ML12292A192
| ML12292A192 | |
| Person / Time | |
|---|---|
| Site: | Millstone  (NPF-049) |
| Issue date: | 10/01/2012 |
| From: | Scace S Dominion Nuclear Connecticut |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 12-530, TAC ME8422 | |
| Download: ML12292A192 (7) | |
Text
Dominion Dominion Nuclear Connecticut, Inc.
Millstone Power Station Rope Ferry Road Waterford, CT 06385 OCT 12012 U. S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555 Serial No.
NSSL/MLC Docket No.
License No.12-530 RO 50-423 NPF-49 DOMINION NUCLEAR CONNECTICUT, INC.
MILLSTONE POWER STATION UNIT 3 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING THE END OF CYCLE 14 STEAM GENERATOR TUBE INSPECTION REPORT (TAC NO. ME8422)
Dominion Nuclear Connecticut, Inc. (DNC) submitted the Millstone Power Station Unit 3 End of Cycle 14 Steam Generator Tube Inspection Report in a letter dated April 6, 2012.
The report documents the results of the steam generator inspections performed in accordance with Technical Specification 6.8.4.g, "Steam Generator Program". In a letter dated August 8, 2012, the NRC transmitted a request for additional information (RAI) to DNC related to the inspections. DNC agreed to respond to the RAI by October 7, 2012. provides DNC's response to the NRC's RAI.
If you have any questions regarding this submittal, please contact William Bartron at (860) 444-4301.
Sincerely, Site Vice President - Millstone Power Station
Attachment:
- 1. Response to Request for Additional Information Regarding End of Cycle 14 Steam Generator Tube Inspection Report Commitments made in this letter:
- 1. None 7k'bo "4
Serial No.12-530 Docket No. 50-423 Page 2 of 2 cc:
U.S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd., Suite 100 King of Prussia, PA 19406-2713 J. S. Kim Project Manager - Millstone Power Station U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 08 C2A Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station
Serial No.12-530 Docket No. 50-423 ATTACHMENT 1 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING END OF CYCLE 14 STEAM GENERATOR TUBE INSPECTION REPORT DOMINION NUCLEAR CONNECTICUT, INC.
MWLLSTONE POWER STATION UNIT 3
Serial No.12-530 Docket No. 50-423 RAI Response to EOC14 SG Tube Inspection Report, Page 1 of 4 Dominion Nuclear Connecticut, Inc. (DNC) submitted the Millstone Power Station Unit 3 (MPS3) End of Cycle 14 (EOC14) Steam Generator (SG) Tube Inspection Report in a letter dated April 6, 2012. The report documents the results of the steam generator inspections performed in accordance with Technical Specification (TS) 6.8.4.g, "Steam Generator Program". In a letter dated August 8, 2012, the NRC transmitted a request for additional information (RAI) to DNC related to the inspections. This attachment provides DNC's response to the NRC's RAI.
RAI 1
Page 3 of Enclosure I to your April 6 letter indicates that secondary side examinations were performed in SG D. Please discuss the results of these examinations.
DNC Response Secondary side visual inspections were performed in all four SGs during refueling outage 3R14. These examinations included performing a post-water lance inspection of the tubesheet annulus and tube lane using an articulating camera to support viewing into the bundle for all four SGs. The inspection also looked for degradation of visible tube supports, the flow distribution baffle, and the wrapper to ensure structural integrity of these components.
Inspection findings were similar in each of the four SGs. The upper bundle flush (UBF) and water lance operations were successful in removing loose deposits throughout the tube bundle and at the top of tubesheet. The inspections at the top of tubesheet in all four SGs revealed mostly clean conditions with minor flake piles remaining in the peripheral regions. The remaining sludge flakes were located mostly at the 90 degree handholes in the stay rod lance shadow zones near the suction feet and totaled less than a cup each. In-bundle views from the periphery showed the tubesheet to be very clean in all four SGs. The no-tube lane was clean and the center stay rod and blowdown piping were in good condition in each of the SGs.
An upper internals inspection, which includes inspection of the steam drum and upper bundle region, was performed in SG D only. The secondary moisture separator chevrons were found in good condition. The perforated holes of the outer plate showed minor buildup of sludge in the bore of the hole. No holes were observed to be plugged. The chevrons were straight and showed a light coating of sludge deposit.
The primary moisture separator swirl vanes were found in good condition. The vanes had a slight deposit on them but the edges were sharp, showing no indication of erosion. It was noted that there was a heavy deposit of sludge on the steam drum shell wall at the upper deck. This deposit became thicker higher up on the shell wall.
Ladders, drains, wedges, supports and associated welds throughout the upper internals were acceptable.
Thirty (30) J-nozzles located on the main feedwater pipe were internally and externally inspected and were found in good condition. Of concern were nozzles 1, 15, 16, and 30 which had a weld overlay applied during a previous outage. Internally, these four
Serial No.12-530 Docket No. 50-423 RAI Response to EOC14 SG Tube Inspection Report, Page 2 of 4 nozzles showed prior erosion damage that has not appeared to have advanced since their last inspection in the spring of 2004 (3RO9). Overspray from the J-nozzles was also noted on the primary separator riser barrels.
The upper bundle inspections were performed after performing the UBF. Internal visual inspections of the steam drum, as well as upper bundle inspections above the seventh tube support plate, found the SG to structurally be in good condition. The majority of the loose sludge deposits in the upper tube bundle region had been removed by the UBF operation. The views obtained of the broached holes at the periphery revealed only a slight ridge of sludge buildup at the bottom side of the seventh tube support plate.
Overall, the secondary sides of the four MPS3 SGs visually appeared to be in an as expected condition with no visible damage, degradation, or abnormalities.
RAI 2
Please discuss the scope and results of any examinations of the plugs.
DNC Response Existing plugs in SGs A and C were visually examined during 3R14. The proper tube number, plug type, and plug position were verified. While a light boric acid coating was noted on some of the plugs, no evidence of leakage or degradation was identified.
RAI 3
Please clarify the "old" and "new" offset columns in Tables 3 and 4.
DNC Response The "old" and "new" offset columns represent the axial position along the tube length of the measured depth of the indication during consecutive outages. The "old" axial position was reported during 3R12 and the "new" position was reported during 3R14.
The offset numbers represent distance relative to the support structure centerline.
Some small variation in the reported location exists due to differences in landmark selection (selecting the centerline of the support) and selection of the wear scar center by different analysts. Another contributor to these small variations in reported locations is due to the probe axial speed variation due to the significant length of probe between the probe head and the axial encoder.
In the hot leg, positive direction originates at the lower tube end (TEH) and extends upward to 08C + 2.00 inches. In the cold leg, positive direction originates at the lower tube end (TEC) and extends upward to and including, 08C + 2.00 inches. Therefore,
Serial No.12-530 Docket No. 50-423 RAI Response to EOC14 SG Tube Inspection Report, Page 3 of 4 for the indication in Table 3 reported at anti-vibration bar five (AVB5) in the tube located in row 22 column 78, the 3R12 analyst measured the depth of the wear scar at the perceived center of the AVB structure and the 3R1 4 analyst measured the depth of the wear scar one tenth of an inch (in the positive direction) from the perceived center of the AVB structure.
RAI 4
In SG A (row 5, column 48), anti-vibration bar (A VB) wear indications were reported approximately 11.5 to 12 inches from the 8th hot-leg support. Confirm that these indications are located at the A VBs. If so, please clarify the location relative to the nearest A VB.
DNC Response The two indications of volumetric wear reported in SG A, row 5, column 48 appear to be located in the apex of the u-bend. Row 5 is not supported by an AVB but had two indications in the apex of the u-bend that were assumed to be caused by the bottom of the AVB supporting the tubes in the row above it.
Although the recorded degradation was minor (estimated to be 5% and 11%), DNC plugged this tube in row 5 for AVB wear because growth rates for this degradation mechanism had not been previously established.
RAI 5
Please clarify the acronym "FK" in Tables 7 and 8. Also, please clarify the cause of the indications attributed to "sled."
DNC Response The acronym "FK" stands for FOTS Key. FOTS is the name given to the Foreign Object Tracking System used by Dominion and FOTS Key is the tracking number assigned to each item entered into the tracking system.
The acronym "sled" is used to identify the Single Volumetric Indications (SVIs) first identified during 3R08 (spring 2002) that were determined to be the result of mechanical wear caused by the sludge lancing mechanism employed in previous outages. These SVIs are in peripheral tubes, often at a protruding edge of the tube bundle, and typically near an elevation of 0.5 inches above the secondary face of the tubesheet.
Serial No.12-530 Docket No. 50-423 RAI Response to EOC14 SG Tube Inspection Report, Page 4 of 4
RAI 6
Please clarify whether any high row tubes have potentially elevated residual stresses, as evidenced by the eddy current data (2-sigma tubes). If there are such tubes, please discuss whether any rotating probe exams were performed on these tubes at locations such as the expansion transition, dents, or dings.
DNC Response During 3R14, eddy current examinations were conducted in SGs A and C. SG A has 67 tubes and SG C has 39 tubes designated as tier 1 tubes (high stress tubes). All tier 1 tubes in these two SGs were examined from tube-end to tube-end with a bobbin coil probe. All tier 1 tubes in these two SGs were examined from the hot-leg tube-end to the first detectable support above the hot-leg tubesheet with an array probe. In addition, rotating coil probes were used on 28 locations in 21 of the tier 1 tubes. These 28 special interest locations included areas with recorded indications of dents, dings, manufacturing burnish marks, volumetric wear, or ambiguous signals with the other probes.