ML071090059
| ML071090059 | |
| Person / Time | |
|---|---|
| Site: | Waterford  |
| Issue date: | 04/24/2007 |
| From: | Fields M NRC/NRR/ADRO/DORL/LPLIV |
| To: | Walsh K Entergy Operations |
| Fields M, NRR/DORL/LP4, 415-3062 | |
| References | |
| TAC MD3152 | |
| Download: ML071090059 (10) | |
Text
April 24, 2007 Mr. Kevin T. Walsh Vice President of Operations Entergy Operations, Inc.
17265 River Road Killona, LA 70057-3093
SUBJECT:
WATERFORD STEAM ELECTRIC STATION, UNIT 3 -
SUMMARY
OF DISCUSSIONS REGARDING THE FALL 2006 STEAM GENERATOR TUBE INSPECTIONS (TAC NO. MD3152)
Dear Mr. Walsh:
On December 4, 6, 7, 8, 12, 15, 18, 19, 20, and 21, 2006, the Nuclear Regulatory Commission (NRC) staff participated in conference calls with Entergy Operations, Inc. (Entergy) representatives regarding the fall 2006 steam generator tube inspections at Waterford Steam Electric Station, Unit 3. The NRC staffs summary of these calls, along with the information supplied by Entergy representatives in support of these discussions, is enclosed.
Sincerely,
/RA/
Mel B. Fields, Senior Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-382
Enclosure:
As stated cc: See next page
ML071090059 NRR-106
- Tech Staff Input OFFICE NRR/LPL4/PM NRR/LPL4/LA NRR/CSGB/BC*
NRR/LPL4/BC NAME MFields JBurkhardt AHiser THiltz DATE 4/23/07 4/20/07 2/7/07 4/24/07
November 2006 Waterford Steam Electric Station, Unit 3 cc:
Vice President, Operations Support Entergy Operations, Inc.
P.O. Box 31995 Jackson, MS 39286-1995 Director Nuclear Safety Assurance Entergy Operations, Inc.
17265 River Road Killona, LA 70057-3093 General Manager Plant Operations Waterford 3 SES Entergy Operations, Inc.
17265 River Road Killona, LA 70057-3093 Manager, Licensing Entergy Operations, Inc.
17265 River Road Killona, LA 70057-3093 Resident Inspector/Waterford NPS P.O. Box 822 Killona, LA 70066-0751 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011 Parish President Council St. Charles Parish P.O. Box 302 Hahnville, LA 70057 Executive Vice President &
Chief Operating Officer Entergy Operations, Inc.
P.O. Box 31995 Jackson, MS 39286-1995 Director, Nuclear Safety & Licensing Entergy Operations, Inc.
1340 Echelon Parkway Jackson, MS 39213-8298 Louisiana Department of Environmental Quality Radiological Emergency Planning and Response Division P.O. Box 4312 Baton Rouge, LA 70821-4312 Louisiana Department of Environmental Quality Office of Environmental Compliance P.O. Box 4312 Baton Rouge, LA 70821-4312 Chairman Louisiana Public Services Commission P.O. Box 91154 Baton Rouge, LA 70825-1697 Richard Penrod, Senior Environmental Scientist/State Liaison Officer Office of Environmental Services Northwestern State University Russell Hall, Room 201 Natchitoches, LA 71497
ENCLOSURE ENTERGY OPERATIONS, INC.
DOCKET NO. 50-382 WATERFORD STEAM ELECTRIC STATION, UNIT 3
SUMMARY
OF DISCUSSIONS - FALL 2006 STEAM GENERATOR TUBE INSPECTIONS On December 4, 6, 7, 8, 12, 15, 18, 19, 20, and 21, 2006, the Nuclear Regulatory Commission (NRC) staff participated in conference calls with Entergy Operations, Inc. (Entergy) representatives regarding the fall 2006 steam generator (SG) tube inspections at Waterford Steam Electric Station, Unit 3. These calls also involved extensive technical discussions regarding broken batwings that were identified during the SG inspections. A summary of the information provided during these calls is provided below.
Waterford 3 has two Model 3410 SGs designed and fabricated by Combustion Engineering.
The mill-annealed Alloy 600 SG tubes have an outside diameter of 0.750-inch and a nominal wall thickness of 0.048-inch. Each SG contains 9,350 tubes. The tubes are explosively expanded for the full depth of the tubesheet at each end and are supported by a number of carbon steel lattice-grid (i.e., eggcrate) tube supports, diagonal bars (also referred to as batwings), and vertical straps. The tubes in rows 1 through 18 are U-bends and the tubes in rows 19 through 147 are square bends. There are no alternate repair criteria (i.e., other than the 40 percent through-wall repair criteria) approved for the plant.
In support of the December 7, 2006, conference call, the licensee provided responses to the discussion points developed by the NRC staff. This document is attached. Additional clarifying information and information not included in the document provided is summarized below:
No new forms of degradation were identified as a result of these inspections.
The number of indications identified at the top of the tubesheet expansion transition or within expanded tubesheet region is greater than the number identified during previous inspections. Representatives for Waterford 3 attribute the increase to a time and temperature aging phenomena.
Eddy current inspections were conducted with a +Point' coil in the tubes adjacent to the broken batwings in SG number 32 (also referred to as the number 2 SG at Waterford Unit 3) in an effort to determine if the batwings were wearing the tubes. These inspections were conducted from the seventh eggcrate support to 6 inches beyond the batwing location. There was no evidence of wear above the batwing locations. Based on this result, the licensee does not believe the broken batwings are lifting from their location as a result of the flow through the SG.
In addition to the eddy current inspections, the staffs interactions with the licensee focused on broken batwings identified in SG 32. During the previous refueling outage (spring 2005),
Waterford 3 discovered two batwing supports in SG 32 which separated at the support bar in the stay cavity region. The batwings serve as a spacer to prevent tube-to-tube contact during normal operation. These two batwings caused minor tube wear which did not compromise tube integrity.
There was no evidence of batwing degradation in SG 31. As a result of eddy current and visual inspections conducted during the fall 2006 refueling outage, an additional 20 broken batwings were discovered in the stay cavity region in SG 32. During inspection of the batwing-to-wrapper bar welds at the outer periphery of the tubes, two of the welds in SG 32 were found to be broken. There were no broken batwings or batwing-to-wrapper bar welds discovered in SG 31.
Waterford performed extensive tube plugging and stabilization as well as weld repair in an effort to protect active tubes from being damaged as a result of the broken batwings.
A summary of the actions taken by the licensee, as well as a list of commitments, was submitted by the licensee on December 20, 2006 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML063600109). The NRC acknowledged the licensees commitments via letter dated December 22, 2006 (ADAMS Accession No. ML063560370). A public meeting was held at NRC headquarters on March 22, 2007, to discuss the licensees root cause failure analysis, mitigative measures, and plans for continued operation. The meeting summary was issued on April 3, 2007 (ADAMS Accession No. ML070870732).
ATTACHMENT Waterford 3 - 12/7/2006 Mid-Outage Call Information Conducted - 1:00 PM CDST 1.
Discuss any trends in the amount of primary-to-secondary leakage observed during the recently completed cycle.
Primary to secondary leakage has remained constant all cycle at approximately 0.4 gallons per day based on tritium analysis.
2.
Discuss whether any secondary side pressure tests were performed during the outage and the associated results.
There are no secondary side pressure tests planned.
3.
Discuss any exceptions taken to the industry guidelines.
There are no exceptions (deviations) being taken.
W3 will eliminate a current deviation that was processed for failure to foreign object search and retrieval during RF13 (CR-WF3-2006-0933) 4.
For each steam generator, provide a description of the inspections performed including the areas examined and the probes used (e.g., dents/dings, sleeves, expansion-transition, U-bends with a rotating probe), the scope of the inspection (e.g.,
100% of dents/dings greater than 5 volts and a 20% sample between 2 and 5 volts), and the expansion criteria.
Area Probe Scope Expansion Full Length Bobbin 100%
None HL TTS Plus Point 100% - C*
CL if > 1%
CL TTS -
periphery Plus Point
~ 10%
Dependent of finding Row 1 & 2 U-bend Plus Point 100%
Additional rows depending on finding Wear Plus Point 100%
None Dents > 2 volt at eggcrates Plus Point 100%
None Dents > 2 volt at batwings Plus Point 20%
100% depending on finding Freespan Dings >
5 volt Plus Point 20%
100% depending on finding 5.
For each area examined (e.g., tube supports, dent/dings, sleeves, etc), provide a summary of the number of indications identified to-date of each degradation mode (e.g.,
number of circumferential primary water stress corrosion cracking indications at the expansion transition).
For the most significant indications in each area, provide an estimate of the severity of the indication (e.g., provide the voltage, depth, and length of the indication). In particular, address whether tube integrity (structural and accident induced leakage integrity) was maintained during the previous operating cycle. In addition, discuss whether any location exhibited a degradation mode that had not previously been observed at this location at this unit (e.g., observed circumferential primary water stress corrosion cracking at the expansion transition for the first time at this unit).
As of 12/07/2006, 0800 data files SG31:
72 tubes with SCC at top of tubesheet expansion transition or within expanded tubesheet region.
5 contain axial ODSCC, longest length 0.29 inch, largest +Pt amplitude 0.32 volt, depth approximately 40%TW.
29 contain axial PWSCC, longest length within 1.5 inches of top of tubesheet 0.49 inch, largest +Pt amplitude 0.69 volt, depth approximately 40%TW. Largest overall length reported at 1.8 inches however multiple axial indications are noted and this length is likely a gross overestimate of the individual flaw lengths. Largest overall
+Pt amplitude is 0.82 volt.
38 contain circumferential PWSCC, longest length 96 degrees, largest +Pt amplitude 2 volts, depth approximately 60%TW.
SG32:
10 tubes with SCC at top of tubesheet expansion transition or within expanded tubesheet region.amplitude is 0.82 volt.
1 contains axial ODSCC, 0.19 inch, 0.11 volt, depth less than 40%TW.
5 contain axial PWSCC, longest overall length 0.33 inch, largest +Pt amplitude 0.74 volt, depth approximately 40%TW.
3 contain circumferential PWSCC, longest length 45 degrees, largest +Pt amplitude 0.74 volts, depth less than 60%TW.
1 contains a small volumetric signal, likely attributed to a manufacturing artifact.
SG31:
94 tubes with axial ODSCC at eggcrates, 1 inch longest length, largest +Pt amplitude 0.85 volt, deepest depth approximately 60%TW.
SG32:
13 tubes with axial ODSCC at eggcrates, 0.9 inch longest length, largest +Pt amplitude 0.32 volt, deepest depth approximately 40%TW.
Deepest structure wear reported is 38%TW. Some new wear sites (about 100 to 150) are reported in both SGs, however new wear depths are consistent with past outages and growth rates are slightly reduced from past outages.
All locations satisfy structural and leakage integrity performance criterion.
No new degradation modes reported.
6.
Describe repair/plugging plans.
Plug all crack-like indications and wear > 40% TW. Stabilizing all circumferential cracks with the exception of those within the tubesheet from -3 inches and lower from TTS.
7.
Describe in-situ pressure test and tube pull plans and results (as applicable and if available).
There are currently no in-situ pressure tests required.
There are no plans for tube pull.
8.
Provide the schedule for steam generator-related activities during the remainder of the current outage.
Complete Special Interest 9.
Discuss the following regarding loose parts:
- a. What inspections are performed to detect loose parts.
A visual inspection was performed on both generators at the TTS. Additionally, eddy current testing using the Plus Point coil was performed on the CL periphery (3 tubes in) and 100% of the HL.
- b. Describe any loose parts detected and their location within the SG if the loose parts were removed from the SG.
During the Refuel 14 FOSAR inspection of SG No. 2, foreign objects were discovered in the annulus and tube lane. All these foreign objects were removed except a 1 x 1 x 1/8 steel object lodged underneath the blowdown line. A summary of the foreign objects discovered is provided below.
1.
Flex gasket (5 x 1/8 x 0.06) in the Hot Leg Tube Lane 2.
Flex gasket (5 x 1/8 x 0.06) at Col 1 Row 9, Cold Leg 3.
Flex gasket (5 x 1/8 x 0.06) at Col 1 Row 9, Cold Leg 4.
Plastic Tie Wrap (1 x 1/8 x 0.03) in the Cold Leg Annulus 5.
Metallic Object (2.5 x 1/4 x 0.03) in the Cold Leg Annulus 6.
Wire (6 long x 0.06 diameter) in the Hot Leg Tube Lane 7.
Metallic Object (1 x 1 x 1/8) lodged underneath Blowdown Line near Col 117 Row 1, Hot Leg Several attempts were made to remove item #7 (i.e. pushing and pulling with FOSAR equipment), and the object would not move.
- c. Indications of tube damage associated with the loose parts.
According to Eddie Current Testing to date, there have been no wear indications at the locations of the loose parts.
- d. Describe the source or nature of the loose parts if known The items found in the SG are likely carried to the SG through the Condensate Feedwater system based on their small size and deformations. The Orange Tie-wrap [orange is now required to be used for FME - easily seen] is not thought to have entered during power operation.
10.
Discuss the results of any secondary side inspections.
- a. The SG31 Upper Internals Upper Batwing welds are intact Some residual sludge on the horizontal surfaces.
- b. The SG32 Lower Visual - FOSAR and Stay Cavity Examination of the Lower Batwings.
6 loose parts - retrieved from annulus areas; wire and flexitallic 20 broken batwings at the center of the central stay cylinder 11.
Discuss any unexpected or unusual results.
Bat Wing (Diagonal Supports) failures in SG32 only. The first failures were identified in RF13 (April 2005) and additional failures were expected.
Some batwing breaks are not at the notch of the horizontal bar at the notch.