ML073200234
| ML073200234 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 11/15/2007 |
| From: | Funderburk C Virginia Electric & Power Co (VEPCO) |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 07-0704 | |
| Download: ML073200234 (7) | |
Text
VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 November 15, 2007 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555 VIRGINIA ELECTRIC AND POWER COMPANY (DOMINION)
NORTH ANNA POWER STATION UNIT 1 STEAM GENERATOR TUBE INSPECTION REPORT Serial No.
NL&OS/ETS Docket No.
License No.
07-0704 50-338 NPF-4 Pursuant to Technical Specification 5.6.7 for North Anna Power Station Unit 1, Dominion is required to submit a 180-day steam generator tube inspection report. The attachment to this letter provides the steam generator tube inspection report for the North Anna Unit 1 fall 2007 refueling outage.
This letter does not establish any new commitments.
Should you have any questions or require additional information, please contact Mr. Thomas Shaub at (804) 273-2763.
Very truly yours, c ~rk. Director Nuclear Licensing and Operations Support Dominion Resources Services, Inc.
for Virginia Electric and Power Company Attachment
cc:
U.S. Nuclear Regulatory Commission Region II Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW Suite 23T85 Atlanta, Georgia 30303 Mr. J. T. Reece NRC Senior Resident Inspector North Anna Power Station Mr. J. E. Reasor, Jr.
Old Dominion Electric Cooperative Innsbrook Corporate Center 4201 Dominion Blvd.
Suite 300 Glen Allen, Virginia 23060 Mr. R. A. Jervey NRC Project Manager - North Anna U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 0-8 G9A Rockville, Maryland 20852 Mr. S. P. Lingam NRC Project Manager - Surry U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike MaiI Stop 0-8 G9A Rockville, Maryland 20852 Serial No. 07-0704 Docket No. 50-338 180-Day SG Report Page 2 of 2
Serial No. 07-0704 Docket No. 50-338 180-Day SG Report ATTACHMENT NORTH ANNA UNIT 1 l80-DAY NRC REPORT REGARDING STEAM GENERATOR TUBE INSPECTION PER TECHNICAL SPECIFICATION 5.6.7
Serial No. 07-0704 Docket No. 50-338 180-Day SG Report NORTH ANNA UNIT 1 - FALL 2007 The following satisfies the North Anna Power Station Technical Specification (TS) reporting requirement section 5.6.7.
During the North Anna fall 2007 refueling outage, steam generator inspections in accordance with TS 5.5.8.d were completed for one of the three steam generators ("A"). This was the initial inspection under the modified Technical Specifications resulting from the TSTF-449 generic specification issued to the industry.
Consequently, the referenced outage is the starting point for compliance to the periodicity and tube inspection coverage requirements of 5.5.8.d.
Initial entry into Mode 4 occurred on October 13, 2007 (10:08 Hrs); therefore, this report is required to be submitted by April 11,2008.
Bold-italicized wording represents TS verbiage.
The required information is provided under each reporting requirement as follows:
A report shall be submitted within 180 days after the initial entry into Mode 4 following completion of an inspection performed in accordance with the Specification 5.5.8, "Steam Generator (SG) Program." The report shall include:
a.
The scope of inspections performed on each SG The following primary side inspections were performed in steam generator "A":
100% full-length inspection utilizing bobbin coil probe for all tubes except for Row 1 U-bends 20% (719 Tubes) hot leg top of tubesheet (+/- 3") utilizing rotating coil probe with tube selection biased toward a secondary side critical area in the sludge zone, peripheral area tubes, and the remainder across the tubesheet.
100% Row 1 (98 tubes) U-bend region utilizing rotating coil probe.
Special interest inspections of freespan dent/bulges> 2 volts with rotating coil probe Inspection of bobbin identified I-codes (i.e. possible indications) with rotating coil probe.
Special interest rotating coil probe exams of anomalies within the tubesheet; overexpansions (OXP).
Hot leg and cold leg primary side tubesheet video scan.
The following secondary side inspections were performed in steam generator "A":
Steam drum upper components visual inspection covering the primary and secondary moisture separators, drain piping, and related components.
Video inspection of the upper tube bundle U-bend area.
Video inspection of the uppermost tube support plate (TSP), i.e. i h TSP in the periphery area and in-bundle at selected tube columns.
The 4th, 5th, and 6th TSPs were video inspected in the center bundle area accessed from the i h TSP.
Video inspection of the inside interface of the feedring to J-nozzle joints, i.e. exit spargers.
UT inspection of selected feedring components.
Page 1 of 4
Serial No. 07-0704 Docket No. 50-338 180-Day SG Report
- b. Active degradation mechanisms found No indication of corrosion degradation was observed during this inspection.
Volumetric wear degradation was observed on three (3) tubes adjacent to TSP quatrefoil contact points.
Similar indications have been observed previously on Unit 2 and reported in required submittals. A total of four (4) of these indications have been observed on Unit 2 with the largest one reported at 40% TW. This is the first instance of this type of indication observed at North Anna Unit 1.
The secondary side inspections on the "A" steam generator indicated no component degradation that would compromise tube integrity.
- c. Nondestructive examination techniques utilized for each degradation mechanism Inspections focused on the following degradation mechanisms listed in Table 1 utilizing the referenced eddy current techniques.
Table 1 - Inspection Method for Applicable Degradation Modes Classification Degradation Location Probe Type Mechanism Bobbin - Detection Potential Tube Wear Anti-Vibration Bars Bobbin and +Point'- Sizing Bobbin - Detection Potential Tube Wear Flow Distribution Baffle Bobbin and +Point'- Sizing Bobbin - Detection Existing Tube Wear Tube Support Plate Bobbin and +Point'- Sizing Straight Leg & AVB Tangents Bobbin - Detection Potential Tube Wear (Row 8,14,26)
Bobbin or +Point'- Sizing Existing Tube Wear Bobbin - Detection (foreign objects)
Freespan and TIS
+Point'- Sizing Hot Leg Top-of-Tubesheet Bobbin and +Point'- Detection Potential ODSCC Sludge Pile Area
+Point'- Sizing Hot Leg Top-of-Tubesheet Relevant/Informational Sludge Pile Area and Within
+Point'- Detection and Sizing PWSCC Tubesheet Inspection Anomaly locations Reievant/Informational ODSCC
+Point'- Detection and Sizing Row 1 U-bends Inspection PWSCC Relevant/Informational
+Point'- Detection and Sizing ODSCC Freespan and Tube Supports Inspection Relevant/Informational OD Pitting Bobbin and +Point'- Detection Inspection Top-of-Tubesheet
+Point'
- Sizing The only degradation noted In (b) above was Identified dunng the bobbin probe examinations. The sizing of the degradation was performed utilizing a rotating coil based eddy current technique.
Page 2 of 4
Serial No. 07-0704 Docket No. 50-338 180-Day SG Report
- d. Location, orientation (if linear), and measured sizes (if available) of service induced indications As noted in the (b) response above, several wear type indications were noted.
Table 2 provides the detailed information regarding these indications.
- e. Number of tubes plugged during the inspection outage for each active degradation mechanism No tubes were plugged during the subject inspection.
f.
Total number and percentage of tubes plugged to date A total of two (2) tubes have been plugged in the North Anna Unit 1 steam generators, i.e.
"A" - 0 (0%), "B" - 0 (0%), "C" - 2 (0.05%) with a total percentage of 0.02 %.
- g. The results of condition monitoring, including the results of tube pulls and in-situ testing The condition monitoring evaluation was completed and steam generator "A" did not exceed any performance criteria during the last cycle since the spring 2006 inspection. No findings at the fall 2007 inspection invalidated the previous operational assessment for any of the three steam generators.
Condition monitoring requirements were met since the detected flaw's TW depth was less than the conservative structural limit for this type of flaw, i.e. 66.4% for bounding 0.6" long 360 degree volumetric degradation. Therefore, no tube pulls or in-situ pressure testing was necessary. As noted, no tubes required plugging since their indicated depth was less than the 40% TW plugging limit and growth projections show acceptable results up to a three cycle operating time.
- h. The effective plugging percentage for all plugging in each SG There are no sleeves installed in the North Anna Unit 1 steam generators. Therefore, the effective plugging percentage remains the same as stated in (f) above.
Page 3 of 4
Serial No. 07-0704 Docket No. 50-338 180-Day SG Report Table 2-Significant Reported Indications Maximum Depth Through Axial Circumferential Wall,As Detectable in Plugging SG Row/Col Location Finding Length Length Measured History Data?
Required?
Reason
@06C Volumetric Does not exceed structural A
2/25 0.60" 0040" 16%
Yes (2001)
No limit within 3 additional
-0.51 Damage operating cycles1
@04C Volumetric Does not exceed structural A
2/91 0.52" 0.34" 10%
No (2001)
No limit within 3 additional
-0.17 Damage operating cycles1
@03H Volumetric Does not exceed structural A
15/9 0.32" 0.35" 11%
Yes (1997)
No limit within 3 additional
+0.50 Damage operating cycles1 Note 1: Assumes applying maximum observed growth rate of tube 2/25 and 95%/50% probability/confidence for technique and analyst uncertainty.
Page 4 of 4