ML091540203
| ML091540203 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 05/20/2009 |
| From: | Jordan A Dominion Nuclear Connecticut |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 09-281, TAC ME0094, FOIA/PA-2011-0115 | |
| Download: ML091540203 (8) | |
Text
Dominion Nuclear Connecticut, Inc.
Millstone Power Station ýý Dominion-Rope Ferry Road Waterford, CT 06385 MAY 2 0 2009 U.S. Nuclear Regulatory Commission Serial No.09-281 Attention: Document Control Desk MPS Lic/MLC RO Washington, DC 20555 Docket No. 50-336 License No. DPR-65 DOMINION NUCLEAR CONNECTICUT. INC.
MILLSTONE POWER STATION UNIT 2 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION 2008 STEAM GENERATOR TUBE INSPECTIONS (TAC NO. ME0094)
By letter dated October 24, 2008 (Serial No. 08-0627), Dominion Nuclear Connecticut, Inc. (DNC) submitted the Millstone Power Station Unit 2 steam generator tube inspection results obtained during the 2008 refueling outage.
On April 13, 2009, the Nuclear Regulatory Commission staff issued a request for additional information (RAI). DNC's response to the RAI is provided as an attachment to this letter.
If you have any questions or require additional information, please contact Mr. William D. Bartron at (860) 444-4301.
Sincerely, A. J/ Jrdan Site VP - Millstone Aoo/
Lt(Lp,
Serial No.09-281 Response to RAI Docket No. 50-336 Page 2 of 2 Attachment Commitments made in this letter: None.
cc: U.S. Nuclear Regulatory Commission Region I Regional Administrator 475 Allendale Road King of Prussia, PA 19406-1415 C. J. Sanders NRC Project Manager U.S. Nuclear Regulatory Commission, Mail Stop 08B3 One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station
Serial No.09-281 Response to RAI Docket No. 50-336 ATTACHMENT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION 2008 STEAM GENERATOR TUBE INSPECTION RESULTS MILLSTONE POWER STATION UNIT 2 DOMINION NUCLEAR CONNECTICUT, INC.
Serial No.09-281 Response to RAI, Attachment Docket No. 50-336 Page 2 of 6 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION In reviewing the Dominion Nuclear Connecticut, Inc. (DNC) report dated October 24, 2008 which summarized the Millstone Power Station Unit 2 (MPS2) end of cycle (EOC) 18 steam generator (SG) tube inspection results (Agencywide Documents Access and Management System (ADAMS) Accession No. ML083090396), the Nuclear Regulatory Commission (NRC) staff has determined that the following information is needed in order to complete its review:
NRC Question No. 1 For each refueling outage and for each SG tube inspection since installation of the SGs, please provide the cumulative effective full-power months that the SGs have operated.
DNC Response Outage Inspection Cumulative EFPM 2R1 1 Pre-service 0.0 2R12 yes 15.7 Mid-Cycle 13 yes 21.7 2R13 yes 31.8 2R14 yes 51.5 2R15 yes 68.4 2R16 yes 84.4 2R17 no 100.6 2R18 yes 117.1 NRC Question No. 2 Eight tubes were plugged in SG 1. Please confirm that the following tubes were plugged in SG 1: (row 2, column 7 (R2C7), R3C8, R4C9, R5C10, R8C1l, R76C141, R78C141). In addition, for SG1, you indicated that by plugging one additional tube that three tubes box the loose part (presumably this is a tube near R76C141 and R78C141). Please discuss how plugging the third tube boxes in the loose part.
DNC Response The above listed tubes were plugged. The additional tube plugged to box the loose part was R77C142. The MPS2 replacement SGs were constructed with a triangular pitch, therefore, three tubes are required to box a loose part. See diagram below:
Serial No.09-281 Response to RAI, Attachment Docket No. 50-336 Page 3 of 6 R78C141 R77C142 R76C 141 NRC Question No. 3 Two tubes were plugged in SG 2. Please confirm that the tube at Ri 18C41 was plugged in SG 2. Please indicate which other tube was plugged since it was adjacent to tubes with wear from loose parts that could not be removed.
DNC Response Tube R1 18C41 in SG 2 was not plugged. The associated loose part was removed in October 2003. No further wear has been observed since 2003.
Tubes R38C81 and R40C81 were plugged. A piece of flexitallic gasket was wrapped around R38C81 and contacting R40C81. Wear was observed on R40C81. No wear was observed on R38C81.
NRC Question No. 4 For SG 2, several tubes with induced indications are listed on page 7 of the October 24, 2008 letter (Serial No. 08-0627). Please discuss the nature of these indications and discuss why they were not plugged. If they were attributed to loose parts, please discuss whether a part was found and removed from these locations. If no part was located at these locations, discuss your basis for concluding that they were a result of a loose part (e.g., visual inspection confirming a wear scar). Please discuss whether any loose parts (in either SG) were left in service. If any parts were left in service, please confirm that you performed an analysis confirming the acceptability of leaving these parts in the steam generator(s).
Serial No.09-281 Response to RAI, Attachment Docket No. 50-336 Page 4 of 6 DNC Response At one location (R40C81) where a loose part was present and not removed, the tube was removed from service. Two of the locations were associated with fan bar wear. For the remaining locations, loose parts had been previously observed in the area, no PLPs were detected during MPS2 refueling outage 18 (2R18),
and no continuing wear was observed over the past several cycles. Twenty-four loose parts were left in service. No wear was detected in any of the tubes in the areas adjacent to any of these loose parts. Analysis confirmed the acceptability of leaving these parts in the SGs. Improved tooling is being developed with the intent of removing them during future outages.
Row Col Discussion 37 120 Fan bar wear, 9 percent through-wall (%TW), increased 3%TW over the past three years.
28 5 Several pieces of flexitallic gasket were previously removed from this area. Wear conservatively sized at 29%TW, unchanged from 2003. No possible loose part (PLP) detected.
29 4 Several pieces of flexitallic gasket were previously removed from this area. Wear conservatively sized at 25%TW, unchanged from 2003. No PLP detected.
40 81 A piece of flexitallic gasket observed and could not be removed.
Wear conservatively sized at 30%TW. The tube and an adjacent tube were plugged.
59 10 Several pieces of flexitallic gasket were previously removed from this area. Wear conservatively sized at 23%TW, unchanged from 2003. No PLP detected.
98 143 Wear conservatively sized at 26%TW. No loose part found, no PLP detected, wear present since 2000.
99 80 Fan bar wear, 11 %TW, no change over the past three years.
118 41 Seven pieces of flexitallic gasket were previously removed from this area. Wear conservatively sized at 11 %TW, unchanged from 2003. No PLP detected.
119 42 Seven pieces of flexitallic gasket were previously removed from this area. Wear conservatively sized at 29%TW, unchanged from 2003. No PLP detected.
123 46 Seven pieces of flexitallic gasket were previously removed from this area. Wear conservatively sized at 27%TW, unchanged from 2003. No PLP detected.
Serial No.09-281 Response to RAI, Attachment Docket No. 50-336 Page 5 of 6 Row Col Discussion 124 45 Seven pieces of flexitallic gasket were previously removed from this area. Wear conservatively sized at 31 %TW, unchanged from 2003. No PLP detected.
125 48 Seven pieces of flexitallic gasket were previously removed from this area. Wear conservatively sized at 37%TW, unchanged from 2003. No PLP detected.
126 49 Seven pieces of flexitallic gasket were previously removed from this area. Wear conservatively sized at 39%TW, unchanged from 2003. No PLP detected.
NRC Question No. 5 Rotating probe inspections were performed on tubes that were observed with flex gasket material protruding from the tube ends. Please clarify the source of flex gasket material and confirm the material was located on the primary side of the tubes. Please discuss whether the gasket material was removed. In addition, please discuss the results of these rotating probe examinations.
DNC Response The reported source of the gasket material was bolted flange joints associated with startup strainer locations in the Residual Heat Removal System. The material was located on the primary side of the SGs. All identified pieces of gasket material were removed from the primary side of the SGs. Each of the tubes containing the gasket material was examined with diagnostic techniques and no degradation was detected.
NRC Question No. 6 Please discuss the extent to which any tubes may be in close proximity to each other. Please discuss whether the number of tubes in close proximity has increased/decreased since the SGs were installed.
DNC Response No tubes have been identified that are close or in contact with each other.
NRC Question No. 7 How many tubes were only partially expanded into the tubesheet, where are they located, and what is the extent of these "partial expansions?"
Serial No.09-281 Response to RAI, Attachment Docket No. 50-336 Page 6 of 6 DNC Response The only partial tube expansion (PTE) located in SG 1 was in tube R69C14. This tube was examined for the full tubesheet depth by diagnostic techniques during 2R18 and was reported as no degradation found (NDF). The tube is not expanded from the tube end hot leg (TEH) + 11.57" to the top of the tube sheet hot leg (TSH). There are no PTEs located in SG 2.
NRC Question No. 8 Please discuss the scope and results of any secondary side inspections.
DNC Response A Secondary Side Inspection (SSI) and Foreign Object Search and Retrieval (FOSAR) effort was conducted on the secondary side of both SGs in the area of the tubesheet and flow distribution baffle. Significant effort was devoted to the prosecution of foreign objects from history, SSI, and eddy current test (ECT) examination data. Many loose parts were removed and efforts to remove the rest were attempted. No indication of degradation or displacement of any of the internal structures such as the wrapper or tube supports was identified.
The upper internals from the U-bend region, up through the primary and secondary separators including decks, the feed ring, piping, and supports of both SGs, was visually inspected. No significant degradation was identified.