ML110840076

Request for Relief RR-ENG-3-02 from ASME Code Requirements for Reactor Pressure Vessel Flange Insert Non-Destructive Examination, Third 10-Year Inservice Inspection Interval

ML110840076
Person / Time
Site:	South Texas
Issue date:	04/05/2011
From:	Balwant Singal Plant Licensing Branch IV
To:	Halpin E South Texas
Singal, B K, NRR/DORL, 301-415-301
References
TAC ME4764, TAC ME4765, RR-ENG-3-02
Download: ML110840076 (7)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 April 5,2011 Mr. Edward D. Halpin President and Chief Executive Officer!

Chief Nuclear Officer STP Nuclear Operating Company South Texas Project P. O. Box 289 VVadsworth, TX 77483

SUBJECT:

SOUTH TEXAS PROJECT, UNITS 1 AND 2 - REQUEST FOR RELIEF RR-ENG-3-02 FROM ASME CODE REQUIREMENTS FOR REACTOR PRESSURE VESSEL FLANGE INSERT NON-DESTRUCTIVE EXAMINATION (TAC NOS. ME4764 AND ME4765)

Dear Mr. Halpin:

By letter dated September 20, 2010, STP Nuclear Operating Company (the licensee) submitted a request for relief (RR-ENG-3-02) from the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, non-destructive examination requirements applicable to the South Texas Project (STP), Units 1 and 2, reactor pressure vessel (RPV) flange inserts. The request is for the third 10-year inservice inspection (lSI) interval for both units. For STP, Unit 1, the lSI interval began on September 25,2010, and ends on September 24,2020; for STP, Unit 2, the lSI interval began on October 19,2010, and ends on October 18, 2020.

The U.S. Nuclear Regulatory Commission (NRC) staff has completed the review of the subject relief request. Based on the enclosed safety evaluation, the NRC staff concludes that the use of straight beam ultrasonic examination of the RPV flange inserts from the top end of the inserts will provide an equivalent or better examination of the entire length of the vessel insert for radial circumferential flaws than the Code-required visual examination. Therefore, based on the above, the staff concludes the proposed alternative provides an acceptable level of quality and safety and the licensee's proposed alternative is authorized pursuant to paragraph 50.55a(a)(3)(i) of Title 10 of the Code of Federal Regulations for the third 1O-year lSI interval at STP, Units 1 and 2.

All other ASME Code,Section XI requirements for which relief was not specifically requested and approved in this relief request remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.

E. Halpin - 2 If you have any questions, please contact the project manager, Balwant Singal, at 301-415-3016 or via e-mail at Balwant.singal@nrc.gov.

Sincerely, Michael T. Markley, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499

Enclosure:

As stated cc w/encl: Distribution via Listserv

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C, 20555*0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION REQUEST FOR RELIEF FROM ASME CODE REQUIREMENTS FOR REACTOR PRESSURE VESSEL FLANGE INSERT NON-DESTRUCTIVE EXAMINATION DURING THIRD 10-YEAR INSERVICE INSPECTION INTERVAL SOUTH TEXAS PROJECT, UNITS 1 AND 2 STP NUCLEAR OPERATING COMPANY DOCKET NOS, 50-498 AND 50-499

1.0 INTRODUCTION

By letter dated September 20,2010 (Agencywide Documents Access and Management System (ADAMS) Accession No, ML102700173), as supplemented by letter dated February 7,2011 (ADAMS Accession No. ML110460034), STP Nuclear Operating Company (STPNOC, the licensee) submitted a request for relief (RR-ENG-3-02) from the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, non destructive examination requirements applicable to the South Texas Project (STP), Units 1 and 2, reactor pressure vessel (RPV) flange inserts. The licensee proposed the use of a straight beam ultrasonic examination of the vessel inserts from the top end of the vessel inserts as an alternate to the Code-required VT -1 visual examination pursuant to Title 10 of the Code of Federal Regulations (10 CFR) 50,55a(a)(3)(i), The request is for the third 10-year inservice inspection (lSI) interval for both units. For STP, Unit 1, the lSI interval began on September 25, 2010, and ends on September 24,2020; for STP, Unit 2, the lSI interval began on October 19, 2010, and ends on October 18, 2020.

2.0 REGULATORY EVALUATION

The regulations in 10 CFR 50,55a{g) specify that lSI of nuclear power plant components shall be performed in accordance with the requirements of the ASME Code,Section XI, except where specific written relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i).

The regulations in 10 CFR 50,55a(g)(6)(i) state that the Commission may grant such relief and may impose such alternative requirements as it determines is authorized by law and will not endanger life or property or the common defense and security and is otherwise in the public interest, given the consideration of the burden upon the licensee, Pursuant to 10 CFR 50.55a(a)(3), alternatives to the requirements of paragraph (g) may be used, when authorized by the U,S. Nuclear Regulatory Commission (NRC), if (i) the proposed alternatives Enclosure

- 2 would provide an acceptable level of quality and safety or (ii) compliance with the specified requirements would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

Pursuant to 10 CFR 50.55a(g)(4), ASME Code Class 1,2, and 3 components (including supports) shall meet the requirements, except the design and access provisions and preservice examination requirements, set forth in the ASME Code,Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components," to the extent practical within the limitations of design, geometry. and materials of construction of the components. The regulations require that lSI of components and system pressure tests conducted during the first 1O-year interval and subsequent intervals comply with the requirements in the latest edition and addenda of Section XI of the ASME Code incorporated by reference in 10 CFR 50.55a(b) 12 months prior to the start of the 120-month interval, subject to the limitations and modifications listed therein.

The applicable ASME Code of record for the third 10-year lSI interval at STP, Units 1 and 2, is the 2004 Edition, No Addenda.

The information provided by the licensee in support of the relief request has been evaluated by the NRC staff and the bases for disposition are documented below.

3.0 TECHNICAL EVALUATION

3.1 Applicable Code Edition and Addenda The Code of record for the third 10-year lSI program at STP, Units 1 and 2, is the ASNIE Code,Section XI, 2004 Edition, No Addenda.

3.2 Component(s) for Which Relief is Requested ASME Code,Section XI, IW8-2500, Table 2500-1, Code Category 8-G-1, Item Number 86.50, Class 1, Reactor Pressure Vessel Roto-Lok flange inserts (bushings). There are 36 flange inserts per unit.

3.3 Applicable Code Requirement ASME Code,Section XI, 2004 Edition No Addenda, Code Category 8-G-1, Item 86.50, requires that all bushings receive a visual, VT-1 examination each inspection interval. Examination of bushings and threads in flange base material is required only when the connections are disassembled. 8ushings may be inspected in place.

3.4 Licensee Proposed Alternative and 8asis for Use (as stated by the licensee)

Pursuant to 10 CFR 50.55a(a)(3)(i), STPNOC proposes to perform a straight beam ultrasonic examination of the vessel inserts from the top end of the vessel inserts as an alternative to the Code-required Visual, VT-1 examination. The proposed alternative examination is to be performed concurrently with that of the vessel flange thread volumetric examination to inspect for radial-circumferential flaws.

-3 Roto-Lok flange inserts (see attached illustration [attachment to letters dated September 20,2010, and February 7,2011]) consist of conventional threads on the outside surface and three rows of lugs on the inside surface. With the Roto Lok flange inserts in place in the reactor vessel flange, portions of the lugs are not accessible for Visual, VT -1 examination.

Performing the examination concurrent with the vessel flange thread ultrasonic examination will reduce the total radiation exposure. The ultrasonic technique will examine the entire length of the vessel insert and is superior to the VT-1 examination. The straight beam ultrasonic examination procedure has been demonstrated to ensure examination adequacy.

3.5 NRC Staff Evaluation ASME Code,Section XI, 2004 Edition No Addenda, IW8-2500, Table IW8-2500-1, Code Category 8-G-1, Item 86.50, requires that all bushings receive a visual, VT -1 examination each inspection interval. In accordance with 10 CFR 50.55a(a)(3)(i), the licensee proposes to perform straight beam ultrasonic examination of the RPV Roto-Lok flange inserts from the top end of the inserts as an alternative to the ASME Code-required VT-1 visual examination The proposed alternative is to be performed concurrently with that of the vessel flange thread volumetric examination to inspect for radial-circumferential flaws. The Roto-Lok flange inserts consist of conventional threads on the outside surface and three rows of lugs on the inside surface. With the Roto-Lok flange inserts in place in the reactor vessel flange, portions of the lugs are not accessible for VT-1 visual examination.

The straight beam ultrasonic examination procedure was demonstrated to ensure adequacy by the licensee; the initial demonstration was performed on December 7, 1998, in accordance with ultrasonic technical instructions. The ultrasonic technical instructions were demonstrated at the Electric Power Research Institute in accordance with the requirements of ASME Code,Section XI, Appendix VIII as modified by the Performance Demonstration Initiative Program.

The calibration block used for the demonstration was prepared in accordance with Table VI-2430-1 of the ASME Code,Section XI, Appendix VI, to examine the entire length of the vessel insert. The calibration block was fabricated from an actual spare RPV insert and included notches at different depths on both the inside and outside surfaces to ensure examination of flaws that would be found in-service. The licensee stated that the demonstration confirmed that all inside and outside surface indications can be easily observed at scanning speeds.

The manual, contact, pulse echo ultrasonic method was utilized with a 1-inch round, O-degree longitudinal wave transducer. The inserts were examined from the top with the beam passing through the length of the insert.

The NRC staff concludes that the use of straight beam ultrasonic examination of the RPV Roto Lok flange inserts from the top end of the inserts will provide an equivalent or better examination of the entire length of the vessel insert for radial-circumferential flaws than the ASME Code

-4 required VT-1 visual examination. Based on the above, the NRC staff concludes that an acceptable level of quality and safety will be maintained when using the licensee's proposed alternative examination.

4.0 CONCLUSION

The NRC staff concludes that the licensee's proposed alternative contained in Relief Request RR-ENG-3-02 to use ultrasonic examination in lieu of visual, VT -1 examination for Roto-Lok flange inserts provides an acceptable level of quality and safety. Therefore, pursuantto 10 CFR 50.55a(a)(3)(i), the proposed alternative is authorized for the third 10-year lSI interval which began on September 25,2010, and ends on September 24,2020, for STP, Unit 1, and which began on October 19,2010, and ends on October 18,2020, for STP, Unit 2.

All other ASME Code,Section XI requirements for which relief was not specifically requested and approved in this relief request remain applicable, including third-party review by the Authorized Nuclear Inservice Inspector.

Principal Contributor: Carol Nove Date: April 5, 2011

E. Halpin -2 If you have any questions, please contact the project manager, 8alwant Singal, at 301-415-3016 or via e-mail at Balwantsingal@nrc.gov.

Sincerely, IRAI Michael T. Markley, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499

Enclosure:

As stated cc w/encl: Distribution via Listserv DISTRIBUTION:

PUBLIC LPLIV Reading RidsAcrsAcnw_MailCTR Resource RidsNrrDciCpnb resource RidsNrrDorlLpl4 Resource RidsNrrPMSouth Texas Resource RidsNrrLAJBurkhardt Resource RidsOgcRp Resource RidsRgn4MailCenter Resource JTrapp, EDO RIV CNove, NRR/DCI/CPNB ADAMS Accession No. ML110840076

• Memo dated 2/22/2011 ICE NRR/LPL4/PM NRR/LPL4/LA NRR/DCI/CPNB/BC NRR/LPL4/BC NAME BSingal JBurkhardt TLupold* MMarkley DATE 4/4/11 4/4/11 2/22/11 4/5111 OFFICIAL RECORD COpy