ML13220A056

NRR E-mail Capture - Relief Request RAI from NRC Conference Call August 2 2013

ML13220A056
Person / Time
Site:	North Anna
Issue date:	08/07/2013
From:	Whalen M Dominion Generation
To:	V Sreenivas Division of Operating Reactor Licensing
References
Download: ML13220A056 (4)

Text

NRR-PMDAPEm Resource From: MP Whalen (Generation - 3) [mp.whalen@dom.com]

Sent: Wednesday, August 07, 2013 3:59 PM To: Sreenivas, V

Subject:

Relief Request RAI from NRC Conference Call August 2 2013 Attachments: 2013-08-07 RAI Response Update .docx V,

Friday, 8/2/13, NRC conference call regarding weld SW41. In our 2010 submittal on page 44 we discuss Weld SW41 and only getting 35% coverage. In the last sentence we take credit for one other weld on the segment with complete coverage that provides an acceptable alternative. The NRC is looking for two items:

1. Information on the other welds inspected this interval with >90 coverage with regards to it being in the same risk informed category, same failure mechanism, and same filler metal.

2. Looking for history of failures that have a similar failure mechanism (i.e., thermal fatigue). Can be our history and/or industry information.

The attached response provides the information to address each item. If you have any questions please advise. Thanks you Michael P. Whalen Dominion Generation Station Licensing North Anna Power Station 1022 Haley Drive Mineral, VA 23117 Phone: 540-894-2572 Fax: 540-894-2830 Pager: 804-273-3030, Pager 3164 Email: MP.Whalen@dom.com CONFIDENTIALITY NOTICE: This electronic message contains information which may be legally confidential and/or privileged and does not in any case represent a firm ENERGY COMMODITY bid or offer relating thereto which binds the sender without an additional express written confirmation to that effect. The information is intended solely for the individual or entity named above and access by anyone else is unauthorized. If you are not the intended recipient, any disclosure, copying, distribution, or use of the contents of this information is prohibited and may be unlawful. If you have received this electronic transmission in error, please reply immediately to the sender that you have received the message in error, and delete it. Thank you.

1

Hearing Identifier: NRR_PMDA Email Number: 799 Mail Envelope Properties (0A47EA17EBFBBD4E984EBCC0A92E221C01A3C2)

Subject:

Relief Request RAI from NRC Conference Call August 2 2013 Sent Date: 8/7/2013 3:59:22 PM Received Date: 8/7/2013 3:59:33 PM From: MP Whalen (Generation - 3)

Created By: mp.whalen@dom.com Recipients:

"Sreenivas, V" <V.Sreenivas@nrc.gov>

Tracking Status: None Post Office: INBE10W803.mbu.ad.dominionnet.com Files Size Date & Time MESSAGE 1806 8/7/2013 3:59:33 PM 2013-08-07 RAI Response Update .docx 37861 Options Priority: Standard Return Notification: No Reply Requested: No Sensitivity: Normal Expiration Date:

Recipients Received:

Friday, 8/2/13, NRC conference call regarding weld SW41. In our 2010 submittal on page 44 we discuss Weld SW41 and only getting 35% coverage. In the last sentence we take credit for one other weld on the segment with complete coverage that provides an acceptable alternative. The NRC is looking for two items:

1. Information on the other welds inspected this interval with >90 coverage with regards to it being in the same risk informed category, same failure mechanism, and same filler metal.

Response

Category R-A, Item R1.11 components (elements subject to thermal fatigue), examined in the 4th Inspection Interval:

N1.R1.11.002, 11715-WMKS-0103AD / 6-RC-21 / SW-21, Elbow to Pipe, 94% coverage N1.R1.11.005, 11715-WMKS-0103AJ / 6-RC-16 / 15, Valve to Elbow, 50% coverage (included in request)

N1.R1.11.008, 11715-WMKS-0103N / 6-RC-17 / 20, Valve to Elbow, 50% coverage (included in request)

N1.R1.11.010, 11715-WMKS-0103N / 6-RC-17 / SW-22, Pipe to Elbow, 100% coverage (geometry indications)

N1.R1.11.011, 11715-WMKS-0103N / 6-RC-17 / SW-23, Elbow to Pipe, 100% coverage (geometry indication)

N1.R1.11.300, 11715-WMKS-0103CD/2-CH-5/20A, Pipe to Pipe, 100% coverage N1.R1.11.301, 11715-WMKS-0103CD / 2-CH-5 / 2A, Pipe to Reducer, 100% coverage N1.R1.11.302, 11715-WMKS-0103CD / 3-CH-A-01 / 19, Pipe to Elbow, 97% coverage N1.R1.11.304, 11715-WMKS-0103AD / 6-RC-21 / 15, Valve to Elbow, 50% coverage (included in request)

N1.R1.11.305, 11715-WMKS-0103AD / 6-RC-21 / SW-22, Pipe to Elbow, 94% coverage N1.R1.11.306, 11715-WMKS-0103BB-1 / 3-RC-215 / SW-54, Elbow to Pipe, 100% coverage The examinations identified no reportable indications (other than the geometry indications at the root and counterbore of the two elbows identified above).

N1.R1.11.037, 11715-WMKS-0109G-2 / 27 1/2-RC-9 / SW-43, Weldolet-Pipe End, is scheduled to be examined in the 3rd period (3rd interval coverage only 22%).

Weld locations where full coverage cannot necessarily be obtained are selected for examination to increase the level of quality and safety of the NAPS inspection program by ensuring that the ISI examination scope includes a representative sample of configurations, locations, line sizes, materials,

etc. Full coverage can usually be guaranteed by selecting only pipe to pipe configurations, and among the risk-informed components subject to thermal fatigue (R-A / R1.11) there are enough to ensure full coverage for every examination. It would reduce the level of quality and safety of the examination program to completely avoid examination of the weldolet connections to branch piping or connections to other components like valves and pumps, where the Code only allows claiming up to 50% coverage.

EPRI developed MRP-146, Materials Reliability Program Management of Thermal Fatigue in Normally Stagnant Non-Isolable Reactor Coolant System Branch Lines, in order to provide screening, evaluation, monitoring, inspection, operations, maintenance, and modification guidance to enable utilities to avoid thermal fatigue cracking due to valve in-leakage or turbulence/swirl penetration effects in affected lines.

Although weld SW-41 is classified in the Risk-Informed ISI Program as R-A / R1.11, subject to thermal fatigue, this branch connection weldolet at the top of the RCS pipe is not considered for evaluation under the MRP-146 guidelines.

Figure 2-12 Examination Zones for Butt-Welded Lines Vertically Upward from RCS Piping

2. Looking for history of failures that have a similar failure mechanism (i.e., thermal fatigue). Can be our history and/or industry information.

Response

North Anna Power Station has not experienced any failures associated with the branch connection lines subject to thermal fatigue. MRP-146, Table B-1, identifies PWR Reactor Coolant Leakage in Non-Isolable Lines Attributed to Thermal Fatigue, and none of the identified failures seems to be at a branch connection weldolet like weld SW-41. Please refer to MRP-146, Table B-1, for a list of relevant events in the industry where thermal fatigue leakage has been observed in reactor coolant systems in PWR plants worldwide.

EPRI Point of

Contact:

Ma, Jennifer [jma@epri.com]