ML092610069
| ML092610069 | |
| Person / Time | |
|---|---|
| Site: | Palo Verde  |
| Issue date: | 09/10/2009 |
| From: | Mims D Arizona Public Service Co, Pinnacle West Capital Corp |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 102-06061-DCM/RJR | |
| Download: ML092610069 (8) | |
Text
10 CFR 50.55a LAPSA subsidiary ofPinnacle West Capital Corporation Dwight C. Mims Mail Station 7605 Palo Verde Nuclear Vice President Tel. 623-393-5403 P. 0. Box 52034.
Generating Station Regulatory Affairs and Plant Improvement Fax 623-393-6077 Phoenix, Arizona 85072-2034 102-06061-DCM/RJR September 10, 2009 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001
Dear Sirs:
Subject:
Palo Verde Nuclear Generating Station (PVNGS)
Unit 2 Docket No. STN 50-529 Request for Relief from the American Society of Mechanical Engineers (ASME) Code, Section Xl - Relief Request No. 45 Pursuant to 10 CFR 50.55a(g)(5)(iii), Arizona Public Service Company (APS) is submitting a request for relief for the Unit 2 second Inservice Inspection (ISI) interval. Specifically, APS is requesting relief from the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI requirements, regarding Class 1 weld and component volumetric examinations as well as Class 2 system leakage tests, which have been determined by APS to be impractical.
No commitments are being made to the NRC by this letter. Should you need further information regarding this relief request, please contact Russell A. Stroud, Licensing Section Leader, at (623) 393-5111.
Sincerely, DCM/RAS/RJR/gat
Enclosure:
Relief Request No. 45 cc:
E. E. Collins Jr.
NRC Region IV Regional Administrator J. R. Hall NRC NRR Project Manager R. I. Treadway NRC Senior Resident Inspector 74 A member of the STARS (strategic Teaming and Resource Sharing) Alliance
ý_fm Callaway 0 Comanche Peak 0 Diablo Canyon 0 Palo Verde 0 San Onofre
- South Texas
- Wolf Creek
ENCLOSURE Relief Request No. 45
Relief Request in Accordance with 10 CFR 50.55a(g)(5)(iii)
Inservice Inspection Impracticality Relief Request No. 45 ASME Code Components Affected PVNGS Unit 2 Code Class: 1 Exam Category Item No.
System or Component Request Section B-D B3.90 Reactor Vessel nozzle-to-vessel welds A
Code Class: 2 Exam Category Item No.
System or Component Request Section Piping C7.30 pressure retaining components C-H Valves B
C7.70 pressure retaining components Aoolicable Code Edition and Addenda Second 10-year Inservice Inspection Interval for PVNGS Unit 2: ASME Code, Section Xl, 1992 Edition and 1992 Addenda.
Part A: B-D, B3.90 Reactor Vessel - Nozzle to Vessel Welds
Background
Due to the one-cycle deferral of the Unit 2 reactor vessel nozzle to vessel weld examinations submitted in Relief Request 34 and approved by the NRC on May 16, 2007, the impracticality of compliance described below was not submitted with APS' original 10 CFR 50.55a(g)(5)(iv) submittal, Relief Request 38. The Unit 2 examinations were performed during the fourteenth refueling outage representing a one-cycle deferral.
Specific ASME Code Requirement Subsection IWB of ASME Section XI, 1992 Edition, 1992 Addenda defines the ASME Class 1 welds and components that are required to be examined. For volumetric examinations it further specifies the associated examination volume. These examination volume requirements were modified using Code Case N-613-1 which provides alternative figures and volumes and Code Case N-460 which provides alternative rules that allow the examination volume to be reduced by 10% under certain conditions.
1
Relief Request No. 45 Impracticality of Compliance ASME Code requires a minimum of 90 percent coverage of the weld volume; but, the configuration of the reactor vessel outlet nozzles and the geometric shape limit the ability to conduct the required examination. Therefore, APS is seeking relief from the Code requirement.
Burden Caused by Compliance Due to component geometry several scans are performed on these nozzles to maximize coverage. To comply with the Code, the reactor vessel nozzle attachment would have to be redesigned and modified to increase the coverage to 90 percent or better.
Alternative The design of the reactor vessel outlet nozzle protrusion (illustrated in Figure 2) provides a geometric limitation to the scanning area. The examination robot and transducer sled are physically limited by this protrusion. Figure 1 illustrates the ISI drawing for Zone 1 and the location of welds 1-15 and 1-18. Figure 2 illustrates where the limitations were documented and a typical transducer sled scanning from the vessel inside diameter. The limitation is the nozzle protrusion as seen in this figure. All accessible reactor vessel surfaces were examined, with the exception of scanning from the radius and protrusion. Examination scanning was performed on these nozzles to obtain the highest examination volume practical. The examination volume coverage was 94% for perpendicular to the weld centerline scans from the nozzle bore. The tangential scans that are parallel to the weld centerline were limited to 56.94%. The overall combined examination volume was 85.1%.
Based on the above evaluation, the proposed alternative is to examine these welds to the extent practical.
Page 2
Relief Request No. 45 1 33P 1-81-19
- NOTES, 1-17 I
AG NO.
2MRCEXOI
- SERIALNO, 79173 (C-E)
N.H NO.
)2513'
____I M27o1
.U0% I.IGAMENS T* I 54 STUD HOLES I-I COINTED CLOCK M Sr5 FROM W V
1 0'
I'LANI' NORTH 11-4 SHELL SEGMIENT 182 114" IA"/4
- CROSS, SýECt ON OUFLIT INLIEr OIGI'E'A"IN (AI"
.REFERENCE DWG:
NOOI-3.OI-I 5 AND 17 NOOI-3,01-41 AND61 RN001-3.01-72 SUPPORT (COLUMNS 40,V1 IA 1ýI 41,A' in 91116"42,VI2A t
43 AT 2B1 SHEAR 1-2 UNIT2 ZONE I REACTOR VESSEL
- REV, FIGURE 1: ISI ZONE DRAWING 1 Page 3
Relief Request No. 45 10-
-R=91.48
-~3 8.8 8 153.75 Ref, 32.53
- to Top of Vesser R=87.a5 to Clad 88.22 START OF RADIUS 12
Nozzle protrusion area limiting scanning (typical) Transducer Sled scanning from the vessel ID The shaded areas indicate the weld volume required.
- ~
FIGURE 2: NOZZLE TO VESSEL PROTRUSION (typical sketch)
Page 4
Relief Request No. 45 Part B: C-H, Pressure Retaining Components, Items C7.30 and C7.70
Background
By letter dated March 14, 2008, as supplemented by letter dated November 14, 2008, APS submitted Relief Request 38 pursuant to 10 CFR 50.55a(g)(5)(iv) for the Unit 2 second ISI interval. During further review of the second ISI interval activities, APS has determined additional relief is required for the testing of the items C7.30 and C7.70.
This omission has been entered into the Palo Verde Corrective Action Program.
Specific ASME Code Requirement ASME Section XI 1992 Edition, 1992 Addenda Category C-H requires a system leakage test for item numbers C7.30 and C7.70. These requirements include essentially 100%
of the pressure-retaining boundary.
Impracticality of Compliance The three chemical and volume control system (CVCS) charging pumps each have a suction stabilizer and pulsation dampener for system stability purposes. These components have a bladder and nitrogen system to moderate the fluid shock in the CVCS to maintain consistent operating characteristics. The nitrogen tubing lines up to and including the first isolation valve from the stabilizer and dampeners are ASME Class 2. Line numbers for this tubing are A-938-HCBA-3/8" and A-937-CCBA-3/8"; B-940-HCBA-3/8" and B-939-CCBA-3/8"; E-942-HCBA-3/8" and E-941 -CCBA-3/8" for the A, B, and E charging pumps respectively. A visual testing level II (VT-2) qualified examiner employs a "snoop" method to detect escaping gas in the form of bubbles on this tubing. This tubing has installation clips and other attachments that prevent 100%
snooping of the tubing. Therefore, APS considers this examination to be limited. Figure 3 depicts a typical installation clip and associated VT-2 limitation.
Page 5
Relief Request No. 45 FIGURE 3: TYPICAL INSTALLATION FOR THE N2 LINES Burden Caused by Compliance Relief is being requested because of physical interference due to plant configuration.
To meet the testing coverage requirements, re-design and modification of components would be required which is contrary to the intent of the Code. Therefore, this option is considered impractical.
Alternative Based on the above evaluation, the-proposed alternative is to examine the above referenced piping to the extent practical.
Duration of Proposed Alternatives The items for which APS is requesting relief were examined to the fullest extent practical. In accordance with 10 CFR 50.55a(g)(5)(iii), PVNGS is requesting relief from conformance with the above code requirements which have been determined to be impractical for the second inspection interval for Palo Verde Unit 2.
References NRC letter dated May 16, 2007, "Palo Verde Nuclear Generating Station, Units 2 and 3
- Supplement to Relief Request No. 34 RE: Request to Extend the Second 10-year Inservice Inspection Program Interval for Reactor Vessel Weld Examinations (TAC NOS. MD3917 and MD3918)."
Page 6