ML17241A477

Safety Evaluation Authorizing Licensee Relief Request 25, from ASME B&PV Code,Section Xi,Requirements for Certain ISI of Reactor Pressure vessel-to-nozzle Welds at Plant,Unit 2, Contained in Second 10-year Interval ISI Program for Unit 2

ML17241A477
Person / Time
Site:	Saint Lucie
Issue date:	10/04/1999
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML17241A476	List: ML17241A475 ML17241A477
References
NUDOCS 9910080055
Download: ML17241A477 (4)

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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BYTHE OFFICE OF NUCLEAR REACTOR REGULATION SECOND 10-YEAR INTERVALINSERVICE INSPECTION PLAN RE VEST FOR RELIEF NO. 25 FOR FLORIDA POWER AND LIGHTCOMPANY ST. LUCIE PLANT UNIT2 DOCKET NUMBER 50-389

1.0 INTRODUCTION

By letters dated April 5, 1999, and July 22, 1999, Florida Power and Light (FPL) Company, (the licensee), requested relief from certain ultrasonic testing (UT) examination requirements at St. Lucie Plant, Unit 2 (St. Lucie). The licensee proposed implementing the criteria from the American Society of Mechanical Engineers (ASME) Code Case (CC) N-613, "Ultrasonic Examination of Full Penetration Nozzles in Vessels, Examination Category B-D, Item Nos.

B3.10 and B3.90, Reactor Vessel-To-Nozzle Welds, Figure IWB-2500-7(a), (b), and (c),

Section XI, Division 1," as an alternative to the examination volume that is required in the ASME Boiling and Pressure Vessel Code (Code). The CC N-613 reduces the volume adjacent to the weld that must be examined with UT techniques.

2.0 BACKGROUND

It is stated inTitle 10 of the Code of Federal Re ulation (10 CFR), Section 50.55a(g)(4) that ASME Code Class 1, 2, and 3 components (including supports) must meet the requirements, except design and access provisions and preservice examination requirements, set forth in Section XI of editions of the Code and Addenda that become effective subsequent to the editions specified in paragraphs (g)(2) and (g)(3) of this section and that are incorporated by reference in 50.55a(b), to the extent practical within the limitations of design, geometry and materials of construction of the components.

2.1 Code Re uirements The applicable edition of Section XI of the Code for St. Lucie for the second ten-year interval is the 1989 Edition with no addenda.

St. Lucie is required to perform volumetric examinations of the pressure-retaining welds in the reactor vessels according to IWB-2500-1, Examination Category B-D. Examination Category B-D states that examination volumes shall apply to the applicable Figures IWB-2500-7(a) through (d).

When using UT for volumetric examinations, IWA-2232 states that UT examinations shall be conducted in accordance with the rules in Appendix I to Section XI of the Code.

The UT examination requirements are contained in Article I-2000 of Appendix I, which states that 99i0080055

'3I9i004 PDR ADQCK 05000389 P

PDR ultrasonic examination of vessel welds greater than two inches thickness shall be conducted in accordance with Article 4 of Section V as supplemented by Appendix I.

2.2 Re uest for A royal of an Alternative It is stated in 10 CFR 50.55a(a)(3) that proposed alternatives to the requirements of paragraphs (c), (d), (e), (f), (g), and (h) of this section, or portions thereof, may be used when authorized by the U.S. Nuclear Regulatory Commission (NRC). The applicant shall demonstrate that: (i) the proposed alternatives would provide an acceptable level of quality and safety, or (ii) compliance with the specified requirements of this section would result in hardship or unusual difficultywithout a compensating increase in the level of quality and safety.

2.3 Basis for Alternative=

In letters dated April 5, 1999, and July 22, 1999, the licensee explained the basis for their request as follows. St. Lucie is currently required to perform inservice examinations of selected welds to nuclear power plant components in accordance with the requirements of 10 CFR 50.55a, plant technical specifications, and the 1989 Edition of Section XI of the Code.

This edition of the Code invokes the examination volume requirements of Figures IWB-2500-7(a) and IWB-2500-7(b). This edition of the Code also invokes the examination requirements of Article 1-2000 to Appendix I which references Article 4 to Section V of the Code.

Article 4 of Section V essentially prescribes 20-year-old examination methodology.

Starting with the 1989 Edition with 1989 Addenda of the Code, performance-based UT examination methodology was added to the Code.

For the reasons presented in St. Lucie's Relief Request 22, dated February 18, 1999, as supplemented May 24, 1999, St. Lucie believes that the performance-based UT methodology in Code Case N-622 "Ultrasonic Examinations of RPV and Piping and Bolts and Studs,Section XI, Division 1," willprovide assurance that the reactor vessel welds are free of service-related flaws thus enhancing quality and ensuring plant safety and reliability.

The examination volume for the reactor vessel nozzle-to-vessel welds extends far beyond the weld itself, and is unnecessarily large. This extends the time for examination significantly, and results in no net increase in safety. The area being examined is simply a base metal region which is not prone to inservice cracking. This region is extensively examined before the vessel is put into service and during the first inservice examination.

3.0 EVALUATION 3.1 Pro osed Alternative Examination The licensee proposed the use of CC N-613 in lieu of the requirements of Figures IWB-2500-7(a) and IWB-2500-7 (b) to the1989 Edition of Section XI of the Code.

The licensee also requested to use CC N-613 in lieu of the requirements of Article 4 of Section V of the Code for the performance of the required volumetric examinations as specified in Table-IWB 2500-1, Examination Category B-D, of the 1989 Edition of Section XI of the Code.

The proposal is for the second inspection interval.

3.1.1 Conductin Alternative Examination The licensee proposed performing the examinations in accordance with CC N-622 (Relief Request No. 22), which was approved by NRC on September 23, 1999.

3.2 Discussion The code case has two parts. The first part identifies a criterion for conducting the examinations. The criterion states that nozzle examinations may be conducted using techniques designed for detection and sizing of surface and subsurface flaws. The phrase "techniques designed for" does not satisfy the 10 CFR 50.55a(a)(3) criterion "to demonstrate."

For this reason, NRC believes CC NW13 may be used only ifthe UT technique is qualified with a performance demonstration.

A UT technique qualified using the performance-based methodology contained in Appendix Villto Section XI of the Code satisfies the demonstration requirement.

However, Appendix Villor an alternative to Appendix Villhas not yet been referenced in regulation. Appendix Villwith an alternative is in the final stages of rulemaking.

In the licensee's proposal, the alternative examination will be conducted using a UT technique that was demonstrated in accordance with CC N-622, a performance-based alternative to Appendix Vill. CC N-622 has not yet been endorsed by the NRC staff. However, the licensee

'as submitted Relief Request No. 22 that proposed using selected parts of CC N-622 for UT examinations as an alternative to the Code.

The NRC staff authorized Relief Request No. 22 in separate correspondence dated September 23, 1999.

The second part of CC N-613 addresses the area next to the weld that must be volumetrically examined.

The code case reduces the examination volume next to the widest part of the weld from half of the vessel wall thickness to one-half inch. The code case removes from examination the base metal that was extensively examined during construction and preservice inspection and that is not in the high residual stress region associated with the weld. Cracks, should they initiate, occur in high-stressed areas of the weld. These high-stressed areas are contained in the volume that is defined by CC N-613 and are subject to examination.

Axial inner radius thermal cracks, should they occur, would also be detected because they would pass through the examination area defined."; CC N13.

Based on the above discussion, the staff has determined that the proposed alternative to use CC N613 in conjunction with the staff's safety evaluation of St. Lucie's Relief Request No. 22 (to use CC N-622) will provide an acceptable level of quality and safety for the reactor vessel-to-nozzle welds.

n.O CO~ICLUSION Based on the above discussion, the staff has determined that the proposed alternative to use CC N-613 in conjunction with the staff's safety evaluation of St. Lucie's Relief Request No. 22 (to use CC M%22) willprovide an acceptable level of quality and safety for the reactor vessel-to-nozzle welds.

Pursuant to 10 CFR 50.55a(a)(3)(i), the proposed alternative performed in conjunction with the staff's safety evaluation of St. Lucie's Relief Request No. 22 is authorized for the above identified reactor vessel-to-nozzle examinations during the second 10-year interval of the St. Lucie Plant, Unit 2.

Principal Contributor.

D. Naujock, NRR Date:

October 4, 1999

Mr. T. F. Plunkett Florida Power and I ight Company ST. LUCIE PLANT CC:

Senior Resident Inspector St. Lucie Plant U.S. Nuclear Regulatory Commission P.O. Box 6090 Jensen Beach, Florida 34957 Joe Myers, Director Division of Emergency Preparedness Department of Community Affairs 2740 Centerview Drive Tallahassee, Florida 32399-2100 M. S. Ross, Attorney Florida Power & Light Company P.O. Box 14000 Juno Beach, FL 33408-0420 Mr. Douglas Anderson County Administrator St. Lucie County 2300 Virginia Avenue Fort Pierce, Florida 34982 Mr. WilliamA. Passetti, Chief Department of Health Bureau of Radiation Control 2020 Capital Circle, SE, Bin ¹C21 Tallahassee, Florida 32399-1741 J. A. Stall, Site Vice President St. Lucie Nuclear Plant 6351 South Ocean Drive Jensen Beach, Florida 34957 Mr. R. G. West Plant General Manager St. Lucie Nuclear Plant 6351 South Ocean Drive Jensen Beach, Florida 34957 E. J. Weinkam Licensing Manager St. Lucie Nuclear Plant 6351 South Ocean Drive Jensen Beach, Florida 34957 Mr. John Gianfrancesco Manager, Administrative Support and Special Projects P.O. Box 14000 Juno Beach, FL 33408-0420 Mr. Rajiv S. Kundalkar Vice President-Nuclear Engineering Florida Power & Light Company P.O. Box 14000 Juno Beach, FL 33408-0420 Mr. J. Kammel Radiological Emergency Planning Administrator Department of Public Safety 6000 SE. Tower Drive Stuart, Florida 34997