ML013480238

Safety Evaluation of Request to Use Alternative Materials Per Associated Code Cases for Steam Generator Channel Head Bowl Drain Nozzle and Weld Repairs

ML013480238
Person / Time
Site:	Catawba
Issue date:	01/18/2002
From:	Richard Laufer NRC/NRR/DLPM/LPD2
To:	Gordon Peterson Duke Energy Corp
Patel C P, NRR/DLPM, 415-3025
References
TAC MB3003
Download: ML013480238 (6)

Text

January 18, 2002 Mr. G. R. Peterson Site Vice President Catawba Nuclear Station Duke Energy Corporation 4800 Concord Road York, South Carolina 29745-9635

SUBJECT:

CATAWBA NUCLEAR STATION, UNIT 2 RE: SAFETY EVALUATION OF REQUEST TO USE ALTERNATIVE MATERIALS PER ASSOCIATED CODE CASES FOR STEAM GENERATOR CHANNEL HEAD BOWL DRAIN NOZZLE AND WELD REPAIRS (TAC NO. MB3003)

Dear Mr. Peterson:

By letter dated September 26, 2001, Duke Energy Corporation requested approval of the proposed alternative to use Alloy 690 welding filler materials (Inconel or Alloy 52/152) and associated American Society of Mechanical Engineers Code Cases 2142-1 and 2143-1 at Catawba Nuclear Station, Unit 2. The request is associated with the use of Alloy 690 type filler material (Inconel 52/152) for the steam generator channel head bowl drain nozzle and weld repairs.

The staff concludes that the use of the proposed alternative for this repair will provide an acceptable level of quality and safety. Therefore, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) Section 50.55a(a)(3)(i), the staff authorizes the use of the proposed alternative. Our evaluation addresses the use of Alloy 690 material and not the repair methodology outlined in the submittal. Our Safety Evaluation is enclosed.

Sincerely,

/RA/

Richard Laufer, Acting Chief, Section 1 Project Directorate II Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-414

Enclosure:

As stated cc w/encl: See next page Mr. G. R. Peterson January 18, 2002 Site Vice President Catawba Nuclear Station Duke Energy Corporation 4800 Concord Road York, South Carolina 29745-9635

SUBJECT:

CATAWBA NUCLEAR STATION, UNIT 2 RE: SAFETY EVALUATION OF REQUEST TO USE ALTERNATIVE MATERIALS PER ASSOCIATED CODE CASES FOR STEAM GENERATOR CHANNEL HEAD BOWL DRAIN NOZZLE

AND WELD REPAIRS (TAC NO. MB3003)

Dear Mr. Peterson:

By letter dated September 26, 2001, Duke Energy Corporation requested approval of the proposed alternative to use Alloy 690 welding filler materials (Inconel or Alloy 52/152) and associated American Society of Mechanical Engineers Code Cases 2142-1 and 2143-1 at Catawba Nuclear Station, Unit 2. The request is associated with the use of Alloy 690 type filler material (Inconel 52/152) for the steam generator channel head bowl drain nozzle and weld repairs.

The staff concludes that the use of the proposed alternative for this repair will provide an acceptable level of quality and safety. Therefore, pursuant to Title 10 of the Code of Federal Regulations (10 CFR) Section 50.55a(a)(3)(i), the staff authorizes the use of the proposed alternative. Our evaluation addresses the use of Alloy 690 material and not the repair methodology outlined in the submittal. Our Safety Evaluation is enclosed.

Sincerely,

/RA/

Richard Laufer, Acting Chief, Section 1 Project Directorate II Division of Licensing Project Management Office of Nuclear Reactor Regulation Docket No. 50-414

Enclosure:

As stated cc w/encl: See next page DISTRIBUTION:

PUBLIC CPatel ACRS PDII-1 R/F CHawes RII RLaufer OGC Accession Number: ML013480238 *See previous concurrence OFC PM/PDII-1 LA/PD PDII-1 EMCB* OGC* ASC/PDII-1 NAME CPatel CPatel for CHawes BElliot RHoefling RLaufer DATE 01/18/02 01/18/02 01/08/02 01/15/02 01/18/02 OFFICIAL RECORD COPY SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST TO USE ALTERNATIVE MATERIALS AND ASSOCIATED CODE CASES FOR REPAIRS ASSOCIATED WITH STEAM GENERATOR CHANNEL HEAD

BOWL DRAIN NOZZLE AND WELDS DUKE ENERGY CORPORATION CATAWBA NUCLEAR STATION, UNIT 2 DOCKET NO. 50-414

1.0 INTRODUCTION

By letter dated September 26, 2001, Duke Energy Corporation (the licensee) requested approval under the provisions of Title 10 of the Code of Federal Regulations (10 CFR)

Section 50.55a(a)(3)(i) to use Alloy 690 weld filler materials (Inconel or Alloy 52/152) in accordance with the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (B&PV) Code Case 2142-1, F-Number Grouping for Ni-Cr-Fe, Classification UNS N06052 Filler Metal,Section XI, and Code Case 2143-1, F-Number Grouping for Ni-Cr-Fe, Classification UNS W86152 Welding Electrode,Section XI. The Alloy 690 material would be used for the repair of nozzles and welds for channel head bowl drain on Westinghouse D5 steam generators at Catawba Unit 2. The referenced Code cases introduce and classify new nickel base weld metals that are compatible with Alloy 690 base metal materials. Code Case 2142-1 establishes welding classifications and other requirements for a bare wire filler metal.

Code Case 2143-1 establishes welding classifications and other requirements for a coated electrode. These two Code cases have not been incorporated by reference into the regulations; therefore, their use requires NRC approval.

Thus, the licensees request consists of two issues:

a. The use of Alloy 690 (Inconel 52/152) weld filler materials in steam generator channel head bowl drain nozzle and weld repair in lieu of Alloy 600 (Inconel 82/182) weld filler materials; and

b. The use of two ASME Code cases that group the new weld filler materials in the same weld categories as other commonly employed nickel base weld filler metals. This allows the use of appropriate existing welding procedures and performance qualifications with the new weld metals.

The Code of Record to be used to repair the steam generator channel head bowl drain nozzle and welds is the 1989 ASME B&PV Code Section XI with no addenda. This code allows, by reference, the use of Alloy 600 (Inconel 82/182) weld filler material, but does not include the use of Alloy 690 (Inconel 52/152) weld filler materials. Industry studies indicate that Alloy 690

(Inconel 52/152) weld filler materials are less susceptible to intergranular stress corrosion cracking (IGSCC) than the Inconel 82/182 materials. Alloy 600 type weld metals (Inconel 82/182) were widely used during the construction of nuclear power plants. Operating experience has shown that Inconel 182 weld material is susceptible to IGSCC, although primarily in boiling-water reactor (BWR) environments.

2.0 DISCUSSION 2.1 Alloy 690 weld filler materials (Inconel 52/152)

The licensee stated that the industry studies have demonstrated that Alloy 690 weld materials possess a high resistance to primary water corrosion. In addition, an evaluation by the licensee of the possible weld dilution concluded that the percentage of chromium in the deposited welds will exceed 22 percent. Consequently, the chromium content of the repaired surfaces containing the proposed Alloy 690 weld material, considering chromium dilution, will exceed that of the original Alloy 600 material, and thus is expected to have good corrosion resistance.

The licensee has proposed the use of alternative Inconel 52/152 materials for weld repairs associated with the steam generator channel head bowl drain nozzle and welds. Laboratory test data have shown that Inconel 52/152 materials are resistant to stress corrosion cracking in simulated pressurized-water reactor (PWR) and BWR environments. The material properties of the existing Alloy 600 (82/182) weld material were compared by the licensee to the new proposed Alloy 690 (52/152) weld material. The thermal expansion coefficient of the 52/152 weld material is somewhat higher than the coefficient of the 82/182 weld material; however, the modulus of elasticity is lower for the 52/152 weld material than the 82/182 weld material. Since the thermal stress is a function of the product of the modulus of elasticity and the thermal expansion coefficient, the effects tend to cancel each other. Thus, the presence of the two weld materials will have an insignificant effect on the thermal stresses in the total weld.

The staff has approved the use of Inconel 52/152 in the replacement of steam generators for a number of PWRs, including V. C. Summer; St. Lucie, Unit 1; McGuire Nuclear Station, Units 1 and 2; Catawba Nuclear Station, Unit 1; and Oconee Nuclear Station, Units 1, 2, and 3. The staff also has approved use of Inconel 52/152 for repair of the cracks found on the Oconee Nuclear Station Units 1 and 3 Control Rod Drive Mechanisms. Therefore, the licensee-proposed use of Inconel 52/152 filler materials for repairs associated with the steam generator channel head bowl drain nozzle and welds is acceptable since it will provide an acceptable level of quality and safety.

2.2 Code Cases 2142-1 and 2143-1 The purposes of a weld metal code case are the establishment of uniform chemical and material properties and the classification of the weld metal with respect to its welding characteristics. This welding characteristics classification is known as an F-No. Weld metals with like characteristics are grouped together for welding and welder qualification purposes in order to eliminate unnecessary duplication.

Code Case 2142-1 lists American Welding Society (AWS) specification (AWS A5.14) and Unified Numbering System (UNS) designation (UNS N06052) conforming to Inco 52 (Inconel 52). It establishes the F-No. of this weld metal as F-No. 43 for both procedure and

performance qualification purposes. Code Case 2143-1 lists appropriate AWS and UNS specifications for a coated electrode matching Inco 152 (Inconel 152) and establishes F-No. 43 for this material for welding purposes. By this set of specifications and F-No. assignments, these materials are completely described for welding purposes as similar in their welding characteristics to many other Code nickel-based weld metals. Thus, these two weld metals (Inconel 52/152) are exempted from the requirements for specific procedure and performance qualifications for non-Code materials.

The staff finds that these two code cases appropriately specify and classify the necessary weld metal parameters and are acceptable for use. The staff has approved the use of these two Code cases in the replacement of steam generators for a number of PWRs, including V. C. Summer; St. Lucie, Unit 1; McGuire Nuclear Station, Units 1 and 2; Catawba Nuclear Station Unit 1; and Oconee Nuclear Station, Units 1, 2, and 3; as well as reactor vessel head penetration repairs for the Oconee Nuclear Station, Unit 1.

3.0 CONCLUSION

The use of Alloy 690 weld filler material (Inconel 52/152) and the associated ASME Code Cases 2142-1 and 2143-1 for the repairs associated with the steam generator channel head bowl drain nozzle and welds will provide superior corrosion protection over that provided by Alloy 600 (Inconel 82/182) material. The use of Alloy 690 has been previously authorized for new construction and other repair activities.

Based on the above evaluation, the staff concludes that the proposed alternative to use Alloy 690 weld filler materials (Inconel 52/152) per Code Cases 2142-1 and 2143-1 for the repairs associated with the steam generator channel head bowl drain nozzle and welds will provide an acceptable level of quality and safety. Pursuant to 10 CFR 50.55a(a)(3)(i), the staff authorizes the use of the proposed alternative. The use of this proposed alternative is also authorized for future repairs of the channel head bowl drain(s) for all steam generators at Catawba Nuclear Station, Unit 2.

Principal Contributor: Chandu P. Patel Date: January 18, 2002

Catawba Nuclear Station cc:

Mr. Gary Gilbert North Carolina Electric Membership Regulatory Compliance Manager Corporation Duke Energy Corporation P. O. Box 27306 4800 Concord Road Raleigh, North Carolina 27611 York, South Carolina 29745 Senior Resident Inspector Ms. Lisa F. Vaughn U.S. Nuclear Regulatory Commission Legal Department (PB05E) 4830 Concord Road Duke Energy Corporation York, South Carolina 29745 422 South Church Street Charlotte, North Carolina 28201-1006 Virgil R. Autry, Director Division of Radioactive Waste Management Anne Cottingham, Esquire Bureau of Land and Waste Management Winston and Strawn Department of Health and Environmental 1400 L Street, NW Control Washington, DC 20005 2600 Bull Street Columbia, South Carolina 29201-1708 North Carolina Municipal Power Agency Number 1 Mr. C. Jeffrey Thomas 1427 Meadowwood Boulevard Manager - Nuclear Regulatory P. O. Box 29513 Licensing Raleigh, North Carolina 27626 Duke Energy Corporation 526 South Church Street County Manager of York County Charlotte, North Carolina 28201-1006 York County Courthouse York, South Carolina 29745 Saluda River Electric P. O. Box 929 Piedmont Municipal Power Agency Laurens, South Carolina 29360 121 Village Drive Greer, South Carolina 29651 Mr. Peter R. Harden, IV VP-Customer Relations and Sales Ms. Karen E. Long Westinghouse Electric Company Assistant Attorney General 6000 Fairview Road North Carolina Department of Justice 12th Floor P. O. Box 629 Charlotte, North Carolina 28210 Raleigh, North Carolina 27602 Elaine Wathen, Lead REP Planner Division of Emergency Management 116 West Jones Street Raleigh, North Carolina 27603-1335

Catawba Nuclear Station cc:

Mr. T. Richard Puryear Owners Group (NCEMC)

Duke Energy Corporation 4800 Concord Road York, South Carolina 29745 Richard M. Fry, Director Division of Radiation Protection North Carolina Department of Environment, Health, and Natural Resources 3825 Barrett Drive Raleigh, North Carolina 27609-7721