ML19209B561

Forwards Interim Rept on Faulty Welding by Lakeside Bridge & Steel on Drywall Vent Structure & Reactor Pressure Vessel Pedestal.Caused by Unacceptable Work & Copper Containment. Defective Buttering & Pedestal Cracking Will Be Repaired

ML19209B561
Person / Time
Site:	Hartsville, Phipps Bend
Issue date:	10/01/1979
From:	Mills L TENNESSEE VALLEY AUTHORITY
To:
References
NUDOCS 7910100133
Download: ML19209B561 (5)

Text

TENNESSEE VALLEY AUTHORITY CH ATTA NCOG A. TENN ESS EE 37101 400 Chestnut Street Tower II October 1, 1979 Mr. Janes P. O'Reilly, Director Office of Inspection and Enforcement U.S. Nuclear kagulatory Comission Region II - Suite 3100 101 Marietta Strest Atlanta, Georgia 30303

Dear Mr. O'Reilly:

HARTSVILLE AND PHIPPS BEND NUCLEAR PLANTS ALL UNITS - REPORTABLE DEFICIENCY - FAULTY WELDING BY LAKESIDE BRIDGE AND STEEL ON DRYWELL VENT STRUCTURE AND REACTOR PRESSURE VESSEL PEDESTAL (NCR'S HNP-A-038, HNP-A-050, HNP-B-024, PBNP-028)

Initial report of the subject deficiency was made to W. B. Swan, NRC-0IE, Region II, on June 6, 1979. The first interim report of the subject deficiency was submitted on July 5, 1979. In compliance with paragraph 50.55(e) of 10 CFR Part 50, we are enclosing the final report of the subject deficiency. If you have Ly questions regarding this matter, pleasa call Tish Jenkins at FTS 854-2014.

Very truly yours, TENNESSEE VALLEY NJTHORITY L. M. Mills, Manager Nuclear Regulation and Safety Enclosure cc: Mr. Victor Stello, Director (Enclosurs) f Office of Inspection and Enforcement i U.S. Nuclear Regulatory Comission Washington, DC 20555

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HARTSVILLE AND PHIPPS BEND NUCLEAR PLANTS - ALL UNITS FAULTY WELDING BY LAKESIDE BRIDGE AND STEEL ON DRYWELL VENT STRUCTURE AND REACTOR PRESSURE VESSEL PEDESTAL 10CFR50.55(e) REPORT NO. 2 (FINAL)

NCR' S HNP-A-038, HNP-A-050, ENP-B-024, AND PBNP-028 On June 6,1979 TVA notified NRC-0IE Region II, Inspector W. B. Swan, of a potentially reportable 10CFR50.55(e) condition that has 10CFR Part 21 implications regarding a breakdown in the quality control program at Lakeside Bridge and Steel (Lakeside). The breakdown involves the shipment of the drywell vent structure and the reactor pressure vessel (RPV) pedestal by Lakeside with weld metal added to the edges (buttering) which has been found by TVA to contain material contamination causing cracking and enough porosity, lack of fusion, and slag inclusion deemed to be unacceptable per the American Welding Society (AWS), Code Dl.l. An interim report en this deficiency was filed on July 5, 1979. This is the final report en the subject reportable deficiency.

Description of Deficiency Drvwell W nt Structure As a result of the butte. ring problem identified on the reactor pressure vessel shield wall (NCR's HNP-A-037 and ENP-A-043), fabricated by Industrial Engineering Works (IEJ), the TVA construction forces inspected the edges of the drywell vent structure fabricated by Lakeside for similar problems with buttering. The results of a spot check of some of the weld prep edges by radiography revealed that buttering had been performed, and that the buttering contained suf ficient defects to be unacceptable by AWS standards. Subsequently, NCR HNP-A-038 was written to document this nonconfoming condition.

None of the drywell vent structures for the Phipps Bend Nuclear Plant (PBNP) had been shipped from Lakeside; therefore, no NCR was written for PBNP.

Reactor Pressure Vessel Pedestal During field erection of the reactor pressure vessel (RPV) pedescal fabricated by Lakeside, a routine veld inspection revealed cracks in an area outside of the zone of the TVA weld. These cracks have a horizontal orientation and appear to be from 1/8 inch to 3/8 inch below the circumferential veld which joins the ring girder to the shell section. Further visual inspection revealed similar cracks apparent at several other locations on the RPV pedestal. The results of preliminary liquid penetrant examination and acid etching indicate that the cracks developed along a line where the vendor apparently fused weld metal to the top edge of the parent metal (i.e.,

buttered the weld joint) to meet dimensional and/or edge geometry require =ents.

Some of the buttered edges which were radiographed by TVA contain sufficient amounts of porosity, lack of fusion, and slag inclusion to be deemed unacceptable under AWS Code Dl.1.

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All segments of the RPV pedeetal for PBNP unit 1 are onsite and none of

. the. RPV pe.destal_for PDhT unic 2.is cusite.

Cause of the Deficiency Drywell Vent Structure The ccuse of the bettering defs.ciencies is due to unaccepteble work which was not given suf ficinct NDE to result in f ts rejection and subsequent replacement. The existence of the buttering deficiencies can be attributed to a disagreemcnt betvean Lakeside and the technical engineer (GE) over whether the procurement specification classifies buttering as e repair or not, and what NDE is r? quired when buccaring is performed. Both organi-zacions agree that the buttering that was performed contains sufficient defects to be considered unacceptable per Nw'$ Code Dl.l.

Reactor Pressure Vessel Fedeceal Chemical and metallurgical examir.ation of a specimen removed from a cracked area of the RPV pedestal revealed the cause of the cracking to be copper contamination in an area which was buttered to meet dimensional requirements. The origin of the copper 16 due to inadvertonc melting of copper backup bars used in conjunction with the buttering procedure.

Safety Implications Bad the defects in the buttering performed by Lakesida, or the crack in the HTN Al RPV pedsstal tone undetected, the structural integrity of the RPV pedestal and drywell vent structurs could be jeopardized under dynamic leading during an earthquake or LOCA.

Corrective Action A. Repair of Defective Buttering For all RPV pedestal and drywell vent structure segments shipped by Lakeside before June .1, 1979, TVA vill perform the follcwing in accordance with procedures that have been approved by the technical engineer (GE) during the field erection of the structures.

1. Locate all buttered edges by either visual inspcetion, acid etching, or radiography, or by using the Lakeside assembly records.

2. Perform 100-percent RT inspection on all buttered edges to locate all defects.

3. Remove unacceptable defects per approved procedure.

4 Perform MT or PT inspection to ensure sound metal where defects are removed.

5. Repair excavated area using a procedure approved by the technical engineer.

6. Perform 100-percent RT of the areas that are repaired. Steps 3 through 6 will be repeated until an acceptable quality buttering weld is attained.

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For all RPV pedestal and drywell vent structure segments shipped from Lakeside on or after June 1, 1979, Lakeside will perform 100-percent RT inspection and repair, as necessary, all buttered selda before the segments are shipped to TVA.

B. Cracks in the Hartsville Unit Al MPV Pedestal Steps as follow were used to repair the cracking in the RPV pedestal:

1. The entire circumference of both the inner and outer cylindrical shell structures were cleared and etched with nitric acid / water solution in the area shere cracking was evident or suspected.

Previous teste on a sample with known levels of copper contamination indicated that such an etching procedure would reveal the presence of copper by " darkening" of the veld beads into which copper had penetrated during welding.

2. Areas exhibiting the presence of copper from the etching, see Item B.l above, were air-are gouged to a depth of 3/4 inch and ground te bright metal.

3. These areas were then magnetic particle inspected to ensure sound metal where the copper contaminated areas were removed.

4. Excavated areas were repaired using the same procedure (SMAW process with AWS E7018 electrode) as used for the adjacent field weld.

5. Completed repairs were given 100-percent examination radiographically and by the magnetic particle method to assure an acceptable repair weld.

Means Taken to Prevent Recurrence A. Repairs Made by Buttering On May 2, 1979, GE sent letter No. GLB-61 to Lakeside stating GE's si.e. , the technical engineer's) interpretation of the requirements of the procurement specification with regard to buttering as follows:

1. Weld edge preparation with weld buildup material (buttering) shall require 100-percent radiography using acceptance standards of the applicable code.

2. If the supplier plans to use weld filler metal (buttering) in his fabrication process, a procedure should be submitted te the technical engineer for approval before buttering.

This action on GE's part should prevent any further misinterpretation by Lakeside of the procurement specification with regard to NDE and approval of buttering procedures. Also, the letters noted in part B should prevent future problems with buttering on this and other IVA nuclear plant.strue_tural steel. contracts.

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B. Cracks in the Hartsville Unit Al RPV Pedestal On July 26, 1979, TVA sent letters to all companies holding contracts to provide structural steel for TVA nuclear plants describing the cracking problem at Hartsville Nuclear Plant and requesting that they refrain from using copper backup bars on their contracts with TVA.

The letters further indicated requirements for TVA approval of weld repair procedures which should detail how the repairs will be made and subsequent nondestructive examination requirements for the repairs.

These notifications should prevent recurrence of this problem in the future for TVA nuclear piants.

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