ML082660914

E-mail from D.Vandeputte to R. Guzman Relief Request 2ISI-007 Summarizing Conference Call on September 17, 2008

ML082660914
Person / Time
Site:	Nine Mile Point
Issue date:	09/22/2008
From:	Vandeputte D Nine Mile Point
To:	Richard Guzman Plant Licensing Branch 1
Guzman R, NRR/DORL, 415-1030
References
TAC MD7688
Download: ML082660914 (1)

Text

From: Vandeputte, Dennis E [Dennis.Vandeputte@constellation.com]

Sent: Monday, September 22, 2008 3:12 PM To: Richard Guzman Cc: Anderson, Edward L; Dosa, John J

Subject:

NMP Unit 2 Risk Informed ISI - Relief Request 2ISI-007 Rich:

In a conference call with the NRC staff on Wednesday, September 17, 2008, we discussed a request posed by the NRC reviewer (Ms. Nove) as part of her review of the proposed Nine Mile Point Unit 2 (NMP2) risk-informed inservice inspection (RI-ISI) program relief request no. 2ISI-007. This relief request was submitted to the NRC by NMPNS letter dated December 14, 2007, and the response to an NRC request for additional information (RAI) concerning the relief request was provided in NMPNS letter dated June 30, 2008. The following request provided by the NRC in an email dated September 10, 2008 was the starting point for the discussion:

On page 3 of 4 of the RAI response (dated June 30, 2008), it states that the overall change from the second ISI to the third ISI interval is a reduction of five inspection locations due to a determination that the crevice corrosion degradation mechanism was no longer applicable; and it states that this resulted from a re-analysis that was performed after the 2nd ISI interval. Wed like to get a more qualitative understanding as to what NMPNS did that resulted in crevice corrosion no longer being applicable.

The following is a summary of the information provided by NMPNS during the discussion with the NRC staff.

The Crevice Corrosion cracking (CC) degradation mechanism was originally assigned to the RPV nozzles consistent with the conservative application of EPRI TR-112657, Revision B-A, Revised Risk-Informed Inservice Inspection Evaluation Procedure, which the NRC has approved. The EPRI TR provided the basic criteria for identifying locations potentially susceptible to crevice corrosion.

While the criteria in the EPRI RI-ISI methodology remains unchanged, the need for enhancement in the application of these criteria was identified in order to distinguish a mechanical crevice from an electrochemical crevice, and also to distinguish classic crevice corrosion from crevice-enhanced stress corrosion cracking. This enhancement has been documented in the EPRI report titled Enhanced Crevice Corrosion Criteria in RI-ISI Evaluations, (report no. 1011946) dated November 2005. This enhancement was used during the NMP2 RI-ISI program update to better define crevice corrosion susceptibility, resulting in a determination that degradation mechanism CC was not applicable for RPV nozzles and relocation of these nozzles from Risk Category 2 to Risk Category 4. This change in risk category also changed the selection criteria from 25% to 10%.

In addition, although the RPV nozzles were relocated to Risk Category 4, the nozzles also have a degradation mechanism of IGSCC Category D assigned to them. Welds with degradation mechanism IGSCC Category D assigned are examined in accordance with NRC Generic Letter (GL) 88-01 at an extent and frequency of 100% every 6 years. IGSCC Category A welds have been incorporated under the EPRI RI-ISI Methodology.

If there are any questions concerning the above information, please let me know.

Dennis Vandeputte NMP Licensing

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Subject:

NMP Unit 2 Risk Informed ISI - Relief Request 2ISI-007 Sent Date: 09/22/2008 3:11:52 PM Received Date: 09/22/2008 3:11:52 PM From: Vandeputte, Dennis E Created By: Dennis.Vandeputte@constellation.com Recipients:

Richard.Guzman@nrc.gov (Richard Guzman)

Tracking Status: None Edward.Anderson@constellation.com (Anderson, Edward L)

Tracking Status: None John.Dosa@constellation.com (Dosa, John J)

Tracking Status: None Post Office:

EXM-OMF-12.Ceg.Corp.Net Files Size Date & Time MESSAGE 16511 09/22/2008 Options Expiration Date:

Priority: olImportanceNormal ReplyRequested: False Return Notification: False Sensitivity: olNormal Recipients received: