ML12124A273

Relief Request Serial # 12-MN-002, Response to Request for Additional Information on Limited Weld Examinations During Refueling Outage 2EOC20

ML12124A273
Person / Time
Site:	Mcguire
Issue date:	04/23/2012
From:	Repko R Duke Energy Carolinas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML12124A273 (6)

Text

REGIS T. REPKO SDuke L'Energy Vice President McGuire Nuclear Station Duke Energy MG01 VP / 12700 Hagers Ferry Rd.

Huntersville, NC 28078 980-875-4111 980-875-4809 fax regis. repko@duke-energy. corn April 23, 2012 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, Unit 2 Docket No. 50-370 Relief Request Serial # 12-MN-002, Response to Request for Additional Information on Limited Weld Examinations during Refueling Outage 2EOC20 By letter dated January 11, 2012, Duke Energy submitted the subject relief request requesting relief from the volumetric coverage requirement for weld examinations specified in the American Society of Mechanical Engineers Boiler and Pressure Vessel Code,Section XI. This relief is requested for McGuire Unit 2 third 10-year inservice inspection interval.

On March 01, 2012, the Nuclear Regulatory Commission staff electronically requested additional information regarding this relief request. Please find enclosed Duke Energy's response to your request for additional information.

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

Sincerely, J~oV

/YA".

Regis T. Repko Enclosure www.duke-energy.com A 4-0 -,,

U. S. Nuclear Regulatory commission April 23, 2012 Page 2 xc:

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

Enclosure McGuire Nuclear Station Unit 2 Relief Request 12-MN-002 Request for Additional Information (RAI) 2EOC-20 Limited Weld Exam Duke Energy Response 12-MN-002 Page 1 of 4

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION Question 1:

Discuss the piping system for which relief is requested. Specify the ASME Code class type (e.g., Class 1, 2, or 3 piping). Provide material specificationsfor the weld and associatedpiping.

Duke Energy Response:

The piping system containing weld 2NV2FW216-60 for which relief is requested is the Nuclear Chemical and Volume Control System (NV). This piping is ASME Section III Class 2. The associated piping material with weld 2NV2FW216-60 is ASME SA 312/TP304 Schedule 160.

The weld material is AWS class ER308 with base materials listed as P8 to P8.

Question 2:

Discuss the ISI examinations history (e.g., inspection years, disposition, and results) of the subject weld. Also, discuss whether any fabrication defects were detected in the pre-service inspection (PSI), and the disposition of identified defects.

Duke Energy Response:

Weld 2NV2FW216-60 was selected for examination per RI-ISI program in the third ISI interval.

It was a new weld added during the second ISI interval with pre-service inspection (PSI) performed in the second interval. This weld was examined per the RI-ISI program for the first time as it was selected to represent a High Safety Significant (HSS) segment during the third interval plan.

No defects were found during the initial radiography examination (construction Code required).

No defects were found during the PSI examinations that established the baseline for future ISI examinations. No defects were found during the UT (limited) performed for ISI examination as defined in 12-RR-002 submittal (attachment A pages 1 and 2). No ISI defects were identified; therefore, no disposition was required.

Question 3:

Section 2.7 on page 3 of RR 12-MN-002 states, "Ultrasonicexamination of the weld for the Item Number M2.R1. 11.0276 was conducted using personnel, equipment, and procedures qualified in accordance with ASME Section Xl, 1998 Edition with the 2000 Addenda." Clarify which sub articles and/orappendices of the ASME Code,Section XI, were used for ultrasonictesting (UT) qualifications.If Appendix VIII was used, provide the supplement(s) number that is applicable to RR 12-MN-002.

12-MN-002 Page 2 of 4

Duke Energy Response:

ASME Section XI Appendix VIII, Supplement 2 was used for the inspection of this weld.

Specifically, PDI-UT-2 (Generic Procedure for the Ultrasonic Examination of Austenitic Pipe Welds). This procedure is identified on page 1 of 6 and 2 of 6 within the UT examination reports submitted with 12-MN-002.

Question 4:

The UT examinations reports on Page 1 and 2 in Attachment A of RR 12-MN-002 show that the result for UT examinations marked as "Reject," even though the reports indicated that no indications were found. Discuss why the results of UT examinations were called "Reject."

Duke Energy Response:

Duke Energy procedures require ASME Code, Section Xl examinations that do not meet the requirements of Code Case N-460 to be marked "reject" for tracking purposes, regardless of whether indications were noted. Therefore, the limited exams in 12-MN-002 without indications were marked "reject".

Question 5:

Table 4.1 1, Examination Category R A, Item No. R1. 11, in the Topical Report (TP) by Westinghouse Owners Group WCAP-14572 Rev. I NP-A, Supplement 2, "Westinghouse Owners Group Application of Risk Informed Methods to Piping Inservice Inspection Topical Report Clarifications,"was referenced in RR 12-MN-002. The NRC staff notes that Item No.

RI. 11 of Table 4.1.1 considers the weld for which relief is requested to be prone to potential degradationby thermal fatigue. Discuss whether any supplemental inspection was performed on the volume not examined by UT to ensure structuralintegrity of the system.

Duke Energy Response:

Pressure test (VT-2) inspection was performed for weld 2NV2FW216-60 every 18 months or scheduled refueling outage. The last test was acceptably completed on April 2, 2011. Based on acceptable results from the covered area by the volumetric examination (UT) and the pressure testing (VT-2) examination, the combination of examinations provides reasonable assurance of structural integrity of the system.

Question 6:

Discuss any industry orplant-specific operating experience regardingpotential degradation (e.g., stress corrosioncracking (SCC) and corrosion) and potential severe loading (e.g.,

vibration, water hammer, and overloading)for the subject weld and associatedcomponents.

Duke Energy Response:

There were no operating experiences of stress corrosion cracking found associated with the subject weld and associated components. McGuire had experienced vibration in the chemical 12-MN-002 Page 3 of 4

and volume control (NV) letdown piping in the vicinity of the letdown orifices. The operating experience has been addressed by the Westinghouse orifice assembly replacements with stacked disc valves. Additionally, the socket welded piping was replaced with butt welded XXS long radius bend piping, to the extent practical. Duke has reviewed NRC Information Notice 98-45 for applicability at McGuire and to this system. Duke's corrective action program was utilized to apply corrective actions at McGuire to redesign the system and the vibration source was eliminated. The OE applicability to this system has been included in the RI-ISI program and is the basis for the ISI inspections assigned to this weld.

McGuire RI-ISI program reviews operating experience (OE) for potential degradation and potential severe loading. Updates to RI-ISI program are made to capture current operating experiences (including recent Information Notice 2007-21), analyze impacts and implement program changes, if needed. This OE review includes internal problems identified in Duke Energy plant specific corrective action program (PIP) along with industry operating experience from piping failures. An engineering evaluation was performed to establish if any failures (from operating experiences) were the result of new failure mechanism and their relevancy to the RI-ISI program. Potential degradation applicable to weld 2NVFW216-60 and its associated high safety significant piping segments are thermal fatigue and vibration. There are no new loadings applicable to this piping segment.

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