ML15204A493

Bb Station Requests for Relief for Alternate Examination Frequency

ML15204A493
Person / Time
Site:	Byron, Braidwood
Issue date:	07/23/2015
From:	Greenlee S, Gullott D Exelon Generation Co
To:	NRC/NRO/DARR
Eva Brown
Shared Package
ML15204A471	List: ML15204A493 ML15204A505
References
Download: ML15204A493 (10)

Text

Braidwood Station and Byron Station Requests for Relief for Alternate Examination Frequency Under ASME Code Case N-729-1 for Reactor Vessel Head Penetration Welds in accordance with 10 CFR 50.55a (a)(3)(i)

Scot Greenlee, Sr. VP Engineering and Technical Services David Gullott, Manager Corporate Licensing July 27, 2015

Purpose

• Provide a brief history of B/B Relief Request related to the RPV Head Nozzles

• Provide technical basis for Re-examination interval requested of every other cycle for Braidwood and Byron Station

-MRP-395

-New sensitivity analyses performed at 95th percentile

• Understand technical questions that may exist on Relief Request 1 Braidwood Station and Byron Station Requests for Relief for Alternate Examination Frequency

B/B RPV Head Nozzle History

• During Byron Station Unit 2 Refueling Outage in Spring 2007 (B2R13) a PWSCC flaw was identified in penetration 68 and it associated J-groove weld

• ASME Code Case N-729-1 was incorporated into 10 CFR 50.55a as an augmented ISI program in September 2008 and allowed volumetric or surface examination every second refueling outage, even with detected flaws

• However, in a final rule action published in the Federal Register (FR) at 73 FR 52730, dated September 10,2008, 10 CFR 50.55a(g)(6)(ii)(D)(5) added a condition modifying ASME Code Case 729-1, Note (8) indicating that if flaws attributed to PWSCC had been identified, the re-inspection interval must be each refueling outage

• Thus, volumetric and/or surface examinations are conducted every outage 2 Braidwood Station and Byron Station Requests for Relief for Alternate Examination Frequency

B/B RPV Head Nozzle History

• In 2010, NRC authorized inspection frequency of every other outage for Byron Station Unit 2 under RR I3R-16, SE also included the statement that if future indications were found, would change inspection frequency to every outage

- Volumetric and/or surface examinations of all penetrations with the exception of penetration 68

• Exelon submitted I3R-20 for Byron Station Units 1 and 2 and I3R-09 for Braidwood Station Units 1 and 2 for use of Westinghouse weld overlay method on reactor vessel head penetration housing and J-groove welds, April 2011

- Included that future indications found would change inspection frequency to every outage

• NRC approved I3R-09 and I3R-20 Revision 1 as a repair method, March 2012

- All repaired nozzle penetrations examined with UT and Surface Examinations (PT) every outage

• Exelon submitted a Revision to the Relief Request for I3R-09 and I3R-20 which requests relief to eliminate surface examinations after successful examinations, September 2014

• Exelon recently provided a revision to the previously submitted Relief Request for I3R-09 and I3R-20, changing the frequency of surface examinations to every other cycle after successful examinations have been obtained 3 Braidwood Station and Byron Station Requests for Relief for Alternate Examination Frequency

Proposed Relief Request

• Requests UT examination inspection frequency interval of every other outage for all reactor vessel closure head penetrations (inclusive of repaired penetrations) for Braidwood Station Unit 1 and Byron Stations Unit 1 and Unit 2

• Request supported by:

-Effectiveness of current inspection requirements, including recent indications found in cold heads (i.e., reactor vessels operating at reactor cold-leg temperature (Tcold) including Braidwood Station and Byron Station)

-Deterministic crack growth rate analysis

-Probabilistic Monte Carlo simulation analysis

-Margin to leakage for flaws detected in cold heads 4 Braidwood Station and Byron Station Requests for Relief for Alternate Examination Frequency

Proposed Relief Request

• Personnel exposure reduced approximately 500-1000 mRem each outage an inspection is not required to be performed

• Implement approved Relief Request to support Byron Station Fall Outage 2015 (B1R20)

• Continued implementation of UT Inspection Frequency Relief Post-Peening application

-Peening application planned for Byron Station Unit 2 Spring 2016 outage (B2R19)

-Inspection Frequency Relief for all nozzles 5 Presentation Title

Technical Basis for Re-examination Interval of Every Second Refueling Outage for PWR Reactor Vessel Heads Operating at Tcold with Previously Detected PWSCC Craig Harrington, EPRI Glenn White, Dominion Engineering 6 Braidwood Station and Byron Station Requests for Relief for Alternate Examination Frequency