IR 05000282/1997020

Insp Rept 50-282/97-20 on 971026-30 & 1117-19.No Violations Noted.Major Areas Inspected:Licensee Steam Generator Insp Program

ML20203E419
Person / Time
Site:	Prairie Island
Issue date:	12/05/1997
From:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
Shared Package
ML20203E378	List: IR 05000282/1997020 ML20203E375
References
50-282-97-20, NUDOCS 9712170057
Download: ML20203E419 (10)

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U.S. NUCLEAR REGULATORY COMMISSION REGION 111 Docket No.: 50-282 License No.: NPF-42 Report No.: 50-282/97020(DRS)

Licensee: Northern States Power Company Facility: Prairie Island Nuclear Generation Plant Location: 1717 Wakonade Drive East Welch, MN 55089 Dates: October 26-30, November 17-19,1997 Inspector: J. Schapker, Reactor inspector Accompanied by: D. Kupperman, Consultant Approved by: J. Gavuta, Chief Engirmering Specialists Branch 1 Division of Reactor Safety 9712170057 97:205 PDR ADOCK 05000282 G PDR .

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EXECUTIVE SUMMARY Prairie Island Nuclear Power Station, Unit i NRC Inspection Report 50-282/97020(DRS)

The licensee's steam generator inspection program is maintained with state of the art procedures and equipment. The Unit i steam generators are Westinghouse Model 51, in whid1 the tubes are histodcally susceptible to intergranular stress corrosion cracking (IGSCC) and intergranular attack. To assure structural adequacy of the tubes experiencing various forms of degradation, the licensee has employed the latest eddy current (ET) technology to inspect the tubing, and performed condition monitoring, which included in situ pressure testing of IGSCC indications to assure that the 4 gradation did not exceed NRC Regulatory Guide 1.121 requirements within the last operating cycle. In addition, the licensee has increased control of the inspection contractor by employing an ET Level 111 resolution analyst and requiring all analysts to be certified as a Qualified Data Analyst (ODA) to EPRI guidelines TR-107569-V1R5 Appendix G. The licensee has an ET Level 111 who has responsibility for the oversight of the steam generator inspection to assure compliance to Technical Specification and ASME requirements. Steam generator sleeving operations appeared to show improved weld quality as a result of enhanced precleaning and visualinspection criteria added to the proces _ - _ _ _ - - -

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l Report Details 11. Maintenanan M1 Conduct of Maintenance M1.1 Inservice insoection flSI) Unit 1 - Review of Procram Insp{tetion ScoDfL(Z3.0!ill inspectors reviewed the licensee's program for inservice inspection and its implementation for compliance with technical specifications, ASME Code and NRC requirements, Observations and Finctngs The SG eddy current examination (ET) inspection scope included 100% bobbin coil examination of all open tubes,100% plus point coil examination of the hot leg tubesheet area, row 1 and 2 U-bend, all unresolved indications, all sleeved tubes and 20% sample cf cold leg tubeshee The liconsee applied for an Altemate Repair Criteria (ARC) for the support plate axial Ir'dications. A Tech Spec revision incorporating the ARC was approved by NR However, a volumetric indication was identified in c le of the tube pulls for the ARC assessment. Preliminary metallurgical data of the volumetric indication appeared to be similar to cold leg thinning (wastage). No evidence of Intergranular Stress Corrosion Cracking (IGSCC) was identified in the volumetric indication. The tube was pressure tested to failure. The tube failed at the volumetric indication at 11,400 PSI (within 100 PSI of the freespan region of the tube).

A conference call on November 21,1997, was held to discuss the disposition of the volut.ietric indications. The licensee recommended that the volumetric indications be sized per the EPRI Appendix H sizing procedure for wall thinning (wear / wastage).

Indications having greater than 40% depth or not sizable by bobbin would be repaired (plugged). The 40% value is based on the Tech Spec requirement for repair of a degraded tube due to wallloss (AVB wear / wastage). Although the licensee presented technical data which appeared to be conservative, the process described for acceptance of the indications had not been evaluated by the NRC staff, as it was not included in the submittal for the ARC. The licensee agreed that the license amendment did not include the volumetric indications and agreed to repair all tubes (plug) with these indications until further testing and evaluation could be accomplished, with results submitted to the NRC for revie CAnclusions Program requirements complied or exceeded technical specification requirements, ASME Code, and Regulatory requirements. The ET scope met PWR Steam Generator ,

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l Examination Guidelines (EPRI TR 107569-V1RS) requirements for sMam generators with an active damage mechanism and demonstrated a conservative steam generator inspection program that was committed to safet M1.2 Inservice insoection - Procedure Review InspDption Scooe (73Q52)

NRC inspectors reviewed ISI procedures ISI-ET-1.0 revision 8 for ET bobbin coil probe inspection and ISI-ET-03 revision 5 for motorized rotating pancake coil probe ET inspections, SG data analysis guidelines, ET analyst performance demonstration procedure, and STD-400-163 revision 4 - ultrasonic examination of sleeve to tube upper welds, used during observed SG inspection activities for compliance with ASME Code and NRC requirement Qbservations and Findings Nondestructive examination procedures reviewed by the inspectors, were approved by the ANil and met ASME Code Section V Article 8, and Section XI Appendix IV, requirement The ET performance demonstration examinations were satisfactory. The selections of the ET degradation data from the previous outages were from pulled tubes which represented both small and large tube degradatio The procedures used for SG ET were qualifieo for detection and/or sizing of anticipated tube degradation in accordance with the PWR Steam Generator Examination Guidelines (EPRI appendix H). CQHCluit0DS Procedures reviewed were found acceptable and in accordance with the applicable ASME Code and regulatory requirements. Review of performance demonstration examination ET data by the inspector concluded that the performance demonstration examination succeeded in providing representative degradation ET data for tecting the data analys M1.3 Inservice insoection - Observations of Work Activities and Data Review Insoection Scoce (73753 and 73755)

The NRC inspectors observed ISI personnel and reviewed data recorded during ISI activities to determine compliance with ASME Code and NRC requirements. The NRC inspector observed the following activities:

. Framatone Corporation, Zetec personnel, ABB-Combustion Engineering and subcontractors performing current ET of Unit 1 SG .

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. In situ pressure testing data of selected tubes with various indications of degradatio . Sleeving activities incli ding cleaning, sleeve placement, expansion, welding, and heat treatment of the weld * Combustion Engineering personnel performing ultrasonic examination and equipment calibration checks steam generator sleeve welds examination . Eddy current examination of sleeve weld Observations and Findings The inspectors observed the licensee's contractor performing eddy current examination of SG tubing utilizing plus point motorized rotating pancake coil probes for hotleg and coldleg tubesheet, low row U-bends, previously installed sleeves and sleeves installed this outage. The bobbin probe was used on all open tubes in both SG ET inspections revealed continued degradation at the tubesheet areas of the SGs. A 2-volt ARC for the axial indications enclosed in the tube support plates was approved by NRR for this inspection. Plus point examination of low row U-bends detected one indication, an axial oriented flaw. In situ testing of this axiciindication was performed with no leakage detected. Support plate indications which exceeded the attemate repair criteria were plugged. Sleeving was performed using Combustion Engineering welded sleeves. Supplemental UT on a sampling basis was conducted after heat treating of the sleeve weld. The UT did not identify any changes in weld quality recorded during the UT prior to heat treatmen The licensee also inspected 680 previously installed sleeves with no service induced degradation noted. However,47 sleeves were plugged based on the conservative interpretation of the Appendix H qualification guidelines coupled with knowledge from the 1996 Prairie Island sleeve pull examination. A total of 223 new sleeves were installed this outage. All sleeves were acceptable, but one sleeve was plugged due to operator error during the welding process. Noted improvement in the welding process was attributed to improved cleaning and visualinspection prior to insertion of the sleeve Four tube pulls were made: one tube from each steam generator for the ARC; one tube with a top of tubesheet indication; and one sleeve with a weld zone indicatio In situ pressure testing of 34 tubes was conducted for condition monitoring assessmen This procedure provides reasonable assurance that indications ' eft in service will be able to withstand the loadings specified in Reg Guide 1.121 for the operating interval between inspections. Pressure tests of cor'servatively selected indications at three

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mes rormal operating pressure f r free span indications and pressure test of

.ndications confined in the tubesheet region were tested at steam line break pressur No leakage was identified from the 34 tubes teste SG-11 ET inspections in March 1986, identified five tubes with wear caused by the flow blocking device located in the blow down tube lane. This device was removed from the SG; one tube was plugged. The remaining tubes were left in service based on ET assessment of wear. There has been no growth detected in subsequent ET inspections. The licensee took facsimile molds of all five wear scars to provide supplementary information to assist in the sizing of the indications as no specifically qualified ET procedure exist to size this type of indication. A demonstration reference wear scar was made to produce a flaw with the gaometry similar to those found in SG 11. A mold was made of the sample wear scar and the SG-11 wear scars at the same time to provide a tolerance reference. The facsimile molds were measured using a calibrated dialindicator. The results of the physical measurements of the wear scars verified the ET sizing was conservativ The inspector reviewed ultrasoni examination data and confirmed the sleeve to tube weids exhibited an adequate bond. Several ET acquisition and resolution analysts personnel were observed while doing setup and calibrations. Resolution analysts were also observed performing analysis of indications called by the primary or secondary analys Teleconferences with NRR and Region ill were conduc.ted throughout the inspection to update the NRC concerning identified degradation and corrective actions planned or take Conclusions The licensee continues to implement a conservative SG inspection program, using state of the art equipment and procedures. ISI personnel effectively detected, sized and evaluated SG tube degradation and complied with applicable procedures and program requirements. The plugging of the 47 sleeves with previously acceptable volumetric indications demonstrates the licensee's safety conscious decision in assessing tube degradation. In addition the licensee's identification of volumetric type indication within the support plates is attributed to an aggressive program to identify the degradation mechanisms within the SG tubin Sleeve weld quality appeared to be generally improved from previous inspections observed by the inspector. This improvement appears to be attributed to improved cleaning and visualinspection requirements recently implemente .

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M1.4 Inservice insoection - Qualifications of NDE oersonnel Insoection Scoce f73753)

Inspectors reviewed Framatone, ABB-Combustion Engineering, Zetec and subcontractor's personnel qualifications and certifications for compliance with ASME Code, SN-TC-1 A and applicable NRC requirements, b, Ob1EIYations and Findings inspectors review of qualification records verified insoection personnel were trained and certified to ASNT TC-1 A and Section XI, of the ASME Code. All ET data analysts were Level llA and certified as Quality Data Analyst (QDA) per EPRI TF '07569-V1RS appendix G. Resolution analysts were Level Ill and ODA certified, All ET analysts including Computer Data Screening (CDS) were required to pass a performance demonstration examinatio ConclusioD1 No V,olations or deviations were identified and personnel certification records were properly documented and reviewed by the licensee personnel and the ANil for ASME Code,Section XI inspection V. Management Meetings X1 Exit Meeting Summary The NRC inspector met with licensee representatives (denoted in paragraph 1) at the conclusion of the inspection on November 19,1997. The inspector also participated in the conference call, on November 21,1997, referenced in paragraph M1.1.b of this report. The NRC inspectors summarized the scope and findings of the inspection activities. The NRC inspectors also discussed the likely informational content of the inspection report with regard to documents or processes to be discussed. The licensee did not identify any such documents / processes as proprietary, v

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t PARTIAL LIST OF PERSONS CONTACTED Licenica K. Albrecht, Engineering Manager G. Eckholt, Licensing M. Heller, Engineering Supervisor J. Hill, QA Manager R. Pearson, SG System Engineer S. Redner, NDc Consulting Specialist J. Sorenson, Plant Manager Framatone Inc K. Fuller, Level Ill Eddy Current M. Harris, Level til Eddy Current Zetec ine N Farabacher, Level til Eddy Current T. Menike, Level 111 T. Wettengel, Level ill NBC S. Ray, Senior Resident inspector The NRC inspectors also contacted and interviewed other licensee and contractor employee O I

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INSPECTION PROCEDURES USED IP 73051: Inservice inspection - Program Review IP 73052: Inservice insoection - Procedure Review IP 73753: Inservice inspection - Observations of Work Activities IP 73755: Inservice inspection Data Review and Evaluation IP 50002: Steam Generators - Maintenance

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LIST OF ACRONYMS USED ANil Authorized Nuclear Inservice inspector ASME American Society of MeWanical Engineers ET Eddy Current Examination EPRI Electric Power Research Institute IGSCC Intergranular Stress Corrosion Cracking ISI inservice Inspection NDD No Detect Detected NDE Non-Destructive Examination NRC Nuclear Regulatory Commission NRR Nuclear Reactor Regulation ODSCC Outside Diameter Stress Corrosion Cracking PWR Pressurized Water Reactor ODA Quality Data Analyst SG Steam Generator UT Ultrasonic Examination

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