NL-06-1777, Response to NRC Request for Additional Information Regarding the 2005 Unit 2 (2R11) Steam Generator Tube Inspection Report
| ML062290288 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 08/16/2006 |
| From: | Grissette D Southern Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-06-1777 | |
| Download: ML062290288 (5) | |
Text
Don E. Grissette Vice President August 16, 2006 Southern Nuclear Operating Company, Inc.
40 lnverness Center Parkway Post Off~ce Box 1295 B~rrningham, Alabama 35201 Docket Nos.:
50-424 50-425 Tel 205.992.6474 Fax 205.992.0341
\\
SOUTHERN &
COMPANY Energy to Serve Your WorldSM U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Vogtle Electric Generating Plant Response to NRC Request for Additional Information Regarding the 2005 Unit 2 (2R11) Steam Generator Tube Inspection Report Ladies and Gentlemen:
On July 17,2006, Southern Nuclear Operating Company (SNC) received four questions by facsimile from the staff concerning the Vogtle Electric Generating Plant (VEGP) 2005 Unit 2 (2R11) Steam Generator Tube Inspection Report, dated January 1 1,2006. The SNC response to these questions is enclosed.
This letter contains no NRC commitments. If you have any questions, please advise.
Sincerely, Don E. ~ r i s s z e
Enclosure:
SNC Response to NRC Request for Additional Information cc:
Southern Nuclear Operating Company Mr. J. T. Gasser, Executive Vice President Mr. T. E. Tynan, General Manager - Plant Vogtle RType: CVC7000 U. S. Nuclear Regulatory Commission Dr. W. D. Travers, Regional Administrator Mr. C. Gratton, NRR Project Manager - Vogtle Mr. G. J. McCoy, Senior Resident Inspector - Vogtle
Vogtle Electric Generating Plant Response to NRC Request for Additional Information regard in^ the 2005 Unit 2 (2R11) Steam Generator Tube Inspection Report Enclosure
Vogtle Electric Generating Plant Response to NRC Request for Additional Information Regarding the 2005 Unit 2 (2R 1 1) Steam Generator Tube Inspection Report Enclosure
- 1.
NRC Question On page 1 of your January 11,2006, report, you stated that you performed +Point rotating pancake coil examinations of 60-80 tubes at tube support plates 6 and 7 on the hot leg side to gage quatrefoil blockage by deposits. Please discuss the results of this investigation.
SNC Response Deposit in the bundle is largely concentrated on the hot leg (HL) side, in the upper portion, of the bundle. TSP-specific discussion for the upper portion follows:
TSP7 The lobes through which the water-steam mixture flows up through the tube bundle are not blocked on the HL side; however, at TSP 7 on the HL side, there are some quatrefoil lobes which are partially blocked by rings of deposit on the tube on the bottom side of the TSP, with one location estimated at 20-30%
blocked.
There are no observable gaps between the tubes and tube support plate (TSP) quatrefoil lands on the HL side for TSP 7; the deposit on the tube and TSP merge to form a continuous field. The gaps between the tubes and tube support plates on the cold leg (CL) side are visible, and only partially filled in a fraction of the tubes.
TSP6 The lobes through which the water-steam mixture flows up through the tube bundle are not blocked on the HL side.
The gaps between the tubes and tube support plate (TSP) quatrefoil lands on the hot leg (HL) side are mostly not visible for TSP 6. The gaps are largely unfilled on the CL side.
The limited partial quatrefoil blockage described above has not resulted in a discernible impact on SG level control. Chemical cleaning of the VEGP Units 1 and 2 SG's for removal of deposit from the secondary-side of the tube bundle and the top of the tubesheet (TTS) is planned for Unit 1 in fall 2006 and in Unit 2 in spring 2007.
- 2.
NRC Question Please confirm that no crack-like indications were identified at Vogtle Unit 2 during the 2005 steam generator (SG) tube inspections.
SNC Response No crack-like indications were identified in the Vogtle Unit 2 2005 outage (2R11)
SG tubing eddy current inspections.
Vogtle Electric Generating Plant Response to NRC Request for Additional Information Regarding the 2005 Unit 2 (2R11) Steam Generator Tube Inspection Report NRC Question On page 2 of your January 11,2006, report, you indicated that possible loose parts indications were identified during the inspection. Please discuss whether a foreign object search and retrieval was performed on each SG. If so, please discuss the scope and results. If any loose parts were identified, discuss whether the loose parts were removed. If the parts were not removed or the locations were not visually inspected, please discuss the results of any evaluations performed to ensure these parts (or suspected parts) would not result in a loss of tube integrity for the period of time between inspections.
SNC Response Foreign object search and retrieval (FOSAR) was performed on all four Vogtle Unit 2 SGs. The standard FOSAR scope is comprised of visual inspection using remote video camera technology of the annulus area at the TI'S and the tubelane which runs through the center of the tube bundle at the TI'S. The possible loose parts (PLP) indications were only in SGl; for SGl only, additional FOSAR scope was the PLP locations.
Information regarding FOSAR results is provided below on an SG-specific basis.
SG1 -
No tube damage was observed. An evaluation was performed to justify leaving SGl Foreign Object #3 in the SG based on conservative analyses showing that there would not be a loss of tube integrity within the next 3 years, which allows another FOSAR to be performed at that location before the end of the 3 year period.
SG2 -
No tube damage was observed.
Vogtle Electric Generating Plant Response to NRC Request for Additional Information Regarding the 2005 Unit 2 (2R11) Steam Generator Tube Inspection Report SG3 -
No foreign objects were observed.
SG4 -
Wear scars were visible on column 93, row 42. This scarring was caused by SG4 foreign object #5.
- 4.
NRC Ouestion
- 4. Wire / flex gasket
- 5. Two Twisted Tie Wires
- 6. Sludge Rock On page 7 of your January 11,2006, report, you reported that one tube (row 12 column 57) in steam generator 4 had an indication at the top of the tubesheet in the hot leg side that measured 14 percent through-wall. Please discuss the nature and cause of this indication.
SNC Resvonse CL This indication is categorized as a volumetric flaw (VOL three letter code), and is assessed as a wear scar, residual from a prior foreign object. This VOL indication was first reported in the 2R10 outage (spring 2004), and sized at 18% through-wall depth (TW). A history lookup was performed for the tube during the 2R10 inspection and it was determined that volumetric signals pre-existed the 2R10 VOL in 2R9 (fall 2002), and that no growth had taken place since the 2R9 eddy current inspection. Based on the 14% TW depth reported in 2R11, the indication has exhibited no growth. It is apparent that an itinerant foreign object is responsible for the wear detected which probably took place during the period from 1999 (2R7 outage) to 2002. No possible loose part signals (PLP three letter code) were reported for the tube at R12C57 during the 2R 1 1,2R 10,2R9, or 2R7 outages.
Tube lane C93/94 R4 1/42 Tube lane Yes Yes Yes Yes Yes Yes 115" 2 114" 114" 3/16" 1/16" dia.
3/16" 3/16" 1 112" 1/32"