roof. Rupture restraints are provided to support this piping during postulated pipe break.

All the questionable RP plates are on the outside face of the exterior shear wall. The piping restraints and embeds in this area will be exposed to the outside atmosphere.

Six RP-18 plates are provided to support the rupture restraints, three each on the north and south exterior shear walls. These restraints are located on the outside of exterior sh~ar e wall, immediately after the main steam and feedwater pipes exit the Reactor Auxiliary Building.

the Administrative Building on the north side, transformer and

, refueling tank area on the south side, and the RAB exterior walls could be exposed to the resulting jet i=pingement and impact loads due to the pipe rupture if the plates fail and allow the support to fail.

Damage to these structures could result with attendant danger to plant personnel and equipment.

Because of the deficiencies previously identified, the structural integrity of the RP plates could not be assured during the postulated pipe breaks without implementing the corrective actions which were taken. Hence, the above deficiency is considered significant and reportable per 10CFR50.55(e).

CORRECTIVE ACTIONS Weld Cracks All plates were reinspected by Magnetic Particle testing method except those plates which were already installed. Based on the inspection results, corrective actions were taken as follows:

1) Where no defects were found, the filler veld metal at corner joints was removed back 1/4" to 3/4" from the corners until faying surfaces between intersecting lugs were visible down to the surface of the base plates.

2) When defects were found, the repairs were made as follows:

a) When the defects were found entirely in the weld metal, the indications were co=pletely removed. Weld metal at the corner was re=oved to the surface of the base metal. The reworked areas were reinspected using MT or PT techniques.

b) When the defects were found to extend into the base plate, the defects were removed by excavating into the base plate.

Defect removal was confirned by PT or HT. The plate was repaired and the thickness of the plate was restored to its original thickness. The repaired area was UT examined to ascertain the soundness.

3) The four RP-29 plates which were installed in the concrete were UT examined. No cracks were found in these plates.

Weld cracks were found only in Types RP-33 and RP-28. Two RP-33 and eight RP-28 plates were involved.

Fought Steel used cold bending procedures to remove a slight warpage in the plates after veldup. Cold bending is a standard mill practice employed-by steel mills to straighten rolled plates to comply with the shape and dimensional tolerances. Fabricators also use the same techniques. ASME Section NC and NF also allow cold bending in the case of steel plates.

i Partial Penetration Welds The plates which had partial penetration velds instead of full penetration welds were UT examined. On the basis of the UT results the plates were reanalyzed for the individual support design loads. All but Type RP-18 were found to be acceptable. Type RP-18 plates were redesigned to acco=modate the load transfer to the supporting wall. A Design Change Notice was issued to rework the plates. The required rework has been completed.

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CORRECTIVE ACTIONS (C0hT'D)

Lack of Post Weld Heat Treatment A comparative study was made of two Type RP plateI samples (RP-16 and RP-38) as welded without post veld heat treatment and new welded sections with post weld heat treatment. The results and analysis are discussed in the following paragraphs:

Fabrication Conditions -

The embedments of concern were fabricated by Fought, employing the flux cored are welding process and a weld energy input of 72 kilojoules/ inch.

Preheats are reported to have ranged from 175 F-250 F for sections up to 2b" thick and 275 F-325 F for thickness over 2 ", the preheat maintained until completion of welding. The preheats used by Fought were in excess of those required by AWS Dl.1, which are, 150 F for up to 2h" thickness, 225 F for greater than 2 ". The weld energy input used by Fought to fabricate the embeds, combined with the preheat and interpass temperatures used, b developed a more favorable, slower cooling rate and a sof ter veld zone.

Hardness Testing Sections from weldments produced by Fought were obtained from embedment RP16 (2" thick) and embedment RP38 (3" thick). Both are identical to the embedments of concern and were welded according to the same procedures. The carbon equivalent of both the RPl6 and RP38 esbedments steel material was found to be .47%.

The test cross-sections, supplied in the saw-cut condition, were prepared for as-welded hardness measurement by polishing and etching.

( Knoop hardness surveys were made at two locations in the weld, one at the toe, where higher hardnesses were expected because this region was not tempered by a subsequent weld bead, and in the throat approximately halfway through the weld. All Knoop readings were converted to Rockwell.

The maximum hardness values obtained in the weld zone of the 2" embed-ment (RP16) was 24 HRC for the weld toe; maximum hardness of the 3" embedment (RP38) weld toe was found to be 25 RRC. All other hardnesses in the RP16 and RP38 embedments were in the 90-95 HRB eange.

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CORRECTIVE ACTIONS (CONT'D)

Lack of Post Weld Heat Treatment (Cont'd)

Post Weld Heat Treatment And Metallographic Evaluation Tb2 Fought embedments test material weld zone maximum hardness of ? ' and 7.5 HRC, was found to be .in excess of the industry-accepted upper is el which is considered suitable for installation without post weld heat treatment.

Recent concerns for notch toughness of pipe rupture restraint materials by the industry prompted furnace treatment testing so as to dispel concerns over the 25 HRC hardness and its notch toughness. Accordingly, a section of Fought embedment, sa=ple RP38, was furnace heat treated for 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> at 1150 F. A hardness traverse, si=ilar to that conducted on the as-welded RP38 test sample, was performed on the heat treated material. Maximum hardness of the material was found to have decreased from 24 HRC to 93 HRB.

The apparent need for an explanation regarding the suitability of material at no=inal 25 HRC for service prompted a microstructural evaluation. The 25 HRC hardness of the as-welded material suggested that a minimal a=ount of martensite, a brittle constituent causing the weld zone hardness, may be present in the hard zone, on the order of 5%. Microscopy was conducted to provide credence for the 5% martensite estimate; this level known to have negligible effect of ductility.

Examination of the structures at 1000X and lesser magnifications did not reveal any martensite. A minor amount of material, considered to be martensite at 300X magnification, was found to be a fine dense pearlite upon examination at higher magnification.

Summary This evaluation has established that embedments composed of carbon steel materials and containing a moderate level of constituents affecting hardenability do not, when fabricated according to suitable conditions, experience significant hardening in the weld zone. This was confirmed by the relatively low hardness values obtained, 25 HRC maximum in the weld zones of duplicates of the welded embedment co=ponents.

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CORRECTIVE ACTIONS (CONT'D) 4 Lack of Post Weld Heat Treatment (Cont'd)

Summary (Cont'd)

The results, as supported by the as-welded hardness values, also confirmed that the use of a relatively high heat input, in combi-nation with the preheat /interpass temperature ranges applied, re-sulted in a cooling rate sufficiently slow to inhibit the forma-tion of an undesirable transformation structure in the weld heat-affected zone. The reduction in hardness determined for the post weld heat treated material was found to have resulted from soften-ing of dense early transformation products in the weld zone. This material is known to be more ductile in the as-welded condition than is the undesirable and more brittle structure, martensite, and does not require thermal treatment for achieving adequate ser-vice performance. The possibility for presence of the martensite phase in the weld zone, owing to the lack of weld process selection controls on fabricators, mandated the inclusion of a post weld heat treatment requirement in the component specification.

Based on the above analysis all plates covered by this report have been accepted without post weld heat treatment.

Breakdown in Quality Assurance Program The contract for the supply of these components is being closed out.

With no components being supplied in the future, no corrective action has been imposed on Fought. The supplier has been informed of these deficiencies.

The responsible Ebasco VQAR assigned to the Vendor's facility was re-moved from the WNP-3/5 Project activities. On site training sessions l have been held for the Vendor Quality Assurance Representatives (VQARs).

The training consisted of visual welding inspection requirements.

Additionally, vendor inspection plans have been reviewed to assure the .

, inclusion of post weld heat treatment verification, as required. The VQARs have been informed of these requirements.

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