IR 05000269/1986023

Insp Repts 50-269/86-23,50-270/86-23 & 50-287/86-23 on 860826-29.No Violation or Deviation Noted.Major Areas Inspected:Inservice Insp,Review of Procedure & Investigation of Techniques Developed for Ultrasonic Exam of Flange

ML20215A216
Person / Time
Site:	Oconee
Issue date:	09/23/1986
From:	Blake J, Coley J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
To:
Shared Package
ML20215A194	List: IR 05000269/1986023 ML20215A191
References
50-269-86-23, 50-270-86-23, 50-287-86-23, NUDOCS 8610030541
Download: ML20215A216 (7)

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NUCLEAR REGULATORY COMMISSION O 's REGloN 11 h k b, f/ '

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Report Nos.: 50-269/86-23, 50-270/86-23, and 50-287/86-23 Licensee: Duke Power Company 422 South Church Street Charlotte, NC 28242 Docket Nos.: 50-269, 50-270, and.50-287 License Nos.- DPR-38, DPR-47, and DPR-55 Facility Name: Oconee 1, 2, and 3 Inspection Conducted: August 26-29, 1986 Inspector: . 9 ~ c2 3 ~ h __

Date Signed J.L. Key Accompanying Personnel: Marsh, Branch Chief, Division of PWR -

Licensing B, Office of Nuclear Reactor Regulation M. R. Hum, Engineer, Division of PWR - Licensing B, Office of Nuclear Reactor Regulation Gieske, NRC Consultant, Sandia National Laboratory Approved by: s p7 - h- 03- Od Bhik'e,' Section Chief Date Signed Erg ptering Branch

[)1v sion of Reactor Safety SUMMARY Scope: This was a special announced inspection in the areas of inservice inspection, review of procedure and investigation of techniques developed for ultrasonic examination of reactor vessel flange to shell weld from the flange face - Unit Results: No violations or deviations were identifie '/26 PDR ADOCK 05000269 0 PDH

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REPORT DETAILS

, Persons Contacted Licensee Employees i

• M. S. Tuckman, Station Manager

• C. B. Cheezem, ISI (Inservice Inspection) Engineer W. R. Hunt, ISI Coordinator R. J. Brackett, Senior QA (Quality Assurance) Engineer

! J. T. McIntosh, Superintendent of Station Services

• C. L. Harlin, Compliance Engineer l J. Forbes, Unit 2 Outage Manager Other licensee employees contacted included engineers, technicians, mechanics, security force members, and office personne Other Organizations Babcock & Wilcox (B&W) Special Products and Integrated Field Services

• A. C. Gladney, ISI Technology Engineer H. W. Stoppelman, ISI Supervisor T. C. Walden, ISI Technician NRC Resident Inspector

• K. Sasser, Resident Inspector

• Attended exit interview Exit Interview The inspection scope and findings were summarized on August 29, 1986, with those persons indicated in paragraph l above. The inspector described the areas inspected and discussed in detail the inspection finding No dissenting comments were received from the licensee. The following new item was identified during this inspectio (0 pen) Inspector Followup Item 269, 270, 287/86-23-01, Verify Adequacy of UT (Ultrasonic Testing) Scanning Speed for Manual Examination of the Reattor Vessel *.:lange Clad Surface, paragraph In addition to the above item, the licensee agreed to provide a report to Region II describing their recent investigation of reactor vessel flange -

to shell weld ultrasonic examination indications. Specific information the licensee stated would be provided in the report was as follows:

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Objectives of investigation

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Results

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Explanation of why indications similar to those observed in the Unit I and 2 vessels were not observed for the Unit 3 vessel

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Cladding composition and application differences that may have affected the examinations conducted during the investigatio The licensee did not identify as proprietary any of the materials provided to or reviewed by the inspector during this inspectio . Licensee Action on Pr.evious Enforcement Matters This subject was not addressed in the inspectio . Unresolved Items Unresolved items were not identified during the inspectio . Inservice Inspection - Investigation of Techniques Developed For Ultrasonic i Examination of Reactor Vessel Flange To Shell Weld From The Flange Face (73753) (73052)

During a scheduled inservice inspection of the Unit I reactor pressure vessel flange to shell weld in March 1986, Duke Power Company detected numerous high amplitude ultrasonic flaw indications. The licensee informed the NRC Region II of these flaw indications and Regional personnel conducted a plant-site evaluation of the technical issu Twenty-two flaw indications were detected, thirteen exceeded the acceptance standards in ASME Section XI Table IWB-3510-1 for pressure retaining welds in the reactor vessel. Essentially all of the examination data was obtained with a single 1-inch diameter transducer with a frequency of 2.25 MH The licensee elected to complete the inservice inspection with the available examination data, install the vessel closure head and perform a fracture mechanics analysis of the flaw indication using the measured dimension Based on the licensee's technical approach, Region II requested that the Office of Nuclear Reactor Regulations (NRR) review the licensee's analysi Two meetings were held with the licensee in the NRC Region II office on April 8 and 21,1986, during which the licensee presented his inspection results, fracture mechanics analysis and his proposed action plan. At the April 8, 1986 meeting, the licensee informed the Region II and NRR that some of the reflectors might be geometric in origin, based on a limited

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qualitative laboratory tests on mocku However, the licensee stated that

he intended to consider the flaw indications as actual flaws and to complete the analysis based on the requirements of ASME Section XI, Subarticle IWB-360 !

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In a letter dated April 24, 1986, the licensee submitted his analysis and a summary of the ultrasonic testing results which located and dimensioned the flaw indications. A safety evaluation report of the licensee's analysis was performed by NR The NRC evaluation concluded that the Oconee Unit 1 plant could be safely returned to full power and operated with actual flaws of the size and location determined in their evaluation while addition confirmatory information could be obtained as to the origin of the ultrasonic reflectors on a mockup at the Babcock and Wilcox, Mt. Vernon facilit i

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On April 23-25, 1986, Region II nondestructive examination (NDE) personnel observed a significant portion of the licensee NDE test program at the Mt. Vernon facility (see Report No. 50-269/86-15). Based on these observations and the review of the licensee's letter dated June 13, 1986,

! which provided additional information concerning the Mt. Vernon test

! results, NRC concluded that (1) geometric indications could be produced during ultrasonic examinations from the flange face in a configuration similar to the Oconee reactor vessels and (2) the licensee had developed a methodology that has the potential for resolving geometric indications detected during the examinations. The licensee also committed to implement this methodology during the inservice inspection on Oconee Unit The Oconee Unit 1 reactor vessel was considered to have actual flaws that exceeded the acceptance standards of ASME Section XI Article IWB-3000 based on the 1986 inservice inspection that was performed pursuant to 10 CFR 50.55a(g)(4). Therefore, the Oconee Unit 1 reactor vessel was

" conditionally accepted" for service by NRR until the licensee either (1) corclusively characterize and dimension the flaw indications as geometric or metallurgical reflectors during a subsequent inservice inspection or (2) performed the augmented inservice inspections required by the regulation On August 26, 1986, the inspector arrived on site, and was joined on August 27, 1986, by representatives from the Division of PWR licensing of NRR and a consultant from the Sandia National Laboratory, to observe the licensee's examination of the reactor vessel flange-to-shell, weld from the flange face, on Unit 2 and to implement the methodology acquired from the Mt. Vernon testing program for resolving geometrical indications, Observation of Work and Work Activities - Unit 2 (73753)

During the Mt. Vernon test program one very important finding was identified. This finding involved the welding techniques that had been used to apply the clad on the calibration block (#50304) and the surface condition of the clad. With the exception of the March 1986 outage of Unit 1 and the 1985 outage of Unit 3, all previous inservice examinations of the reactor vessel flange to shell weld had been performed from the vessel ID and OD surface The ID of the reactor vessel had been clad with 304 stainless steel using a strip cladding technique. Calibration block #50304 had also been clad using the

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same technique. The cladding.on the calibration block was left in the as-weld condition to represent the vessel 10. The clad on the reactor vessel flange however, was applied using an automatic subarc process in accordance with welding procedure 12-2-WP-6. This welding procedure required that 308L stainless steel, 1/8 inch in diameter be used as filler material and the clad surface was machined to a 125RMS finish. In order to determine what effect the difference in clad processing would have on the examination, the licensee had Babcock and Wilcox apply a clad for one-half the width of the unclad side of the calibration block using the same welding procedure / filler material that was used on the flange face. The new clad surface allowed for calibrations from the three side drilled holes. The surface finish of the new clad was machined until it was equivalent to clad on the flange fac Ultra-sonic calibration sensitivities were recorded for (1) the full clad side, (2) the unclad side, (3) the new clad in the as weld condition and (4) the new clad in the machined condition. The result of the calibration comparison data revealed that a calibration developed on an as-clad surface condition resulted in a severely over-sensitive calibration if it is used on a machined clad surface such as the vessel flange. The calibration difference of 30 decibels was recorded between the full clad side in the as weld condition and the one-half clad side machined to a surface finish equivalent to the clad on the reactor vessel flange. As a result of the differences in sensitivity noted above and the data obtain during the Mt. Vernon mockup investigation, the licensee decided to apply these new techniques to the Unit 2 reactor vessel flange in order to (1) determine the examination sensitivity difference on a Oconee reactor vessel when the calibration is performed on a machine clad surface that has been welded with the same welding procedure as the clad on the vessel flange versus an as-weld clad that was applied using a different welding procedure, and (2) determine if the methodology acquired at Mt. Vernon for resolving geometric indications would worked on Oconee Unit 2 vessel if indications were observed on the flange to shell wel degrees of the Unit 2 vessel flange was to be examined starting at the W-axis and going clock-wise to the Y-axi The first examination was to be performed with a calibration that used the new machined clad surface of the calibration bloc In addition, the licensee planned to examine several areas on the vessel flange using the as-weld surface of the calibration block to determine if reflectors similar to those detected on Unit 1 could be detected on Unit On August 28, 1986, the licensee accompanied by the inspector, NRR personnel and a NRC consultant observed the calibrations / examinations discussed above. The inspector also observed tho examinations to verify that the following requirements were met:

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An approved procedure was available, and was being followe The procedure specified the nondestructive cxamination equipment that was being use _ _

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Examination personnel were knowledgeable of the examination method and operation of the test equipmen Examination results were being recorded as specified in the nondestructive examination procedur The preliminary results of the above examinations indicated the following: The calibration difference between the old as-weld clad on the calibration block and the new machine clad was 22 decibels with the old clad being the more sensitive, Examination performed after calibration on as-weld clad surface produced recordable reflectors very similar to those recorded on Unit 1 and the Mt. Vernon reactor vesse Examinations performed after calibration on the machine clad surface did not produce recordable reflector The methodology acquired at Mt. Vernon for resolving geometric indications appears to work in most cases for discriminating geometrical reflectors in the vessel side wall from discontinuities in the wel The proper calibration surface for ASME Code examinations of the reactor vessel flange clad surface appears to be the machined surface of calibration block #5030 At the conclusion of the above examinations, a technical meeting was held with the licensee to discuss the inspection findings. During this meeting the licensee stated that Unit I would be re-examined during a subsequent outage and the indications recorded in the March-1986 outage would be classified as geometrical reflectors or defects using the methodology obtained during the Mt. Vernon test program and confirmed on the Unit 2 vesse . Inservice Inspection - Review of Procedures Units 1, 2 and 3 (73052)

The inspector reviewed the Babcock & Wilcox procedure (ISI-187, Revision 0)

for the ultrasonic examination of the reactor vessel flange to shell weld from the flange top surface to determine whether the procedure adequately covered all require? aspects of the approved inservice inspection progra The applicable code for the review wasSection XI, of the American Society of Mechanical Engineers (ASME), Boiler and Pressure Vessel Code (80W80).

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i The procedure was reviewed to determine if the following essential elements were properly addressed:

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Calibration reflectors

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Method of demonstrating penetration was established i

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Acceptance limits established or referenced i

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During the review of the procedure and also during the Unit 2 examination of the reactor vessel flange to shell weld, the inspector was concerned that the procedure allowed a scanning speed of six-inches per second. Although

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recognizes that the ultrasonic examination of austenitic weld metal is usually more difficult than in ferritic materials, because of the wide

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variations that may occur in acoustic properties of austenitic welds, even those in alloys of the same composition, product form, and heat treatment.

l The code, therefore states that, it may be necessary to modify and/or

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supplement the normal examination requirements when examining such

! materials. The inspector became particularly concerned when he observed how

) difficult it appeared for the examiners to peak the calibration reflectors during static calibrations on the clad calibration bloc l l However, the same examiners would ignore indications that failed to reach

recordable levels when they were scanning at a rate of six inches per second

} on the clad vessel flange. The license agreed to evaluate the adequacy of j the scanning speed in the procedure by performing calibrations in the static j mode and then comparing them to calibrations at various scanning speeds.

i This item was identified as inspector followup item 269, 270, 287/86-23-01, l Verify Adequacy of UT (Ultrasonic Testing) Scanning Speed for Manual l

Examination of the Reactor Vessel Flange Clad surface.

i l Within the areas examined, no violations or deviations were identified.

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