NOC-AE-07002211, Relief Request (RR-ENG-2-50) for the Second 10 Year ISI Interval from 10 CFR 50.55a for the Purpose of Invoking Code Case N-698, Design Stress Intensities and Yield Strength Values For...

Relief Request (RR-ENG-2-50) for the Second 10 Year ISI Interval from 10 CFR 50.55a for the Purpose of Invoking Code Case N-698, Design Stress Intensities and Yield Strength Values For...

ML072830449
Person / Time
Site:	South Texas
Issue date:	10/02/2007
From:	Berg M South Texas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
G25, NOC-AE-07002211, RR-ENG-2-50, STI: 32206405
Download: ML072830449 (6)

Text

Nuclear Operating Company South Texas Project Electrc GeneratingStatlon PO. Box 289 Wadsworth, Teas 77483 A October 2, 2007 NOC-AE-07002211 File No.: G25 10 CFR 50.55a U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738 South Texas Project Units 1 and 2 Docket No. STN 50-498, STN 50-499 Relief Request (RR-ENG-2-50) for the Second 10 Year ISI Interval for Units 1 and 2 from 10 CFR 50.55a for the Purpose of Invoking Code Case N-698, "Design Stress Intensities And Yield Strength Values for UNS N06690 With a Minimum Specified Yield Strength of 35 KSI (240 MPa), Class 1 Components,"

for Construction of Replacement Reactor Vessel Heads in Units 1 and 2 In accordance with the provisions of 10 CFR 50.55a(a)(3)(i), STP Nuclear Operating Company (STPNOC) requests NRC approval of ASME Code Case N-698, "Design Stress Intensities and Yield Strength Values for UNS N06690 With a Minimum Specified Yield Strength of 35 ksi (240 MPa), Class 1 Components," as an alternative to the requirements of Section III of the 1989 Edition of the ASME Code for the fabrication of a replacement reactor vessel head for South Texas Project (STP) Units 1 and 2. Use of ASME Code Case N-698 as an alternative to certain requirements of NB-3112.4 for the new construction of the replacement reactor vessel head for each STP unit will provide an acceptable level of quality and safety. The details of the request are attached.

Similar alternatives have been approved for the Farley Nuclear Plant and the Comanche Peak Nuclear Plant.

STP requests approval of this relief request by September 1, 2008. This date was selected to support the replacement of the first reactor vessel head in Unit 1 planned for the Fall of 2009.

The replacement of the Unit 2 reactor vessel head is planned for the Spring of 2010.

There are no commitments in the attached request.

STI: 32206405 KI C4-K

NOC-AE-07002211 Page 2 of 3 If there are any questions, please contact either Mr. K. J. Taplett at (361) 972-8416 or me at (361) 972-7030.

M. J. Berg Engineering Manager, Strategic Projects KJT

Attachment:

South Texas Project - Proposed Use of Code Case N-698 (RR-ENG-2-50)

NOC-AE-07002211 Page 3 of 3 cc:

(paper copy) (electronic copy)

Regional Administrator, Region IV A. H. Gutterman, Esquire U. S. Nuclear Regulatory Commission Morgan, Lewis & Bockius LLP 611 Ryan Plaza Drive, Suite 400 Arlington, Texas 76011-8064 Mohan C. Thadani U. S. Nuclear Regulatory Commission Mohan C. Thadani Thad Hill Senior Project Manager Eddy Daniels U.S. Nuclear Regulatory Commission Marty Ryan One White Flint North (MS 7 D1) Harry Holloway 11555 Rockville Pike Steve Winn Rockville, MD 20852 NRG South Texas LP Senior Resident Inspector Ed Alarcon U. S. Nuclear Regulatory Commission J. J. Nesrsta P. 0. Box 289, Mail Code: MN1 16 R. K. Temple Wadsworth, TX 77483 Kevin Polio City Public Service C. M. Canady Jon C. Wood City of Austin Cox Smith Matthews Electric Utility Department 721 Barton Springs Road C. Kirksey Austin, TX 78704 City of Austin Richard A. Ratliff Bureau of Radiation Control Texas Department of State Health Services 1100 West 49th Street Austin, TX 78756-3189

Attachment NOC-AE-07002211 Page 1 of 3 SOUTH TEXAS PROJECT PROPOSED USE OF CODE CASE N-698 (RELIEF REQUEST RR-ENG-2-50) 1.0 ASME Code System/Component(s) Affected Relief is requested for Reactor Pressure Vessel (RPV) closure heads manufactured to the requirements of Section III of 1989 Edition of the ASME Boiler and Pressure Vessel Code.

2.0 Applicable Code Edition and Addenda

The replacement reactor vessel head manufactured to the requirements of Section III of the 1989 Edition of the ASME Code, Section NB-3112.4 requires the use of design stress intensity values for materials listed in the tables of Section II, Part D, Subpart 1.

Table 2B of Section II, Part D contains the design stress intensity values for Type Designation UNS N06690 for the SB-1 67 specification for Class 1 components.

3.0 Proposed Subsequent Code Edition and Addenda and Code Case Pursuant to 10 CFR 50.55a(a)(3)(i), STP Nuclear Operating Company (STPNOC) is requesting approval to use Code Case N-698 as an alternative to the requirements of Section III of the ASME Code, 1989 Edition, Section NB-3112.4 in fabricating the replacement RPV closure heads for South Texas Project (STP) Units 1 and 2.

4.0 Reason for Request

Section II, Part B, Table 3 of the SB-167 specification provides an UNS N06690 yield strength that is dependent on manufactured condition. For seamless pipe and tube that are less than or equal to 5.0 inch outside diameter, Table 3 specifies a minimum yield strength of 30 kilopounds per square inch (ksi) for hot-worked or hot-worked annealed and 35 ksi for cold-worked annealed.

The UNS N06690 penetration tubes in the replacement reactor vessel closure head are manufactured using a hot-working process. Evaluation of the hot-worked UNS N06690 tubing has shown that a minimum yield strength of 35 ksi is inherent to the material.

Because of the large margin in the minimum yield strength in SB-1 67 Section II, Part B, Table 3, an ASME Code Case was needed to permit the use of higher design stress intensity values (23.3 ksi in lieu of 20 ksi) when the minimum yield strength is specified as 35 ksi for hot-worked UNS N06690 Class 1 components.

5.0 Proposed Alternative ASME developed Code Case N-698, "Design Stress Intensities and Yield Strength Values for UNS N06690 with a Minimum Specified Yield Strength of 35 ksi (MPa), Class 1 ComponentsSection III, Division 1,," permitting the use of higher stress intensities

Attachment NOC-AE-07002211 Page 2 of 3 associated with 35 ksi minimum yield strength, hot-worked UNS N06690 SB-1 67.

STPNOC is requesting that Code Case N-698 be approved as an alternative to the requirements of Section III of the ASME Code, 1989 Edition, Section NB-3112.4 in fabricating the replacement RPV closure heads for South Texas Project (STP) Units 1 and 2, pursuant to 10 CFR 50.55a(a)(3)(i).

6.0 Basis for Using the Code Case Pursuant to 10 CFR 50.55a(a)(3)(i), approval to apply the Code Case is requested on the basis that the proposed alternative provides an acceptable level of quality and safety.

7.0 Duration of Proposed Alternative This proposed alternative is for application during the service life of the affected Unit 1 and Unit 2 components.

8.0 Implementation The replacement reactor vessel head is planned for installation during the South Texas Project Unit 1 Fall 2009 and Unit 2 Spring 2010 refueling outages. NRC approval is requested by September 1, 2008, to support scheduling for completion of activities during the outage.

9.0 Precedent 9.1 Farley Nuclear Plant (Reference SER dated May 26, 2004, TAC Nos. MC1598 and MC1599) 9.2 Comanche Peak Plant (Reference SER dated April 4, 2005, TAC Nos. MC4909) 10.0 Reference Code Case N-698 (enclosed on following page)

Attachment NOC-AE-07002211 Page 3 of 3 CASE:

NM-698 CASES OF AS*,M BOUJ AM RESSURsE VE.sM CODE Approval Date. November 16,42003 See Numeric Index for expiretion.

0 and'any reaffltnairton dares..

'Case. NM698 TABLE .1

.Design Stress,.lntensilies: and Yield:.Strength DESIGNtSTRESS INTENSITY AND YIEL )-STRREN&TH.

,VAL*UES Values for UNS N06690: Nith a Minimum Specified Yield.Strength of 35 ksl (240 .MPa), Teiperathre Design Stress Intensity. Yield .Sten.th, Class 1 Compohentf r .Vahles,. S al (MPa), ksl (MPa),

Se*cion III, D6vislon I 100 2.3 (161.S) 35.0 (240.0)

Inquiry:. Is I perrmissible in the contrution of class 300 23.3 (161.S) 29.8 (204.0)

I componentsi conforming to the requirements otSection 400 23.34(161.5) 28.7 .(19&5-)

II1. Division 1,. to use a nickcl.chromium-iron .UNS 500. 23.3 (161.5) 27.8 (193.0) 600 23.3 (16L5) 2 7.6 (191.0).

N046690 hot-worked and annealed condition with mini- 700 23.3 (161.5) 27.6 (291.0) mum yield strength of 35:ks] (240 MPa) otherwise ..ao 3.3 (d61.,) 27. (191.0) conforming to matcrial Specificafion SB-1671 Reply: It: Is the. opinion of the Commnittec that, the (c) For external pressure the required thickness shall mnaterial specified In the Inquiry. May be used in the be determined in accordance with.NB- 3133 using Fig.

NFN4 in Section II. Part D .Subpart..3.

construction of Class :' components under the rules of Section ILL, Division 1. providcd the following additional fd) Welding procedures and performance qualifiaes lion shallbe in accordance with Section IX and this requiremenrs are met.

Code Case. The material shall be considered: to be P-(a)The. design stress intensity and yield strength No. 43.

values:shall be as shown In Table. I. (e) This, Case number shall be shown on the Data (b)"WTh outer di amet r is equal.to or. less than.,NPS Report for the .omponent and the madrkidg anddcertifica-5 (DN :125). tion of the material.

1213 SUPP 11-NC