MNS-14-026, Risk-Informed Inservice Inspection Program Response to Request for Additional Information

Risk-Informed Inservice Inspection Program Response to Request for Additional Information

ML14073A464
Person / Time
Site:	McGuire, Mcguire
Issue date:	03/03/2014
From:	Capps S Duke Energy Carolinas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
13-MN-002, MNS-14-026, TAC MF2609, TAC MF2610
Download: ML14073A464 (5)

Text

Steven D. Capps (DUKE Vice President ENERGY. McGuire Nuclear Station Duke Energy MG01VP 1 12700 Hagers Ferry Road Huntersville, NC 28078 o: 980.875.4805 f: 980.875.4809 Steven.Capps@duke-energy.com Serial No.: MNS-14-026 March 3, 2014 10 CFR 50.55a U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

SUBJECT:

Duke Energy Carolinas, LLC (Duke Energy)

McGuire Nuclear Station Units 1 and 2 Docket Numbers 50-369 and 50-370 Relief Request 13-MN-002 Risk-Informed Inservice Inspection Program Response to Request for Additional Information (TAC NOS. MF2609 and MF2610)

By letter dated August 13, 2013, Duke Energy submitted Relief Request (RR) 13-MN-002 to propose the use of a Risk-Informed Inservice Inspection (RI-ISI) program as an alternative to the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code Section XI, ISI program for Class 1 and 2 piping welds (Examination Categories B-F, B-J, C-F-i, and C-F-2).

By letter dated January 30, 2014, the NRC issued a Request for Additional Information (RAI) regarding this RR. Attached is Duke Energy's response to this RAI.

If you have any questions or require additional information, please contact P. T. Vu of Regulatory Affairs at (980) 875-4302.

Sincerely, Steven D. Capps Attachment 404-1 0 (_4, www.duke-energy.com

f U. S. Nuclear Regulatory Commission March 3, 2014 Page 2 xc:

Victor McCree, Region II Administrator U.S. Nuclear Regulatory Commission Marquis One Tower 245 Peachtree Center Ave., NE Suite 1200 Atlanta, GA 30303-1257 Jason Paige, Project Manager U. S. Nuclear Regulatory Commission 11555 Rockville Pike Mail Stop 0-8 G9A Rockville, MD 20852-2738 John Zeiler NRC Senior Resident Inspector McGuire Nuclear Station

41 .

ATTACHMENT MCGUIRE NUCLEAR STATION Relief Request 13-MN-002 Response to NRC Request for Additional Information

Relief Request 1 3-MN-002, Response to NRC Request for Additional Information Attachment, Page 1 of 2 March 3, 2014 Question 1:

In Section 2 of the request it is stated that the Code of Record for Unit 1 will change with the start of the second period. What is the start date for the second period?

Response

The start date for the second period is scheduled for December 01, 2014.

Question 2:

In Section 3.3.4 of Enclosure I you state that relief requests for cases where less than 90%

coverage is obtained will be submitted. Please describe the efforts in weld selection such that

>90% coverage is attainablein the RI-ISI program, both going forwardand in previously examined welds that will be credited towards satisfying the RI-ISI program inspections. Will examinationsthat have already been performed that achieved <90% weld coverage be credited to satisfy RI-ISI program inspection requirements?

Response

The ASME Code Case (CC) N-716, paragraph 4 has several weld selection requirements that must be met (e.g., selecting welds with degradation mechanisms, a required weld selection distribution within the Reactor Coolant Pressure Boundary, worker exposure, etc.). In addition, Duke Energy weld selections consider whether >90 percent coverage can be obtained. However, there may be cases where meeting both the >90 percent coverage requirement and the CC requirements are not possible. This may occur when there are a limited number of welds susceptible to a particular degradation mechanism (or combination of degradation mechanisms),

or when a limited number of welds are located between the Inside First Isolation Valve and the reactor pressure vessel. CC N-716 permits substitutions within the requirements of the CC if

>90 percent coverage cannot be obtained, a higher than expected dose exists, or access has become more restrictive. If limitations are encountered, Duke Energy will evaluate the availability of weld substitutions that will meet both the >90 percent coverage requirement and the CC requirements. If an evaluation determines the only weld capable of meeting the CC requirements involves a limitation, a relief request would be submitted.

Welds that have already been performed that achieved <90 percent coverage will be credited to satisfy the RI-ISI program inspection requirements only after a substitution evaluation determines no other welds can be inspected to obtain >90 percent coverage that also meet the CC requirements. A relief request will be submitted in these cases as required.

Relief Request 1 3-MN-002, Response to NRC Request for Additional Information Attachment, Page 2 of 2 March 3, 2014 Question 3:

Regulatory Position 4.1 of Regulatory Guide 1.178, Revision 1, "An Approach for Plant Specific Risk-Informed Decisionmakingfor Inservice Inspection of Piping," states that the results of the licensee's inservice inspection-specific analysis should include the degradationmechanisms for each segment used to develop the failure potential of each segment.

Section 3.4.1, "QuantitativeAnalysis," of the submittal states a review was conducted that verified that the low safety significant piping was not susceptible to water hammer. However, the NRC staff could not find a similar statement about high safety significant (HSS) piping in the submittal.

Confirm that HSS piping that has a degradationmechanism potential (as identified in Tables 3.4a, "Unit I Risk Impact Analysis Results," and 3.4b, "Unit2 Risk Impact Analysis Results," of the submittal) is not susceptible to water hammer, such that the pipe failure frequency used to characterizethe risk increasefrom discontinued inspections in the change in risk evaluation would increase to the high failure potentialrank.

Response

Confirmed. The HSS piping in the submittal was evaluated and it is not susceptible to water hammer.