BW150045, Response to Request for Additional Information Regarding the Steam Generator Tube Inspection Report Refueling Outage 17

Response to Request for Additional Information Regarding the Steam Generator Tube Inspection Report Refueling Outage 17

ML15117A126
Person / Time
Site:	Braidwood
Issue date:	04/27/2015
From:	Kanavos M Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
BW150045
Download: ML15117A126 (15)

Text

{{#Wiki_filter:April 27, 2015 BW150045 n ti n Exelon Generation Braidwood Station 35100 South Route Suite 84 Braceville. 60407*9619 www.exeloncoro.com U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

Subject:

Braidwood Station, Unit 2 Facility Operating License No. NPF-77 NRC Docket No. STN 50-457 Response to Request for Additional Information Regarding the Steam Generator Tube Inspection Report for Braidwood Station, Unit 2, Refueling Outage 17

References:

(1) Letter from M. E. Kanavos (Exelon Generation Company, LLC) to NRC, "Braidwood Station, Unit 2 Steam Generator Tube Inspection Report for Refueling Outage 17," dated November 14, 2014 (2) Email from J. S. Wiebe (NRC) to P. J. Raush (Exelon Generation Company, LLC), "RAls Related to Braidwood Station, Unit 2 Steam Generator Inspection Report for Refueling Outage 17," dated April 6, 2015 In Reference 1, in accordance with Technical Specification 5.6.9, "Steam Generator (SG) Tube Inspection Report," Exelon Generation Company, LLC (EGC) submitted the results of the SG inspections that were completed during the Braidwood Station, Unit 2 Refueling Outage 17. In Reference 2, the NRC notified EGC that additional information was needed in order to complete their review of the subject report. The requested information is provided in Attachment 1 of this letter. As noted in Reference 2, this response is due to the NRC by May 6, 2015; i.e., 30 days from the data of the email. This letter contains no new regulatory commitments.

April 27, 2015 U.S. Nuclear Regulatory Commission Page 2 If you have any questions concerning this letter, please contact Mr. Phillip Raush, Regulatory Assurance Manager, at (815) 417-2800. Respectfully, /flA!ifa.~m~--{:t Mark E. Kanavos Site Vice President Braidwood Station cc: NRG Regional Administrator, Region Ill NRG Senior Resident Inspector - Braidwood Station NRG Project Manager, NRR - Braidwood and Byron Stations Illinois Emergency Management Agency-Division of Nuclear Safety

ATIACHMENT1 Response to Request for Additional Information Regarding the Steam Generator Tube Inspection Report for Braidwood Station, Unit 2 Refueling Outage 17 In Reference 1, in accordance with Technical Specification 5.6.9, "Steam Generator (SG) Tube Inspection Report," Exelon Generation Company, LLC (EGC) submitted the results of the SG inspections that were completed during the Braidwood Station, Unit 2 Refueling Outage 17. In Reference 2, the NRC notified EGC that additional information was needed in order to complete their review of the subject report. The requested information is provided below. NRC RAI In reviewing the Exelon Generation Company, LLC's (Exelon's) submittal dated November 14, 2014 (Agency wide Document and Management System Accession No. ML14318A211), related to Braidwood, Unit 2, Steam Generator Tube Inspection Report for Refueling Outage 17, the NRG staff has determined that the following information is needed in order to complete its review: RAl#1 In a response to a request for additional information regarding the SG tube inspections for RFO 16 (ADAMS Accession No. ML13219A320), it is stated that prior to the start of RFO 16, there were 71 previously known "-2 sigma tubes." The tube located at row 44, column 47 in SG 2C does not appear to be included in the 71 tubes. It is also stated that 2 of the 71 previously known "-2 sigma tubes" were preventatively plugged, apparently leaving 69 "-2 sigma tubes" in service. The scope for RFO 17 states that 68 tubes having potentially increased residual stress were inspected. Clarify the number of tubes identified in all four SGs as being "-2 sigma tubes."

Response

The response to the request for additional information erroneously identified 71 "-2 sigma tubes" previously known prior to the start of RFO 16 (Reference 3, Section 5.2.1 ). The total number previously known prior to the start of RFO 16 was actually 70 "-2 sigma tubes". This oversight was attributed to not updating the total count after RFO 15. During RFO 15, Row 15, Column 7 tube in the 28 SG was plugged due to potential secondary side foreign objects, and the location was inaccessible to perform a visual inspection (Reference 4, Table 5.1.2). This tube was a "-2 sigma tube." Therefore the total "-2 sigma tubes" decreased after RFO 15 from 71 to 70 "-2 sigma tubes" (Reference 4, Section 4.2.3). During RFO 16 it was identified that one tube in the 2C SG, Row 44, Column 47, had been missed during the screening performed in 2003. This increased the total number to 71 "-2 sigma tubes" at the time of RFO 16, which was subsequently reduced to 68 when three "-2 sigma tubes", including Row 44, Column 47 tube in the 2C SG, were plugged during RFO 16. In summary there were a total of 68 "-2 sigma tubes" at the start of RFO 17 and all of them presently remain in-service. The number of "-2 sigma tubes" per SG at the start of RFO 17 are clarified in Table 1 below. A historical summary of "-2 sigma tubes" per SG can be found in Appendix A. Page 1 of 3

ATTACHMENT 1 Response to Request for Additional Information Regarding the Steam Generator Tube Inspection Report for Braidwood Station, Unit 2 Refueling Outage 17 T bl 1 T t I " 2 s* T b SG t d ft RFC 17 a e. oa - 1gma u es per prior o an a er 2A 28 2C 20 Total

1. "-2 sigma tubes" 11 15 14 28 68 in-service RAl#2 Your November 14, 2014 submittal stated that there were no "anomalies" observed during the plug visual inspections. Was any degradation observed?

Response

No degradation was observed during the plug visual inspections performed during RFO 17. RAl#3 The plugging summary table on page 9 of your November 14, 2014, submittal discusses two tubes that were plugged due to large magnetic permeability indications, which resulted in a high noise portion of the tube that could potentially mask flaws. Discuss how you confirmed structural integrity of these tubes in the presence of the large magnetic permeability indications.

Response

The Westinghouse Data Union Software (DUS) was applied to inject the signal response from a flaw smaller than the structurally significant size flaw (i.e. 68% through wall (TW) x 0.5 long axial outer diameter stress corrosion cracking (ODSCC)) into the magnetic permeability (PVN) signal from the field +Point' rotating coil data obtained from the two tubes with large permeability signals. The flaw was simulated by a uniform depth 60% TW x 0.5" long axial OD EDM notch scaled back to the voltage of an equivalent depth axial ODSCC crack. Analyst review of the resultant (combined) signal demonstrated detectability of the structurally significant flaw even in the presence of the noise from the PVN signal. Therefore, the +Point data from the two tubes with the large PVN indications was determined not to have masked signals from structurally significant flaws, if any were present, hence providing the basis for meeting one cycle condition monitoring structural integrity. RAl#4 Discuss whether there was any evidence of the unknown red substance that was observed during RFO 16. Discuss whether there are any new insights on the cause/nature of these red spots.

Response

There was no evidence of the red substance observed during RFO 17. Page 2 of 3

ATTACHMENT 1 Response to Request for Additional Information Regarding the Steam Generator Tube Inspection Report for Braidwood Station, Unit 2 Refueling Outage 17 Visual examination was performed in the 2C SG preheater to determine if any red substance was present. Additionally, the affected tubes were examined with an X-probe. No degradation was detected, and visually there was no evidence of the red substance at the same location and no evidence it had migrated elsewhere. Although there was no sample of the red substance remaining to analyze, it was concluded that the red substance was likely organic material, because it was no longer present. It is assumed that it decomposed during an 18-month operating period. No tube degradation was detected. RAl#5 Your November 14, 2014, submittal indicated that three tubes deep around the entire periphery, including the no tube lane and T-slot, were inspected in all four SGs with an X-probe. Clarify the axial extent of these exams (e.g., tube-end to tube-end, H* distance to first support on both hot-leg and cold-leg). Discuss whether or not these exams included both hot-leg and cold-leg regions.

Response

The axial extent was the tube end to flow distribution baffle (1st Tube Support Plate {TSP) -01 C or 01 H) for the entire periphery scope, including the no tube lane and T-slot. In the "head" of the T-slot on the hot leg, the extent of the exam was extended from 01 H to 03H. The exams included both the hot leg and cold leg regions. This is shown in the attached tube sheet maps in Attachment B. REFERENCES

1. Letter from M. E. Kanavos (Exelon Generation Company, LLC) to NRG, "Braidwood Station, Unit 2 Steam Generator Tube Inspection Report for Refueling Outage 17," dated November 14, 2014 (ADAMS Accession No. ML14318A211)

2. Email from J. S. Wiebe (NRG) to P. J. Raush (Exelon Generation Company, LLC), "RAls Related to Braidwood Station, Unit 2 Steam Generator Inspection Report for Refueling Outage 17," dated April 6, 2015

3. Letter from Letter from D. Enright (Exelon Generation Company, LLC) to NRG, "Braidwood Station, Unit 2 Steam Generator Tube Inspection Report for Refueling Outage 16," dated February 5, 2013 (ADAMS Accession No. ML13039A042)

4. Letter from D. J. Enright (Exelon Generation Company, LLC) to NRG, "Braidwood Station, Unit 2 Steam Generator Tube Inspection Report for Refueling Outage 15," dated August 1 O, 2011 (ADAMS Accession No. ML11227A037)

Page 3 of 3

ATTACHMENT 1 Response to Request for Additional Information Regarding the Steam Generator Tube Inspection Report for Braidwood Station, Unit 2 Refueling Outage 17 Appendix A Historical Summary of "-2 Sigma Tubes" Totals in High Rows (Rows 10-49) Outage SG2A SG28 SG2C SG2D Total Notes After 2003 Screening 13 16 17 28 74 (prior to RFO 10) Plugged during Tubes were plugged due -1 0 -2 0 -3 to ODSCC RFO 10 (Note 1). Prior to RFO 11 12 16 15 28 71 Plugged during RF011,RF012, 0 0 0 0 0 RFO 13, RFO 14 Tube was preventatively Plugged during 0 -1 0 0 -1 plugged for possible RFO 15 loose part (Note 2). Erroneously reported Prior to RFO 16 12 15 15 28 70 71 tubes (Note 3). Missed "-2 Sigma Note: One tube was Tube" and added 0 0 +1 0 +1 initially missed during durinq RFO 16 2003 screenina. Plugged during -1 0 -2 0 -3 RFO 16 Remaining "-2 Sigma Tubes" 11 15 14 28 68 prior to RFO 17 Plugged during 0 0 0 0 0 RFO 17 Remaining "-2 Sigma Tubes" 11 15 14 28 68 after RFO 17 Notes:

1. Reference ADAMS Accession No. ML040540452, Attachment 8.6 Tubes Containing ODSCC Tube sheet Maps.

2. Reference ADAMS Accession No. ML11227A037, Table 5.1.2.

3. Reference ADAMS Accession Nos. ML13219A320, RAI No. 3 and ML13039A042, Section 5.2.1.

A.1

ATTACHMENT 1 Response to Request for Additional Information Regarding the Steam Generator Tube Inspection Report for Braidwood Station, Unit 2 Refueling Outage 17 Appendix B Three-Tube Periphery Array Probe (X-probe) Inspections Tube sheet Maps B.1

ATTACHMENT 1 Response to Request for Additional Information Regarding the Steam Generator Tube Inspection Report for Braidwood Station, Unit 2 Refueling Outage 17 SG -A HOT LEG 3-TUBE PERIPHERY.610ARRAY PROGRAM Braidwood A2R17 COE 05 a 100 PLUGGED TUBE ue 195 lH 95 15 10 45 45 40 40 ........ Cl*** ............... **Cf* ... * *00 O*. I .... Ill I.... ... '*C O*. I 35 35 f *00 O* ........ .... =*.* '........... 38 JD .... itt I............... Z5 25 t t *O C*. I...... f I t0 Qt I I t t *0 Ct t t...... ...... t t tOi O* t t ze 20 I Ill............................................ 15 15 ........................................................ *Cl** Ot' t........ tOOC..................... ocoo I I 10................ 000*........ I I *C 19 19 O*........ OCJ.................... c 0................ flfl\\ 0*........ t I tO 0000................ ****1 000*........ 5 - I. 5 110 195 lH 95 99 65 Sil 75 70 65 69 55 50 45 40 35 38 25 ze 15 18 ~E9:71e~U.C*!:1°Mal 05.tt~14 OUU6 B.2

ATTACHMENT 1 Response to Request for Additional Information Regarding the Steam Generator Tube Inspection Report for Braidwood Station, Unit 2 Refueling Outage 17 SG -A COLD LEG 3-TUBE PERIPHERY.610 ARRAY PROGRAM Braidwood A2R17 COE 05 a 100 PLUGGED TUBE 110 l** 9' 98 78 55 ..4~.. ~'.'! *- ~ %8.. 19 4* 45 I I It........ Cit tt.... I Ot 1.... D t t t.... ........ ** *0 40 49

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