ML062360217

Steam Generator Tube Inspection Discussion Points, Enclosure 1 to 05/09/2006 Meeting Summary for Conference Call Spring 2006 Steam Generator Inspection at Oconee, Unit 3

ML062360217
Person / Time
Site:	Oconee
Issue date:	05/09/2006
From:	Olshan L NRC/NRR/ADRO/DORL/LPLII-1
To:	Duke Power Co
Olshan L N, NRR/DORL, 415-1419
Shared Package
ML062340511	List: ML062340490 ML062360217
References
TAC MD1492
Download: ML062360217 (4)

Text

NRC Conference Call (5/9/06)

Steam Generator Tube Inspection Discussion Points Oconee Nuclear Station, Unit 3

Background

• This is the first in-service inspection on the Oconee Unit 3 replacement steam generators (steam generators were replaced in fall, 2004) - first cycle operation was 1.27 EFPY

• The steam generators are of the once-through design type and were manufactured by Babcock & Wilcox - Canada

• The tubing is thermally treated Alloy 690

• The SG has 15 support plates, the support plates are made of 410 SS, the support openings are of the trifoil broach design, with the exception of some drilled openings at the 14th TSP

• The tubes are hydraulically expanded into the tubesheet to a depth of 13 inches

• Widespread tube wear was discovered during the first inspection on the Oconee Unit 1 replacement steam generators; similar but less widespread wear was observed on Unit 2; similar wear was expected on Unit 3 because of the similarity in steam generator design and operating characteristics between units NRC Generic Questions

1. Discuss any trends in the amount of primary-to-secondary leakage observed during the recently completed operating cycle.

There has been no primary-to-secondary leakage during the recently completed operating cycle.

2. Discuss whether any secondary side pressure tests were performed during the outage and the associated results.

No secondary side pressure tests have been performed. None are planned.

3. Discuss any exceptions taken to the industry guidelines.

No exceptions have been taken to the EPRI PWR Steam Generator Examination Guidelines.

4. For each steam generator, provide a description of the inspections performed including the areas examined, the probes used, and the expansion criteria. Also, discuss the extent of rotating probe inspections performed in the portion of the tube below the expansion transition region.

A full length inspection is being performed on all in-service tubing in both steam generators using combination x-probes. Indications identified by bobbin are being further characterized with an array probe. No rotating coil inspections are being performed.

Enclosure 1

5. For each area examined, provide a summary of the number of indications found to date for each degradation mode. For the most significant indications in each area, provide an estimate of the severity of the indication. In particular, address whether tube integrity was maintained during the previous operating cycle. In addition, discuss whether any location exhibited degradation mode that had not previously been observed at this location in this unit.

Wear is the only degradation that has been observed to date during this inspection. This is the first in-service inspection on this unit, so this degradation mode has not been previously observed on these steam generators. However, similar wear was identified during the Unit 1 and 2 inspections in April and October, 2005, respectively.

SG A - The inspection on the 3A steam generator is 88% complete. See Attachment A for a summary of results and comparison to Unit 1 and 2.

SG B - The inspection on the 3B steam generator is 72% complete. See Attachment A for a summary of results and comparison to Unit 1 and 2.

None of the wear indications approach tube integrity limits.

6. Describe repair/plugging plans.

Determination of tube repair criteria is underway. Tentatively, no tubes have been identified for plugging.

7. Describe in-situ pressure test and tube pull plans and results.

No in-situ pressure testing or tube pulls are planned.

8. Provide the schedule for steam generator related activities during the remainder of the current outage.

SG A Schedule

- complete eddy current testing (Wednesday)

- perform tube plugging and stabilization if required (Thursday-Friday)

- perform secondary side visual inspection at 9th - 11th TSP locations (Friday-Saturday)

- install instrumented inspection port covers (Sunday-Monday)

SG B Schedule

- complete eddy current testing (Wednesday)

- perform tube plugging and stabilization if needed (Thursday-Friday)

9. Discuss the following regarding loose parts: What inspections are performed to detect loose parts, a description of loose parts identified and their location within the steam generator, if loose parts were removed, tube damage associated with loose parts, and the source or nature of the loose parts.

No indications of loose parts have been identified via eddy current.

10. For OTSGs, if you have Babcock& Wilcox welded plugs installed in the steam generators, discuss the actions taken in response to Framatomes notification of the effect of tubesheet hole dilation on the service life of the welded plugs.

Not applicable. No plugs are installed in the Unit 3 steam generators.

11. For OTSGs, discuss any actions taken in response to the severed tube issue during the outage (reference NRC IN 2002-02).

No actions taken. This problem is not applicable to the Oconee replacement steam generators.

Attachment A Unit 3 EOC 22 Unit 2 EOC 21 Unit 1 EOC 22 3A SG

• 3B SG

• 2A SG 2B SG 1A SG 1B SG

1. of wear indications 1852 717 627 902 2439 1769

1. of tubes with indications 1477 567 495 698 1798 1450

% tubes with indications 10.7% 4.4% 3.2% 4.5% 11.5% 9.3%

Maximum wear depth 23% 26% 22% 32% 42% 42%

Average wear depth 7.4% 7.6% 8.0% 8.4% 10.0% 9.7%

EFPY 1.27 1.27 1.31 1.31 1.24 1.24 Average depth per EFPY 5.8% 6.0% 6.1% 6.4% 8.0% 7.8%

1. indications > 40% TW 0 0 0 0 3 2

1. indications > 30% TW 0 0 0 2 20 16

1. indications > 20% TW 2 1 3 8 88 85

1. tubes plugged 0 ** 0 ** 0 3 30 18

• Unit 3 data is based on 88% inspection completion on 3A SG and 82% inspection completion on 3B SG

• • Projected number of tubes to be plugged