ML19345C014

Final Deficiency Rept Re Use of Improper Preheat of Heavy Structural Members Prior to Welding,Initially Reported on 800418.Physical Test Program Has Been Conducted.Welds Are Acceptable as Is

ML19345C014
Person / Time
Site:	Callaway
Issue date:	11/28/1980
From:	Bryan J UNION ELECTRIC CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
10CFR-050.55E, 10CFR-50.55E, ULNRC-400, ULNRC-400.55E, NUDOCS 8012030726
Download: ML19345C014 (8)

Text

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UNION El ECTRIC' COMPANY seos onArsor armeer ST. Louis.- MissoU RI November 28, 1980 , , , , , , , , , , , , ,

-. JOHN M. IIRYAN P. O. R O u .4.

. . . . . .v. 6avi.. w..ouR. .....

Mr. James G. Keppler U. S. Nuclear Regulatory Commission Region III 799 Roosevelt Road Glen Ellyn, IL 60137 ULNRC- 400

Dear Mr. Keppler:

FINAL 10CFR50.55(e) REPORT IMPROPER PREHEAT OF HEAVY STRUCTURAL MEMBERS PRIOR TO WELDING CALLAWAY PLANT UNIT 1 On April 18,'1980 we-provided the NRC Resident Inspector-at Callaway verbal notification of a potential 10CFR50.55(e) report regarding use of improper preheat when welding pipe supports to heavy structural. steel. members. The above notification was made after discrepancies-in weld control records were identified by the Resident Inspector. The discrepancies identified by the Resident Inspector are covered by NRC Inspection Report No.

50-483/80-12. Further investigation indicated that these same discrepancies existed for some welds on HVAC ductwork supports and on some -Upairs to structural steel.

Our final report, which shows that the welds in question are acceptable as is, is enclosed.

Since evaluation of this deficiency included a physical test program on sample welds of representative material trickness an-earlier submittal of this final report was not. practicable.

Very truly yours,

-J W N'f h

_ J n K. Bryan ,

RPW/sla Enclosure cc: H. M. Wescott, Region III w/ enc. ON B. H. Grier,' Region I w/ enc.

g Victor Stello, Jr., Director I&E w/ enc./

W. A. Hansen, NRC Resident Inspection w/ enc.

Mo. Public Service Commission, W. enc. //

80120307h .s I

10CFR50.55(e) FINAL REPORT IMPROPER PREHEAT OF HEAVY STRUCTURAL MEMBERS PRIOR TO WELDING CALLAWAY PLANT UNIT 1 INTRODUCTION This final report, submitted in accordance with 10CFR50.55(e),

describes the disposition of welds made on heavy (1 " thickness and greater) carbon steel structural members without preheat treatment. prescribed by the AWS and ASME' Codes. This deficiency

-was initially reported on April 18, 1980 after discrepancies in weld control records-were identified by the NRC Resident Inspector and is covered in NRC Inspection Report No. 50-483/80-12, and UnionLElectric. response ULNRC-358, dated June 6, 1980.

DESCRIPTION OF DEFICIENCY The' applicable AWS and ASME Codes require preheating of material 1 " thick and greater to 1500F or higher. Review of all Weld Control Records for welding on heavy members indicated that proper preheat temperatures had not been designated and used for welds on some pipe hangers, HVAC duct hangers and structural steel repairs. Table 1 provides a summary of the welds involved.

ANALYSIS OF SAFETY IMPLICATIONS Carbon st- snd to harden when they aire heated to a high temperature an. .en rapidly cooled. The extent of hardening and the hardness achieved is dependent on the composition of the steel, particularly its carbon content. When these steels are welded, the area adjacent to the weld, called the heat-affected-zone

-(HAZ), undergoes a heating and rapid cooling cycle for each weld pass that is made. However, hardening in this area is of secondary concern. The primary concern is the possibility of embrittlement which can result from the hardening. The embrittlement, in combin-ation with other adverse conditions, such as restraint due to geometrical conditions surrounding the weld, thickness, and the presence of hydrogen, can give rise to a type of cracking called.

"underbead cracking".

Such cracking could possibly propagate and result'in failure of members'or supports with potential safety implications.

Hardening in the heat-affected-zone, and its associated embrittlement, can be reduced by slowing down the cooling rate from the high temperature'Inr applying a preheat to the weld. area.

One of the principal' reasons for preheating the weld area during.

welding operations is to effectively ~ slow down the cooling rate

-from the high temperature of the weld, thereby reducing the hardening in the heat-affected-zone, andLits associated embrittlement.-

. - - ~ . . -

The amount of preheat required depends primarily on the composition of the steel, its thickness, the amount of restraint, and type of welding material. For plain, low-carbon steels, the need for preheat is minimal, unless there is a high level of restraint in the weld area. Steels with a carbon content of less than 0.3%,

such as ASTM A-36 used for the. members in question, fall into this category. Application of preheat for ASTM A-36 steel is standard practice for thicknesses in excess of about 1 inch, without regard to joint design or_ restraint conditions, or even welding material type. The use of preheat is a conservative measure which is not absolutely necessary to control underbead cracking for the applica-tions in question, i.e., fillet welding of unrestrained attachments using low-hydrogen welding electrodes. To support the above conclusion that preheating was not necessary to control underbead cracking for the welds in question, a test program was conducted by Bechtel Power' Corporation on sample welds of representative material thickness which were not preheated.

The' test program consisted of field welding three attach-ments to a 3-inch thick carbon steel plate in accordance with the Preheat Test Procedure and Preheat Test Coupon shown on Figures 1 and 2. The attachments and the weld sizes were selected to be-representative of types of attachments and sizes of the actual welds involved in the reported nonconformances. The carbon content of the 3-inch thick plate equaled .25%, the highest carbon content available, and representative of the upper limit for structural steel. The 3-inch thick plate was selected to maximize the quench effect by acting as a large heat sink. Both of these parameters were selected to-increase the potential of underbead cracking in the test samples. Overhead welding was specified to minimize heat input. The test was conducted at the Callaway site on July 21, 1980.

l No indications of underbead cracking were noted on the unprepared

cut sections.

The unprepared cut sections were shipped to the Bechtel Power Corporation Gaithersburg office and from there were sent to Artech Corporation, Falls Church, Virginia for grinding, etching,

- and photographing. _ The ground and etched cross sections of all the welds were examined visually for the presence of cracks in the entire weld areas. No cracking, or any other form of defect, was found which could be attributed to lack of preheat. Photomicro-

_graph s of the test welds sections are on file with the complete Bechtel Power Corporation Report.

Although a preheat of 150 F to 200 F minimum would normally be' applied during the fillet welding of attachments to lh" and thicker carbon steel material,fthe tests performed have indicated.

that the absence of such. preheat has not caused detrimental effects

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to the weldments or to the. base metal. This can be attributed to the low carbon content of the base material, the lack of restraint at-the joints and to.the use of low hydrogen welding electrodes.

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CORRECTIVE ACTION TAKEN Corrective Action Report No. 2-G-0006 was issued by Daniel International to implement review of all welds to heavy structural members and to prevent recurrence of improper designa-tion of preheat requirements on Wold Control Records. Noncon-formance Reports were issued for welds made with improper preheat as summarized in Table 1. Based on the results of the Bechtel Power Corporation Test program all Nonconformance Reports, except the one covering pipe hanger welds within the jurisdictional boundary of ASME Section III, will be dispositioned "USE AS IS".

Because of administrative requirements involved with the hanger welds within the jurisdictional boundary of ASME Section III, the Nonconformance Report covering these welds will be dispositioned

" REPAIR" as an expediency to construction.

RPW t

11/?:/80 l

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TABT.E 1 - Surnmary of NCRs NCR No. Description Cat. Bechtel Spec. Material i Required Actual NCR Govern. Code Thickness Preheat Preheat Disposition 2SN HVAC Duct Hangers M-618.2 4 1\" 500F USE AS IS 1893 R-1216 (Aux.) Q AWS Op 1h" 1500F None DIC to C R-3091 (Control) D1.1-75 )P 25" 225 F revise weld, procedures 2SN Non-Q Pipe M-205 USE 1918 s Hangers attached Q ANSI  ?> ik" 1750F . 600F AS

. P to Q Steel B31.1 IS (22) ,

~2SN Q Pipe Hangers M-204 1919 (21) Q ASME )>1%" 2000F 60 F REPAIR P Sec t . - III 2SN Q Steel Repairs C-121 Varies 1500F 60 F USE 2010 Aux. Bldg. Columns , Q C-122 See 2250F 150/600F AS

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C (13 cases) AWS NCR IS i

D1.1-75

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Table 1, continued NCR No., Description Cat. Iechtal S Pec. Material Required Actual NCR

> Covern. Code Thickness Preheat Preheat Disposition 2NN II/I Pipe llanger Non M-205 USE 1223 (1) Q ANSI > 1\" 175 F 60 F AS P B31.1 IS

[

2NN HVAC Duct llangers M-635.2 /1" 50 F USE AS IS 1193 H-4001 Non AWS 71" 150*F

• None DIC Weld f

M H-4027 Q D1.1-75 7 '25" 225 F procedures (Turbine Bldg.) to be revised.

. 2NN llVAC Dact llangers M-635.2 4 li" 500F USE AS IS t

1194 R-3218 Non -

> 1\" 150 F None DIC weld M R-3298 Q AWS 7 2)" 2250F procedures (Control Bldg.) D1.1-75 to be revised

.T 2NN Non-Q' Steel C-121 Varies Varies Varies USE 1314 Repairs Non C-122 See See See AS C . Turbine Bldg. Cols. Q AWS NCR NCR NCR IS i

(18 cases) D1.1-75

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PROCEDURE FOR PREHEAT TEST i

The following details shall be followed for the preparation of a simulated test plate to assess the effects of insufficient preheat.

1. The tes t plate (ASD'. A516, Gr. 70, 4' x l' x. 3") shall be cleaned on one side of all scale, loose rust, Erease, etc.

2 The th: ee attachment pieces shall be located approximately as shown in the sketch, and tack-weAded in place. .

3. The attachments shall be welded to the test plate with fillet velds of the size shown, using a preheat trzperature of 707 naxin.nn, and an interpass temperature of 100F maxiz:um for each separate attachment.

4 The welding electrode used shall be E7018.

l 5. All" welding shall be performed in the overhead position.

6. The welding procedure used shall be the one nor= ally used by DIC for making similar production welds (understood to be N-1-1).

7. A Bechtel welding engineer shall witness the welding activities.

8. On completion of the welding the test plate shall be sawcut at the locations shown on the sketch, and one side of each cut chall be prepared for macroexamination of the exposed weld cactions. Further sawing for ease of handling shall be perfor=ed if deemed necessary.

9. The exposed welds shcIl be etched and examined for the presence of underbead cracking by Bechtel.

10. At the direction of the Bechtel enginee'r, photographs of the welded assembly before, during and after co=pletion of welding shall be taken. Photomacrographs of the etched specimens shall also be taken. ,

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