ML022190359

Inservice Inspection Summary Report for Class CC Component Examinations Completed by End of Refueling Outage 20

ML022190359
Person / Time
Site:	Oconee
Issue date:	07/29/2002
From:	Mccollum W Duke Energy Corp
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML022190359 (11)

Text

Duke Duke Energy Oconee Nuclear Station 7800 Rochester Highway Seneca, SC 29672 (864) 885-3107 OFFICE W R. McCollum, Jr. (864) 885-3564 FAX Vice President July 29, 2002 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555-0001

SUBJECT:

Duke Energy Corporation Oconee Nuclear Station - Unit 1 Docket No. 50-287 Inservice Inspection Summary Report for Class CC Component Examinations Completed by End of Refueling Outage 20 Pursuant to 1 OCFR50.55a(b)(2)(viii), Duke Energy Corporation submits the attached ISI Summary Report for ASME Class CC In-service Inspections completed between March 1, 2002 and the end of refueling outage 20.

Please note that IWA-6000 of the ASME Code, Section Xl, 1992 Edition with the 1992 Addenda requires an ISI Summary Report to be completed only for Class 1 and 2 components. As such, an ISl Summary Report is not required by the ASME Boiler and Pressure Vessel Code, Section Xl, for Class CC components. However, because 10CFR50.55a(b)(2)(viii) requires specific information regarding Class CC examinations be included in the Summary Report, a Class CC ISI Summary Report has been prepared. This report includes only that information required by 1 OCFR50.55a.

Questions regarding the attached report may be directed to R. V. Hester at (864) 885-4333.

Very truly yours, W. R. McColium, Jr.

Site Vice President

Attachment:

Oconee Nuclear Station Unit 1, Class CC ISI Summary Report for Refueling Outage EOC20 CC: L. A. Reyes L. N. Olshan M. E. Shannon

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Oconee Nuclear Station, Unit 1 Class CC ISI Summary Report for Refueling Outage EOC20 By: V.Date: 9-He3 -02 (R. V. He 'ter", P.E. IWL Responsible Engineer)

Reviewed By: Date: F-S -OZ TMark V. Ferlisi, P.E.)

Approved By: Date: 1-a3-OZ ANII Review By: Date: 7-ZY-OZ (Authorized Nucleaar Inservice Inspector)

Oconee Nuclear Station, Unit 1 Class CC ISI Summary Report Refueling Outage EOC20 Page 2 of 10 Table of Contents Section Subject Page A. ASME Code and Regulatory Requirements for Class 3 CC ISI Summary Reports B. General Description of Examinations and 4 Conditions Requiring Reporting C. Detailed Description of Reportable Conditions 5

Oconee Nuclear Station, Unit 1 Class CC ISI Summary Report Refueling Outage EOC20 Page 3 of 10 A. ASME Code and Regulatory Requirements for Class CC ISI Summary Reports 10CFR50.55a(g) (4) (v) (C) requires that concrete containment pressure retaining components and their integral attachments, and the post-tensioning systems of concrete containments must meet the inservice inspection, repair, and replacement requirements applicable to components which are classified as ASME Code Class CC.

This inservice inspection summary report addresses requirements of 10CFR50.55a(b) (2) (viii) for inservice inspections conducted in accordance with the ASME Code,Section XI, Subsections IWL for the Oconee Unit 1 concrete containment.

ASME Section XI, Subsections IWE and IWL, 1992 Edition with the 1992 Addenda, Article IWA-6000, Records And Reports, paragraph IWA-6210, requires the Owner to prepare inservice inspection summary reports for inservice inspections performed on Class 1 and 2 pressure retaining components and their supports.

IWA-6000 does not address inservice inspection summary reports for Class CC pressure retaining components and their supports, and the Code does not require preparation and submittal of summary reports for Class CC components. As such, this Class CC ISI Summary Report does not contain all of the information specified in IWA-6220 or IWA-6230. Please note that this report is being submitted within 90 calendar days following the completion of the refueling outage at Oconee Unit 1, in accordance with IWA-6240(b).

Duke Energy Corporation is maintaining a separate Inservice Inspection Program for Class CC pressure retaining components.

Therefore, this ISI Summary Report contains only that inservice inspection information applicable to Class CC components. ISI Summary Reports for other Code Class components are submitted separately.

This Summary Report includes all applicable information required by 10CFR50.55a (b) (2) (viii) (C), 10CFR50.55a (b) (2) (viii) (D), and 10CFR50.55a(b) (2) (viii) (E).

Oconee Nuclear Station, Unit 1 Class CC ISI Summary Report Refueling Outage EOC20 Page 4 of 10 B. General Description of Examinations and Conditions Requiring Reporting Conditions were observed during refueling outage EOC20 that require inclusion in this Class CC ISI Summary Report, as required by 10CFR50.55a(b) (2) (viii) (C), (D) (1), (D) (2), and (E). These conditions were identified during the performance of ASME Code,Section XI, IWL Examinations in accordance with Table IWL-2500-1, Category L-B.

Observed Conditions Condition #1:

Elongation corresponding to a specific load (adjusted for effective wires or strands) during retensioning of tendons differed by more than 10 percent from that recorded during the last measurement.

This condition was determined to require reporting in accordance with 10CFR50.55a(b) (2) (viii) (C).

Condition #2:

Free water was detected in one dome tendon end cap. The specific tendon affected is detailed later in this report.

Insufficient grease was available for testing at one end of two vertical tendons. Although there was no evidence to indicate the presence of water, this sample is assumed to contain chemically combined water exceeding 10 percent by weight. The specific tendons affected are detailed later in this report.

This condition requires reporting in accordance with 10CFR50.55a(b) (2) (viii) (D) (1).

Condition #3:

The absolute difference between the amount of filler grease removed and the amount replaced exceeded 10 percent of the tendon net duct volume for 10 tendons inspected. The specific tendons affected and the amount of exceedance is detailed later in this report.

This condition requires reporting in accordance with 10CFR50.55a(b) (2) (viii) (D) (2).

Oconee Nuclear Station, Unit 1 Class CC ISI Summary Report Refueling Outage EOC20 Page 5 of 10 Condition #4:

Bearing plate settlement noted and degraded concrete observed beneath bearing plate at top end of vertical tendon Mark 12V9. This condition was determined to require reporting in accordance with 10CFR50.55a(b) (2) (viii) (E).

C. Detailed Description of Reportable Conditions Condition #1:

10CFR50.55a(b) (2) (viii) (C)requires when the elongation corresponding to a specific load (adjusted for effective wires or strands) during retensioning of tendons differs by more than 10 percent from that recorded during the last measurement, an evaluation must be performed to determine whether the difference is related to wire failures or slip of wires in anchorage. A difference of more than 10 percent must be identified in the ISI Summary Report required by IWA-6000. Tendon 23V17, when loaded to the original seating load (adjusted for effective wires), experienced an elongation 14% greater than that recorded during the last measurement, as determined based on the shim stack height.

Technical Evaluation:

The type anchorage utilized in the Post-Tensioning system at Oconee does not allow for slip of wires in anchorage. All wires are passed through holes in an anchor head and deformed to create buttonheads. The tensioning force is maintained by shims between the anchor head and the bearing plate. There was no audible indication of wire failures. The average lift off force between the two ends of 23V17 was 673 kips, greater than the lift off force for any of the other four vertical tendons so tested, and 44 kips greater than the lift off force predicted for this tendon at this time. A wire was removed from tendon 23V17 and inspected along its full length. The entire length was described as bright metal with no visible oxidation along its entire length. No free water was discovered in the sheath.

The above evaluation is judged sufficient to demonstrate that the measured elongation in tendon 23V17 is not the result of wire failure or slip of wires in the tendon.

Oconee Nuclear Station, Unit 1 Class CC ISI Summary Report Refueling Outage EOC20 Page 6 of 10 Condition #2:

10CFR50.55a(b) (2) (viii) (D) (l)requires when the presence of free water is detected, or the grease contains chemically combined water exceeding 10% by weight, it shall be reported in the ISI Summary Report.

When one tendon cap for dome tendon 3D5 was removed, 12 gallons of water was collected as it drained from the tendon sheath. Free water was not detected in tendon sheaths of any other inspected tendon.

When the upper tendon caps of tendons 12V13 and 56V17 were removed, there was insufficient grease volume available to collect for laboratory testing. Although there was no evidence to indicate the presence of water or chemically combined water, these samples are assumed to contain chemically combined water exceeding 10 percent by weight.

Although 10CFR50.55a(b) (2) (viii) (D) (1) does not require that an evaluation of this condition be submitted in this ISI Summary Report, an evaluation is provided below. This condition is also addressed with Condition #4.

Technical Evaluation Prior to regreasing dome tendon 3D5, the tendon sheath was pressurized with compressed air in order to verify the correct high point vent has been opened and a free path for regreasing existed. During the pressurization of 3D5, air was heard escaping from the vicinity of the top bearing plate for vertical tendon 12V9. The sheaths for dome tendon 3D5 and vertical tendon 12V9 pass in close proximity about one foot below the bearing plate for 12V9. Further examination revealed that the air was escaping along the edge of the bearing plate for 12V9 and along a nearby construction joint. Grease staining was noted around the tendon cap for tendon 12V9. It had been assumed the source of the grease was the top grease cap for tendon 12V9, but it now appears the grease was forced through the concrete when 3D5 was initially greased. Rainwater can pass in the reverse direction and enter the sheath for 3D5. It is considered likely that the source of the 12 gallons of water contained in the sheath for tendon 3D5 was rainwater entering from the roof through the same leakage paths from which air was heard escaping.

Oconee Nuclear Station, Unit 1 Class CC ISI Summary Report Refueling Outage EOC20 Page 7 of 10 The water was tested for pH and was slightly basic. Free water was found only in one end of the tendon near the anchorage. A visual exam of the metallic components of the anchorage reported bright eotal1with no visible oxidation.

The tendon was tested f~f lilt-bff. The lift-off force, measured as the average of the two ends, was acceptable and was higher than the other dome tendons tested. No wire was removed from this tendon.

No other indications of abnormal conditions were observed for this tendon and tendon 3D5 is considered acceptable at this time.

See Condition #4 for additional information related to the 12V9 bearing plate.

The metallic anchorage components of all tendons were visually inspected. The anchor head and bearing plate of vertical tendon 12V13 and the bearing plate of vertical tendon 56V17 were reported as having a reddish brown color with no pitting. All other components were bright metal with no oxidation. The average lift off force for 12V13 was acceptable and higher than the expected value for this type tendon at this point in time. No lift off test was conducted for 56V17. No wire was removed from either of these tendons. There was no indication of degradation of tendon wire or anchorage components of these tendons.

Condition #3:

10CFR50.55a(b) (2) (viii) (D) (2)requires when the absolute difference between the amount of sheathing filler grease removed and the amount replaced exceeds 10 percent of the tendon net duct volume, it shall be reported in the ISI Summary Report. The following table lists tendons for which the absolute difference between the amount of sheathing filler grease removed and the amount replaced exceeded 10 percent of the tendon net duct volume, and the percentage by which the net duct volume was exceeded.

Oconee Nuclear Station, Unit 1 Class CC ISI Summary Report Refueling Outage EOC20 Page 8 of 10 TENDON ID GREASE INSIALLICk AS % of NET DUCT VOLUME ID27 23 2D24 >10 3D32 25 3D5 Not refilled. Assume > 10%

1D25 43 3D50 20 12V13 13 45V25 28 Although 10CFR50.55a(b) (2) (viii) (D) (2) does not require that an evaluation of this condition be submitted in this ISI Summary Report, an evaluation is provided below.

Technical Evaluation All of the above tendons were visually examined for corrosion, and no corrosion of the metallic components of the anchorages was noted. Tendon 2D24 had a wire removed and examined for its full length. No corrosion was present. All tendons were inspected for grease coverage of the anchorage components and all were found to have adequate coverage.

Experience at Oconee site has been that adequate coverage of components during initial grease filler installation prevents corrosion even if some filler material is lost due to leakage.

Condition #4:

10CFR50.55a(b) (2) (viii) (E) requires an evaluation of the acceptability of inaccessible areas when conditions exist in accessible areas that could indicate the presence of or result in degradation to such inaccessible areas.

Oconee Nuclear Station, Unit 1 Class CC ISI Summary Report Refueling Outage EOC20 Page 9 of 10 Description of the Type and Estimated Extent of Degradation and Conditions that Led to the Degradation The top bearing plate of tendon 12V9 was noted as having settled approximately 7/16" to 1/2" relative to the surrounding concrete. When compressed air was introduced to surveillance Dome Tendon 3D5, air was heard escaping from the vicinity of Tendon 12V9. The sheaths for tendons 3D5 and 12V9 are in close proximity about one foot below the top bearing plate for 12V9. It was determined that the air was escaping both along the bearing plate for tendon 12V9, and along approximately six feet of an adjacent circumferential vertical construction joint. This condition creates a path for rainwater to access inaccessible regions of the containment structure. Water drained from the sheath for tendon 3D5 (see also Condition #2, above). Grease staining was evident near tendon 12V9 which evidently formed when tendon 3D5 was initially filled with filler grease.

Regreasing of tendon 3D5 has been delayed until repairs can be accomplished. Problem Investigation Process Report (PIP)

1. 0-02-03261 was generated to document these conditions and address this degradation.

There appears to be a lack of concrete consolidation beneath the bearing plate and a lack of bonding between the two adjacent pours at the construction joint. Voids beneath horizontal or nearly horizontal embedded plates are not uncommon when concrete is not adequately vibrated, and there is no provision to allow air trapped beneath the plate to escape. The void in this case either extends to the sheath for 3D5, or communicates with the crack in the construction joint. Tendon 12V9 and the vertical tendons to each side were inspected for water at their lower caps and none was found. Dome tendons adjacent to 3D5 were also inspected for water and none was found.

Evaluation of the Degradation and Evaluation Results PIP #0-02-03261 documents the acceptability of the containment. The conditions associated with vertical tendon 12V9 and dome tendon 3D5 do not affect the structural integrity of the containment. Although corrective actions are necessary, no immediate corrective actions are required to ensure continued structural integrity of the containment.

The entire dome coating system was replaced immediately following EOC20. The new coatings were extended to bridge and seal the edges of all vertical tendon top bearing plates, eliminating the path for future rainwater intrusion.

The construction joint from which air was heard escaping and

Oconee Nuclear Station, Unit 1 Class CC ISI Summary Report Refueling Outage EOC20 Page 10 of 10 into which rainwater apparently leaked was also sealed to prevent future rainwater intrusion.

Description of Necessary Cbfkective Actions Corrective actions are being planned for the 4 th quarter of 2002 to detension tendon 12V9 and to identify the extent of repairs needed to any void or crack that may exist beneath the top bearing plate. Tendon 3D5 will be refilled with grease during EOC21, following completion of any necessary concrete repairs in the vicinity of tendon 12V9.