ML20054A269

Response to Request for Additional Information - Relief Request 64 - Unit 1 Impractical Examinations for the Third 10-Year Inservice Inspection Interval

ML20054A269
Person / Time
Site:	Palo Verde
Issue date:	02/19/2020
From:	Rash B Arizona Public Service Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
102-08060-BJR/MSC
Download: ML20054A269 (10)

Text

10 CFR 50.55a BRUCE 3. RASH Oaps 102-08060-BJR/MSC Vice President, Nuclear Engineering Palo Verde Nuclear Generating Station February 19, 2020 P.O. Box 52034 Phoenix, AZ 85072 U. S. Nuclear Regulatory Commission Mail station 7602 ATTN: Document Control Desk Tel 623.393.5102 Washington, DC 20555-0001

Subject:

Palo Verde Nuclear Generating Station Unit 1 Docket No. STN 50-528 Renewed Operating License No. NPF-41 Response to Request for Additional Information - Reiief Request 64 -

Unit 1 Impracticai Examinations for the Third 10-Year Inservice Inspection Intervai By letter number 102-07950, dated July 17, 2019 (Agencywide Documents Access and Management System Accession Number ML19198A340), Arizona Pubiic Service Company (APS) submitted relief request 64 in accordance with 10 CFR 50.55a(g)(5)(iii). Certain ultrasonic examinations of weids required by Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, sub-articles IWB-2500 and IWC-2500 were determined to be impractical for the Unit 1 third 10-Year inservice inspection interval.

The Nuclear Regulatory Commission (NRC) staff requested additionai information to complete their review with regard to the ASME Code examinations that were determined to be impractical for Unit 1. A clarifying phone call was held between the NRC staff and APS on January 21, 2020, to discuss the additional information needed. The APS response to the request for additional information is provided in the enclosure to this letter.

No new commitments are being made in this submittal. If you have any questions about this request, please contact Matthew S. Cox, Section Leader, Nuclear Regulatory Affairs, at (623) 393-3945.

Sincerely, BJR/MSC

Enclosure:

Response to Request for Additional Information - Relief Request 64, Unit 1 Impractical Examinations for the Third 10-Year Inservice Inspection Interval cc: S. A. Morris NRC Region IV Regional Administrator S. P. Lingam NRC NRR Project Manager for PVNGS C. A. Peabody NRC Senior Resident Inspector for PVNGS A member of the STARS Alliance LLC Callaway

• Diablo Canyon

• Palo Verde

• Wolf Creek

Enclosure Response to Request for Additional Information Relief Request 64 Unit 1 Impractical Examinations for the Third 10-Year Inservice Inspection Interval

Enclosure Response to Request for Additional Information - Relief Request 64 - Unit 1 Impractical Examinations for the Third 10-Year Inservice Inspection Interval 10 CFR 50.55a Request Number 64 Response to Request for Additional Information Unit 1 Inservice Inspection Impracticality Third 10-Year Inservice Inspection Interval By letter number 102-07950, dated July 17, 2019 (Agencywide Documents Access and Management System Accession Number ML19198A340), Arizona Public Service Company (APS) submitted relief request 64 in accordance with 10 CFR 50.55a(g)(5)(iii). Certain ultrasonic examinations of welds required by Section XI of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (BPV) Code, sub-articles IWB-2500 and IWC-2500 were determined to be impractical for the Unit 1 third 10-Year inservice inspection interval.

The Nuclear Regulatory Commission (NRC) staff has requested additional information (RAI) to complete their review with regard to the ASME Code examinations that were determined to be impractical for Unit 1. The APS response to the request for additional information is provided in this enclosure.

NRC RAM:

The licensee described the examination coverage achieved for all the welds referenced in RR-

64. However, the license did not provide information on results of the limited-coverage examinations in the third 10-year ISI interval. Information on examination results for the referenced welds, including the disposition of any found indications in accordance with ASME Section XI requirements, is relevant to the safety case for this RR. Please provide a written description of the third-interval examination results for the welds referenced in RR-64, including disposition of found indications. Examination results from the first and/or second 10-year ISI intervals may also be included, if deemed relevant by the licensee.

APS Response:

Examination resuits for the limited-coverage examinations referenced in Table 1 of Relief Request 64 are provided in Table 1-A of Attachment 1. Examination results from the first and/or second 10-year ISI intervals were not included in Table 1-A as they were not deemed relevant. Weld 1-10 is discussed in RAI-2 and, therefore, is not discussed in detaii in Table 1-A. The Impractical examinations contained within Table 2 of Relief Request 64 were not performed and, therefore, are not discussed as limited-coverage examinations.

NRC RAI-2:

In the description for Category B-A welds, the licensee states that the inlet and outlet nozzles interfere with examination of weld 1-10 above and below the weld. However, Location Figure 1-1 indicates that the inlet and outlet nozzles may interfere only from below the weld. Please clarify the access limitations for weld 1-10.

APS Response:

The simplified illustration previously submitted in Location Figure 1-1 provided a general configuration of the reactor vessel. Additional explanation and figures are provided herein to illustrate the access limitations associated with circumferential weld 1-10.

The uppermost portion of each of the six nozzles extends upward from the intermediate shell into the upper shell near the top of each nozzle. As the upper shell assembly was originally prepared for nozzle installation, the reactor vessel shell circumferential weld was partially 1

Enclosure Response to Request for Additional Information - Relief Request 64 - Unit 1 Impractical Examinations for the Third 10-Year Inservice Inspection Interval removed at each of the six nozzle locations. The nozzle-to-shell weld of each inlet and outlet nozzle, therefore, intersects the reactor vessel shell circumferential weld 1-10, interrupting the continuity of weld 1-10, as shown in Figure 2-A of Attachment 1.

As the circumferential shell weld 1-10 approaches each of the four inlet nozzles, the nozzle configuration and corresponding opening of each inlet nozzle impacts the double-sided examination. The configuration allows for some additional single-sided scanning from above weld 1-10; however, the configuration below weld 1-10 limits scanning from below as the weld approaches the nozzle. This is illustrated by the scan plan shown in Figure 2-B of .

The two outlet nozzles are larger in diameter than the four inlet nozzles and have a different configuration at the inside surface of the reactor vessel. The outlet nozzles extend horizontally into the vessel to channel flow from the core barrel to the hot legs to minimize mixing of outlet flow and inlet flow within the annulus. This "nozzle boss," or protrusion, creates a geometry which limits the approach of the transducer as shown in Figure 2-C. Single sided scanning from above the weld was also performed for the outlet nozzles to the extent shown in the scan plan In Figure 2-B of Attachment 1.

Single-sided scanning of weld 1-10 was performed to the extent practical.

Within the 80 percent calculated coverage for weld 1-10, a total of nine recordable indications were reported which were all sized and determined to be acceptable as shown in Table 2-A of . The evaluations of recordable indications were performed to the acceptance standards of the ASME BPV Code,Section XI, 2001 Edition through 2003 Addenda. Previous data was reviewed from the prior inspection and has been reconciled against the current examination results to determine that no changes have occurred. The recordable indications were characterized as fabrication flaws of acceptable size. These indications are all subsurface and not considered to be service related.

The sections of weld 1-10 that were determined to have limited examination coverage are immediately adjacent to the nozzle-to-shell welds of the inlet and outlet nozzles. The nozzle-to-shell welds that intersect weld 1-10 were also specifically examined as part of the 10-year reactor vessel examinations, but are not included in the discussion and calculations of circumferential weld 1-10. There were 11 recordable indications within the six nozzle-to-shell welds which were determined to be acceptable as shown in Table 2-B of Attachment 1. The acceptable examination results of those adjacent welds provides additional assurance that the structural integrity of weld 1-10 near the areas of limited coverage remains in an acceptable condition.

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Enclosure Response to Request for Additional Information - Relief Request 64 - Unit 1 Impractical Examinations for the Third 10-Year Inservice Inspection Interval Attachment 1 Figure 2-C Outlet Nozzle Cross Section near Circumferential Weld 1-10 Note: This cross section is not representative of top dead center of the nozzle, but near where weld 1-10 approaches the nozzle.

(Upper Shell)

Weld 1-10 Centerline LJ J Outlet Nozzle Profile Outlet Flow 8