ML24326A361
| ML24326A361 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 11/21/2024 |
| From: | Meeden A Arizona Public Service Co |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| 102-08881-ARM/MDD | |
| Download: ML24326A361 (1) | |
Text
10 CFR 50.55a A member of the STARS Alliance LLC Callaway
- Diablo Canyon
- Palo Verde
- Wolf Creek 102-08881-ARM/MDD November 21, 2024 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
Subject:
Palo Verde Nuclear Generating Station Unit 1 Docket No. STN 50-528, Renewed Operating License Nos. NPF-41 Response to Request for Additional Information - Relief Request 72 By letter dated July 31, 2024 (Agencywide Documents and Access Management System (ADAMS) Accession No. ML24213A329), Arizona Public Service Company (APS or the licensee) requested Nuclear Regulatory Commission (NRC) staff approval of Relief Request Number 72 from the flaw characterization requirements of American Society of Mechanical Engineers (ASME) Code,Section XI, paragraphs IWC-3420 and IWA-3300.
Pursuant to 10 CFR 50.55a(z)(1), licensees may request authorization to implement alternative methodologies that deviate from regulatory requirements provided they achieve an acceptable level of quality and safety.
On October 22, 2024, the NRC staff provided a request for additional information (RAI) to support their review of the requested relief. The Enclosure to this letter provides the APS response to the NRC RAI.
No new commitments are being made to the Nuclear Regulatory Commission by this letter.
Should you need further information regarding this submittal, please contact Michael D.
DiLorenzo, Department Leader Nuclear Regulatory Affairs - Licensing at (623) 393-3495.
Sincerely, ARM/MDD/cr
Enclosure:
PVNGS Unit 1 - Response to Request for Additional Information -
Relief Request 72 cc:
J. D. Monninger NRC Region IV Regional Administrator W. T. Orders NRC NRR Project Manager for PVNGS L. N. Merker NRC Senior Resident Inspector for PVNGS Rex Meeden VP Nuclear Engineering Palo Verde Nuclear Generating Station P.O. Box 52034 Phoenix, AZ 85072 Mail Station 7602 Tel: 623-393-6582 Meeden, Alfred R(Z99870)
Digitally signed by Meeden, Alfred R(Z99870)
Date: 2024.11.21 17:11:17
-07'00'
Enclosure PVNGS Unit 1 Response to Request for Additional Information -
Relief Request 72
PVNGS Unit 1 Response to Request for Additional Information Relief Request 72 1
Introduction By letter dated July 31, 2024 (Agencywide Documents and Access Management System (ADAMS) Accession No. ML24213A329), Arizona Public Service Company (APS or the licensee) requests Nuclear Regulatory Commission (NRC) staff approval of Relief Request Number 72 from the flaw characterization requirements of American Society of Mechanical Engineers (ASME) Code,Section XI, paragraphs IWC-3420 and IWA-3300. Pursuant to 10 CFR 50.55a(z)(1), licensees may request authorization to implement alternative methodologies that deviate from regulatory requirements provided they achieve an acceptable level of quality and safety.
The NRC staff requested the following additional information to complete its review of the relief request. The NRC request for additional information (RAI) is stated first followed by the APS response.
NRC RAIs and APS Responses Question 1
RAI-1
Issue Section I of Relief Request No. 72 states that the affected ASME Code Item is C2.20 for the safety injection tank nozzles.Section II of the relief request states that the code of record for the fourth inservice inspection is the 2013 Edition of the ASME Code,Section XI. The NRC staff notes that the 2013 Edition of the ASME Code,Section XI, Table IWC-2500-1, Examination Category C-B, does not provide inspection provisions for Examination Item number C2.20. Rather, Examination Item number C2.20 includes subcategories of C2.21, Nozzle-to-Shell (Nozzle-to-Head or Nozzle-to-Nozzle) Weld and C2.22, Nozzle Inside Radius Section. Examination Items C2.21 and C2.22 do contain inspection requirements. It seems to the NRC staff that if the subject safety injection tank vent nozzle is classified as Item number C2.20, the subject vent nozzle would be inspected in accordance with Item number C2.21 and/or C2.22.
The NRC staff recognizes that the relief request proposes not to perform inspection of the original partial penetration weld of the vent nozzle at the inside diameter of the safety injection tank. However, the NRC staff seeks information regarding the inspection of the new pressure boundary weld at the outside diameter of the safety injection tank.
Request Identify which Inspection Item (C2.21 or C2.22) under the ASME Code,Section XI, Table IWC-2500-1, Examination Category C-B, Inspection Item C2.20 establishes the inspection requirements for the new pressure boundary weld at the subject safety injection tank vent nozzle during the 5th and 6th ISI interval.
Discuss whether inspections were performed on the new pressure boundary weld (at the outside diameter of the safety injection tank) at the vent nozzle since 2008. If affirmative, provide inspection performed and results. If not, provide the basis that this new pressure boundary weld was not inspected.
PVNGS Unit 1 Response to Request for Additional Information Relief Request 72 2
Response for RAI-1 Neither C2.21 nor C2.22 exams are applicable to the safety injection tank nozzle with the pressure retaining weld moved to the outside surface of the safety injection tank.
The safety injection tank nozzle addressed in relief request 72 is attached to 2-inch NPS piping, 1PSIEL210. 1PSIEL210, the safety injection tank vent line pipe is exempt from examination per ASME Section XI, IWC-1221 (a)(1) (Figure 1), that excludes piping 4-inch and smaller. With C-F-1 and Code Case N-716-1 exams not applicable to 1PSIEL210, C2.21 and C2.22 type examinations are not applicable to the safety injection tank nozzle, Ref. Note 5 in Table IWC-2500-1, C-B (Figure 2).
Figure 1: IWC-1221
PVNGS Unit 1 Response to Request for Additional Information Relief Request 72 3
Figure 2: Table IWC-2500-1, C-B Note: Similar exemptions of notes 4 and 5 of Figure 2 are included in Table IWC-2500-1 notes 1 and 2 of the 2001 Edition/2003 Addenda of ASME Section XI used in the 3rd 10-year Interval of the ISI program, when Relief Request 39 was submitted and approved.
No surface or volumetric examinations have been conducted since 2008 for the safety injection tank nozzle to shell weld. See above response for justification.
PVNGS Unit 1 Response to Request for Additional Information Relief Request 72 4
Question 2
RAI-2
Issue Second paragraph of the Background in the relief request states that On Thursday, June 5, 2008, Palo Verde Nuclear Generating Station (PVNGS) declared the Unit 1 SIT 1A inoperable when a small leak was identified at the annulus between the tank and the vent line during the performance of a leak test The NRC staff notes that the ASME Code,Section XI, Table IWC-2500-1, Examination Category C-H, Item No. C7.10 requires a system leakage test each inspection period. Also, the NRC staff seeks information on defense-in-depth measures to ensure structural integrity of the repaired subject safety injection tank vent nozzle.
Request (a) Discuss whether a system leakage test is performed on the subject vent nozzle every inspection period in accordance with the ASME Code,Section XI, Category C-H, Item No. C7.10.
(b) Discuss whether there are sensor(s) that could detect the nitrogen leak at the safety injection tank vent nozzle and provide signals to the control room to notify the operator(s). If such sensor(s) does not exist, discuss any method that could detect potential leak.
Response for RAI-2 (a) Yes, a system leakage test is performed each inspection period for Category C-H, as contained within PVNGS ISI program documents.
(b) Each Safety Injection Tank (SIT) is equipped with one (1) wide range pressure transmitter and two (2) narrow range pressure transmitters to provide indication and/or alarms in the Control Room. The transmitters specific to Unit 1 SIT 1A are as follows:
- i.
1JSIAPT0331: Wide-range pressure transmitter that provides pressure indication in the Control Room, Remote Shutdown Panel, and Emergency Response Facility Data Acquisition and Display System (ERFDADS).
ii.
1JSINPT0332: Narrow-range pressure transmitter that provides pressure indication in the Control Room and Plant Computer, and also supplies high-and low-pressure alarms.
iii.
1JSIAPT0333: Narrow-range pressure transmitter that provides pressure indication in the Control Room and Plant Computer, and also supplies high-and low-pressure alarms.
These instrument loops are used for monitoring SIT pressure and occurrences of the low-pressure alarms would alert the operators of a low-pressure condition that necessitates the appropriate action per the alarm response procedure. Instances of SIT nitrogen leakage have been identified during an operating cycle by trending indicated pressure and the frequency of low-pressure alarms compared to that of the other SITs.