ML13296A016

Request for Alternative 13-ISI-01 to Extend the Reactor Vessel Weld Inservice Inspection Interval

ML13296A016
Person / Time
Site:	Watts Bar
Issue date:	10/18/2013
From:	James Shea Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
13-ISI-01
Download: ML13296A016 (8)

Text

Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402 October 18, 2013 10 CFR 50.4 10 CFR 50.55a ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 1 Facility Operating License No. NPF-90 NRC Docket No. 50-390

Subject:

Request for Alternative 13-ISI-01 to Extend the Reactor Vessel Weld Inservice Inspection Interval In accordance with Title 10 of the Code of Federal Regulations (10 CFR), Part 50.55a, "Codes and Standards," paragraph (a)(3)(i), the Tennessee Valley Authority (TVA) proposes an alternative to the requirements of the American Society of Mechanical Engineers (ASME)

Boiler and Pressure Vessel (B&PV) Code,Section XI, "Rules for Inservice Inspection of Nuclear Power Plant Components," as applicable to Watts Bar Nuclear Plant (WBN), Unit 1.

The Code of Record for the current second 10-year interval for WBN, Unit 1, is the ASME Section X1 B&PV Code, 2001 Edition with Addenda through 2003.

TVA is submitting Request for Alternative (RFA) 13-ISI-01 for Nuclear Regulatory Commission (NRC) approval of a proposed alternative to the requirement of ASME Code,Section XI, Paragraph IWB-2412, "Inspection Program B," requiring volumetric examination of essentially 100 percent of reactor pressure-retaining welds identified in Table IWB-2500-1 once each 10-year interval. The proposed alternative is to extend this examination frequency to once each 20-year interval.

TVA proposes to apply the alternative to the second and third 10-year Inservice Inspection (ISI) Program intervals to extend the interval for the examination of reactor vessel welds (Examination Category B-A) and nozzle-to-vessel welds (Examination Category B-D) from 10 years to 20 years. TVA has concluded that the proposed alternative provides an acceptable level of quality and safety, in accordance with 10 CFR 50.55a(a)(3)(i). The requisite supporting information and basis for use are provided in the enclosed RFA 13-ISI-01 for WBN, Unit 1.

Printed on recycled paper

U.S. Nuclear Regulatory Commission Page 2 October 18, 2013 TVA requests approval of the RFA by July 1, 2014 to support refueling outage planning milestones. WBN, Unit 1, is currently in its second ISI Program interval, which extends from May 27, 2007 to May 26, 2016. The next examinations of the Examination Category B-A and B-D welds are scheduled for 2015.

This RFA is similar to recent alternatives granted for Duke Energy's McGuire Nuclear Station, Unit 2, by letter dated September 6, 2012 [ADAMS Accession No. MLI 2249A1 751, and Dominion's Surry Power Station, Units 1 and 2, by letter dated April 30, 2013

[ADAMS Accession No. ML13106A140].

There are no regulatory commitments associated with this submittal. If you have any questions about this request, please contact Clyde Mackaman at (423) 751-2834.

Respe Ily, J. .hea ice president, Nuclear Licensing

Enclosure:

Request for Alternative 13-ISI-01 cc (Enclosure):

NRC Regional Administrator - Region II NRC Senior Resident Inspector - Watts Bar Nuclear Plant

Enclosure TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT, UNIT 1 SECOND 10-YEAR INTERVAL REQUEST FOR ALTERNATIVE 13-ISI-01

1. ASME Code Component(s) Affected The affected component is the Watts Bar, Unit 1, reactor vessel (RV), specifically the following American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (BPV) Code, Section Xl (Reference 1) examination categories and item numbers covering examinations of the RV. These examination categories and item numbers are from IWB-2500 and Table IWB-2500-1 of the ASME BPV Code, Section Xl.

Category B-A welds are defined as "Pressure Retaining Welds in Reactor Vessel" Category B-D welds are defined as "Full Penetration Welded Nozzles in Vessels" Examination Category Item No. Description B-A B1.11 Circumferential Shell Welds B-A B1.21 Circumferential Head Welds B-A B1.22 Meridional Head Welds B-A B1.30 Shell-to-Flange Weld B-A B1.40 Head-to-Flange Weld B-D B3.90 Nozzle-to-Vessel Welds B-D B3.100 Nozzle Inside Radius Section (Throughout this request the above examination categories are referred to as "the subject examinations" and the ASME BPV Code, Section Xl, is referred to as "the Code.")

2. Applicable Code Edition and Addenda

ASME Code Section Xl, "Rules for Inservice Inspection of Nuclear Power Plant Components,"

2001 Edition through 2003 Addenda (Reference 1).

3. Applicable Code Requirement

IWB-2412, "Inspection Program B," requires volumetric examination of essentially 100 percent (%) of reactor vessel pressure-retaining welds identified in Table IWB-2500-1 once each 10-year interval. The Watts Bar, Unit 1, second 10-year inservice inspection (ISI) interval began on May 27, 2007 and is scheduled to end on May 26, 2016. The applicable Code for the third 10-year ISI interval will be selected in accordance with the requirements of Title 10 of the Code of Federal Regulations (10 CFR) 50.55a.

4. Reason for Request

An alternative is requested from the requirement of IWB-2412, "Inspection Program B," that volumetric examination of essentially 100% of reactor vessel pressure-retaining Examination Category B-A and B-D welds be performed once each ten-year interval. Extension of the interval between examinations of Category B-A and B-D welds from 10 years to up to 20 years will result in a reduction in man-roentgen equivalent man (man-rem) exposure and examination costs.

E-1 of 6

Enclosure TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT, UNIT 1 SECOND 10-YEAR INTERVAL REQUEST FOR ALTERNATIVE 13-ISI-01

5. Proposed Alternative and Basis for Use The Tennessee Valley Authority (TVA) proposes to not perform the ASME Code required volumetric examination of the Watts Bar, Unit 1, reactor vessel full penetration pressure-retaining Examination Category B-A and B-D welds for the second inservice inspection, currently scheduled for 2015. TVA will perform the second ASME Code required volumetric examination of the Watts Bar, Unit 1, reactor vessel full penetration pressure-retaining Examination Category B-A and B-D welds in the third inservice inspection interval in 2024 plus or minus one refueling outage in accordance with the applicable Code for the third 10-year ISI interval. The applicable Code for the third 10-year ISI interval will be selected in accordance with the requirements of 10 CFR 50.55a. The proposed inspection date is a deviation from the latest revised implementation plan, OG-1 0-238 (Reference 2). The impact to the implementation plan in OG-1 0-238 would increase the number of inspections in 2024, and decrease the number of inspections in 2020 from six to five. Based on Figures 3 and 4 of OG-10-238, this proposed inspection schedule is considered to have a minor impact on the future inspection plan and the distribution of inspections over time.

In accordance with 10 CFR 50.55a(a)(3)(i), an alternate inspection interval is requested on the basis that the current interval can be revised with negligible change in risk by satisfying the risk criteria specified in Regulatory Guide 1.174 (Reference 3).

The methodology used to conduct this analysis is based on that defined in the study WCAP-16168-NP-A, Revision 3, "Risk-Informed Extension of the Reactor Vessel In-Service Inspection Interval" (Reference 4). This study focuses on risk assessments of materials within the beltline region of the RV wall. The results of the calculations for Watts Bar, Unit 1, were compared to those obtained from the Westinghouse pilot plant evaluated in WCAP-16168-NP-A, Revision 3. Appendix A of the WCAP identifies the parameters to be compared. Demonstrating that the parameters for Watts Bar, Unit 1, are bounded by the results of the Westinghouse pilot plant qualifies Watts Bar, Unit 1, for an ISI interval extension. Table 1 below lists the critical parameters investigated in the WCAP and compares the results of the Westinghouse pilot plant to those of Watts Bar, Unit 1. Tables 2 and 3 provide additional information that was requested by the NRC and included in Appendix A of Reference 4.

Table 1: Critical Parameters for the Application of Bounding Analysis for Watts Bar, Unit 1 Additional Pilot Plant Plant-Specific Evaluation Parameter Basis Basis Required?

Dominant Pressurized Thermal Shock NRC PTS Risk Study PTS Generalization No (PTS) Transients in the NRC PTS (Reference 5) Study (Reference 6)

Risk Study are Applicable Through-Wall Cracking Frequency 1.76E-08 Events per 1.58E-10 Events per No (TWCF) year (Reference 4) year (Calculated per Reference 4)

Frequency and Severity of Design 7 heatup/cooldown Bounded by 7 No Basis Transients cycles per year heatup/cooldown (Reference 4) cycles per year Cladding Layers (Single/Multiple) Single Layer No (Reference 4) Single Layer E-2 of 6

Enclosure TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT, UNIT 1 SECOND 10-YEAR INTERVAL REQUEST FOR ALTERNATIVE 13-ISI-01 Table 2 below provides a summary of the latest reactor vessel inspection for Watts Bar, Unit 1, and an evaluation of the recorded indications. This information confirms that satisfactory examinations have been performed on the Watts Bar, Unit 1, reactor vessel.

Table 2: Additional Information Pertaining to Reactor Vessel Inspection for Watts Bar, Unit 1 Inspection methodology: The latest ISI was conducted in accordance with the ASME Code, Section Xl, 1995 Edition, with the 1996 Addenda. Examinations of Category B-A and B-D welds were performed to ASME Section Xl, Appendix VIII, 1992 Edition with Addenda through 1993. Future inservice inspections will be performed to ASME Section Xl, Appendix VIII requirements.

Number of past One 10-Year inservice inspection has been performed.

inspections:

Number of indications There were zero indications identified in the beltline region during the most found: recent inservice inspection; therefore, the inservice inspection results for Watts Bar, Unit 1, inherently satisfy the requirements of the Alternate PTS Rule, 10 CFR 50.61a (Reference 7).

Proposed inspection The second inservice inspection is scheduled for 2015. This inspection schedule for balance of will be performed in 2024 plus or minus one refueling outage. The plant life: proposed inspection date is a deviation from the latest revised implementation plan, OG-1 0-238 (Reference 2). The impact to the implementation plan in OG-10-238 would increase the number of inspections in 2024, and decrease the number of inspections in 2020 from six to five. Based on Figures 3 and 4 of OG-10-238, this proposed inspection schedule is considered to have a minor impact on the future I inspection plan and the distribution of inspections over time.

E-3 of 6

Enclosure TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT, UNIT 1 SECOND 10-YEAR INTERVAL REQUEST FOR ALTERNATIVE 13-ISI-01 Table 3 summarizes the inputs and outputs for the calculation of through-wall cracking frequency (TWCF).

Table 3: Details of TWCF Calculation for Watts Bar, Unit 1, at 32 Effective Full-Power Years (EFPY)

Inputs Reactor Coolant System Temperature, Tc [°F]: N/A IS & LS Twa,, [inches]: 8.623 Region and C () N1 F(1) (1) Fluence [1019 Regionand Material Cu Ni~l) R.G. 1.99 CF(') RTNDT(u) Neutron/cm2, No. Component Heat No. [wt%] [wt%] Pos.1 ) [OF] [OF] 2 Description E > 1.0 MeVI 1 Intermediate (IS) Forging Shell 527536 0.16 0.80 1.1 123 47 1.75 2 LowerShell(LS) 528522 0.08 0.83 1.1 51 5 1.75

___ Forging _ _ _ _ ____ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

3 IS to LS Circ. Weld 895075 0.04 0.73 2.1 20.7 -43 1.75 Outputs Methodology Used to Calculate AT30 : Regulatory Guide 1.99, Revision 2(2)

Controlling Fluence [1019 FF Material Region RTMAx-xx Neutron/cm 2, (Fluence AT3o TWCF9 5 -

No. (From [R] E>1.0 MeV Factor) [OF Above)

Limiting Forging - FO 1 648.59 1.75 1.154 141.92 6.70E-11 Limiting Circ. Weld - CW 1 648.59 1.75 1.154 141.92 3.68E-15 TWCF95_TOTAL(aFoTVVCF 9 5_FO + acwTWCF 95_cw): 1.58E-1 0 (1) Reference 8 (2) Reference 9

6. Duration of Proposed Alternative This request is applicable to the Watts Bar, Unit 1, inservice inspection program for the second and third 10-year inspection intervals.

7. Precedents

• "Palo Verde Nuclear Generating Station, Units 1, 2, and 3 - Relief Request No. RR-40, Reactor Vessel Weld Examination Interval Extension (TAC Nos. ME1634, ME1635, and ME1636)," dated February 22, 2010 (ADAMS Accession Number ML100290415)

• "Safety Evaluation of Relief Requests to Extend the Inservice Inspection Interval for Reactor Vessel Examinations for Salem Nuclear Generating Station, Unit Nos. 1 and 2 (TAC Nos.

ME1478, ME1479, ME1480 and ME1481)," dated February 22, 2010 (ADAMS Accession Number ML100491550)

E-4 of 6

Enclosure TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT, UNIT 1 SECOND 10-YEAR INTERVAL REQUEST FOR ALTERNATIVE 13-ISI-01

• "Arkansas Nuclear One, Unit 2 - Request for Alternative ANO2-1SI-004, to Extend the Third 10-Year Inservice Inspection Interval for Reactor Vessel Weld Examinations (TAC No. ME2508)," dated September 21, 2010 (ADAMS Accession Number ML102450654)

• "Joseph M. Farley Nuclear Plant, Unit 2 (Farley Unit 2) - Relief Request for Extension of the Reactor Vessel Inservice Inspection Date to the Year 2020 (Plus or Minus One Outage)

(TAC No. ME301 0)," dated July 12, 2010 (ADAMS Accession Number ML101750402)

• "Three Mile Island Nuclear Station, Unit 1 (TMI-1) - Request to Extend the Inservice Inspection Interval for Reactor Vessel Weld and Internal Examinations, Proposed Alternative Request Nos. RR-09-01 and RR-09-02 (TAC Nos. ME2483 and ME2484)," dated September 21, 2010 (ADAMS Accession Number ML102390018)

• "Surry Power Station Units 1 and 2 - Relief Implementing Extended Reactor Vessel Inspection Interval (TAC Nos. ME8573 and ME8574)," dated April 30, 2013 (ADAMS Accession Number ML13106A140)

• "McGuire Nuclear Station, Unit 2, Relief 10-MN-002 to Extend the Inservice Inspection Interval for Reactor Vessel Category B-A and B-D Welds (TAC Nos. ME7329 and ME 7330)," dated September 6, 2012 (ADAMS Accession Number ML12249A175)

8. References

1. ASME Boiler and Pressure Vessel Code,Section XI, 2001 Edition through 2003 Addenda, American Society of Mechanical Engineers, New York

2. OG-10-238, "Revision to the Revised Plan for Plant Specific Implementation of Extended Inservice Inspection Interval per WCAP-16168-NP, Revision 1, 'Risk-Informed Extension of the Reactor Vessel In-Service Inspection Interval.' PA-MSC-0120," July 12, 2010 (ADAMS Accession Number ML11153A033)

3. NRC Regulatory Guide 1.174, Revision 1, "An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis," U.S. Nuclear Regulatory Commission, November 2002

4. Westinghouse Report WCAP-1 6168-NP-A, Revision 3, "Risk-Informed Extension of the Reactor Vessel In-Service Inspection Interval," October 2011 (ADAMS Accession Number ML113060207)

5. NUREG-1874, "Recommended Screening Limits for Pressurized Thermal Shock (PTS),"

U.S. Nuclear Regulatory Commission, March 2010

6. NRC Letter Report, "Generalization of Plant-Specific Pressurized Thermal Shock (PTS)

Risk Results to Additional Plants," U.S. Nuclear Regulatory Commission, December 14, 2004 (ADAMS Accession Number ML042880482)

E-5 of 6

Enclosure TENNESSEE VALLEY AUTHORITY WATTS BAR NUCLEAR PLANT, UNIT 1 SECOND 10-YEAR INTERVAL REQUEST FOR ALTERNATIVE 13-ISI-01

7. Code of Federal Regulations, 10 CFR Part 50.61 a, "Alternate Fracture Toughness Requirements for Protection Against Pressurized Thermal Shock Events," U.S. Nuclear Regulatory Commission, Washington D.C., Federal Register, Volume 75, No. 1, dated January 4, 2010 and No. 22 with corrections to part (g) dated February 3, 2010, March 8, 2010, and November 26, 2010

8. Westinghouse Report WCAP-16761-NP, Revision 0, "Watts Bar Unit 1 Heatup and Cooldown Curves for Normal Operation," November 2007

9. NRC Regulatory Guide 1.99, Revision 2, "Radiation Embrittlement of Reactor Vessel Materials," U.S. Nuclear Regulatory Commission, May 1988 E-6 of 6