NL-08-0247, Response to NRC Request for Additional Information Regarding the 2007 Unit 2 (2R12) Steam Generator Tube Inspections
| ML080570195 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 02/25/2008 |
| From: | David Jones Southern Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-08-0247 | |
| Download: ML080570195 (6) | |
Text
David H. Jones Southern Nuclear Vice President Operating Company, Inc.
Engineering 40 Inverness Center Parkway Birmingham. Alabama 35242 Tel 205.992.5984 Fax 205.992.0341 SOUTHERNA COMPANY February 25, 2008 Energy to Serve lOurWorM'"
Docket No.:
50,.425 NL-08-0247 U. S. Nuclear Regulatory Commission AnN: Document Control Desk Washington, D. C. 20555-0001 Vogtle Electric Generating Plant Response to NRC Request for Additional Information Regarding the 2007 Unit 2 (2R12) Steam Generator Tube Inspections Ladies and Gentlemen:
On January 28, 2008, Southern Nuclear Operating Company (SNC) received a Request for Additional Information (RAI) from the NRC concerning the Vogtle Electric Generating Plant (VEGP) 2007 Unit 2 (2R12) Steam Generator Tube Inspections. The SNC response to the subject RAI is enclosed.
This letter contains no NRC commitments. If you have any questions, please advise.
David H. Jo s
Vice President - Engineering DHJ/DRG/daj
Enclosure:
Response to NRC Request for Additional Information (RAI)
Regarding the 2007 Unit 2 (2R12) Steam Generator Tube Inspections cc:
Southern Nuclear Operating Company Mr. J. T. Gasser, Executive Vice President Mr. T. E. Tynan, Vice President - Vogtle RType: CVC7000 U. S. Nuclear Regulatory Commission Mr. V. M. McCree, Acting Regional Administrator Mr. S. P. Lingam, NRR Project Manager - Vogtle Mr. G. J. McCoy, Senior Resident Inspector - Vogtle
Vogtle Electric Generating Plant Enclosure Response to NRC Request for Additional Information (RAI)
Regarding the 2007 Unit 2 (2R12) Steam Generator Tube Inspections
Enclosure Response to NRC Request for Additional Information (RAI)
Regarding the 2007 Unit 2 (2R12) Steam Generator Tube Inspections Page 1 of 4
- 1.
NRC Question For each refueling outage and steam generator tube inspection outage since the steam generators were placed in service, please provide the cumulative effective full power months the steam generator has operated.
SNC Response Steam generator (SG) tubing eddy current examinations were conducted in each of the outages listed in the following table. The elapsed effective full power months (EFPM) from start of Vogtle Unit 2 commercial operation until the associated outage is listed in the following table.
Refueling Outage Cumulative EFPM 2R1 15.0 2R2 29.8 2R3 45.5 2R4 60.9 2R5 78.2 2R6 95.0 2R7 111.9 2R8 128.9 2R9 146.1 2R10 161.9 2R11 177.4 2R12 192.7
Enclosure Response to NRC Request for Additional Information (RAI)
Regarding the 2007 Unit 2 (2R12) Steam Generator Tube Inspections Page 2 of 4
- 2.
NRC Question Regarding the scope of examinations in the U-bend region of rows 1 and 2, please confirm that you have examined all of the tubes (in this region) prior to the completion of your current inspection period (presumably the 90 effective full power month period).
SNC Response Eddy current inspection scope performed during the 2R12 outage and prior outages within the current inspection period has resulted in 100% of Rows 1 and 2 U-bends in steam generators (SG) 1, 2, 3, and 4 having been inspected during the current inspection period. The current inspection period is the 90 effective full power months (EFPM) sequential period; the upcoming fall outage (2R13) is the last planned SG eddy current inspection in the 90 EFPM sequential period.
- 3.
NRC Question You indicated that the steam generators were chemically cleaned during your 2007 outage. Please discuss the results of the chemical cleaning.
SNC Response The chemical cleaning, along with the follow-up mechanical cleaning techniques removed 4,957 pounds of deposits from the SG secondary side of the four Vogtle Unit 2 SGs.
- 4.
NRC Question Please discuss the scope and results of any secondary side inspections.
Enclosure Response to NRC Request for Additional Information (RAI)
Regarding the 2007 Unit 2 (2R12) Steam Generator Tube Inspections Page 3 of 4 SNC Response Discussed in paragraphs (1) through (4) below are the four types of SG secondary-side inspections performed during the Vogtle 2R12 outage.
(1) SG Foreign Object Search and Retrieval (FOSAR) inspection The inspection scope for the SG FOSAR inspections performed during the Vogtle 2R12 outage was the periphery of the tube bundle at the top-of-tubesheet (TTS) and the no-tube-lane at the TTS for all four SGs. The results were that two small-diameter wires and a small screw were detected and removed. Minimal TTS scale deposit was detected and no anomalous conditions were observed.
(2) Inspection of potential loose parts wear volumetric flaws The indications potentially attributable to loose parts wear which were detected in the SG eddy current inspection were visually inspected on the secondary side. These inspections were performed in SG 2 for the Row 1 Column 46 tube in response to a differential free span signal (DFI) on the hot leg (HL) side at 9.4 inches above the TTS and a volumetric indication on the cold leg (CL) side at 10.7 inches above the TTS. The visual inspections confirmed the eddy current program conclusions that no tubing defect had occurred at the noted location on the HL side and that there was a volumetric indication at the noted location on the CL side. No foreign objects were detected in relation to SG 2 Row 1 Column 46.
(3) Inspections using the Consolidated Edison Combined Inspection and Lance (CECIL) system The CECIL system was deployed in the VEGP Unit 2 SGs for the purpose of cleaning and inspecting the TTS after the 2R12 chemical cleaning was completed. The intertube inspection portion of the system was deployed down several HL side columns in the manway and nozzle sides in SGs 1 and 4. The initial inspections performed in the CECIL deployment, prior to intertube water lancing in SG 1 and SG 4, found small amounts of hard scale deposit. A foreign object was observed in SG 1; the object was later removed by FOSAR as described in paragraph (1) above. The inspections performed after completion of the CECIL cleaning showed that there were no additional foreign objects or scale observed, except for residual amounts of hard deposit.
Enclosure Response to NRC Request for Additional Information (RAI)
Regarding the 2007 Unit 2 (2R12) Steam Generator Tube Inspections Page 4 of 4 (4) In-bundle inspections above the 7th tube support plate (TSP)
In-bundle inspections were performed above the 7th TSP in all the rows of CL and HL columns 77-78, 87-88, 97-98, and 107-108. The columns were found to be free of foreign objects and sludge. The quatrefoil lobes and lands were clean and open. No anomalous conditions were observed in the 7th TSP inspection.
- 5.
NRC Question Please confirm that the "one non-pluggable volumetric indication" is the same volumetric indication that was reported in steam generator 2 in row 1 column 46. Please also confirm that the indication was attributed to wear and that the indication is "non-pluggable" because it did not exceed the tube repair criteria (rather than the tube could not be plugged). In addition, discuss the cause of the wear (e.g.,
interaction with cleaning equipment, etc.)
SNC Response The one non-pluggable volumetric indication is the same volumetric indication that was reported in the SG 2 tube at Row 1 Column 46 at approximately 11 inches above the TTS on the CL side. This tube was not plugged, because the measured depth of the volumetric indication using qualified sizing techniques was 21% through-wall, which is less than the tube repair criteria. This indication is interpreted as a wear scar associated with 2R11 secondary side maintenance tooling.