ET 05-0027, CFR 50.55a Request Number I2R-33 Regarding ASME Section XI Requirements for Examination Coverage of the Reactor Pressure Vessel Nozzle-to-Vessel Welds

CFR 50.55a Request Number I2R-33 Regarding ASME Section XI Requirements for Examination Coverage of the Reactor Pressure Vessel Nozzle-to-Vessel Welds

ML053340299
Person / Time
Site:	Wolf Creek
Issue date:	11/22/2005
From:	Garrett T Wolf Creek
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
ET 05-0027
Download: ML053340299 (8)

Text

W4LFCREEK

-- 'NUCLEAR OPERATING CORPORATION Terry J. Garrett -

Vice President Engineering November 22, 2005 ET 05-0027

- U. S. Nuclear Regulatory Commission -

ATTN: Document Control Desk Washington, DC 20555 -

Subject:

Docket No. 50-482: 10 CFR 50.55a Request Number 12R-33 Regarding

- - ASME Section XI Requirements for Examination Coverage of the Reactor' Pressure Vessel Nozzle-to-Vessel Welds Gentlemen:

Pursuant to 10 CFR 50.55a(g)(5)(iii), Wolf Creek Nuclear Operating Corporation (WCNOC) requests relief from certain examination coverage requirements imposed by the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section Xl, "Rules for Inservice Inspection'of Nuclear Power Plant Components," for the Wolf Creek Generating Station (WCGS).

The attachment provides 10 CFR 50.55a Request- 12R-33 to the WCNOC Second Interval Inservice Inspection (ISI) Program Plan. This 10 CFR 50.55a request is for weld examinations of the outlet nozzle to vessel welds, performed during'the' 2005 refueling outage, where the.

required coverage of 'essefntially 100 percenit" could'not'be obtained when examined to the extent practical. The basis-for the 10 CFR 50.55a request is that compliance with the specified requirements is impractical due to plant design.

WCNOC requests NRC approval of 10 CFR 50.55a Request 12R-33 by September 2, 2006,

' which is 12 months following the end of the second ten-year ISI interval. This will meet the

- - requirements-of 10 CFR 50.55a(g)(5)(iv), which requires the basis for such requests to be demonstrated to the satisfaction of the NRC not later than '12 months after the expiration of the 120 month inspection interval.'

- There are no commitments contained within this letter.- If you have any questions concerning this matter, please contact me at (620) 364-4084, or Mr. Kevin Moles at (620) 364-4126.

Sinr

-'rry J. Garrett TJG/rIg -. --- CI4f17 PO. Box 411/ Burlington, KS 66839 I Phone: (620) 364-8831 An Equal Opportunity Employer MIFIHCNVET

ET 05-0027 Page2of2

Attachment:

10 CFR 50.55a Request Number 12R-33 cc: J. N. Donohew (NRC), w/a W. B. Jones (NRC), w/a B. S. Mallett (NRC), w/a Senior Resident Inspector (NRC), wla

Attachment to ET 05-0027 Page 1 of 6 10 CFR 50.55a Request Number 12R-33 Relief Request In Accordance with 10 CFR 50.55a(g)(5)(iii)

--Inservice Inspection Impracticality--

1. ASME Code Component(s) Affected Class 1 Reactor Pressure Vessel Pressure-retaining Nozzle-to-Vessel welds as listed.

NOZZLE NVELDS CODE CATEGORY B-D Code Description Weld No.

Item B3.90 Loop A Outlet Nozzle to Vessel Weld RV-107-121-A B3.90 Loop B Outlet Nozzle to Vessel Weld RV-107-121-B B3.90 Loop C Outlet Nozzle to Vessel Weld RV-107-121-C B3.90 Loop D Outlet Nozzle to Vessel Weld RV-107-121-D

2. Applicable Code Edition and Addenda

The applicable Code edition and addenda is ASME Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components," 1989 Edition, with no Addenda. In addition, as required by 10 CFR 50.55a, ASME Section XI, 1995 Edition, 1996 Addenda is used for Appendix Vil, Performance Demonstration for Ultrasonic Examination Systems.

3. Applicable Code Requirement

ASME Section Xl, Figure IWB-2500-7 (a) 1989 Edition with no addenda requires volumetric examination of a minimum volume of base material on each side of the weld equal to a distance of tS2 (one half of the RPV shell thickness adjacent to the weld).

In a letter dated May 17, 2005, the NRC approved WCNOC relief request 12R-32, which is the use of a reduced UT examination volume, shown in Figure 1 of Code Case N-613-1, which extends to 1/2 inch from the widest part of the weld in lieu of the examination volume requirements of ASME Code, Section Xl, Figure IWB-2500-7(a).

The WCNOC second ten-year interval inservice inspection program plan also implements Code Case N-460, which is endorsed by the NRC in Regulatory Guide 1.147. Code Case N-460 states in part, "when the entire examination volume or area cannot be examined due to interference by another component or part geometry, a reduction in examination coverage on any Class 1 or Class 2 weld may be accepted provided the reduction in coverage for that weld is less than 10 percent."

NRC Information Notice (IN) 98-42 termed a reduction in coverage of less than 10 percent to be "essentially 100 percent." IN 98-42 states in part, 'The NRC has adopted and further refined the definition of "essentially 100 percent" to mean "greater than 90 percent"...has been applied to all examinations of welds or other areas required by ASME Section XI.'

Attachment to ET 05-0027 Page 2 of 6 10 CFR 50.55a Request Number 12R-33

4. Impracticality of Compliance The examination of the subject components is limited by the geometry of the nozzle design. During the Cycle 14 refueling outage in the spring of 2005 the outlet nozzle to shell welds were examined by remote tool (automated examination) from the nozzle bore, and from the vessel shell interior using circular and radial scanning paths around the nozzle opening to examine for transverse defects and defects parallel to the weld axis. The vessel shell circular scans are commonly called tangential scans, and the radial scans are referred to as star scans. The bore and star scans provide perpendicular coverage (searching for circumferential flaws parallel to the nozzle to shell weld) and the tangential scan provides parallel coverage (searching for axial flaws perpendicular to the nozzle to shell weld). As shown on the attached figures 1 and 2, the proximity of the nozzle protrusion to the outlet nozzle to shell welds limits the scans from the vessel shell. The combined perpendicular coverage is estimated at 92.51%, the combined parallel coverage is estimated at 68.04%

resulting in a combined average of 80.27%. See Table 1 for a breakdown of the beam angle coverage's.

5. Burden Caused by Compliance The design configuration restrictions of the outlet nozzles at WCNOC make the Code required examination coverage requirements impractical. Plant modifications or the replacement of components designed to allow for complete coverage would be needed to meet the ASME Code requirements. This would impose a considerable burden to WCNOC.

6. Proposed Alternative and Basis for Use Proposed Alternative The following alternatives are proposed in lieu of the required examination coverage of essentially 100 percent:

1. The performance of qualified volumetric examination (UT) of the subject welds to the maximum extent practical due to design configuration restrictions during the second ten-year interval.

2. Visual examinations were performed as required by Code Category B-N-1 during the second ten-year interval and no degradation identified.

3. Pressure test VT-2 visual examination as required by Code Category B-P was performed as required during the second ten-year interval and no evidence of leakage has been identified for these components.

Basis for Use The basis for use of these alternatives is that they provide the best examination coverage possible within the limitations of the current design configuration. The volumetric examination was performed using a system (procedures, personnel, and equipment) qualified in accordance with Appendix VilI, Supplements 4, 6, and 7.

7. Duration of Proposed Alternative The second ten year ISI interval which began September 3, 1995 and ended September 2, 2005.

Attachment to ET 05-0027 Page 3 of 6 10 CFR 50.55a Request Number 12R-33

8. Precedents a) Southern California Edison Letter, dated April 16, 2004, Docket Nos. 50-361 and 50-362, Second Ten-Year Inservice Inspection (ISI) Interval Relief Request RR-B-2-08, Regarding American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code Inspection Requirements for Item No B3.90, Nozzle to Vessel Welds, San Onofre Nuclear Generating Station Units 2 and 3, and the associated NRC Safety Evaluation Report dated July 20, 2004 (TAC Nos. MC2736 and MC2737)

• Attachment to ET 05-0027 Page 4 of 6 10 CFR 50.55a Request Number 12R-33

. I Table 1 Beam An le Breakdown for Outlet Nozzle-to-Vessel Welds Beam Direction 45 Shear 45 L Single 45 L Dual Combined Bore/Star Weld Volume Weld Volume Weld Volume Weld Volume TAN Scan 50.00 41.12 50.00 67.09 100.0 100.00 (parallel) 0 .

Combined 94.72 90.30 Bore&Star (perpendicular)

Average 45.56 58.55 100.00 92.51 Coverage calculation is based on the Bore and Star Scan (combined) as perpendicular, and the TAN Scan (parallel).

Combined Perpendicular: 92.51%

Combined Parallel: 68.04%

Combined Average: 80.27%

22' Nozzle- 1-RV-107-121-A - U> 4 158' Nozzle- I-RV-107-121-B a )

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