ML082840494

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SE for the Continued Use of Risk-Informed Inservice Inspection Program
ML082840494
Person / Time
Site: Saint Lucie NextEra Energy icon.png
Issue date: 11/26/2008
From: Boyce T
Plant Licensing Branch II
To: Stall J
Florida Power & Light Co
Mozafari B, NRR/ADRO/DORL, 415-2020
References
TAC MD7739
Download: ML082840494 (6)
v • d • e


Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 November 26, 2008 Mr. J. A. Stall Senior Vice President, Nuclear and Chief Nuclear Officer Florida Power and Light Company P.O. Box 14000 Juno Beach, Florida 33408-0420

SUBJECT:

ST. LUCIE PLANT UNIT 1 - SAFETY EVALUATION FOR THE CONTINUED USE OF A RISK-INFORMED INSERVICE INSPECTION PROGRAM FOR THE FOURTH 10-YEAR INSERVICE INSPECTION INTERVAL, REQUEST FOR RELIEF 1 (TAC NO. MD7739)

Dear Mr. Stall:

By letter dated December 7,2007, as supplemented by letter dated August 20,2008, Florida Power & Light Company (FPL), the licensee, submitted Relief Request NO.1 for the fourth 1O-year inservice inspection (lSI) interval for St. Lucie Unit 1. This submittal requests relief from American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code Section XI requirements for the selection and examination of Class 1 piping welds. The relief request proposes to use a risk-informed lSI (RI-ISI) program developed based on the methodology contained in Westinghouse Owners Group (WOG) Topical Report WCAP-14572, Revision 1-NP-A, 'Westinghouse Owners Group Application of Risk-Informed Methods to Piping Inservice Inspection Topical Report," instead of a program developed according to the ASME Code requirements for Class 1 piping welds. The Nuclear Regulatory Commission (NRC) endorsed the WOG RI-ISI methodology in its safety evaluation dated December 15, 1998.

FPL had requested and received relief to use a RI-ISI program for Class 1 piping welds at St. Lucie Unit 1 for the third 10-year lSI interval. FPL is requesting the use of a RI-ISI program based on the same methodology for the fourth 10-year interval.

The NRC staff has reviewed the licensee's proposed alternative and has concluded that the licensee's proposed alternative as specified in Relief Request No.1 may be authorized pursuant to Title 10 of the Code of Federal Regulations Section 50.55a(a)(3)(i) on the basis that it

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J. Stall -2 provides an acceptable level of quality and safety. Further details on the bases for the NRC staff's conclusions are contained in the enclosed safety evaluation. If you have any questions regarding this issue, please feel free to contact Brenda Mozafari at (301) 415-2020.

Sincerely,

~~

Thomas H. Boy{je, Chief Plant Licensing Branch 11-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket 1\10. 50-335

Enclosure:

Safety Evaluation cc: Distribution via ListServ

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555*0001 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RISK-INFORMED INSERVICE INSPECTIOI\I PROGRAM RELIEF REQUEST NUMBER 1 FLORIDA POWER AND LIGHT COMPANY ST. LUCIE PLANT UNIT 1 DOCKET NO. 50-335 1.0 II\ITRODUCTION By letter dated December 7, 2007 (Reference 1), as supplemented in letter dated August 20, 2008 (Reference 2), Florida Power & Light (FPL) submitted Relief Request NO.1 for approval of alternate risk-informed inservice inspection (RI-ISI) selection and examination criteria to be used during St. Lucie Unit 1's fourth 10-year inspection interval (the fourth interval). The licensee's proposed RI-ISI program is an alternative pursuant to Section 50.55a(a)(3)(i) of Title 10 of the Code of Federal Regulations (10 CFR). The scope of the alternate RI-ISI program is applicable to the American Society of Mechanical Engineers Boiler and Pressure Vessel Code (ASME Code),Section XI, 2001 Edition through the 2003 Addenda, Class 1 piping, Categories B-F and B-J piping welds.

By letter dated July 30, 2003, FPL submitted a similar request for relief to implement an RI-ISI program for the remainder of its previous 1O-year interval (the third interval). The Nuclear Regulatory Commission (NRC) staff approved FPL's RI-ISI program for use during the third interval by letter dated March 25, 2004 (Reference 3). The licensee is proposing to use a RI-ISI program based on the same methodology for the fourth interval which begins February 11, 2008, and ends February 12, 2018.

1.0 REGULATORY EVALUATION

As required by 10 CFR 50.55a(g), lSI of the ASME Code Class 1, 2, and 3 components must be performed in accordance with Section XI of the ASIV1E Code, "Rules for Inservice Inspection of Nuclear Power Plant Components" (hereinafter called Code) and applicable addenda, except where specific relief has been granted by the Commission pursuant to 10 CFR 50.55a(g)(6)(i).

The regulation 10 CFR 50.55a(a)(3) states, in part, that alternatives to the requirements of paragraph (g) may be used, when authorized by the NRC, if the licensee demonstrates that the proposed alternatives would provide an acceptable level of quality and safety, or if the specified requirement would result in hardship or unusual difficulty without a compensating increase in the level of quality and safety.

The proposed RI-ISI program is developed consistent with the staff approved RI-ISI process and methodology delineated in Westinghouse Owners Group Topical Report WCAP-14572, Revision 1-NP-A, 'Westinghouse Owners Group Application of Risk-Informed Methods to Piping Inservice Inspection Topical Report" (WCAP-TR) (ML042610469). The staff reviewed the

-2 proposed RI-ISI program based on guidance and acceptance criteria provided in the following documents

  • NRC RG 1.178, Revision 1, "An Approach for, Plant-Specific, Risk-Informed Decisionmaking for Inservice Inspection of Piping," U.S. NRC, September 2003.
  • NUREG-0800, Chapter 3.9.8, Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants, "Risk-Informed Inservice Inspection of Piping,"

U.S. NRC, September 2003.

2.0 TECHNICAL EVALUATION

The licensee is requesting relief that would permit continued use of a RI-ISI program for the fourth 10-year lSI interval instead of the ASME Section XI program. A RI-ISI program is acceptable and provides an acceptable level of quality and safety if it meets the five key principles of risk-informed decisionmaking, discussed in RGs 1.174 and 1.178. These principles are:

1) The proposed change meets the current regulations unless it is explicitly related to a requested exemption or rule change.
2) The proposed change is consistent with the defense-in-depth philosophy.
3) The proposed change maintains sufficient safety margins.
4) When proposed changes result in an increase in core damage frequency and/or large early release frequency (LERF), the increases should be small and consistent with the intent of the Commission's Safety Goal Policy Statement.
5) The impact of the proposed change should be monitored by using performance measurement strategies.

The first principle is met in this relief request because an alternative lSI program may be authorized pursuant to 10 CFR 50.55a(3)(i) and, therefore, an exemption request is not required.

The second and third principles require assurance that the alternative program is consistent with the defense-in-depth philosophy and that sufficient safety margins are maintained, respectively.

The licensee stated in Reference 2 that the methodology used to develop the fourth interval RI-ISI program interval utilizes the identical methodology that was approved by the staff for use in the third interval as discussed in the staff's safety evaluation in Reference 3. Therefore, the staff concludes that the FPL's application of the methodology approved for use in the third interval to develop its proposed program for the fourth interval prOVides assurance that the second and third principles are met.

-3 The fourth principle requires an estimate of the change in risk. The change in risk is dependent on the number and location of inspections in the proposed lSI program compared to the number and location of inspections that would be inspected using the requirements of ASME Section XI.

In Reference 1, the licensee reported that a new change in risk evaluation was performed and the risk from the revised RI-ISI program continues to remain constant when compared to the last deterministic Section XI inspection program. Relief was granted in Reference 3 from selected requirements in the 1989 edition of Section XI, which was the licensee's code of record when relief was requested. The licensee stated in Reference 1 that its code of record for the fourth interval is the ASME Section XI 2001 edition through 2003 Addenda. This change in the code of record might require changes to a few inspection locations for the fourth interval ASME inspection program from which the licensee is requesting relief. Minor changes in ASME locations may affect the risk calculation required by the RI-ISI methodology. However, the change in risk calculation uses simple bounding calculations to access the acceptability of the proposed program. Such minor changes do not warrant development of a new ASME inspection program to be used simply as a baseline program for determing the change in risk calculation. Therefore, the staff finds the comparison of the risk estimate between the proposed RI-ISI program and the ASIVIE program based on the code of record from which relief was granted in Reference 3 appropriate and acceptable. The reported result obtained by using the methodology in the WCAP-TR satisfies the change in risk guidelines in the WCAP-TR and therefore the fourth principle is met.

The fifth key principle is that the impact of the proposed change should be monitored by using performance measurement strategies. In the PRA update process discussed above, the licensee notes that consequence evaluation, degradation mechanism assessment, risk ranking, and element selection steps encompass the complete living program process applied under the St. Lucie Unit 1 RI-ISI program. The licensee noted that the number of inspection locations decreased from a total of 24 welds to 19 welds. The primary goal of a performance measurement strategy is to confirm that the analyses conducted to develop the risk-informed program remain valid over time. The licensee's update program provides confidence that the analyses remain valid or, when necessary, identifies required changes to the RI-ISI program.

Therefore, the fifth key principal is met. The licensee identified the following reasons for changes between the two Rl-ISI programs:

1) A change in the definition of Category B-F in the 2001 Edition with 2003 Addenda
2) One examination location was deleted due to a configuration change. An elbow welded to a pipe was replaced with a bent pipe, eliminating the pipe-to-elbow weld.
3) Because twenty-four PWSCC [primary water stress-corrosion cracking]

susceptible welds are covered by the St. Lucie 1 Alloy 600 inspection program and are not subsumed into the RI-ISI program, four segments were reduced to four elements in each. This alternative process of

-4 selecting 25% of the elements not within the scope of the Alloy 600 program in each High Safety Significance segment results in a reduction of 4 examination locations.

Due to recent ongoing issues related to degradation due to PWSCC in components that contain alloy 600/82/182, the NRC staff requested additional information related to welds containing alloy 82/182. The licensee responded that it will perform the visual and volumetric examinations in accordance with the industry Electric Power Research Institute Materials Reliability Program (MRP) guidance contained in "Primary System Piping Butt Weld Inspection and Evaluation Guideline (MRP-139)," dated July 14, 2005, throughout the inspection interval as an augmented examination program for dissimilar metal welds.

The changes in the RI-ISI program reported by the licensee are consistent with the type of changes that the approved living program would be expected to identify. Changes in the ASME Code requirements and recognition of configuration changes during the life of the program are essential to ensure effective implementation. The use of industry guidance under MRP-139 to inform the RI program and provide augmented examination program is warranted. Therefore, the staff concludes that the licensee has demonstrated that it has implemented a living RI-ISI program and that the fifth key principle is met.

3.0 CONCLUSION

S Based on the information provided in the licensee's submittals, the NRC staff has determined that the proposed alternative provides an acceptable level of quality and safety. Therefore, the licensee's proposed Relief Request l'Jo. 1 is authorized pursuant to 10 CFR 50.55a(a)(3)(i) for the fourth 10-year lSI interval at St. Lucie Unit 1.

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.

4.0 REFERENCES

1. Letter from Gordon L. Johnston (Florida Power & Light), to NRC, dated December 7,2007, transmitting "St. Lucie Unit 1, Docket No. 50-335, Inservice Inspection Plan, Fourth Ten-year Interval Unit 1 Relief Request."
2. Letter from Gordon L. Johnston (Florida Power & Light), to NRC, dated August 20, 2008, transmitting "St. Lucie Unit 1, Docket No. 50-335, Fourth Ten-year Interval Unit 1 Relief Request, RAI Reply (TAC MD8041 )."
3. Letter from William F. Burton (NRC) to Mr. J. A. Stall (Florida Power & Light), dated March 25, 2004, transmitting "St. Lucie Nuclear Plant, Unit No.1 - Relief Request No. 19 Regarding Risk-Informed Inservice Inspection Program (TAC No. MC0244)."

Principal Contributors: Stephen Dinsmore Jay Collins Date: November 26, 2008

ML082840494 NRR-028 OFFICE LPL2-2/PM LPL2-2/PM LPL2-2/LA DCI/CPNB DRAIAPLA OGC(NL LPL2-2/BC 0)

NAME ..IPaige BMoroney for BClayton TChan SChapman MBaty TBoyce BMozafari for MRubin DATE 11/19/08 11/20/08 11/19/08 Memo 10/14/08 11/12/08 11/26/08 dated 09/29/08

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