IR 05000341/1985049

Safety Insp Rept 50-341/85-49 on 851203-05 & 860109.No Violation or Deviation Noted.Major Areas Inspected:Piping Replacement for Steam Bypass Line Failure & Followup on Allegations

ML20137C055
Person / Time
Site:	Fermi
Issue date:	01/10/1986
From:	Danielson D, Jeffrey Jacobson NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
Shared Package
ML20137C045	List: IR 05000341/1985049 ML20137C041
References
50-341-85-49, NUDOCS 8601160183
Download: ML20137C055 (5)

Text

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U.S. NUCLEAR REGULATORY-COMMISSION

REGION III

Report No. 50-341/85049(DRS)

Docket No. 50-341 License No. NPF-33 Licensee: Detroit Edison Company 2000 Second Avenue Detroit, MI 48224 Facility Name: Fermi Nuclear Power Plant, Unit 2 Inspection At: Fermi 2 Site, Monroe, MI Inspection Conducted: December 3-5, 1985 and January 9, 986 ffe<

Inspector: J. Jacobson l!l o! Oh Date Y"

Approved By: D. Danielson, Chief / 0!Ob Materials and Processes Section Date Inspection Summary Inspection on December 3-5, 1985 and January 9, 1986 (Report No. 341/85049(DRS))

Areas Inspected: Special announced safety inspection of piping replacement for the steam bypass line failure ,and followup on allegations resulting from this effort. The inspection involved a total of 16 inspector-hours onsite by one NRC inspecto Results: No violations or deviations were identifie B60 g4g PDR ADOCK PDR O .

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DETAILS 1. Persons Contacted Detroit Edison Co. (DECO)

• • J. Conen, Licensing Engineer

• D. Spiers, Director, Field Engineering

• J. Contoni, Lead Engineer, Mechanical

• J. Quinn, Maintenance Welding Engineer

• J. Malaric, Plant Modifications Engineer

• J. Rotondo, Senior Quality Specialist

• Denotes those attending the onsite exit meeting on December 5, 1985.

• • Denotes those telephonically contacted on January 9,1986, for the final exit intervie . Followup on Allegations (Closed) Allegation RIII-A-85-0200: Weld quality deficiencies of auto.matic welds performed on steam bypass piping replacemen It should be noted that this particular system is not a safety-related syste As part of the steam bypass piping replacement, DECO elected to utilize automated flux-cored arc welding techniques on accessible welds. The decision to use this process was based on the decreased welding time when

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compared with manual welding. Two individuals contacted the NRC with four quality concerns, these concerns were reviewed by the NRC inspector as follows:

Concern (1)

A downhill welding technique was used by the automatic welding operator The alleger stated that in his many years of (manual) welding experience he had not seen downhill welding used in a powerhous NRC Review The automated welding procedure utilizes the flux-cored arc welding process. This process involves welding currents considerably higher than manual welding and consequently requires techniques which diffe Depositing the root pass using the automatic flux-cored process in the uphill direction would cause excessive heat input and burn through. This procedure was properly qualified for a downhill root pass and is technically acceptabl Concern (2)

The alleger stated that the welding procedures were not Detroit Edison's (DECO) procedures and that they were obtained from Texa . _ _ - _ _-__

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NRC Review When the licensee elects to contract a work task, the contractor's procedures may also be approved and utilized. In addition, a DECO representative was sent to the contractors shop (Texas) to participate in the procedure development and qualification. No violations of NRC requirements or industry standard practice was foun Concern (3)

The alleger stated that the backing rings utilized to aid in welding of the pipe joint roots are not adequately fused. This observation was based on the alleger's involvement in the cut out of a weld joint due to improper pipe length. Furthermore, the alleger stated that the weld was of poor qualit NRC Review The automatic welding procedure was found to be properly qualified in accordance with the requirements of Section IX of the ASME Code. The governing code for installation and weld inspection was ANSI B3 '

While this code requires only a final visual inspection of the weld, DECO elected to utilize magnetic particle examination of both the partial and completed welds. This enhanced inspection and proper procedure qualification coupled with the complete removal of the weld noted by the Alleger, gives assurance that the installed welds will adequately meet the design requirements per the governing cod The NRC inspector examined a weld joint mock-up welded with the automatic proces During the initial examination, three pieces of the backing ring, each approximately 2" in length, were removed from the weld joint. The backing ring sections exhibited adequate fusion and the weld joint exhibited full penetration of the roo Subsequent to this examination, the NRC inspector observed the removal of approximately 25" of the backing ring utilizing hammers and chisels. The inspector concluded that the automatic welding process produced complete joint penetration and adequate fusion of the backing rin The alleger also stated that the weld mock-up was, "a lot different from the welds in the plant in that the mock-up was stress relieved and that it helped fuse the backing ring." Stress relieving, or more properly called post weld heat treatment, is required per ANSI B31.1 on pipe with a wall thickness of 3/4" or greater. All welds requiring post weld heat treatment, including the mock-up received this process. Post weld heat treatment is performed to relieve residual stresses caused by the welding process and in no way helps to fuse the backing ring to the join Concern (4)

The alleger stated that two root passes instead of the required one had been used on a wel Also that some welds were made using incorrect polarit b

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NRC Review The use of two weld passes for the root is not considered an essential variable per ASME Section IX and therefore did not require requalification of the procedure. This technique for welding the root is technically acceptable when backing rings are used in the join The flux-cored arc welding process will not operate with incorrect polarity and therefore could not have been used to deposit a wel Conclusioni (1) This item was substantiated in that a dowrhill welding technique was used. This technique however, was properly qualified and is technically acceptabl (2) This item was substantiated in that the welding procedure was not a DECO qualified procedure. The practice of licensee review and approval of a contractors procedure to be used on contracted work is acceptabl (3) This item was partially substantiated in that during the cut out of a weld joint due to improper dimensions, it was apparent that the backing ring was not completely fused to the weld joint. Since this weld joint was completely removed, it has no effect on the piping system. Weld quality using this procedure was properly demonstrated by a successful ASME,Section IX qualification tes In addition, the NRC inspector examined a weld mock-up which demonstrated complete joint penetration and adequate fusion of the backing ring. Furthermore, weld joint quality of the installed piping was demonstrated by the use of magnetic particle examinatio This examination was performed on all welds though the code required a visual examination onl (4) This item could not be substantiated in that the process will not operate using incorrect polarity. The use of two weld passes instead of one could not be substantiated, and even if substantiated, is of no technical significanc It was noted that several instances of tampering with the automatic equipment, by persons unknown, were reported during the welding operation. This tampering did not effect weld quality although some production time was los Although some of these allegations were substantiated, none had any impact of plant safet . Review of Steam Bypass Line Repair As outlined in NRC Inspection Report No. 341/85045(DRS) the steam bypass lines experienced acoustic vibration induced failures. As a result of

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these failures, the licensee proceeded to replace the affected pipin Due to engineering considerations modifications to the original design of this piping installation were mad The system, as originally designed, contained piping with a 30" diameter and 3/8" thick wall which was connected by means of a reducer to a 24" diameter pipe with a 3/8" thick wall. This configuration was ch" led so that the system employed 30" diameter piping with a 1" thick wall and 24" diameter piping with a 1" thick wall. The increase in pipe wall thickness serves to substantially reduce the stress levels associated with the acoustic vibration Orifice plates were installed in the piping system in an effort to reduce the acoustic energy created at the discharge of the bypass valves. The source of the acoustic vibration is the large pressure differential across the throat of the bypass valve. The orifice plates serve to reduce the vibration due to back pressure and attenuatio The bypass line failures originated at points on the outside of the wall where welded attachments were located. Apparently any disruption of the natural vibratory pattern results in a localized stress intensification. To alleviate this problem, the welded attachments were removed during the modificatio The NRC inspector reviewed DECO EDP 4410 for design information and inspected the installed piping system. Strain gages were installed at 11 locations to be used by DECO during operation to determine the effect of these design change . Exit Interview The inspector met with licensee representatives (denoted in Paragraph 1)

at the conclusion of the onsite inspection. The inspector summarized the scope and findings of the inspections noted in this report. 'The inspector also discussed the likely informational content of the inspection report with regard to documents or processes reviewed by the inspector during the inspection. The licensee did not identify any such documents / processes as proprietary. Additional information was discussed telephonically with a licensee representative (denoted in Paragraph 1) on January 9,198 t