Text

Issuance of Amendment Nos. 418, 420 and 419 TSTF-421, Revision to RCP Flywheel Inspection Program
	ML20296A281
Person / Time
Site:	Oconee
Issue date:	11/25/2020
From:	Shawn Williams; Plant Licensing Branch II
To:	Burchfield J; Duke Energy Carolinas
	Williams S A-NRR/DORL 301-415-1009
References
	EPID L-2020-LLA-0076
	Download: ML20296A281 (22)
	v • d • e

November 25, 2020 Mr. J. Ed Burchfield, Jr.

Vice President, Oconee Nuclear Station Duke Energy Carolinas, LLC 7800 Rochester Highway Seneca, SC 29672-0752

SUBJECT:

OCONEE NUCLEAR STATION, UNITS 1, 2, AND 3 - ISSUANCE OF AMENDMENT NOS. 418, 420, AND 419 RE: TSTF-421, REVISION TO RCP FLYWHEEL INSPECTION PROGRAM (EPID L-2020-LLA-0076)

Dear Mr. Burchfield:

The U.S. Nuclear Regulatory Commission (NRC, the Commission) has issued the enclosed Amendment No. 418 to Renewed Facility Operating License (RFOL) No. DPR-38, Amendment No. 420 to RFOL No. DPR-47, and Amendment No. 419 to RFOL No. DPR-55 for Oconee Nuclear Station (Oconee), Units 1, 2, and 3, respectively. The amendments consist of changes to the Oconee Technical Specifications (TSs) in response to the application from Duke Energy Carolinas, LLC dated April 13, 2020.

The amendments revise the TS requirements for the Reactor Coolant Pump (RCP) flywheel inspection program based on Technical Specifications Task Force (TSTF) Traveler TSTF-421, Revision 0, Revision to RCP Flywheel Inspection Program (WCAP-15666). The availability of TSTF-421 for adoption by licensees was announced in the Federal Register on October 22, 2003 (68 FR 60422).

The NRC staff's safety evaluation of the amendments is enclosed. The Notice of Issuance will be included in the Commissions monthly Federal Register notice.

J. E. Burchfield, Jr. If you have any questions, please contact me at (301) 415-1009 or by e-mail to Shawn.Williams@nrc.gov.

Sincerely,

/RA/

Shawn Williams, Senior Project Manager Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-269, 50-270, 50-287

Enclosures:

1. Amendment No. 418 to DPR-38

2. Amendment No. 420 to DPR-47

3. Amendment No. 419 to DPR-55

4. Safety Evaluation cc: Listserv

DUKE ENERGY CAROLINAS, LLC DOCKET NO. 50-269 OCONEE NUCLEAR STATION, UNIT 1 AMENDMENT TO RENEWED FACILITY OPERATING LICENSE Amendment No. 418 Renewed License No. DPR-38

1. The U.S. Nuclear Regulatory Commission (the Commission) has found that:

A. The application for amendment to the Oconee Nuclear Station, Unit 1 (the facility), Renewed Facility Operating License No. DPR-38, filed by Duke Energy Carolinas, LLC (the licensee), dated April 13, 2020, complies with the standards and requirements of the Atomic Energy Act of 1954, as amended (the Act), and the Commissions rules and regulations set forth in 10 CFR Chapter I; B. The facility will operate in conformity with the application, the provisions of the Act, and the rules and regulations of the Commission; C. There is reasonable assurance (i) that the activities authorized by this amendment can be conducted without endangering the health and safety of the public, and (ii) that such activities will be conducted in compliance with the Commissions regulations; D. The issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public; and E. The issuance of this amendment is in accordance with 10 CFR Part 51 of the Commissions regulations and all applicable requirements have been satisfied.

Enclosure 1

2. Accordingly, the license is amended by changes to the Technical Specifications as indicated in the attachment to this license amendment, and paragraph 3.B of Renewed Facility Operating License No. DPR-38 is hereby amended to read as follows:

3.B. Technical Specifications The Technical Specifications contained in Appendix A, as revised through Amendment No. 418 are hereby incorporated in the license. The licensee shall operate the facility in accordance with the Technical Specifications.

3. This license amendment is effective as of the date of its issuance and shall be implemented within 120 days of issuance.

FOR THE NUCLEAR REGULATORY COMMISSION Michael T. Digitally signed by Michael T. Markley Date: 2020.11.25 11:08:35 -05'00' Markley Michael T. Markley, Chief Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Attachment:

Changes to the Renewed Facility Operating License and Technical Specifications Date of Issuance: November 25, 2020

DUKE ENERGY CAROLINAS, LLC DOCKET NO. 50-270 OCONEE NUCLEAR STATION, UNIT 2 AMENDMENT TO RENEWED FACILITY OPERATING LICENSE Amendment No. 420 Renewed License No. DPR-47

1. The U.S. Nuclear Regulatory Commission (the Commission) has found that:

A. The application for amendment to the Oconee Nuclear Station, Unit 2 (the facility), Renewed Facility Operating License No. DPR-47, filed by Duke Energy Carolinas, LLC (the licensee), dated April 13, 2020, complies with the standards and requirements of the Atomic Energy Act of 1954, as amended (the Act), and the Commissions rules and regulations set forth in 10 CFR Chapter I; B. The facility will operate in conformity with the application, the provisions of the Act, and the rules and regulations of the Commission; C. There is reasonable assurance (i) that the activities authorized by this amendment can be conducted without endangering the health and safety of the public, and (ii) that such activities will be conducted in compliance with the Commissions regulations; D. The issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public; and E. The issuance of this amendment is in accordance with 10 CFR Part 51 of the Commissions regulations and all applicable requirements have been satisfied.

Enclosure 2

2. Accordingly, the license is amended by changes to the Technical Specifications as indicated in the attachment to this license amendment, and paragraph 3.B of Renewed Facility Operating License No. DPR-47 is hereby amended to read as follows:

3.B. Technical Specifications The Technical Specifications contained in Appendix A, as revised through Amendment No. 420 are hereby incorporated in the license. The licensee shall operate the facility in accordance with the Technical Specifications.

3. This license amendment is effective as of the date of its issuance and shall be implemented within 120 days of issuance.

FOR THE NUCLEAR REGULATORY COMMISSION Michael T. Digitally signed by Michael T. Markley Date: 2020.11.25 11:09:21 -05'00' Markley Michael T. Markley, Chief Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Attachment:

Changes to the Renewed Facility Operating License and Technical Specifications Date of Issuance: November 25, 2020

DUKE ENERGY CAROLINAS, LLC DOCKET NO. 50-287 OCONEE NUCLEAR STATION, UNIT 3 AMENDMENT TO RENEWED FACILITY OPERATING LICENSE Amendment No. 419 Renewed License No. DPR-55

1. The U.S. Nuclear Regulatory Commission (the Commission) has found that:

A. The application for amendment to the Oconee Nuclear Station, Unit 3 (the facility), Renewed Facility Operating License No. DPR-55, filed by Duke Energy Carolinas, LLC (the licensee), dated April 13, 2020, complies with the standards and requirements of the Atomic Energy Act of 1954, as amended (the Act), and the Commissions rules and regulations set forth in 10 CFR Chapter I; B. The facility will operate in conformity with the application, the provisions of the Act, and the rules and regulations of the Commission; C. There is reasonable assurance (i) that the activities authorized by this amendment can be conducted without endangering the health and safety of the public, and (ii) that such activities will be conducted in compliance with the Commissions regulations; D. The issuance of this amendment will not be inimical to the common defense and security or to the health and safety of the public; and E. The issuance of this amendment is in accordance with 10 CFR Part 51 of the Commissions regulations and all applicable requirements have been satisfied.

Enclosure 3

2. Accordingly, the license is amended by changes to the Technical Specifications as indicated in the attachment to this license amendment, and paragraph 3.B of Renewed Facility Operating License No. DPR-55 is hereby amended to read as follows:

3.B. Technical Specifications The Technical Specifications contained in Appendix A, as revised through Amendment No. 419 are hereby incorporated in the license. The licensee shall operate the facility in accordance with the Technical Specifications.

3. This license amendment is effective as of the date of its issuance and shall be implemented within 120 days of issuance.

FOR THE NUCLEAR REGULATORY COMMISSION Michael T. Digitally signed by Michael T. Markley Date: 2020.11.25 11:09:53 -05'00' Markley Michael T. Markley, Chief Plant Licensing Branch II-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Attachment:

Changes to the Renewed Facility Operating License and Technical Specifications Date of Issuance: November 25, 2020

ATTACHMENT TO AMENDMENT NO. 418 TO RENEWED FACILITY OPERATING LICENSE NO. DPR-38 AMENDMENT NO. 420 TO RENEWED FACILITY OPERATING LICENSE NO. DPR-47 AMENDMENT NO. 419 TO RENEWED FACILITY OPERATING LICENSE NO. DPR-55 OCONEE NUCLEAR STATION, UNITS 1, 2, AND 3 DOCKET NOS. 50-269, 50-270, AND 50-287 Replace the following pages of the Renewed Facility Operating Licenses and the Appendix A Technical Specifications (TSs) with the attached revised pages. The revised pages are identified by amendment number and contain marginal lines indicating the areas of change.

Remove Insert License License DPR-38, page 3 DPR-38, page 3 DPR-47, page 3 DPR-47, page 3 DPR-55, page 3 DPR-55, page 3 TSs TSs 5.0-12 5.0-12

A. Maximum Power Level The licensee is authorized to operate the facility at steady state reactor core power levels not in excess of 2568 megawatts thermal.

B. Technical Specifications The Technical Specifications contained in Appendix A, as revised through Amendment No. 418 are hereby incorporated in the license. The licensee shall operate the facility in accordance with the Technical Specifications.

C. This license is subject to the following antitrust conditions:

Applicant makes the commitments contained herein, recognizing that bulk power supply arrangements between neighboring entities normally tend to serve the public interest. In addition, where there are net benefits to all participants, such arrangements also serve the best interests of each of the participants. Among the benefits of such transactions are increased electric system reliability, a reduction in the cost of electric power, and minimization of the environmental effects of the production and sale of electricity.

Any particular bulk power supply transaction may afford greater benefits to one participant than to another. The benefits realized by a small system may be proportionately greater than those realized by a larger system. The relative benefits to be derived by the parties from a proposed transaction, however, should not be controlling upon a decision with respect to the desirability of participating in the transaction. Accordingly, applicant will enter into proposed bulk power transactions of the types hereinafter described which, on balance, provide net benefits to applicant. There are net benefits in a transaction if applicant recovers the cost of the transaction (as defined in ¶1 (d) hereof) and there is no demonstrable net detriment to applicant arising from that transaction.

1. As used herein:

(a) Bulk Power means electric power and any attendant energy, supplied or made available at transmission or sub-transmission voltage by one electric system to another.

(b) Neighboring Entity means a private or public corporation, a governmental agency or authority, a municipality, a cooperative, or a lawful association of any of the foregoing owning or operating, or proposing to own or operate, facilities for the generation and transmission of electricity which meets each of Renewed License No. DPR-38 Amendment No. 418

A. Maximum Power Level The licensee is authorized to operate the facility at steady state reactor core power levels not in excess of 2568 megawatts thermal.

B. Technical Specifications The Technical Specifications contained in Appendix A, as revised through Amendment No. 420 are hereby incorporated in the license. The licensee shall operate the facility in accordance with the Technical Specifications.

C. This license is subject to the following antitrust conditions:

Applicant makes the commitments contained herein, recognizing that bulk power supply arrangements between neighboring entities normally tend to serve the public interest. In addition, where there are net benefits to all participants, such arrangements also serve the best interests of each of the participants. Among the benefits of such transactions are increased electric system reliability, a reduction in the cost of electric power, and minimization of the environmental effects of the production and sale of electricity.

Any particular bulk power supply transaction may afford greater benefits to one participant than to another. The benefits realized by a small system may be proportionately greater than those realized by a larger system. The relative benefits to be derived by the parties from a proposed transaction, however, should not be controlling upon a decision with respect to the desirability of participating in the transaction. Accordingly, applicant will enter into proposed bulk power transactions of the types hereinafter described which, on balance, provide net benefits to applicant. There are net benefits in a transaction if applicant recovers the cost of the transaction (as defined in ¶1 (d) hereof) and there is no demonstrable net detriment to applicant arising from that transaction.

1. As used herein:

(a) Bulk Power means electric power and any attendant energy, supplied or made available at transmission or sub-transmission voltage by one electric system to another.

(b) Neighboring Entity means a private or public corporation, a governmental agency or authority, a municipality, a cooperative, or a lawful association of any of the foregoing owning or operating, or proposing to own or operate, facilities for the generation and transmission of electricity which meets each of Renewed License No. DPR-47 Amendment No. 420

A. Maximum Power Level The licensee is authorized to operate the facility at steady state reactor core power levels not in excess of 2568 megawatts thermal.

B. Technical Specifications The Technical Specifications contained in Appendix A, as revised through Amendment No. 419 are hereby incorporated in the license. The licensee shall operate the facility in accordance with the Technical Specifications.

C. This license is subject to the following antitrust conditions:

Applicant makes the commitments contained herein, recognizing that bulk power supply arrangements between neighboring entities normally tend to serve the public interest. In addition, where there are net benefits to all participants, such arrangements also serve the best interests of each of the participants. Among the benefits of such transactions are increased electric system reliability, a reduction in the cost of electric power, and minimization of the environmental effects of the production and sale of electricity.

Any particular bulk power supply transaction may afford greater benefits to one participant than to another. The benefits realized by a small system may be proportionately greater than those realized by a larger system. The relative benefits to be derived by the parties from a proposed transaction, however, should not be controlling upon a decision with respect to the desirability of participating in the transaction. Accordingly, applicant will enter into proposed bulk power transactions of the types hereinafter described which, on balance, provide net benefits to applicant. There are net benefits in a transaction if applicant recovers the cost of the transaction (as defined in ¶1 (d) hereof) and there is no demonstrable net detriment to applicant arising from that transaction.

1. As used herein:

(a) Bulk Power means electric power and any attendant energy, supplied or made available at transmission or sub-transmission voltage by one electric system to another.

(b) Neighboring Entity means a private or public corporation, a governmental agency or authority, a municipality, a cooperative, or a lawful association of any of the foregoing owning or operating, or proposing to own or operate, facilities for the generation and transmission of electricity which meets each of Renewed License No. DPR-55 Amendment No. 419

Programs and Manuals 5.5 5.5 Programs and Manuals 5.5.7 Pre-Stressed Concrete Containment Tendon Surveillance Program This program provides controls for monitoring any tendon degradation in pre-stressed concrete containments, including effectiveness of its corrosion protection medium, to ensure containment structural integrity. The program shall include baseline measurements prior to initial operations. The Tendon Surveillance Program, inspection frequencies, and acceptance criteria shall be in accordance with Section XI, Subsection IWL of the ASME Boiler and Pressure Vessel Code and applicable addenda as required by 10 CFR 50.55a, as amended by relief granted in accordance with 10 CFR 50.55a(a)(3).

The provisions of SR 3.0.3 are applicable to the Tendon Surveillance Program inspection frequencies.

5.5.8 Reactor Coolant Pump Flywheel Inspection Program This program shall provide for the inspection of each reactor coolant pump flywheel per the recommendations of Regulatory Position C.4.b of Regulatory Guide 1.14, Revision 1, August 1975.

In lieu of Position C.4.b(1) and C.4.b(2), a qualified in-place UT examination over the volume from the inner bore of the flywheel to the circle one-half of the outer radius or a surface examination (MT and/or PT) of exposed surfaces of the removed flywheels may be conducted at 20 year intervals.

5.5.9 Inservice Testing Program (Deleted)

Note: See Section 1.1 for the definition of INSERVICE TESTING PROGRAM.

OCONEE UNITS 1, 2, & 3 5.0-12 Amendment Nos. 418, 420, 419

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION FOR AMENDMENT NO. 418 TO RENEWED FACILITY OPERATING LICENSE NO. DPR-38 AMENDMENT NO. 420 TO RENEWED FACILITY OPERATING LICENSE NO. DPR-47 AMENDMENT NO. 419 TO RENEWED FACILITY OPERATING LICENSE NO. DPR-55 DUKE ENERGY CAROLINAS, LLC OCONEE NUCLEAR STATION, UNITS 1, 2, AND 3 DOCKET NOS. 50-269, 50-270, AND 50-287

1.0 INTRODUCTION

By application dated April 13, 2020 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML20104A384), Duke Energy Carolinas, LLC (the licensee) requested changes to the Technical Specifications (TS) for Oconee Nuclear Station (ONS, Oconee),

Units 1, 2, and 3.

The proposed change would modify TS 5.5.8, Reactor Coolant Pump [RCP] Flywheel Inspection Program to adopt the provisions of Industry/Technical Specification Task Force (TSTF) Traveler TSTF-421, Revision to RCP Flywheel Inspection Program (WCAP-15666)

(ADAMS Accession No. ML013390280). The availability of TSTF-421 for adoption by licensees was announced in the Federal Register on October 22, 2003 (68 FR 60422).

2.0 REGULATORY EVALUATION

2.1 System Description The function of the RCP in the reactor coolant system (RCS) is to maintain an adequate cooling flow rate by circulating a large volume of primary coolant water at high temperature and pressure through the RCS. Following an assumed loss of power to the RCP motor, the flywheel, in conjunction with the impeller and motor assembly, provides sufficient rotational inertia to assure adequate primary coolant flow during RCP coastdown, thus resulting in adequate core cooling.

Additional information regarding the RCP Flywheel can be found in Oconees Updated Final Safety Analysis Report (UFSAR), Revision 28, Chapter 5, Section 5.4.4.2 (ADAMS Accession No. ML20189A080).

Enclosure 4

2.2 Description of Proposed Changes The licensee proposed to revise TS 5.5.8, Reactor Coolant Pump Flywheel Inspection Program by modifying RCP flywheel inspection methods and extending the inspection frequency for the RCP motor flywheel to an interval not to exceed 20 years.

Current TS 5.5.8 states:

This program shall provide for inspection of each reactor coolant pump flywheel.

At approximately three-year intervals, the bore and keyway of each reactor coolant pump flywheel shall be subjected to an in-place, volumetric examination.

Whenever maintenance or repair activities necessitate flywheel removal, a surface examination of exposed surfaces and a complete volumetric examination shall be performed if the interval measured from the previous such inspection is greater than 6 2/3 years. The interval may be extended up to one year to permit inspections to coincide with a planned outage.

Revised TS 5.5.8 would state This program shall provide for the inspection of each reactor coolant pump flywheel per the recommendations of Regulatory Position C.4.b of Regulatory Guide 1.14, Revision 1, August 1975.

In lieu of Position C.4.b(1) and C.4.b(2), a qualified in-place UT examination over the volume from the inner bore of the flywheel to the circle one-half of the outer radius or a surface examination (MT and/or PT) of exposed surfaces of the removed flywheels may be conducted at 20 year intervals.

2.3 Regulatory Guidance and Requirements The regulatory requirements and guidance documents that are applicable to the review of the LAR are listed below.

The Atomic Energy Commission (AEC) issued the construction permits for Oconee on November 6, 1967. The plants design approval for the construction phase was based on the proposed general design criteria (GDC) published by the AEC in the FR (32 FR 10213) on July 11, 1967. The GDC which constitute the licensing bases for Oconee are those described in the UFSAR, Revision 28, Chapter 3.1, Conformance with NRC [U. S. Nuclear Regulatory Commission] General Design Criteria (ADAMS Accession No. ML20189A074) and in applicable UFSAR sections. As discussed in the UFSAR, the licensee made changes to the facilities and committed to some of the GDC from Title 10 of the Code of Federal Regulations (10 CFR) Part 50, Appendix A. Based on its review of the UFSAR and the licensees submittal, the staff identified the following Oconee UFSAR Criterion as being applicable to the proposed amendment.

UFSAR, Section 3.1.40, Criterion 40, Missile Protection (Category A), states, in part, Protection for engineered safety features shall be provided against dynamic effects and missiles that might result from plant equipment failures.

The regulations in 10 CFR Part 50, Section 50.36, Technical Specifications, establish the requirements for TSs. Specifically, 10 CFR 50.36(c)(5), Administrative controls, states, in part, Administrative controls are the provisions relating to organization and management, procedures, recordkeeping, review and audit, and reporting necessary to assure operation of the facility in a safe manner.

Regulatory Guide (RG) 1.14, Reactor Coolant Pump Flywheel Integrity, Revision 1, August 1975 (ADAMS Accession No. ML003739936).

RG 1.174, An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decision on Plant-Specific Changes to the Current Licensing Basis, Revision 3, January 2018 (ADAMS Accession No. ML17317A256)

Westinghouse Report WCAP-14535A, Topical Report on Reactor Coolant Pump Flywheel Inspection Elimination, November 1996 (ADAMS Accession No. ML18312A151).

Westinghouse Report WCAP-15666, "Extension of Reactor Coolant Pump Motor Flywheel Examination," August 24, 2001 (ADAMS Accession No. ML012420149). The NRC accepted WCAP-15666 for referencing in license applications in its letter dated May 5, 2003 (ADAMS Accession No. ML031250595).

TSTF 421, Revision to RCP Flywheel Inspection Program (WCAP-15666), Revision 0, was approved by the NRC as documented in the NRC Notice of Availability published on October 22, 2003 (68 FR 60422).

3.0 TECHNICAL EVALUATION

3.1 Background

A concern regarding the overspeed of the RCP and its potential for failure led to the issuance of RG 1.14, Reactor Coolant Pump Flywheel Integrity, Revision 1, dated August 1975. RG 1.14 describes a method acceptable to the NRC staff of addressing concerns related to RCP vibration and the possible effects of missiles that might result from the failure of the RCP flywheel. The need to protect components important to safety from such missiles are included in General Design Criterion 4, Environmental and Dynamic Effects Design Basis, of Appendix A, General Design Criteria for Nuclear Power Plants, to 10 CFR 50, Licensing of Production and Utilization Facilities and for Oconee this is included in UFSAR Section 3.1.40, Criterion 40, Missile Protection.

Specific requirements to have an RCP flywheel inspection program consistent with RG 1.14 or previously issued relaxations from the RG are included in the administrative controls section of the TS. The purpose of the testing and inspection programs defined in the TS is to ensure that the probability of a flywheel failure is sufficiently small such that additional safety features are not needed to protect against a flywheel failure. The RG provides criteria in terms of critical speeds that could result in the failure of an RCP flywheel during normal or accident conditions.

In addition to the guidance in RG 1.14, the NRC issued RG 1.174, An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis, which provides guidance and criteria for evaluating proposed changes that use risk-informed justifications.

The NRC-approved Topical Report (TR), WCAP-14535A, Topical Report on Reactor Coolant Pump Flywheel Inspection Elimination, provides the technical basis for the extension and alternate inspection requirements for RCP motor flywheels to an interval not to exceed 10 years.

This report was applicable to all operating domestic Westinghouse plants and several Babcock and Wilcox (B&W) plants, including Crystal River Unit 3, Oconee Units 1, 2, and 3, Davis Besse, and Three Mile Island Unit 1.

A proposed justification for extending the RCP flywheel inspections from a 10-year inspection interval to an interval not to exceed 20 years was provided by the Westinghouse Owners Group (WOG) in TR WCAP-15666, "Extension of Reactor Coolant Pump Motor Flywheel Examination."

WCAP-15666 addressed the proposed extension for all domestic Westinghouse plants. The NRC accepted the TR for referencing in license applications in a letter dated May 5, 2003.

WCAP-15666, Risk Results and Conclusions, states, in part:

Given the extremely low failure probabilities for the RCP motor flywheel during normal/accident conditions and the extremely low probability of LOCA/LOOP, and even assuming a CCDP [conditional core damage probability] of 1.0 (complete failure of safety systems), the CDF and change in risk would still not exceed the NRC's acceptable guidelines in RG-1.174 (<1.0E-6 per year).

3.2 Licensees Proposal The current TS 5.5.8 specifies that the RCP flywheels shall be subjected to an in-place, volumetric examination at 3-year intervals. Prior to TSTF-421, the NRC staff generically accepted an allowable interval for alternate inspections of approximately 10 years. The licensee stated, Although ONS did not adopt previously accepted generic changes (i.e. alternate inspections to RG 1.14 and inspection intervals of 10 years), the technical basis for the change, as described in the NRC-approved topical report WCAP-15666, is valid to incorporate the allowable alternative to the inspections described in RG 1.14 and to adopt the 20-year inspection interval.

The licensee stated that the justification for the proposed change is provided in the NRC-approved WCAP-15666 and that although Oconee is a B&W plant, its RCP flywheels are the same material type as the flywheels evaluated in WCAP-15666 and is, therefore, bounded by the WCAP analysis. The licensee stated that the risk assessment in WCAP-15666 is applicable to Oconee and included Oconee plant-specific information to confirm that the risk results and conclusions in WCAP-15666 apply to Oconee.

The licensee stated that its submittal is consistent with an NRC-approved precedent amendment for Crystal River, Unit 3, dated July 27, 2005 (ADAMS Accession No. ML051890348), that adopted TSTF-421.

3.3 NRC Staff Evaluation 3.3.1 WCAP-14535A The WCAP-14535A provides a deterministic technical basis for an inspection frequency extension and alternate inspection requirements for RCP motor flywheels (flywheels) from 3 years to an interval not to exceed 10 years. The NRC staff reviewed the WCAP and finds that WCAP-14535A is applicable to the Oconee flywheels.

The WCAP-14535A, Appendix G, includes NRC staffs safety evaluation (SE). The SE states that for a plant-specific application the licensee needs to confirm that the flywheels are made of SA-533B material. In the LAR, the licensee stated that the Oconee flywheels are made of SA-533B, therefore, NRC staff finds that Oconee has met this condition.

The WCAP-14535A SE also states, in summary, that licensees with Group 10 flywheels need to confirm that their flywheels have an adequate shrink fit to preclude loss of shrink fit of the flywheel at maximum overspeed or to provide an evaluation demonstrating that no detrimental effects would occur if the shrink fit was lost at maximum overspeed.

In its LAR, the licensee stated that the Oconee flywheels are Group 10 and that the critical crack for flywheel overspeed to 1500 revolutions per minute that includes shrink fit stresses was provided in a WCAP-14535A request for additional information response dated June 17, 1996 (ADAMS Accession No. ML18312A114). Therefore, NRC staff finds that Oconee has met this condition.

The NRC staff finds that Oconee has met the WCAP-14535A conditions to use an alternate inspection requirement and extend the inspection frequency of the flywheels from 3 years to an interval not to exceed 10 years.

3.3.2 TSTF-421 and WCAP-15666 NRC-approved TSTF-421 approves the use of WCAP-15666 as the technical basis for a licensee to request extending the RCP flywheel inspection from a 10-year inspection interval to an interval not to exceed 20 years. The technical basis is a risk assessment in accordance with RG 1.174.

NRC-approved TSTF-421 is applicable to NUREG-1431, Standard Technical Specifications, Westinghouse Plants (ADAMS Accession No. ML12100A222). Oconee is a Babcock and Wilcox (B&W) plant. In a WOG letter to the NRC dated September 8, 2003 (ADAMS Accession No. ML032830622), the WOG indicated that WCAP-15666 may be applied to the B&W plants listed in Table 2-3 of the WCAP, provided that the licensees confirm the applicability of the WCAP to their plants. ONS Units 1, 2 and 3 are included in WCAP-15666, Table 2-3. The licensee stated that the Oconee design is bounded by the analyses performed in WCAP-15666.

In the Notice of Availability for TSTF-421 (68 FR 60422), the NRC stated:

The NRC staff acknowledges that some of the supporting material for TSTF-421 may also help to support plant-specific applications for the B&W units included in portions of WCAP-15666. The NRC staff will work with licensees for the applicable B&W units to ensure that our processes work as efficiently as possible for those applying for license amendments similar to that described in TSTF-421.

In the Crystal River, Unit 3, precedent, the NRC staff noted that WCAP-15666 outlines six risk evaluation assumptions that a licensee can use to define plant-specific application and to confirm the change in risk does not exceed the NRC criteria in RG 1.174.

In its letter dated April 13, 2020, ONS used the WCAP-15666 risk evaluation assumptions and the Oconee plant-specific data to confirm the WCAP applies to ONS. The licensee stated, in part, that:

1. The conditional core damage probability given an RCP flywheel failure is assumed to be 1.0 in WCAP-15666. This is a conservative and bounding assumption acknowledged by the NRC in the Crystal River Unit 3 precedent.