ML090690557
| ML090690557 | |
| Person / Time | |
|---|---|
| Site: | Seabrook  |
| Issue date: | 04/07/2009 |
| From: | Chernoff H Plant Licensing Branch 1 |
| To: | St.Pierre G Florida Power & Light Energy Seabrook |
| Egan, Dennis; NRR/DORL 301-415-2443 | |
| References | |
| TAC MD9784 | |
| Download: ML090690557 (6) | |
Text
~p.R REGlI (j\\-
l."I
~..;:,
~O UNITED STATES it -
11""
/0.
NUCLEAR REGULATORY COMMISSION
('l
<t' 0
I-
~
WASHINGTON, D.C. 20555-0001 ell
~
~
r;
"/."'I)
<t\\0 *'
P-pril 7, 2009
SUBJECT:
SEABROOK STATION, UNIT NO.1 - RELIEF REQUEST FOR REACTOR PRESSURE VESSEL SHELL TO FLANGE WELD EXAMINATION FOR THE SECOND INSERVICE INSPECTION INTERVAL (TAC NO. MD9784)
Dear Mr. St. Pierre:
By letter dated September 30, 2008 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML082760467) FPL Energy Seabrook, LLC, submitted a relief request from certain examination requirements of the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code (Code) at the Seabrook Station, Unit 1. Specifically, the licensee proposed examining the reactor pressure vessel (RPV) upper shell-to-flange weld with procedures and personnel qualified to ASME Code,Section XI, Appendix VIII, Supplements 4 and 6 requirements. The request is for the remainder of the second 10-year inservice inspection interval.
The Nuclear Regulatory Commission (NRC) staff has reviewed the licensee's analysis in support of the request for relief. The request is approved pursuant to Title 10 of the Code ofFederal Regulations (10 CFR), Part 50, Section 55a(a)(3)(i), on the basis that the proposed alternative provides an acceptable level of quality and safety.
The NRC staffs' evaluation and conclusions are contained in the enclosed safety evaluation.
This completes the NRC staffs efforts on TAC No. MD9784.
If you have any questions, please contact the Seabrook Project Manager, Mr. Dennis Egan, at 301-415-2443.
Sincerely, 1~/I/tL.
Harold K. Chernoff, Chief Plant Licensing Branch 1-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-443
Enclosure:
As stated cc w/encls: Distribution via Listserv
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELIEF REQUEST ASSOCIATED WITH THE SECOND INSERVICE INSPECTION INTERVAL FPL ENERGY SEABROOK, LLC SEABROOK STATION, UNIT NO.1 DOCKET NO. 50-443
1.0 INTRODUCTION
By letter dated September 30, 2008 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML082760467) FPL Energy Seabrook, LLC, submitted a relief request from certain examination requirements of the American Society of Mechanical Engineers (ASIVIE) Boiler and Pressure Vessel Code (Code) at the Seabrook Station, Unit 1 (Seabrook). Specifically, the licensee proposed examining the reactor pressure vessel (RPV) upper shell-to-flange weld with procedures and personnel qualified to ASME Code,Section XI, Appendix VIII, Supplements 4 and 6 requirements. The request is for the remainder of the second 10-year inservice inspection interval which began August 18, 2000, and is scheduled to end August 17,2010.
2.0 REGULATORY EVALUATION
Title 10 of the Code of Federal Regulations (10 CFR), Part 50, Section 50.55a(g), "Inservice Inspection Requirements," requires, in part, that ASME Class 1, 2, and 3 components must meet the inspection examination requirements set forth in the applicable editions and addenda of the ASME Code, except where alternatives have been authorized by the Nuclear Regulatory Commission (NRC) pursuant to 10 CFR 50.55a(a)(3)(i) or (a)(3)(ii).
10 CFR 50.55a(a)(3) states in part that alternatives to the requirements of paragraph (g) may be authorized by the NRC, if the applicant demonstrates that: (i) the proposed alternatives 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.
The Code of Record for the second 10-year lSI interval at the Seabrook Station, Unit 1 is the 1995 Edition through 1996 Addenda of the ASME Code,Section XI.
ENCLOSURE
- 2
3.0 TECHNICAL EVALUATION
3.1 Affected Component ASME Code Class 1, RPV upper vessel shell-to-flange weld, Table IWB-2500-1, Category B-A, Item Number B1.30, Seabrook lSI Component identification RC RPV-101-121.
3.2 Applicable Code The 1995 Edition through 1996 Addenda of the ASME Code,Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components," Subsection IWA-2232, requires that "Ultrasonic examinations shall be conducted in accordance with Appendix I." Appendix I, paragraph 1-211 O(b), states that "[u]ltrasonic examinations of reactor vessel-to-flange welds shall be conducted in accordance with Article 4 of ASME Section V, except that alternative examination beam angles may be used. These examinations shall be further supplemented by Table 1-2000-1."
3.3 Proposed Alternative The licensee proposes using the procedures, personnel, and equipment qualified to the requirements of ASME Section XI, Appendix VIII, Supplements 4 and 6, of the 1995 Edition through the 1996 Addenda as administered by the Electric Power Research Institute's (EPRI)
Performance Demonstration Initiative (PDI) program.
3.4 Licensee Basis for the Alternative ASME Section XI, Appendix I, paragraph 1-2100(b) requires that ASME Section V, Article 4 ultrasonic testing (UT) techniques shall be used for the RPV-to-flange weld. ASME Section V, Article 4 describes the required techniques to be used for UT examination of the welds in ferritic pressure vessels with wall thicknesses greater than 2 inches. The ASME Section V, Article 4 UT technique calibrations, recording criteria and flaw sizing capabilities are based upon the use of a distance-amplitude-correction curve (DAC) derived from machined reflectors in a basic calibration block. UT performed in accordance with Section V, Article 4, uses recording thresholds known as percent of DAC for recording and reporting of indications within the examination volume. Indications detected in the exam volume, with amplitudes below these thresholds, are not required to be recorded and/or evaluated. The recording thresholds in Section V, Article 4 are generic and do not take into consideration such factors as flaw orientation, which can influence the amplitude of UT responses.
The RPV-to-flange weld is the only circumferential shell weld in the RPV that is not examined with ASME Section XI, Appendix VIII, Supplement 4 and 6 UT techniques. Procedures, equipment and personnel qualified via the PDI Appendix VIII Supplement 4 and 6 programs have been demonstrated to have a high probability of detection and are generally considered superior to the techniques employed during earlier Section V, Article 4 RPV examinations. Use of the detection criterion is more conservative and the procedure requires the examiner to evaluate all indications determined to be flaws regardless of their amplitude.
EPRI Report NP-6273, "Accuracy of Ultrasonic Flaw Sizing Techniques for Reactor Pressure Vessels," dated March 1989, contains a comparative analysis of sizing accuracy for several
- 3 different techniques. The results show that UT flaw sizing techniques based on tip diffraction are the most accurate. The proposed alternative Appendix VIII UT qualified detection and sizing methodologies use analysis tools based upon echo dynamics and tip diffraction. This methodology is considered more sensitive and accurate than the Section V, Article 4 processes.
Accordingly, approval of this alternative examination and evaluation process is requested pursuant to 10 CFR 50.55a(a)(3)(i).
3.5
NRC Staff Evaluation
The 1995 Edition through 1996 Addenda of the ASME Code,Section V, Article 4, as supplemented by Appendix I, Article 1-2100(b) provides a prescriptive process for qualifying UT procedures. The licensee proposes using procedures, equipment, and personnel qualified in accordance with performance-based criteria as administered by the POI program for the examination of RPV welds. The POI program implements the requirements of Section XI, Appendix VIII, Supplements 4 and 6 as modified by 10 CFR 50.55a(b)(2)(xv).
When prescriptive Section V, Article 4 UT procedures are applied in a controlled setting containing real flaws in mockups and the sizing results are statistically analyzed according to the performance-based screening criteria in Section XI, Appendix VIII, the prescriptive-based sizing results were determined to be equal to or less effective than the sizing results from performance - based Section XI, Appendix VIII procedures1. The better sizing results are attributed to the echo-dynamic motion and tip diffraction criteria used by performance-based UT compared to the less accurate amplitude drop criteria of prescriptive Section V, Article 4 requirements.
Recently, the ASME Code Committee approved a change that permitted licensees to use Appendix VIII qualified procedures, personnel, and equipment for examinations of components to which Appendix VIII is not applicable provided the component materials, sizes, and shapes are within the scope of the qualified examination procedures. The NRC staff participated in the ASME Code Committee consensus process and supported this action. The basis for support of this change in Code is that Appendix VIII UT qualifications are more rigorous than ASME Section V, Article 4 qualifications. Appendix VIII qualifications are based on passing a blind test performed on representative mockups containing representative flaws while an ASME Section V, Article 4 qualification process relies on non-blind detection of machined marks in a calibration block.
Based on the above information, the staff concludes that the Appendix VIII POI program results in an increased reliability of inspections for weld configurations within the scope of the POI program.
4.0 CONCLUSION
Based on the increased reliability of inspections within the scope of the Appendix VIII POI program, as discussed above, the staff concludes that the licensee's proposed alternative to use UT procedures, equipment, and personnel qualified to the 1995 Edition through 1996 Addenda 1EPRI Report NP-6273, "Accuracy of Ultrasonic Flaw Sizing Techniques for Reactor Pressure Vessels," dated March 1989.
-4 of the ASME Code Section XI, Appendix VIII, Supplements 4 and 6 as modified by 10 CFR 50.55a for the RPV shell-to-flange weld provides an acceptable level of quality and safety.
Therefore, pursuant to 10 CFR 50.55a(a)(3)(i), the proposed alternative is authorized for the subject weld at Seabrook Station, Unit1 for the second 10-year lSI interval.
All other ASME Code,Section XI requirements for which relief was not specifically requested and approved remain applicable, including third party review by the Authorized Nuclear Inservice Inspector.
Principal Contributor: Don Naujock Date: April 7, 2009
'.. ML090690557 OFFICE LPL1-2/PM LPL1-2/LA CPNB/BC OGC LPL1-2/BC NAME DEQan ABaxter TLChan BHarris HChernoff DATE 3/17/09 3/17109 3/17109 3/25/09 4/7109