NOC-AE-03001542, Revised Request for Approval of ASME Section XI Code Case N-516-2 for Underwater Welding of Core Barrel Locking Tab (Relief Request RR-ENG-2-30)

Revised Request for Approval of ASME Section XI Code Case N-516-2 for Underwater Welding of Core Barrel Locking Tab (Relief Request RR-ENG-2-30)

ML031560419
Person / Time
Site:	South Texas
Issue date:	06/02/2003
From:	Jordan T South Texas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NOC-AE-03001542 RR-ENG-2-30
Download: ML031560419 (10)

Text

Nuclear Operating Company Souhth T=s ProEect Elkctlc Gcnccaftin Station PCt Bon2a3 K wb TcZ 774334 June 2, 2003 NOC-AE-03001542 10CFR50.55a U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852 South Texas Project Unit 1 Docket No. STN 50-498 Revised Request for Approval of ASME Section XI Code Case N-516-2 for Underwater Welding of Core Barrel Locking Tab (Relief Request RR-ENG-2-30)

Reference:

Letter, T. J. Jordan to Document Control Desk, "Request for Approval of ASME Section XI Code Case N-516-2 for the Second Ten-Year Inservice Inspection Interval (Relief Request RR-ENG-2-30)," dated May 8, 2003 (NOC-AE-03001529)

The referenced letter submitted a request for NRC approval of Code Case N-516-2 for use as applicable during the second ten-year inservice inspection interval at the South Texas Project.

The NRC staff posed some informal questions that were discussed during a conference call with South Texas Project personnel. The attached revised relief request is for approval of a single specific application of the Code Case rather than for approval for generic use. Specific responses to the informal request for additional information are included in the attached relief request.

STPNOC requests approval on an expedited basis by June 30, 2003, based on the schedule for restart from the current forced outage.

If there are any questions regarding this supplemental information, please contact Michael S.

Lashley at (361) 972-7523 or me at (361) 972-7902.

Vice President Engineering & Technical Services

Attachment:

Revised 10CFR50.55a Relief Request RR-ENG-2-30 A.N9 STI: 31613775

NOC-AE-03001542 Page 2 of 2 cc:

(paper copy) (electronic copy)

Ellis W. Merschoff A. H. Gutterman, Esquire Regional Administrator, Region IV Morgan, Lewis & Bockius LLP U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 L. D. Blaylock Arlington, Texas 76011-8064 City Public Service U. S. Nuclear Regulatory Commission Mohan C. Thadani Attention: Document Control Desk U. S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike R. L. Balcom Rockville, MD 20852 Texas Genco, LP Richard A. Ratliff A. Ramirez Bureau of Radiation Control City of Austin Texas Department of Health 1100 West 49th Street C. A. Johnson Austin, TX 78756-3189 AEP Texas Central Company Cornelius F. O'Keefe Jon C. Wood U. S. Nuclear Regulatory Commission Matthews & Branscomb P. O. Box 289, Mail Code: MN116 Wadsworth, TX 77483 C. M. Canady City of Austin Electric Utility Department 721 Barton Springs Road Austin, TX 78704

NOC-AE-03001542 Attachment Page 1 of 8 Revised 10CFR50.55a Relief Request RR-ENG-2-30 Proposed Alternative in Accordance with 10 CFR 50.55a(a)(3)(i)

-- Alternative Provides Acceptable Level of Quality and Safety--

1. ASME Code Components Affected Unit 1 reactor vessel core barrel and its Roto-Lock insert locking tabs that secure the inserts and prevent their rotation.

2. Applicable Code Edition and Addenda

American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code,Section XI, 1989 Edition with no Addenda.

3. Applicable Code Requirement

IWA-4000 of Section XI does not address underwater welding. However, Code Case N-516-2, "Underwater Welding,Section XI, Division 1," includes alternative procedure, performance, and filler metal qualifications, and alternative examination requirements to those contained or referenced in IWA-4000 for use when the welding is performed underwater.

4. Reason for the Request Approval for the use of Code Case N-5 16-2 is requested for underwater fillet welding of a Roto-Lock insert locking tab to the reactor vessel core barrel to secure the insert and prevent its rotation.

5. Proposed Alternative and Basis for Use STP Nuclear Operating Company (STPNOC) requests relief from the requirements of IWA4000 in accordance with 10CFR50.55a(a)(3)(i) in order to perform underwater welding for repairs. IWA-4000 of the Section XI code of record at the South Texas Project does not address underwater welding. STPNOC requests NRC approval of ASME Section XI Code Case N-516-2 for use at South Texas on the basis that it provides an acceptable level of quality and safety.

NOC-AE-03001542 Attachment Page 2 of 8 The NRC documented their conditional acceptance of Code Case N-516-2 in Draft Regulatory Guide DG-1091 (Proposed Revision 13 of Regulatory Guide 1.147) published in December 2001. However, neither proposed Revision 13 nor the proposed rulemaking to reference this revision in 10CFR50.55a has been issued.

STP Nuclear Operating Company requests approval for use of Code Case N-516-2 in order to deposit three each 0.180-inch fillet welds on one locking device. These welds were made using a weld procedure specification (WPS) qualified in accordance with Code Case N-516-2 and were visually examined. The WPS was qualified with tensile and bend tests in accordance with ASME Section IX, and with an additional chemical, ferrite, and tensile test performed in accordance with Code Case N-516-2.

A confirmation weld was performed on 1/2-inch plate using the WPS and the same weld material as that to be used in the production weld. The confirmation weld was subject to the same inspection requirement as the production weld.

The subject fillet welds are to prevent the Roto-Lock insert from backing out and potentially becoming a loose part. They are not structural or pressure boundary welds.

The requirements imposed on the welds is conservative with respect to the safety function of the welds.

These additional requirements, combined with the alternative requirements of Code Case N-516-2, provide an acceptable level of quality and safety for underwater welding.

6. Duration of Proposed Alternative This relief request will be implemented during the current forced outage for repairing bottom mounted instrument guide tubes.

NOC-AE-03001542 Attachment Page 3 of 8 Location of Weld

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NOC-AE-03001542 Attachment Page 6 of 8 Response to Informal Request for Additional Information for South Texas Project Underwater Welding (RR-ENG-2-30)

1. Will ASME Section IX guided bend tests per QW-160 be performed on the welding procedure qualification tests?

Response: ASME Section IX guided bend tests per QW-160 have been performed.

2. Is this welding wet or dry hyper baric, dry chamber, dry spot, etc.?

Response: This specific application is for wet welding.

3. What is the specific item to be welded using underwater welding?

Response: Code Case N-516-2 was used for making three underwater fillet welds to attach one Roto-Lock insert locking tab to the core barrel to secure the Roto-Lock insert and prevent its rotation.

4. What material is the item to be welded using underwater welding made of? (ASME SA Number, type, and grade; heat treatment condition)

Response: The locking tab is A-240 Tp 304L. The core barrel is SA-182 F304H.

5. What is the specific filler material to be used for the welding? (filler metal classification)

Response: The iller metal is SFA 5.4 E316L-17.

6. What welding process or processes are to be used?

Response: The shielded metal arc welding (SMAW) process was used.

7. What process or processes are to be used for cutting or metal removal?

Response: Cutting was done with a rotary file.

8. Will any additional NDE be done on this weld?

Response: No.

NOC-AE-03001542 Attachment Page 7 of 8

9. What NDE will be done on this weld?

Response: Remote visual examination by a certified South Texas inspector was performed.

10. Will any Examination be done on this item on an ongoing basis? (Every outage or every other outage, etc.)

Response: No examination will be done on this item on an ongoing basis.

11. What is the fluence level in the area to be welded?

Response: The total neutron fluence at the vessel flange area is expected to be no higher than 1.2E+17 n/cm2 after 40 calendar years of plant operation.

12. Will the mock-up material have the same fluence level applied to it?

Response: No, the mockup material did not have the same fluence level applied to it. The application is not Class 1 and is non-structural and non-pressure retaining.

Additionally, the locking tab and core barrel are not ferritic materials and, therefore, not subject to neutron embrittlement.

13. The high neutron fluence welding mock-up testing, procedure, data and results shall be attached to the relief request.

Response: This is not applicable to this specific application.

14. What is the licensee's basis that the proposed alternative provides an acceptable level of quality and safety?

Response: Refer to Section 5 in the relief request.

15. Provide information on the depth of the water at which the repair will be performed.

Response: The Performance Qualification Record for the tensile test was performed at a depth of 35 feet. This qualifies the filler material to a depth range of from 2 to 45 feet. The weld filler material weld pad was welded at a depth of 20 feet, which qualifies the filler material to a depth of from 0 to 30 feet. The replacement weld was performed at a depth of 29 feet. The combination of the tests performed meet the qualification requirements of Code Case N-516-2 for welding at a depth of 29 feet.

NOC-AE-03001542 Attachment Page 8 of 8

16. Confirmation tests for welders shall be performed prior to the commencement of production work. The confirmation test requirements specified in AWS D 3.6 shall be followed.

Response: A confirmation weld was performed on 1/2-inch plate using the same WPS and weld material as that to be used in the production weld. The confirmation weld was subject to the same inspection requirement as the production weld.

17. The licensee should provide test results of filler metal qualifications per paragraph 4.0 of code case 516-2. The minimum required ferrite number of the weld metal shall be specified in the relief request.

Response: STP determined that the requirements of the code case have been met.

The results are summarized below.

Procedure qualification results are as follows:

- 2 root and 2 face bends - acceptable

- 2 tensile tests (88,000 PSI and 88,500 PSI)

- Chemistry test results certified that the weld pad was welded with a 3/32" diameter E316L-17 electrode of Lot #19479H. The weld pad was welded at a water depth of 20'. Chemistry conforms to the chemical requirements of ASME SFA 5.4, AWS Classification E316L-XX.

- Carbon .035

- Chromium 17.52

- Nickel 12.43

- Molybdenum 2.84

- Manganese .64

- Silicon .69

- Phosphorus .038

- Sulfur .009

- Copper .16

- Six (6) delta-ferrite readings were taken on the weld pad and resulted in an average of 9.1FN. This complies with site requirements for a minimum of 5FN and a maximum of 25FN. The six readings were 10.0, 8.5, 9.5, 11.0, 8.5 and 7.5.

18. The items above shall be included in or attached to the relief request.

Response: This attachment fulfills the requirement.