ML16343A252

NRR E-mail Capture - Preliminary Request for Additional Information (RAI) Regarding Relief Request I4R-10

ML16343A252
Person / Time
Site:	Byron
Issue date:	12/08/2016
From:	Joel Wiebe Plant Licensing Branch III
To:	Krejcie J Exelon Corp
References
Download: ML16343A252 (3)

Text

NRR-PMDAPEm Resource From: Wiebe, Joel Sent: Thursday, December 08, 2016 10:50 AM To: Jessica Krejcie

Subject:

Preliminary Request for Additional Information (RAI) Regarding Relief Request I4R-10

Jessica, Here is the preliminary RAI for relief request I4R-10. If you need a clarification conference call, let me know within 1 week. Otherwise, a response is requested within 30 days of this e-mail.

REQUEST FOR ADDITIONAL INFORMATION RELIEF REQUEST I4R-10 PROPOSED ALTERNATIVE REQUIREMENTS FOR THE REPAIR OF REACTOR VESSEL HEAD PENETRATIONS BYRON STATION UNITS 1 AND 2 EXELON GENERATION COMPANY, LLC DOCKET NOS. 50-454 AND 50-455 By letter dated August 16, 2016, (Agencywide Documents Access and Management System (ADAMS) Accession No. ML16229A250), Exelon Generation Company, LLC (the licensee) requested the U.S. Nuclear Regulatory Commission (NRC) to authorize an alternative to the requirements of the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code) regarding the repair of reactor vessel head penetrations (VHPs) at Byron Station Units 1 and 2 (Byron) for the fourth 10-year ISI interval. The licensees request also included inservice inspection (ISI) examination requirements for future VHP repairs as well as previously repaired VHPs.

The licensees alternative to use its VHP repair method during the third 10-year ISI interval, which ended on July 15, 2016, was approved by the NRC on March 29, 2012 (ADAMS Accession No ML120790647). This alternative was later revised by the licensee and approved by the NRC on January 21, 2016 (ADAMS Accession No ML16007A185). The revision was limited to alternative ISI examinations of repaired nozzles. The licensees current alternative request indicates that 6 VHPs were repaired during the third 10-year ISI interval. To the NRC staffs knowledge, all of these repairs involved embedded flaws in the J-groove weld.

The Byron plant specific analysis, to support the embedded flaw technique, is documented in WCAP-16401, Revision 0, Technical Basis for Repair Options for Reactor Vessel Head Penetration Nozzles and Attachment Welds: Byron and Braidwood Units 1 and 2, 2005. This document was submitted to the NRC as part of the licensees submittal for its alternative in the third 10-year ISI interval and is referenced in the licensees current proposed alternative for the fourth 10-year ISI interval.

WCAP-16401, Revision 0, Section 3.3.3, states The fatigue crack growth result indicates that the repaired weld can last at least 10 years of service life based on the conservatively assumed initial flaw depth. The NRC staffs safety evaluation, as documented in the March 29, 2012 letter referenced above, states The NRC staff finds WCAP-16401 provides a basis for any remaining ligaments of the flaws identified by the licensee in VHP nozzle J-groove weld material to be safely encapsulated for 10 years of operation. The NRC staff notes that all 6 previously repaired nozzles at Byron will exceed 10 years of operation during the current fourth 10-year ISI interval. The licensee has included these repaired VHPs in its current alternative.

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Provide information that demonstrates that the previously repaired nozzles are acceptable for service during the duration of the 4th ISI Interval (e.g., revision to the WCAP-16401 and modifications, as necessary, to the relief request) or otherwise demonstrate that the previously repaired nozzles will be taken out of service (e.g., repaired/replaced in accordance with the ASME Code prior to reaching the 10th anniversary of their repair).

2

Hearing Identifier: NRR_PMDA Email Number: 3204 Mail Envelope Properties (Joel.Wiebe@nrc.gov20161208104900)

Subject:

Preliminary Request for Additional Information (RAI) Regarding Relief Request I4R-10 Sent Date: 12/8/2016 10:49:38 AM Received Date: 12/8/2016 10:49:00 AM From: Wiebe, Joel Created By: Joel.Wiebe@nrc.gov Recipients:

"Jessica Krejcie" <Jessica.Krejcie@exeloncorp.com>

Tracking Status: None Post Office:

Files Size Date & Time MESSAGE 3431 12/8/2016 10:49:00 AM Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

Recipients Received: