RNP-RA/08-0070, Response to NRC Request for Additional Information on the Steam Generator Inservice Inspection Results
| ML081790164 | |
| Person / Time | |
|---|---|
| Site: | Robinson  |
| Issue date: | 06/24/2008 |
| From: | Castell C Progress Energy Carolinas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| RNP-RA/08-0070 | |
| Download: ML081790164 (4) | |
Text
- @ Progress Energy Serial
- RNP-RA/08-0070 JUN 2 4 2008 United States Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 H. B. ROBINSON STEAM ELECTRIC PLANT, UNIT NO. 2 DOCKET NO. 50-261/LICENSE NO. DPR-23 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION ON THE STEAM GENERATOR INSERVICE INSPECTION RESULTS Ladies and Gentlemen:
The steam generator inservice inspection results for Refueling Outage 24 (RO-24) at H. B. Robinson Steam Electric Plant (HBRSEP), Unit No. 2, were previously submitted to the NRC by letters dated August 2, 2007, and November 1, 2007. A response to request for additional information was provided by letter dated April 30, 2008. Electronic mail messages received from the NRC Project Manager for HBRSEP, Unit No. 2, on May 8 and May 13,2008, requested additional information pertaining to the RO-24 results.
The response to the request for additional information is provided in the attachment to this letter.
If you have any questions regarding this matter, please contact me at (843) 857-1626.
Sincerely, Curt Castell Supervisor - Licensing/Regulatory Programs CAC Attachment c:
L. A. Reyes, NRC, Region II M. G. Vaaler, NRC, NRR NRC Resident Inspector Progress Energy Carolinas, Inc.
Robinson Nuclear Plant A 047 3581 West Entrance Road Hartsville, SC 29550
United States Nuclear Regulatory Commission Attachment to Serial: RNP-RA/08-0070 Page 1 of 3 H. B. ROBINSON STEAM ELECTRIC PLANT, UNIT NO. 2 RESPONSE TO REOUEST FOR ADDITIONAL INFORMATION The steam generator inservice inspection results for Refueling Outage 24 (RO-24) at H. B. Robinson Steam Electric Plant (HBRSEP), Unit No. 2, were previously submitted to the NRC by letters dated August 2, 2007, and November 1, 2007. A response to request for additional information (RAI) was provided by letter dated April 30, 2008.
Electronic mail messages received from the NRC Project Manager for HBRSEP, Unit No. 2, on May 8 and May 13, 2008, requested additional information pertaining to the RO-24 results.
NRC Request:
Question 6 of the RAI asks for the number of tubes with non-optimal tube processing and the rotating probe examinations performed on these tubes. The response seems to discuss the rotating probe examinations that were performed throughout the tube bundle (rather than focusing on the tubes with non-optimal tube processing). Please clarify.
[The following is the clarification of non-optimal tube processing from the May 13, 2008, electronic mail message.]
Non-optimal tube processing is a term used to describe tubes with an increased susceptibility to cracking. These tubes exhibit a unique eddy current offset that is a result of higher residual stresses in these tubes. The term was used in the context of the cracks that were detected at Seabrook in 2002. Additional information is contained in NRC Information Notice 2002-21, Supplement 1 dated April 1, 2003.
The industry has developed criteria/guidelines for determining tubes with this eddy current offset. In the lower row tubes (i.e., those that were stress relieved after bending),
the offset is clearer than in the higher row, tubes where a statistical criteria is used to identify those tubes that may be more susceptible to cracking.
HBRSEP, Unit No. 2, Response:
The outside diameter stress corrosion cracking (ODSCC) reported at Seabrook was in Rows 1 through 9 described as "low row tubes." In 2003, ODSCC was also confirmed at another plant in rows greater than row 9 described as "long row tubes."
The eddy current data for the SG tubes at H.B. Robinson were examined to assess if any of them exhibit eddy current signals similar to degraded tubes at Seabrook (short rows) or are identified as potentially susceptible (long rows). The tubes that have been identified as potentially susceptible are listed in the table provided and have been identified for
United States Nuclear Regulatory Commission Attachment to Serial: RNP-RA/08-0070 Page 2 of 3 continued monitoring. The table also lists inspections performed on these tubes in RO-
- 24. There were no susceptible tubes identified in low rows.
The Plus Point inspections from 4 inches above the tubesheet to 2 inches below (+4/-2) were performed to detect cracking at the tubesheet expansions. The Plus Point inspections from 4 inches above the tubesheet to 17 inches below (+4/-17) were performed to detect cracking at Bulges and Over-expansions. No degradation was observed in these tubes.
Row Column Bobbin Full Length Hot Leg Inspection Hot Leg Inspection Inspection Plus Point +4/-2 Plus Point +4/-17 Steam Generator A 16 67 X
X 18 88 X
X 21 14 X
X 31 68 X
X 34 57 X
X Steam Generator B 13 72 X
X 15 22 X
X 18 25 X
X 22 40 X
X 25 46 X
X 28 81 X
X 29 64 X
X 29 75 X
X 30 73 X
X 32 73 X
X Steam Generator C 12 41 X
X 12 65 X
X 13 48 X
X 15 22 X
X 15 24 X
X
.15 27 X
X 15 37 X
X 16 18 X
X 17 85 X
X 19 21 X
X 21 10 X
X 21 19 X
X 21 25 X
X 24 26 X
X
United States Nuclear Regulatory Commission Attachment to Serial: RNP-RA/08-0070 Page 3 of 3 Row Column Bobbin Full Length Hot Leg Inspection Hot Leg Inspection Inspection Plus Point +4/-2 Plus Point +4/-17 25 19 X
X 26 19 X
X 26 54 X
X 27 27 X
X 28 18 X
X 28 57 X
X 28 58 X
X 30 44 X
X 30 55 X
X 30 58 X
X 30 72 X
X 36 56 X
X
- 37.
25 X
X