NL-14-2025, Response to Request for Additional Information on Spring 2013 Steam Generator Tube Inspections
| ML15013A023 | |
| Person / Time | |
|---|---|
| Site: | Vogtle  |
| Issue date: | 01/12/2015 |
| From: | Pierce C Southern Co, Southern Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-14-2025, TAC MF4288 | |
| Download: ML15013A023 (5) | |
Text
Charles R. Pierce Southern Nuclear Regulatory Affairs Director Operating Company, Inc.
40 Inverness Center Parkway Post Office Box 1295 Birmingham.AL35242 A
Z SOUTHERNS JAN 1 2 W5 Docket No.:
50-425 NL-14-2025 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D. C. 20555-0001 Vogtle Electric Generating Plant, Unit 2 Response to "Request for Additional Infonnation on Spring 2013 Steam Generator Tube Inspections (TAC No. MF4288V' Ladies and Gentlemen; By letters dated July 2, 2013 (Agencywide Documents Access and Management System (ADAMS) Accession Number ML13184A269) and September 26,2013 (ADAMS Accession Number ML14170A021), Southern Nuclear Operating Company, Inc. (SNC) submitted informationsummarizing the results of the spring 2013 steam generator (SG) tube inspections performed at Vogtle Electric Generating Plant, Unit2. These inspections were performed during refueling outage 16 (RFC 16). In a letter dated April 25,2013 (ADAMS Accession Number ML13112A225), the U.S. Nuclear Regulatory Commission (NRC)staff summarized two conference calls that were held with the licensee during RFO 16.
The NRC issued a request for additional informationvia a letter dated November 13,2014 (ADAMS Accession Number ML14314A878). The enclosure to this letter contains the SNC responses to that request.
This letter contains no NRC commitments. Ifyou have any questions, please contact Ken McElroy at (205) 992-7369.
Respectfully submitted, C. R. Pierce Regulatory Affairs Director CRP/EGA Swor^toandsubscribedbeforeme this hZ. dayof 2015.
GAJJUl_
Notary Pubiic f^y commission expires: /6 '
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U. S. Nuclear Regulatory Commission NL-14-2025 Page 2
Enclosure:
SNC Response to Request for Additional Information cc:
Southern Nuclear Operating Company Mr. S. E. Kuczynski, Chairman, President &CEO Mr. D. G. Bost, Executive Vice President & Chief Nuclear Officer Mr. D. R. Madison, Vice President - Fleet Operations Mr. M. D. Meier, Vice President - Regulatory Affairs Mr. B. K. Taber, Vice President - Vogtle 1 &2 Mr. B. J. Adams, Vice President - Engineering Mr. G.W. Gunn, Regulatory Affairs Manager - Vogtle 1 &2 (Acting)
RType: CVC7000 U. S. Nuclear Reaulatorv Commission Mr. V. M. McCree, Regional Administrator Mr. R. E. Martin, NRR Senior Project Manager - Vogtle 1 &2 Mr. L M. Cain, Senior Resident Inspector-Vogtle 1 &2
Vogtle Electric Generating Plant, Unit 2 Response to "Request for Additional Information on Spring 2013 Steam Generator Tube Inspections (TAG No. MF4288)"
Enclosure SNC Response to Request for Additional Information
Enclosure to NL-14-2025 SNC Response to Request for Additional Information NRC Question 1 Please discuss the results ofthe tube plug visual inspections. Were allplugs confirmed to be present and free of degradation?
SNC Response to RA11 All installedtube plugs were visually inspected from the steam generator (SG) primary side on both the hot leg and cold leg primarytubesheet. All tube plugs were confirmed present with no indications of degradation in any of the tube plugs.
NRC Question 2 Please discuss the results of the SG channel head visual inspections.
SNC Response to RAl 2 The channel head visual inspections that were performed were on the hot leg and cold leg of the primary side. No degradation was observed during the SG channel head primary side visual inspections in any of the four steam generators.
NRC Question 3 Please clarify what is meant by "legacy items" in reference to the foreign object search and retrieval inspection. Does this mean that visual inspections were performed at locations where loose parts were known to be present from prior inspections?
SNC Response to RAl 3 Correct. Visual inspections were performed in areas where loose parts were identified in prior inspections and assumed to remain in the steam generators. These locations on the secondary side of the steam generators at the top of the tubesheet were noted in the inspection report as "legacy items." No degradation was identifiedat these locations.
NRC Question 4 Possible loose part indications and wear attributed to loose parts were identifiedon the hot-leg side of the SG. Is wear attributed to loose parts a potential degradation mechanism at Vogtle, Unit2, on the cold-leg side of the SG? If so, please discuss whether the bobbin coil is qualified to detect such degradation near the top of the tubesheet on the cold-leg side of the SG. If the bobbin coil is not qualified, please discuss why a probe capable of detecting such degradation and that may satisfy the applicable tube repair criteria was not employed at those locations where the potential for this degradation mechanism exists (e.g., peripheral tubes).
SNC Response to RAl 4 The Degradation Assessment identifieswear due to loose parts as an existing degradation mechanism for the Vogtle Unit2 steam generators. There are only three indications and no plugged tubes due to foreignobject wear at Vogtle Unit 2. Although the bobbin probe has been effective inidentifying loose part wear above the top-of-tubesheet, itis not qualified to detect foreign object wear right at the top-of-tubesheet interface. The most likely area forforeign E-1
Enclosure to NL-14-2025 SNC Response to Request for Additional Information objects to migrateand cause wear is inperipherytubes and tubes along the tube free lane. A secondary side visual inspection was perfomried ofthe coldlegperiphery tubes and alongthe tube free lane in order to supplement the bobbin coil inspections.
NRC Question 5 A "historical" tube wear indication in SG 4 was reported. In reviewing the priorinspection report submitted to the NRC, no reference was made to this indication. Please confinn that this indication was detected in the prior inspection and that all indications are being reported.
SNC Response to RAI5 Tube SG4 R12C57 was previously identified as a volumetric indication associated with Mechanical Wear and Wall Loss from Secondary Side Cleaning activities reported in the Unit 2 Refueling Outage 13 inspection report (Reference ADAMS Accession Number ML090990606).
This indication has been re-categorized as loose part wear based on evaluation of location and eddy current signal character in the Unit 2 Refueling Outage 16. No progression of growth has been identified, and no foreign objects have been associated with this indication. Indications are reported as they are identified. The indication associated with SG4 R12C57 was identified prior to Unit 2 Refueling Outage 15 (2R15), and discussion of this tube indication was not included in the 2R15 inspection report.
NRC Question 6 With respect to the accident induced leakage performance criteria it was indicated that:
There was no SG primary to secondary leakage present during Cycle 16. The calculated accident induced leakage rate is zero; therefore, the performance criteria for Cycle 16 with respect to the H* permanent alternate repair criteria have been satisfied.
No operational leakage was reported during the previous cycle; therefore, the calculated accident induced leakage rate is zero.
Please clarify these statements. The NRCstaff notes the following: (1)there is no separate accident induced leakage rate limit for the H* permanent alternate repair criteria(rather the accident induced leakage rate limit applies to leakage from all possible sources) and (2) the absence ofoperational leakage does not necessarily mean that the calculated accident induced leakage rate is zero (sincethere could be other sources of leakage such as from tube plugsand from degradation mechanisms other than those that may be permittedto remain in service under the H* criteria).
SNC Response to RAI 6 None of the indications reported duringthe Vogtle 2R16 steam generator inspections are evaluated to have primary to secondary leakage at accident induced conditions. Therefore, the accident induced leakage rate forthese indications would be zero, and the accident induced leakage perfonnance criteria is satisfied. There was no leakagefrom the portion oftubing within the H* depthforwhich to apply the leak rate factorassociated with the alternate repaircriteria.
There was no calculated leakage from any other sources and none of the tube plugs installed in the Vogtle Unit2 SGs require considerations for leakage.
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