ML18143B497

Update for Subsequent License Renewal: WCAP-14535A, Topical Report on Reactor Coolant Pump Flywheel Inspection Elimination and WCAP-15666-A, Extension of Reactor Coolant Pump Motor Flywheel Examination.

ML18143B497
Person / Time
Site:	99902037
Issue date:	05/31/2018
From:	Hall G Z, Schneider R E PWR Owners Group
To:	Office of Nuclear Reactor Regulation
References
OG-18-123, PA-BSC-1500 PWROG-17011-NP, Rev. 1
Download: ML18143B497 (56)

Text

PRESSURIZED WATER REACTOR OWNERS GROUP PWROG-17011-NP Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 Update for Subsequent License Renewal: WCAP-14535A, "Topical Report on Reactor Coolant Pump Flywheel Inspection Elimination" and WCAP-15666-A, "Extension of .Reactor Coolant Pump Motor Flywheel Examination" Materials Committee PA-MSC-1500 May 2018 @Westinghouse

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WESTINGHOUSE NON-PROPRIETARY CLASS 3 PWROG-17011-NP Revision 1 Update for Subsequent License Renewal: WCAP-14535A, "Topical Report on Reactor Coolant Pump Flywheel Inspection Elimination" and WCAP-15666-A, "Extension of Reactor Coolant Pump Motor Flywheel Examination" PA-MSC-1500 Gordon Z. Hall* Structural Design and Analysis -I Raymond E. Schneider*

Risk Applications and Methods -11 May 2018 Reviewer: Earnest S. Shen* Structural Design and Ana l ysis -I Reviewer: John White* Risk Applications and Methods -II Approved:

John McFadden*, Manager Aging Management

& License Renewal Approved: James P. Molkenthin*, Program Director PWR Owners Group PMO *Electronically approved records are authenticated in the electronic document management system. Westinghouse Electric Company LLC 1000 Westinghouse Drive Cranberry Township , PA 16066 , USA © 2018 Westinghouse Electric Company LLC All Rights Reserved WESTINGHOUSE NON-PROPRIETARY CLASS 3 iii ACKNOWLEDGEMENTS Th i s report was developed and funded by the PWR Owners Group under the leadersh i p of the participating utility representatives of the Materials Comm i ttee. PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 i v WESTINGHOUSE ELECTRIC COMPANY LLC PROPRIETARY LEGAL NOTICE This report was prepared as an account of work performed by West i nghouse Electric Company LLC. Neither Westinghouse E l ectric Company LLC , nor any person acting on its beha l f: 1. Makes any warranty or representation , express or imp l ied includ i ng the warrant i es of fitness for a particular purpose or merchantabil i ty , with respect to the accuracy , completeness , or usefu l ness of the informat i on conta i ned in th i s report , or that the use of any information , apparatus , method , or process disclose d i n this report may not i nfringe privately owned rights; or 2. Assumes any l iabilities with respect to the use o f , or for damages resulting from the use of , any information , apparatus , method , or process disclosed i n this report. COPYRIGHT NOTICE Th i s report has been prepared by Westinghouse Electric Company LLC and bears a Westinghouse Electric Company copyr i ght notice. Information i n this report i s the property of , and contains copyright material owned by , Westinghouse Electric Company LLC and /or i ts subcontractors and suppl i ers. It is transm i tted to you i n confidence and trust , and you agree to treat this document and the material contained there i n in strict accordance with the terms and co n d i tions of the agreement under which i t was prov i ded to you. DISTRIBUTION NOTICE This report was prepared for the PWR Owners Group. This D i stribution Not i ce is intended to es t ablish gu i dance for access to this information. This report (includ i ng proprietary and non-proprietary versions) i s not to be provided to any individua l or organization outside of the PWR Owners Group program participants without prior written approva l of the PWR Owners Group Program Management Office. However , prior written approval is not required for program participants to provide copies of Class 3 Non-Proprietary reports to third parties that are supporting implementat i on at their plant , or for subm i ttals to the USN RC. PWROG-1701 1-NP May 2018 R evi s i o n 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 V PWR Owners Group United States Member Participation*

for PA-MSC-1500 Utility Member Plant Site(s) Participant Yes No Ameren Missour i Callaway (W) X Amer i can Electric Po w e r D.C. Cook 1 & 2 (W) X Arizona Public Serv i ce Palo Verde U nit 1 , 2 , & 3 (CE) X Domin i on Connecticu t Mi llstone 2 (CE) X M illstone 3 (W) X Domi ni on VA North Anna 1 & 2 (W) X Su r ry 1 & 2 (W) X Catawba 1 & 2 (W) X Duke Energy Carol in as McGui r e 1 & 2 (W) X Oconee 1 , 2 , & 3 (B&W) X Duke Energy Progress Robinson 2 (W) X Shearon Harr i s (W) X Entergy Pal i sades Palisades (CE) X Entergy N u clear Northeast I n dian Po i nt 2 & 3 (W) X Arkansas 1 (B&W) X Entergy Opera t ions South A r kansas 2 (CE) X Waterford 3 (CE) X B r a i dwood 1 & 2 (W) X Byron 1 & 2 (W) X Exelon Genera t ion Co. LLC T MI 1 (B&W) X Calvert Cliffs 1 & 2 (CE) X Ginna (W) X FirstEnergy Nuclear Operat i ng Co. Beaver Valley 1 & 2 (W) X Dav i s-Besse (B&W) X S t. Lucie 1 & 2 (CE) X Florida Po w er & Ligh t\ NextEra Turkey Point 3 & 4 (W) X Seabrook (W) X P t. Beach 1 & 2 (W) X Luminant Power Comanche Peak 1 & 2 (W) X Omaha Public Power D i strict Fort Calhoun (CE) X Pac i fic Gas & Electric D i ablo Canyon 1 & 2 (W) X PSEG -Nuclear Salem 1 & 2 (W) X South Carolina Elect r ic & Gas V.C. Summer (W) X So. Texas Project N u clear Operating Co. South Texas Project 1 & 2 (W) X Southern Nuclear Ope r ating Co. Farley 1 & 2 (W) X Vogtle 1 & 2 (W) X Tennessee Valley Authority Sequoyah 1 & 2 (W) X Watts Bar 1 & 2 (W) X Wolf Creek Nuclear Ope r ating Co. Wolf Creek (W) X Xcel Energy P r a i rie Island 1 & 2 (W) X

• Project participants as of the date the final deliverable was completed. On occasion , additional members will join a project. Please contact the PWR Owners Group Program Management Office to verify participation before sending this document to participants not listed above. PWROG-170 1 1-NP May 2018 Revis i on 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 vi PWR Owners Group I t f n erna 1ona I M b P rf . f

• f PA MSC 1500 em er a 1c1pa 10n or --Participant Utility Member Plant Site(s) Yes No Asoc i aci6n Nuclear Asc6-Vandell6s Asco 1 & 2 (W) X Vandellos 2 (W) X AxpoAG Beznau 1 & 2 (W) X Centrales Nucleares Almaraz-Trillo Almaraz 1 & 2 (W) X EDF Enerav Sizewell B (W) X E l ectrabel Doel 1 , 2 & 4 (W) X Tihange 1 & 3 (W) X Electricite de F r ance 58 Units X Eletronuclear

-Eletrobras Angra 1 (W) X Emirates Nuclear Enerav Corporation Barakah 1 & 2 X EPZ Borssele X Eskom Koeberg 1 & 2 (W) X Hokkaido Tomari 1, 2 & 3 (MHI) X Japan Atomic Power Company Tsuruga 2 (MHI) X Mihama 3 (W) X Kansai Electr ic Co., LTD Ohi 1 , 2 , 3 & 4 (W & MHI) X Takahama 1 , 2 , 3 & 4 (W & MHI) X Kori 1 , 2 , 3 & 4 (W) X Korea Hydro & Nuclear Power Corp. Hanbit 1 & 2 (W) X Hanbit 3 , 4 , 5 & 6 (CE) X Hanul 3 , 4 , 5 & 6 (CE) X Kyushu Genka i 2 , 3 & 4 (MHI) X Sendai 1 & 2 (MHI) X Nuklearna Electrarna KRSKO Krsko (W) X R in ghals AB Ringhals 2 , 3 & 4 (W) X Shikoku lkata 1 , 2 & 3 (MHI) X Taiwan Power Co. Maanshan 1 & 2 (W) X

• Project participants as of the date the final deliverable was completed.

On occasion, additional members will join a project. Please contact the PWR Owners Group Program Management Office to verify participation before sending this document to participants not listed above. PWROG-1701 1-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 vii TABLE OF CONTENTS 1 INTRODUCTION

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............. 1-1 2 BACKGROUND

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..................................................................................................................... 2-1 2.1 DESIGN AND FABRICATION

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........... 2-1 2.2 INSPECTION

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2-3 2.3 STRESS AND FRACTURE EVALUATION

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............. 2-5 2.3.1 Selection of Flywheel Groups for Evaluation

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.............................................................. 2-5 2.3.2 Ductile Failure Analysis ...............................................................

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2-5 2.3.3 Non-ductile Failure Analysis ...................................................................................

................ 2-5 2.3.4 Fatigue Crack Growth ...............................

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.......... 2-6 2.3.5 Excessive Deformation Analysis .......................

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2-6 2.4

SUMMARY

OF STRESS AND FRACTURE RESULTS ....................

............................................ 2-7 3 RISK ASSESSMENT

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3-1 3.1 RISK-INFORMED REGULATORY GUIDE 1.174 METHODOLOGY

............................................ 3-1 3.2 FAILURE MODES AND EFFECTS ANALYSIS ............................................................................. 3-7 3.3 FLYWHEEL FAILURE PROBABILITY

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......................................................... 3-9 3.3.1 Method of Calculation Failure Probabilities

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............. 3-10 3.3.2 Sensitivity Study ......................

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..... 3-14 3.3.3 Failure Probability Assessment Conclusions

....................................................................... 3-16 3.4 CORE DAMAGE EVALUATION

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... 3-21 3.4.1 What is the Likelihood of the Event... .......................

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......... 3-22 3.4.2 What are the Consequences?

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3-23 3.4.3 Risk Calculation

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......... 3-23 3.5 CONSIDERATION OF UNCERTAINTY

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..... 3~29 3.5.1 Initiating Event Frequency

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..... 3-30 3.5.2 Conditional Flywheel Failure Probabil i ty .................................

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...... 3-30 3.5.3 Conditional Core Damage/Large Early Release Probability Associated with a Flywheel Failure Event ........................................................................................................................................ 3-30 3.5.4 Conclusion Regarding Treatment of Uncertainty

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.......................................... 3-31 3.6 RISK RESULTS AND CONCLUSIONS

....................................................................................... 3-31 4 CONCLUSIONS

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......................... 4-1 5 REFERENCES

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............... 5-1 PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 v i ii APPENDIX A: CALVERT CLIFFS UNIT 1 & 2 RCP MOTOR FLYWHEEL EVALUATIONS FOR EXTENSION OF ISi INTERVAL .................

............................................................................................ A-1 PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 i x List of Tables Table 2-1: RCP Flywheel Inspection Data .....................................

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.......... 2-3 Table 2-2: Flywheel Inspection Data Recordable Indications

..................................................... 2-4 Table 2-3: Flywheel Groups Evaluated for Program MUHP-5043

[2] .............

............................ 2-5 Table 2-4: Ductile Failure Limiting Speed ..............................

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2-5 Table 2-5: Critical Crack Lengths for Flywheel Overspeed of 1500 rpm (Considering LBB) ...... 2-6 Table 2-6: Fatigue Crack Growth Assuming 6000 RCP Starts and Stops ..............................

... .2-6 Table 2-7: Flywhee l Deformation at 1500 rpm ........................................................................... 2-7 Table 3-1: Variables for RCP Motor Flywheel Failure Probability Model. ................................. 3-11 Table 3-2: Input Values for RCP Motor Flywheel Failure Probability Model. ............................ 3-12 Table 3-3: Cumulative Probability of Failure over 40 , 60 and 80 Years with and without lnservice Inspection (1 l ....................................

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......... 3-14 Table 3-4: Effect of Flywheel Risk Parameter on Failure Probability

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............... 3-15 Table 3-5: Summary of Flywheel Ana l ysis Parameters

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.................. 3-21 Table 3-6: Estimated RCP Motor Flywheel Failure Probabi li ties .............................................. 3-22 Table 3-7: Westinghouse RCP Motor Flywheel Evaluation Group 1 ........................................ 3-26 Table 3-8: RCP Motor Flywheel Evaluation Group 2 ......................................................

.......... 3-27 Table 3-9: Calvert Cliffs Units 1 and 2 RCP Motor Flywheel Evaluation

.................................. 3-28 Table 3-10: CDF Sensitivity to Variations in PRA evaluation assumptions for RCP Flywheel Failure R i sk Assessment for Extending 10-year inspection intervals to 80 years -(Flywheel Group 1) ...............................................

............................................ 3-31 Table 3-11: Evaluation with Respect to Regulatory Guide 1.174 (Key Principles)

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3-32 Table A-1: Critical Crack Length in Inches and% Through Flywheel.

....................................... A-2 PWROG-17011

-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 X List of Figures Figure 2-1: Example of a Typical Westinghouse RCP Motor Flywheel ...................................... 2-2 Figure 3-1: NRC Regulatory Guide 1.174 Basic Steps .......................

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........ 3-2 Figure 3-2: Pr i nciples of R i sk-Informed Regulation

[5) ..........

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3-4 Figure 3-3: West i nghouse PROF Program Flow Chart for Calcu l ating Fa i lure Probability

...... 3-17 Figure 3-4: Probability of Failure for Flywheel Evaluation Group 1 ......................

.................... 3-18 Figure 3-5: Probability of Failure for Flywheel Evaluation Group 2 ..........................................

3-19 Figure 3-6: Probability of Failure for Calvert Cliffs Units 1 and 2 ..................

.......................... 3-20 PWROG-17011-NP May 2018 Rev i s i on 1 B&W CCDP CCL CCNPP CDF CE DEGB OLE FCG FSAR FSAR GOA ISi 1ST LBB LERF LOCA LOOP MT NOE NRC OD PMSC PRA PROF PT PWROG RCP RCPM RCS RG rpm RT N DT SER SLR SRP SRRA SSCs USAR UT w WOG W-PROF WESTINGHOUSE NON-PROPRIETARY CLASS 3 List of Acronyms Babcock and Wilcox conditional core damage probability critical crack length Calvert C l iffs Nuclear Power Plant core damage frequency Combustion Engineer i ng doub l e ended gui ll otine break design lim i ting events fatigue crack growth final safety analysis report final safety analysis report graded qua l ity assurance inservice i nspection inservice testing leak-before-break large ear l y release frequency loss of coolant accident loss offsite power magnet i c particle testing non-destructive examination Nuclear Regulatory Commission outer diameter Pump & Motor Services probab i list i c risk assessment probab i l i ty of failure penetrant testing Pressur i zed Water Reactor Owne r s Group reactor coolant pump reactor coolant pump motor reactor coolant system regulatory gu i de revolutions per minute reference nil-ductility transition temperature safety evaluation report subsequent license renewal standard rev i ew plan structural reliability and r i sk assessment systems , structures and components updated safe t y analys i s report ultrasonic examination

/ultrason i c test Westinghouse Westinghouse Owners Group Westinghouse PROF Software Lib r ary PWROG-170 11-NP x i May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 1-1 1 INTRODUCTION The purpose of this topical report (TR) is to extend the applicability of WCAP-14535A

[1] and WCAP-15666-A

[2] to subsequent license renewal (SLR), i.e., 80 years of operation. Westinghouse provided the technical basis in WCAP-14535A

[1] for the elimination of inspection requirements for the reactor coolant pump (RCP) motor flywheels for all operating domestic Westinghouse and several B&W plants. The NRC issued a Safety Evaluat i on Report (SER) in September 12, 1996 , accepting the technical arguments but did not allow for total elimination of examinations as WCAP-14535A

[1] requested. The SER provided partial relief from the reactor coolant pump (RCP) motor flywheels examination requirements in NRC RG 1.14 [3], by allowing an extension in the examination frequency from 40 months to 10 years. It further relaxed the RG 1.14 examination guidance by recommending an in-place ultrasonic examination (UT) over the volume from the inner bore of the flywheel to the circle of one-half the outer radius or an alternative surface examination, i.e., magnetic particle testing (MT) and/or liquid penetrant testing (PT), of the exposed surfaces defined by the volume of disassembled flywheel.

As Section 3.6 of the SER for [1] stated , NRC staff relied solely on the deterministic methodology to review the submittal.

The risk assessment was not included in [1] and was not reviewed.

WCAP-14535A

[1] is applicable to the RCP motor flywheels in all domestic Westinghouse nuclear steam supply system (NSSS) plants , and Oconee Units 1, 2 , and 3, Davis Besse, and Three Mile Island Unit 1, which are Babcock and Wilcox (B&W) NSSS plants. WCAP-15666-A

[2] is a fol low-up TR that justified extending the 10-year inspection frequency that was approved by the NRC in WCAP-14535A

[1] to 20 years. WCAP-15666-A [2] demonstrated that the deterministic results in WCAP-14535A

[1] remain valid , and also performed a failure probability analysis to show that the change in risk for a 20-year inspection frequency meet the RG 1.17 4 [5] acceptance guidelines. The NRC SER for WCAP-15666-A

[2] concluded that both the deterministic and probabilistic calculations contained in [2] were acceptable , and approved the 20-year inspection frequency. WCAP-15666-A

[2] is applicable to plants with Westinghouse-designed NSSS plants. Although it included some data for B&W NSSS plants , however , the TR and the NRC SER did not specifically address the applicability of the risk assessments and other evaluations to the three B&W NSSS plants that WCAP-14535-A

[1] was applicable to. The following is a quote from the NRC SER for [2]. " The NRG 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 WGAP-15666.

The NRG 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.

The affected licensees are encouraged to discuss this matter with the NRG staff before submitting an application." PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 1-2 This same applicability is carried over for the TR presented herein. This TR is not applicable to Combustion Engineering (CE) NSSS plants , with the exception of Calvert Cliffs Units 1 and 2. This TR is applicable to Calvert Cliff Units 1 and 2 as these plants have Westinghouse RCP motors and flywheels. However, these flywheels and motor operating speeds are different than those evaluated in WCAP-15666-A

[2]. Westinghouse performed a plant-specific evaluation for Calvert Cliffs Unit 1 and 2 , that applied the using the same methods detailed in WCAP-15666-A

[2] for 60 years of operation. This 60-year evaluation is extended to 80 years of operation in this TR. Revision 1 of this TR removes unnecessary contents that are duplicates in WCAP-14535A [1] and WCAP-15666-A

[2]. Change bars are not used. All evaluation results and conclusions are unchanged. PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 2-1 2 BACKGROUND

2.1 DESIGN

AND FABRICATION Westinghouse RCP motor flywheels consist of two large stee l discs that are shrunk fit directly to the RCP motor shaft. The individual flywheel discs are bolted together to form an i ntegral flywheel assembly , wh i ch i s l ocated above the RCP rotor core. Typica ll y , each flywhee l d i sc is keyed to the motor shaft by means o f three vert i ca l keyways , pos i t i oned at 120° interva l s. The bottom d i sc usually has a c i rcumferent i a l notch a l ong the outs i de d i ameter bottom surface for placement of anti-rotat i on pawls. See Figure 2-1 for t he configu r at i on of a typ i cal West i nghouse flywhee l. Westinghouse has manufactured the RCP motors for all operating Westinghouse plants. All of the RCP motor flywheels for West i nghouse p l ants are made of SA-533 Grade B C l ass 1 steel. As i n WCAP-15666-A

[2], a range of RT N oT va l ues from 0°F t o 60°F was assumed i n the i ntegrity evaluations of [1 ), which are d i scussed l ater in th i s r eport. West i nghouse designed flywheels are also used for Calvert C li ffs Units 1 and 2. They w ill be addressed separate l y in Section 3 for the ri sk assessment , and i n APPENDIX A: for t he deterministic eva l uat i ons. Cons i stent w i th t he evaluat i ons performed i n [1 ), l arger f l ywhee l outside d i ameter for the f l ywheel assembly i s used i n this TR , because i t i s conservat i ve with respect to stress and fracture. PWROG-17011-NP May 2018 Revis i on 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 0 2.0 2 IM DIA. BOLT NOLES+j~11 1.2~ ti DIA. GAGE HOL£S r--I t 0 **oo.t .. I . o o I t 0 37.5 Iii HD. _.. 7 t* RAD. 32.S II UO. Figure 2-1: Example of a Typical Westinghouse RCP Motor Flywheel PWROG-17011-NP 2-2 7.5 IN 6. S 111 May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 2-3 2.2 INSPECTION Plant A B C D E F G H I J K L M N Total Flywheels are inspected at the plant or during motor refurbishment at an offsite facility. Inspections are conducted under the ASME Boiler and Pressure Vessel Code ,Section XI [4], which identifies the standard practice for control of instrumentation and personnel qualification. Ultrasonic test (UT) level II and Ill examiners conduct the inspections. WCAP-15666-A

[2] discussed the examination volume , approach , access and exposure in detai l. This discussion remains applicable for SLR. Inspection History The flywhee l inspection results and the summary of recordable indications from the MUHP-5042 study are presented in Tab l e 2-3 and Table 2-4 of WCAP-15666-A

[2] Inspection History Update A summary of all Westinghouse RCP flywheels that were inspected by Framatome (formerly AREVA) is summarized in Table 2-1. Four RCP flywheels where determined to have recordable indications. All four indications were determined to be non-relevant

no repairs were required to be performed on any of those RCP flywheels. The four recordable indications are discussed in Table 2-2. Table 2-1

RCP Flywheel Inspection Data Total Total Number Total Number of Number of Number of of Inspection Number of Indications Flywheels Flywheel with No Indications Inspection With Affecting or Non-recordable Recordable Flywheel Inspections Indications Indications lntegritv 9 9 8 1 0 9 9 8 1 0 2 2 2 0 0 9 14 14 0 0 2 2 2 0 0 3 3 3 0 0 7 7 7 0 0 13 13 13 0 0 1 1 1 0 0 9 9 8 1 0 1 1 1 0 0 8 9 8 1 0 1 1 1 0 0 1 1 1 0 0 75 81 77 4 0 PWROG-17011-NP May 2018 Revision 1 Plant A B J L PWROG-1701 1-NP WESTINGHOUSE NON-PROPRIETARY CLASS 3 2-4 Table 2-2: Flywheel Inspection Data Recordable Indications Year 2015 2006 2005 2012 Description of Recordable Indications A Recordable UT indication

-Accepted. Lamination w i th 50% of back wall loss 1" x 4". Procedurally recordable UT indicat i ons were ident i fied i n the bottom flywheel plate during the 45 degree shear wave exam i nat i on. -Accepted per NB-2530. I ndications were i dentified i n two of three keyways i n the lower th i ckness. The indicat i ons were d i spositioned as acceptable because they are considered to be " non-relevant due to the machining process." These were determined to be non-relevant ind i cat i ons. There were several l o w ampl i tude responses that w ere i dent i fied dur i ng the r ad i al examinations.

These responses were i ndicat i ve of small machine grooves or marks that extend 360° around the flywheel.

May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 2-5 2.3 STRESS AND FRACTURE EVALUATION Section 2.3 of WCAP-15666-A

[2] summarized the stress and fracture evaluation. The ductile and br i ttle fa il ure mechanisms were cons i dered in flywhee l eva l uation. The methodo l ogy i s unchanged for this TR. The eva l uation requ ir ements are pe r RG 1.14 [3]. 2.3.1 Selection of Flywheel Groups for Evaluation As discussed i n [2], stresses i n the f l ywheel are a st r ong funct i on of the outer diameter (approx i mate l y proportional to t he square of the OD d i mens i on). Therefore , the two groups shown i n Table 2-3 w i th the l argest flywheel outer diameter (Groups 1 and 2) bound a ll othe r groups defined in WCAP-15666-A

[2], and were se l ected for the determ i nistic and probabil i st i c evaluat i ons. Table 2-3: Flywheel Groups Evaluated for Program MUHP-5043 (2) Flywheel Outer Bore Keyway Rad i al Comme nt s Eva l ua t ion Group D i ameter (i nch) (inch) Length (i nch) 1 76.50 9.375 0.937 Max i mum OD. 2 75.75 8.375 0.906 La r ge OD , m i n i m u m bore. 2.3.2 Ductile Failure Analysis The f l ywheel stresses are dependent on dimensions and rotat i on speed. Extending the operat i ng per i od to 80 years does not affect the stress calculat i on. Therefore , the duct il e fai l ure analys i s in [2] rema i ns valid for 80 years of operation. These results from [2] are summarized i n Table 2-4. The RG 1.14 acceptance criteria for duct i le failure of the flywheels are sat i sfied. Table 2-4: Ductile Failure Limiting Speed Assuming No Cracks Crack Length (as measured f r om the max i mum radial location of the keyway) F l ywheel Neglecting Considering Eva l uation Group Keyway Keyway 1" Crack 2" Crack 5" Crack 10" Crack Radial Radial Length Length 1 3487 3430 3378 3333 3240 3012 2 3553 3493 3435 3386 3281 3060 2.3.3 Non-ductile Failure Analysis The flywheel stress intensity factor , K 1 , i s dependent on geometry , postu l ated flaw dimensions and stress cond i tion (due to rotation speed). Extending the operating period to 80 years does not affect the K 1 calculations. Furthermore , the flywheel i s not local or ad j acent to the reactor core; therefore , the effect of i rrad i ated embr i ttlement i s negligible , and the fracture toughness , K ie does not change due to the 80-year extension. Therefore , the non-ductile failure analys i s in [2] rema i ns valid for 80 years of operation. PWROG-1 7011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 2-6 The results from [2] are shown in Table 2-5. The ambient temperature of 70°F was conservatively used as the operating temperature , while the typica l containment ambient temperature is 100°F to 120°F. At the maximum flywheel overspeed condition of 1500 rpm (considering LBB), the critical crack lengths were calculated for cracks emanating radially from the keyway. The crack length is defined as radially from the keyway. The percentage through the flywhee l is defined as the crack length divided by the radial length from the maximum radial keyway location to the flywheel outer radius, i.e., percentage through-wall.

The critical crack lengths are quite large, even when consider i ng higher values of RT NDT and a lower than expected operating temperature. Table 2-5: Critical Crack Lengths for Flywheel Overspeed of 1500 rpm (Considering LBB) Flywheel Critical Crack Length in Inches and % through Flywheel Evaluation Group RT ND T = 0°F RT NDT = 30°F RT ND T = 60°F 1 16.6" 7.7" 3.1" (50%) (24%) (9%) 2 17.5" 8.5" 3.6" (53%) (26%) (11%) 2.3.4 Fatigue Crack Growth FCG is dependent on the flywheel K 1 at operating and rest states (~K 1}, and the number of start and shutdown cycles. As discussed previously , the 80-year extension has no impact on the K 1 calculations. The 6000 cycles used in the FCG calculation of [2] was determ in ed to be bounding for 80 years of operation. The 6000 cycles f or 80 years of operation must be confirmed to be applicable on a plant-specific bas i s. The FCG calculations assumed the 6000 cycles of RCP start and shutdown for the 80-year plant life. The FCG results from [2] are applicable and are shown in Table 2-6. The crack growth is negligible over an 80-year life of the flywheel, even when assuming a conservative initial crack length as shown in Table 2-6. Table 2-6: Fatigue Crack Growth Assuming 6000 RCP Starts and Stops Keyway Length Assumed Crack Flywheel Flywheel Flywheel Radial From Initial b.K 1 Growth Evaluation OD Bore Length Keyway to Crack (ksi" in) afte r 6000 Group (inch) (inch) Length cycles (inch) OD (inch) (inch) (inch) 1 76.50 9.375 0.937 32.63 3.26 38 0.08 2 75.75 8.375 0.906 32.78 3.28 37 0.08 2.3.5 E xcessive Deformati o n Analysis The deformation of the flywheel is only dependent on the rotation speed and physical attributes of the flywheel.

The 80-year extension has no impact on the excess i ve deformation analys i s of the flywheel.

The results in [2] remain appl i cable to 80 years of operation. At the flywheel over speed condition of 1500 rpm (1 57.08 radians/secon d}, the change in the bore radius and outer radius is shown in Table 2-7. A maximum deformation of 0.006 inch is anticipated for the flywheel over speed condition.

As deformation is proportional PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 2-7 to the square of angular speed , o}, this represents an increase of 56% over the normal operating deformation of 0.004 inch. This increase would not result in any adverse conditions such as excessive vibrational stress leading to crack propagation , since the f l ywheel assemblies are typ i cally shrunk fit to the f l ywheel shaft , and the deformations ca l culated are negligible. Table 2-7: Flywheel Deformation at 1500 rpm Flywheel Evaluation Group Change i n Bore Rad i us (i nch) Cha n ge in Outer Radius (i nch) 1 0.003 0.006 2 0.003 0.006 2.4

SUMMARY

OF STRESS AND FRACTURE RESULTS The deterministic integrity evaluations i n WCAP-15666-A

[2] remain appl i cable for 80 years of operat i on. The evaluations conc l uded that the RCP motor flywheels have a very high tolerance for the presence of flaws , especially with the 1500 rpm overspeed due to the application of LBB [2]. As noted in [2], the probabilistic assessment evaluates all credible f l ywheel speeds. This TR uses the same probabilistic assessment methodology as [2], which is d i scussed in Section 3. There are no s i gnificant mechanisms for inservice degradation of the flywheels , since they are isolated from the primary coolant environment.

The evaluations presented in this section have shown there is no significant deformation of the f l ywheels , even at maximum overspeed cond i tions. FCG calculations have shown that even w i th a large assumed flaw , the crack growth .for 80 years of operat i on is negligible. Therefore , based on these deterministic evaluations , the flywhee l inspections completed following manufacture and prior to service are sufficient to ensure their integrity during 80 years of service. As discussed in Section 2.2 and [1 and 2), the most likely source of i nservice degradation i s damage to the keyway region that could occur during disassembly or reassembly for refurbishment and inspection. PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-1 3 RISK ASSESSMENT The quantitative risk assessment discussed below provides the justification for applying the WCAP-15666-A

[2] 20-year flywheel inspection interval for 80 years of operation. Specifically, the risk analyses confirms that applying the inspection extension to flywheels in operation up to 80 years has a negligible impact on risk (CDF and LERF), i.e., it is with i n the risk acceptance criteria of RG 1.17 4 [5]. This sect i on provides a discussion on the requirements of [5], and extends the previous flywheel failure probability assessment in [2] to 80 years of operation. 3.1 RISK-INFORMED REGULATORY GUIDE 1.174 METHODOLOGY The NRC risk-informed regulatory framework for modifying a plant's licensing basis is contained in RG 1.17 4, Revision 2 [5]. The intent of this risk-informed process is to allow insights derived from probabilistic risk assessments to be used in combination with traditional engineering analysis to focus licensee and regulatory attention on issues commensurate with their importance to safety. Additional regulatory guidance is contained in [6]. The approach described in RG-1.17 4 is used in each of the application-specific RGs/SRPs , and has four basic steps as shown in Figure 3-1. The four (4) basic steps are discussed below. PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 Define Change Traditional Analysis \ I \ I I \ I \ I \ I \ I \ I \ I ---I I I I I I I I " I " I,,' \ I \ I I , " ... ... Perform -" Engineering

-,.... Analysis PRA " " " " " " " " ,, , , I mplementation and Monitoring Program 3-2 Submit r+ Proposed Change Principal Elements of Risk-Informed, Plant-Specific Decisionmaking (from NRC Regulatory Guide RG-1.174)

Figure 3-1: NRC Regulatory Guide 1.17 4 Basic Steps Step 1: Define the proposed change This element includes identifying

1. Those aspects of the plant's licensing bases that may be affected by the change 2. All systems , structures , and components (SSCs), procedures , and act i vit i es that are covered by the change and consider the original reasons for inclusion of each program requirement

3. Any engineering studies , methods , codes , applicable plant-speci fi c and industry data and operational experience , PRA findings , and research and analysis results relevant to the proposed change. Step 2: Perform engineering analysis This element includes performing the evaluation to show that the fundamental safety principles on wh i ch the plant design was based are not compromised (defense-in-depth attributes are maintained) and that sufficient safety margins are maintained. The engineering analysis includes both traditional deterministic analysis and probab ili stic risk assessment.

The evaluation of risk impact should also assess the expected change in CDF and LERF , including a treatment of uncertainties. The resu lt s from the traditional PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-3 analysis and the probabilistic risk assessment must be considered in an integrated manner when making a decision. Step 3: Define implementation and monitoring program This e l ement's goal is to assess SSC performance under the proposed change by establishing performance monitoring strategies to confirm assumptions and analyses that were conducted to just i fy the change. This is to ensure that no unexpected adverse safety degradation occurs because of the changes. Decisions concerning implementation of changes should be made in light of the uncertainty associated with the results of the evaluation. A monitor i ng program should have measurable parameters , objective criteria , and parameters that provide an early indication of problems before becoming a safety concern. In addition , the monitoring program should include a cause determination and corrective action plan. Step 4: Submit proposed change This element includes: 1. Carefully reviewing the proposed change in order to determine the appropriate form of the change request 2. Assur i ng that information required by the relevant regulation(s) in support of the request is developed

3. Preparing and submitting the request in accordance w i th relevant procedural requirements. PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-4 Five (5) fundamental safety principles are described which should be met for each application for a modification. These are shown in Figure 3-2 and are discussed below. Chcrlge meets rurrent regulations unless it is explicitly related 1o a requested exen,:rtion or rule charge. Use rreasurement strategies to rronitor the change. Qlange is oonsistent wi1h defense-in-depth philosophy.

Integrated Decisionmaking Maintain sufficient safety margins. Proposed increases in COF or risk are small and are oonsistent

'Mth the Cormission

's Safety Policy 9atement.

Figure 3-2: Principles of Risk-Informed Regulation

[5] Principle 1: Change meets current regulations unless it is explicitl y related to a requested exemption or rule change The proposed change is evaluated against the current regulations (including the general design criteria) to either identify where changes are proposed to the cur r ent regulations (e.g., technical specification , license conditions, and FSAR), or where additional information may be required to meet the current regulations. Principle 2: Change is consistent with defense-in-depth philosophy Defense-in-depth has traditionally been applied in reactor design a n d operation to provide a multiple means to accomplish safety functions and prevent the release of radioactive material.

As defined in RG-1.17 4 , defense-in-depth is maintained by assuring that:

• A reasonable balance among prevention of core damage , prevention of containment failure , and consequence mitigation is preserved

• Over-reliance on programmatic activities to compensate for weaknesses in plant design is avoided PWROG-17011-NP May 2018 Revision 1 i -WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-5

• System redundancy , independence , and d i versity are preserved commensurate with the expected frequency and consequences to the system (e.g., no risk outliers)

• Defenses against potential common cause failures are preserved and the potent i a l for i ntroduct i on of new common cause failure mechanisms i s assessed.

• Independence of barriers is no t degraded (the barriers are identified as the fue l cladd i ng , reactor coolant press u re boundary , and containment structure)

• Defenses against human errors are preserved Defense-in-depth philosophy is not expected to change unless:

• A sign i ficant increase i n the existing challenges to the integrity of the barriers occurs

• The probability of fa il ure of each barrier changes significantly ,

• New or addit i onal fai l ure dependencies are i ntroduced that i ncrease the likelihood of fai l ure compared to the existing cond i tions , or

• The overall redunda n cy and d i versity in the ba r r i ers changes. Pr i nciple 3: Maintain suff i cient safety margins Safety margins must also be maintained. As desc r ibed in RG-1.174 , suff i cient safe t y marg i ns are ma i ntained by assuring that:

• Codes and standards , or alternatives proposed for use by the NRC , a r e met , and

• Safety analysis acceptance criteria i n the licens i ng basis (e.g., FSARs , supporting analyses) are met , or proposed rev i sions provide sufficient marg i n to account for analys i s and data uncertainty.

Pr i nc i ple 4: Proposed increases in GDF or risk are small and are consistent with the Commissions Safety Goal Policy Statement To evaluate the proposed change w i th regard to a possible inc r ease in ri sk , the risk assessment should be of sufficient qual i ty to eva l uate the change. The expected change in CDF and LERF are evaluated to address this principle.

An assessment of the uncertainties associated with the evaluation is conducted. Additional qualitative assessments are also performed.

There are two acceptance guidelines , one for CDF and one for LERF , both of which shou l d be used. The guidelines for CDF are:

• If the application can be clearly shown to result in a decrease in CDF , the change will be considered to have satisfied the relevant principle of r i sk-informed regulation with respect to CDF.

• When the calculated i ncrease in CDF is very small , which is taken as l ess than 10-5 per reactor year , the change will be considered regardless of whether there is a ca l culation of the total CDF. PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-6

• When the calculated increase in CDF i s in the range of 1 o-6 per reactor year to 10-5 per reactor year , applications w i ll be considered only if i t can be reasonably shown that the total CDF i s less than 1 0-4 per reactor year.

• Applications which result in increases to CDF above 10-5 per reactor year would not normal l y be considered. AND The guidelines for LERF are:

• I f the app li cat i on can be clearly shown to resu l t in a decrease in LERF , the change wi ll be considered to have sa t isfied the relevant pr i nc i p l e of risk-informed regulation w i th respect to LERF

• When the calculated increase in LERF i s very small , which is taken as being less than 10-7 per reactor year , the change will be considered regardless of whether there is a calculation of the total LERF.

• When the ca l culated increase in LERF i s in the range of 10-7 per reacto r year to 10-5 per reactor year , applications will be considered only if it can be reasonably shown that the total LERF is less than 10-5 per reactor year.

• Applications wh i ch result i n i ncreases to LERF above 10-5 per reactor year would not normally be considered. These guidelines are i ntended to provide assurance that proposed i ncreases in CDF and LERF are small and are cons i stent with the intent of the Comm i ss i on's Safety Goal Policy Statement.

Principle 5: The impact of the proposed change should be monitored using performance

-measurement strategies to monitor the change Performance-based implementation and monitoring strategies a r e a l so addressed as part of the key e l ements of the evaluation as described previously. The following sections address the principle elements of the RG-1.17 4 process and the principles of risk-i nformed regulat i on to RCP motor flywheel exam i nation frequency reduct i on. PWROG-1701 1-NP May 20 1 8 Rev is ion 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-7 3.2 FAILURE MODES AND EFFECTS ANALYSIS A failure modes and effects analysis is used to identify the potential failure modes of a RCP motor flywheel and the effect that each failure mode would have on the plant SSCs in relation to overall plant safety. Failure Modes The primary failure mode of the RCP motor flywheel is growth of an undetected fabrication induced flaw in the keyway of the flywhee l that emanates radially from that locat i on to a point such that it reaches a critical flaw size during normal or accident conditions. Once the critical flaw size i s reached during plant operation , the flywheel has the potential to catastrophically fail, resulting in flywheel fragments , which are essentially high energy missiles that could impact other SSCs i mportant to plant safety. The growth of a flaw is primarily re l ated to stresses generated from changes in the flywheel speed. The flywheel inspection process , which itself has the potent i al to i ntroduce flywheel damage as discussed in [1], i s not considered in the assessment.

This is because the purpose of the assessment is to support interval extension, which will reduce unnecessary occurrences for introducing potential damage. As discussed i n [1], the normal operating speed of the RCP motor flywheel for Westinghouse RCPs is 1189 revolutions per minute (rpm), w i th a synchronous speed of 1200 rpm. It is designed for an overspeed of 1500 rpm , which is 125% of the synchronous speed. The flywheel speed can a l so vary as a result of plant events , including acc i dents such as a double ended guillotine break (DEGB) in the main reactor coolant loop piping. Westinghouse designed flywheels are also used for Calvert Cliffs Units 1 and 2. These plants include Byron-Jackson designed pumps and motors and therefore have different normal flywheel operating speeds and different flywheel accident responses.

The normal operating speed of the RCP motor flywheel for these RCPs is 900 rpm , with a design limiting speed of 1125 rpm. The maximum overspeed following a design basis LOCA is limited to 1368 rpm as stated in the Calvert Cliffs UFSAR and WCAP-15666-A

[2]. When operating as a motor , the rotor of a polyphase induction machine rotates in the direction of , but slightly lower than , the rotating magnetic flux provided by the stator. This slight speed difference is typically expressed in percent and designated slip. If the shaft of the machine is driven above synchronous speed by a prime mover (with line voltage maintained on the stator) the rotor conductors rotate faster than the magnetic flux and the slip becomes negative. The rotor current and consequently the stator current reverse under the condition of negative slip and the machine operates as an induction, or asynchronous , generator.

The RCP motor functions as an efficient torque producer under normal conditions. In the unlikely event that a hydraulic torque is applied to the motor. shaft in the direction of increasing shaft speed (thus acting as a prime mover), the slip would become negative and , with the stator connected to the grid, the motor would function as a dynamic brake. PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-8 If the power supply to the motor is interrupted (zero voltage}, the motor torque would be reduced to a negligible value , since torque is proportional to the supplied voltage. However , a design feature of Westinghouse NSSS plants ensures that the electrical power supply to the RCP will be maintained for at least 30 seconds after a turbine trip following a LOCA. This design feature is also mainta i ned following a loss of offsite power (LOOP); for the expected case of available off-site power , power to the RCP would continue through the LOCA transient.

As a result , reverse torque is provided. Westinghouse also performed several sensitivity studies to evaluate the effect of the break opening area on the RCP flywheel speed for typical Westinghouse NSSS plants. Specifically , break sizes equal to a DEGB of the main coolant piping , 60% of that DEGB, and a 3 ft 2 have been analyzed.

A 3 ft2 break size corresponds to a pipe of approx i mately 23 inches in inside diameter; the only RCS piping greater than this , is the main coolant loop piping. The first two breaks have blowdown times equal to or less than the RCP trip time; therefore, the applied voltage prevents overspeed. The latter break has an extended blowdown time , but the RCP flow at the time of RCP trip is reduced such that the speed decreases.

Smaller breaks are not limiting even though the voltage is maintained for only 30 seconds. Results of these studies were discussed i n [1]. To investigate the consequences of RCP overspeed , [2] analyzed a spectrum of LOCA events resulting in a range of flywheel transients. Results of that analysis indicated that the limiting event was the DEGB with an instantaneous loss of power , this led to a peak flywheel speed of 3321 rpm. It was also noted that the 3 ft 2 break area case showed a decrease in speed such that the normal operating speed is not exceeded. Based on the WCAP-15666-A assessments, the following scenarios are associated with the primary mode of potential failure in the Westinghouse RCP motor flywheel that are related to operating speed and potential overspeed during various conditions

• Failure during normal plant operation resu l ting in a plant tr i p (1200 rpm peak speed)

• Failure of the RCP motor flywheel associated with a plant transient or LOCA event with no loss of electrical power to the RCP (1200 rpm peak speed)

• Failure of the RCP motor flywheel associated with a plant transient or LOCA event (up to 3 ft 2 with an instantaneous loss of electrical power to the RCP (1200 rpm peak speed)

• Failure of the RCP motor flywheel associated with a DEGB coincident with an instantaneous loss of electrical power , such as LOOP (3321 rpm peak speed). This case bounds and is conservatively applied to all flywheel transients for LOCA break areas. WCAP-15666-A

[2] was limited in scope to RCPs with Westinghouse supplied pumps and flywheels. It is also the intent of this topical report to extend the applicability of the flywheel inspection extension to Calvert Cliffs Units 1 and 2 which contain Byron Jackson RCPs but use Westinghouse supplied flywheels. It is important to note that as a result of significant design differences between the Westinghouse and Calvert Cliffs PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-9 units , the Calvert Cliffs RCP operational and transient conditions are different.

Specifically , Calvert Cliffs pumps normally operate at 900 rpm with a design speed of 1125 rpm. Furthermore , the peak RCP post LOCA speed is limited to 1368 rpm. Therefore , the Calvert Cliffs Units 1 and 2 Pump/Flywheel Combinations analyses were based on the following:

• Failure during normal plant operation resulting in a plant trip (1125 rpm peak speed)

• Failure of the RCP motor flywheel associated with a plant transient or LOCA event w i th no loss of electrical power to the RCP (1125 rpm peak speed)

• Failure of the RCP motor flywheel associated with a plant transient or LOCA event ( up to 3 ft 2) with an instantaneous loss of electrical power to the RCP ( 1125 rpm peak speed)

• Failure of the RCP motor flywheel associated with a DEGB coincident with an instantaneous loss of electrical power , such as , loss of offsite power (LOOP) (1368 rpm peak speed). As for the Westinghouse flywheel analysis , this case is conservatively assumed to bound all flywheel transients for LOCA break areas resulting from equivalent reactor coolant pipe breaks greater than a 3.0 ft 2 break and less than a double ended break. Failure Effects The failure of the RCP motor flywheel during normal plant operation would directly result in a reactor trip. However , the potential indirect or spatial effects associated with a postulated flywheel failure present a greater challenge in terms of failure effects or consequences. As discussed previously , the flywheel has the potential to catastrophically fail , resulting in flywheel fragments , which are essentially high energy missiles , which could impact other SSCs important to plant safety. Failure of these other SSCs could potentially impact the overall plant safety in terms of core damage (e.g., as a result of the loss of safety injection) or large, ear l y release (as a result of potential impacts on containment structures or systems). In order to address plant specific design differences on a generic basis, it is conservatively assumed that failure of the RCP motor flywheel results in core damage and a large early release, i.e., the flywheel failure frequency is equal to CDF and LERF. Section 3.3 d i scusses the process for estimating the likelihood of the primary failure mode of the RCP motor flywheel.

Section 3.4 then combines this failure probability estimation with the likelihood of various plant events and consequences to estimate the change in risk for extending the flywhee l examination interval from 1 O years to 20 years , for RCP/Flywheels in service up to 80 years. 3.3 FLYWHEEL FAILURE PROBABILITY To investigate the effect of flywheel inspections on the risk of failure, a structural reliability and risk assessment is performed , a 40-year plant life including up to 80 years PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-10 of operation. Twelve (12) month operating (or fuel) cycles are conservatively assumed for the evaluation. This section discusses the methodology used and summarizes the results from this assessment.

As described in Section 3.2, the Westinghouse RCP has a normal operating speed of 1189 rpm , a synchronous speed of 1200 rpm , and a design speed of 1500 rpm , per [2]. Therefore , a peak speed of 1500 rpm is conservatively used in the evaluation of RCP motor flywheel integrity to represent all conditions except a OEGB coincident with an instantaneous loss of electrical power. For this more limiting event , a peak speed of 3321 rpm is used. The structural reliability evaluation for a Westinghouse RCP utilizes the work previously performed and summarized in [1], where the 1500 rpm design speed had been assumed. In addition , this evaluation builds upon the initial analysis discussed in [2]. The structural reliability evaluation for the Calvert Cliffs RCP is based on plant-specific analyses and flywheel failure probabilities which are based on nominal and transient flywheel operation at 1125 rpm and a post design basis LOCA flywheel transient overspeed of 1368 rpm. 3.3.1 Method of Calculation Failure Probabilities The method for calculating flywheel failure probabilities is based on the method in WCAP-15666-A

[2]. The probability of failure of the RCP motor flywheel as a function of operating time t , Pr(t < t1 ), is calculated directly for each set of input values using Monte-Carlo simulation with importance sampling.

The Monte-Carlo simulation does not force the calculated distribution of time to failure to be of a fixed type (e.g., Weibull, Log-normal or Extreme Value). The actual failure distribution is estimated based upon the dist r ibutions of the uncertainties in the key structural reliability model parameters and plant specific input parameters. Importance sampling, as described by Witt [7], is a variance reduction technique to greatly reduce the number of trials r equired for calculating small failure probabilities. In this technique, random values are selected from the more severe regions to increase the probability of an observable failure occurring.

However , when a failure is calculated , the count is corrected to account for the lowe r probability of simultaneously obtaining all of the more severe random values. The application of the probability of failure methodology is described based on the Westinghouse RPFWPROF program which is generally described in WCAP-14535A

[1] and WCAP-15666-A

[2]. The description of the key input parameters and associated data used in the RPFWPROF program is presented in Table 3-1 and Table 3-2. Table 3-1 includes the key parameters needed for failure probability calculation. Its usage in the program is specified as shown in the last column of Table 3-1 and schematically in the flow chart of Figure 3-3. " Initial" conditions do not change with time , " Steady-State" is not needed for RPFWPROF , " Transient" calculates fatigue crack growth and "Failure" checks to see if the accumulated crack length exceeds the critical length. In addition , parameter OLE is included in the model to address the impact of design limiting events (OLE). PWROG-17011-NP May 2018 Revision 1

,-------WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-11 Table 3-1: Variables for RCP Motor Flywheel Failure Probability Model No. Name Description of Input Variable Usage Type 1 ORAD I US Outer Flywheel Radius (inch) I nitial 2 IRADIUS Inner Flywheel Radius (inch) Initial 3 PFE-PSI Probability of Flaw Existing (PFE) after Preservice ISi Initial 4 ILENGTH Initial Radial Flaw Length (inch) I nitial 5 CY1-I SI Operating Cycle for F i rst lnservice Inspect i on Inspection 6 DCY-ISI Operating Cycle between lnservice Inspect i ons Inspection 7 POD-ISi Flaw Detection Probability per l nservice Inspection Inspection 8 DFP-ISI Fraction PFE Increases per lnservice Inspection Inspection 9 NOTR/CY Number of Transients per Operating Cycle Transient 10 DRPM-TR Speed Change per Transient (RPM) Transient 11 RATE-FCG Fatigue Crack Growth Rate (In ch/Transient)

Transient 12 KEXP-FCG Fatigue Crack Growth Rate SIF Exponent Transient 13 RPM-OLE Speed for Design Limiting Event (RPM) Failure 14 TEMP-F Temperature for Design Lim iti ng Event (F) Failure 15 RT-NDT Reference Nil Ductility Transition Temperature (F) Failure 16 F-KIC Crack Initiation Toughness Factor Failure 17 DLENGTH Flywheel Keyway Radial Length (Inch) Failure Variables 5 to 8 are available to calculate the effects of an ISi in the RPFWPROF program. The effect of ISi calculated using these equations , which are used in the SRRA model for the effect of ISi, are consistent with those described in the pc-PRAISE Code User's Manual [1 O]. The parameters needed to describe the selected ISi program are the time of the first inspection , the frequency of subsequent inspections (expressed as the number of fuel or operating cycles between inspections) and the probability of non-detection as a function of crack length. For the RCP motor flywheel , the detection probability, which is independent of crack length , is simply one minus a constant value of detection probability , variable 7 (POD-ISi) in Table 3-1. An i ncrease in failure probability due to RCP inspection (chance of incorrect disassembly and reassembly) is included in the ISi model but conservat i vely not used (variable 8 set to zero) in this evaluation. The median input values and their uncertainties for each of the parameters of Table 3-1 are shown in Table 3-2. The median is the value at 50% probability (half above and half below this value); it is also the mean (average) value for symmetric distributions , like the normal (bell-shaped curve) distribution. Uncertainties are based upon expert engineering judgment and previous structural reliabil i ty modeling experience. For example, the fracture toughness for initiation as a function of the RT N or and the uncertainties on these parameters are based upon prior probabilistic fracture mechanics analyses of the reactor pressure vessel (RPV) [11]. Also note that the stress intensity factor calculation for crack growth and failure used the flywheel keyway radial length in addition to the calculated flaw length. PWROG-17011-NP May 2018 Revision 1 No. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 * ** *** **** WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-12 Table 3-2: Input Values for RCP Motor Flywheel Failure Probability Model Name Median Distribution Uncertainty*

ORADIUS Per Flywheel Group Constant --*---IRADIUS Per Flywheel Group Constant --*--*-PFE-PSI 1.000E-01 Constant ----*-ILENGTH 1.000E-01 Log-Normal 2.153E+OO CY1-ISI 3.000E+OO Constant ----DCY-ISI 4.000E+OO Constant ----POD-ISi 5.000E-01 Constant -*----DFP-ISI O.OOOE+OO Constant -----NOTR-CY 1.000E+02 Normal 1.000E+01 DRPM-TR**** 9.00E+02 (CCNPP) Normal 9.00E+01 (CCNPP) 1.200E+03 (W) 1.200E+02 (W) RATE-FCG 9.950E-11 Log-Normal 1.414E+OO KEXP-FCG 3.070E+OO Constant ---*--RPM-DLE 1.500E+03** Normal 1.500E+02** TEMP-F*** 7.0E+01 (CCNPP) Normal 1.250E+01 9.500E+01 (W) RT-NDT 3.000E+01 Normal 1.700E+01 F-KIC 1.000E+OO Normal 1.000E-01 DLENGTH Per Flywheel Group Constant ---*--The uncertainty is a normal standard dev i ation , the range (med i an to max i mum) for uniform distr i butions or the corresponding factor for logarithmic distr i but i ons. RPM-DLE is mod i fied in each case to allow for risk analys i s of various p l ant conditions and their associated flywheel speeds for both Westinghouse Plants and Calvert C li ffs U n its 1 and 2. The values used for th i s variable are discussed in Table 3-3. TEMP-F is set to 95°F for Westinghouse P l ants (W) and 70°F for Calvert Cliffs Un i ts 1 and 2 (CCNPP). DRPM-TR is set to 1200 RPM for Westinghouse plants (W) and 900 RPM for Calvert C li ffs Units 1 and 2 (CCNPP). PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-1 3 Group specific input variables used in the probability of failure calculations are summarized below: Flywheel Group ORadius (inch) !Radius (inch) Dlength (inch) Group1 38.25 4.6875 0.937 Group 2 38.875 4.1875 0.906 Calvert Cliffs 41.00 4.719 0.937 Evaluations were performed to determine the effect on the probability of flywheel failure for continuing the previously approved current inservice inspections in accordance with Reference

[2] over the life of the plant through 80 years of operation and for discontinuing the inspections.

The evaluation also calculated the effects of the inspections being discontinued after ten years. This calculation bounds the effects of any subsequent inservice inspections at 10-to 20-year intervals.

The probability of failure determined by these evaluations is a conservatively calculated parameter because the evaluation conservatively assumes that the probability of a flaw existing after the preservice inspection is 10%, and that the ISi flaw detection probability is only 50%. In reality , most preservice inspection and ISi flaws would be detected , especially for the larger flaw depths which could result in failure. Therefore , the calculated values are very conservative. (The effects of some important parameters on the calculated probability of failure are discussed later in this section). The most important result of the evaluation is the change in calculated probability of failure from continuing versus discontinuing the ISi after 1 O years of plant life. As shown in Figure 3-4 , Figure 3-5 and Figure 3-6 and Table 3-3, the ISi provides a negligible benefit for minimizing the potential of failure of the flywheel.

The results of this assessment are summarized as follows for a plant life of 40 , 60 , and 80 years. PWROG-17011-NP May 2018 Revision 1 l -*-* ---------------------WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-14 Table 3-3: Cumulative Probability of Failure over 40, 60 and 80 Years with and without lnservice Inspection

<1> Cumulative Probability of Cumulative Probability of % Increase in Cumulative Design Flywheel Flywheel Failure with ISi at 4-Failure Probability for Limiting Failure Year Intervals Prior to 10 Years Eliminating Inspections Flywheel Speed with ISi at and without ISi after 10 Years Group (rpm) 4-Year Intervals Over 40, 60 Over 40 Over 60 Over80 Over Over 60 Over 80 40 & 80 Years Years Years Years Years Years Years 1 1500 2.39E-7 2.44E-7 2.49E-7 2.52E-7 2.2% 4.5% 5.4% 2 1500 1.29E-7 1.32E-7 1.34E-7 1.35E-7 2.4% 3.5% 4.5% 1 3321 9.87E-3 9.89E-3 9.89E-3 9.99E-3 0.1% 0.2% 1.2% 2 3321 9.0 1 E-3 9.09E-3 9.09E-3 9.09E-3 0.1% 0.1% 0.1% Calvert 1125 1.50E-8 1.51 E-8 1.51 E-8 1.52E-8 0.5% 0.6% 0.8% Cliffs Calvert 1368 5.56E-6 5.56E-6 5.62E-6 5.63E-6 0.3% 1.4% 1.5% Cliffs Note: (1) Results a r e s li ght l y d i fferen t f r om Tab l e 3-8 i n [2]. D i fferences a r e on t h e o r de r o f 2% and d o no t i mpact a ny co n c l us i ons i n th i s ana l ys i s or i n (2]. As can be seen in Table 3-3 , continuing inspection after 1 O years has a very minimal impact on the failure probabilities.

Note that for the l imiting speed of 3321 rpm , the flywheel failure probability i s -1.0E-2 from the first through the 80th year of operation for Flywheel Group 1. It is approximately constant at 9.09E-3 from the first through the 80th year of operation for Flywheel Group 2. The post LOCA limiting speed of Calvert Cliffs Units 1 and 2 of 1368 RPM resulted in reduced failure probabilities , w i th the equivalent post-LOCA failure probability for a Westinghouse RCP (with a peak speed of 3321 rpm). The Calvert Cliffs cumulative flywheel failure probability for the limiting DEGB LOCA overspeed event was only -5.6E-6. 3.3.2 Sensitivity Study A sensitivity study was performed to determine the effect of select flywheel risk assessment parameters on the probability of failure , as done in [2]. Consistent with [2], sensitivity studies were performed on a Westinghouse Group 1 O flywheel , as this flywheel is representative of average Westinghouse and Byron Jackson flywheel dimensions and configuration. The intent of the sensitivity studies was to illustrate the impact of relatively significant changes to model input parameters on probability of failure predictions. The specific parameters evaluated in this sensitivity study were the PWROG-1701 1-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-1 5 probability of detection and the in i t i a l flaw le n gth. The results of th i s study are summarized i n the Table 3-4 and sections 3.3.2.1 and 3.3.2.2. Table 3-4: Effect of Flywheel Risk Parameter on Failure Probability (Flywheel Group 10) Description of Flywheel Risk Probability of Flywheel Probability of Flywheel Parameter Varied Failure after 40 years Failure after 40 years with with ISi prior to and ISi prior to 1 O years and after 1 O years without ISi after 1 O years Base Case (G r oup 10 of [1]) 1.00E-07 1.04E-07 P r obabil i ty of Detection of 1 0% 1.02E-07 1.04E-07 Probability of Detect i on of 80% 1.00E-07 1.04E-07 In iti al flaw leng t h of 0.05 inches 4.57E-08 4.71 E-08 Init i al flaw length of 0.20 inches 2.97E-07 3.00E-07 The values for the base case were for:

• 10% probability of a f l aw ex i st i ng after preserv i ce inspect i on

• an i ni ti a l f l aw lengt h of 0.1 0 i nch (1.006 i nc h wi th keywa y)

• an i n iti al ISi at 3 years of plant life , and subsequent inspec t io n s at 4-year i nterva l s

• probab ili ty of detect i on of 50% per ISi (see [1], Table 5-5 , flywheel Group 1 0) A d i scussion of the resu l ts of the sens i t i v i ty studies a r e summar i zed below. 3.3.2.1 Sensitivity to Change in Flaw Detection Probability The flaw detection probab ili ty was var i ed f r om the base case 50% to 10% and 80%. The fa il ure probab ili ty increased approximate l y 3% for a decrease i n fla w detection probabi l ity from 50% to 10%. The fa i lure probabi li ty did not change for an i ncrease i n flaw detection probability from 50% to 80%. Therefore , the flaw detection probability , wh i ch i s a measure of how well the inspections are performed , has essent i a ll y no effec t on the f l ywheel fa i lure probability. 3.3.2.2 Sensitivity to Initial Flaw Length The initial flaw l ength was varied from the base case value of 0.1 0 inch to 0.05 i nch , and 0.20 i nch. The failure probab i lity decreased by 54% for a decrease in initia l flaw length from 0.1 O inch to 0.05 i nch , and the failure probability tripled for an increase i n in i tia l flaw length from 0.1 O inch to 0.20 i nch. Therefore , the in i tial flaw length does affect the flywheel failure probability , but the failure probab i l i ty i s small , even for l arger in i tial fla w lengths. Moreover , it is expected that the probab ili ty of the larger flaw be i ng missed during preservice i nspect i on i s smaller than the assumed 10% based on rev i ews of preserv i ce i nspection records i n [2]. PWROG-1701 1-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-16 3.3.3 Failure Probability Assessment Conclusions An evaluation of flywheel structural reliability was performed for each of the flywheel groups selected for evaluation following the process outlined in WCAP-15666-A.

Using conservative input values for; preservice flaw existence , initial flaw length , inservice flaw detection capabil ity and RCP start/stop transients , it was shown that flywheel inspections beyond ten years of plant life have no sign i ficant benefit relative to the probability of flywheel failure. The reasons are that most flaws that could lead to failure would be detected during the preservice inspection or early in the plant life , and the crack growth is negl i gible over the plant life. It should be noted that the effect on potential flywheel failure from damage through disassemb l y and reassembly for inspection has not been evaluated. This is because the purpose of the assessment is to support an inspection interval extension , wh i ch will reduce unnecessary occurrences for i ntroducing potential damage. Sensitiv i ty studies showed that improved flaw detection capability and more inspections result in a small relative change in the calculated failure probability. The failure probability is most affected by the initial flaw length and its uncertainty. These parameters are determined by the accuracy of the preservice inspection. The uncertainty cou l d be reduced using the results from the first inservice i nspection , but would probably not change much during subsequent i nspections. The failure probability estimates identified i n [2] show that inspections after 10 years have a very minimal impact on the failure probabilities. These resu l ts bound the effects of any subsequent ISi at 10 to 20 year intervals.

No credit has been t aken for other indications of potential degradation such as pump vibration mon i tor i ng and pump maintenance PWROG-1701 1-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-17 READ IN I NtTIAL.IZE STEADY-STATE CHANGES -UNCERTAINTIES PARAMETERS e:. \} TRANSIENT CHANGES \] CME:CK 11'" NO NEXT FAILURE _r-.. TIME -OCCURS? STEP YES YES \} \} NO CALCULATE EFFECTS O F PRINT OUT NE.XT PROBAB I LITY RANDOM FJ FAILURE I Si OR -T R I AL? PROBAB I LITY MONITORING WITH TIME Figure 3-3: Westinghouse PROF P r ogram Flow Chart for Calculating Failure Probability PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 Probability of Failure: Westinghouse Group 1 Flywheel 3.00E-07 .,------------------

2.80E-07 +-----------------

2.60E-07 r--------:.,~--~IRI_.._

Probability of _ __/ Failure PWROG-17011-NP

-2.40E-07 -+------------------

2.20E-07 +------------------

2.00E-0 7 +-----------------

0 20 40 Year 60 80 Figure 3-4: Probability of Failure for Flywheel Evaluation Group 1 3-18 ..,._Group 1: w/o I S i _._Group 1: w/ I S i May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-1 9 Probability of Failure: Westinghouse Group 2 Flywheel 2.00E-07 1.80E-07 1.60E-07 Probability of ---Failure ------:.. .. -=----=--------G r oup 2: w/o I S i 1.40E-07 --Gr oup 2: w/l S I 1.20E-07 1.00 E-07 0 20 40 60 80 Yea r Figure 3-5: Probability of Fa il ure for Flywheel Evaluation Group 2 PWROG-1701 1-NP May 2018 Revision 1 _j PWROG-17011-NP WESTINGHOUSE NON-PROPRIETARY CLASS 3 0 Probability of Failure: Calvert Cliffs Flywheel 20 40 Year 60 8 0 ~CCw/151 -CCw/olSI 3-20 Figure 3-6: Probability of Failure for Calvert Cliffs Units 1 and 2 May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-21 3.4 CORE DAMAGE EVALUATION The objective of the risk assessment is to evaluate the core damage risk from the extension of the examination of the RCP motor flywheel, over an extended 80 year service duration, relative to other plant risk contributors through a qualitative and quantitative evaluation. RG 1.17 4, Revision 2 [5] provides the basis for this evaluation and also provides the acceptance guidelines to make a change to the current licensing basis. Risk is defined as the combination of likelihood of an event and severity of consequences of an event. Therefore , the following two questions are addressed:

• What is the likelihood of the event?

• What are the consequences?

The following sections discuss the likelihood and postulated consequences. The likelihood and consequences are then combined in the risk calculation and the results of the evaluation are presented. Several different scenarios have been identified for potential RCP motor flywheel failures that are related to its operating speed and potential overspeed under certain conditions.

These scenarios are summarized in Table 3-5. Table 3-5: Summary of Flywheel Analysis Parameters Westinghouse RCP/Flywheel (rpm) Failure during normal plant opera tion resulting in a 1500* plant trip Failure of the RCP motor flywheel associated with 1500* a plant transient or LOCA event with NO loss of electrical power to the RCP Failure of the RCP motor flywheel associated with 1500* a plant transient or LOCA event (up to a three square foot break in the main loop) with loss of electrical power to the RCP Failure of the RCP motor flywheel associated with 3321 a large LOCA (from a greater than 3 ft2 break up to the DEGB of the RC loop piping) coincident with an instantaneous electrical power loss (e.g., loss of offsite power (LOOP) or loss of electrical power to the RCP) and therefore no electrical braking to the RCP

• RPM are based on the maximum design speed. PWROG-17011-NP Calvert Cliffs RCP/Flywheel (rpm) 1125* 1125* 1125* 1368 May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-22 3.4.1 What is the Likelihood of the Event The likelihood is addressed by identifying a plant transient or LOCA event combined with the postulated failure of the flywheel and estimating the probability

/fr equency of these events. The likelihood of the flywheel failure is discussed in Section 3.3 and the results are provided in Table 3-3 for the two flywheel evaluation groups that bound the other flywheel groups and for the Calvert Cliffs Units 1 and 2 flywheels.

The estimated failure probab iliti es for the different conditions for the various flywheel types and event combinations are shown in Table 3-6. Table 3-6: Estimated RCP Motor Flywheel Failure Probabilities Cumulative Probabilities of Flywheel Cumulative Probabilities of Failure over 60 Years* Flywheel Failure over 80 Years* With ISi at 4-Year With ISi at 4-Flywheel Group Year Intervals and Conditions*

With ISi at 4-Year Intervals Prior to With ISi at 4-Prior to 10 Intervals 10 Years and Year Intervals Years, and without ISi after without ISi after 10 Years 10 Years Group 1 -2.39E-07 2.49E-07 2.39E-07 2.52E-07 Normal/ Accident* Group 1 -9.87E-03 9.89E-03 9.87E-03 9.99E-03*** LOCA/LOOP* Group 2 -1.29E-07 1.34E-07 1.29E-07 1.35E-07 Normal/Accident

• Group 2 -9.09E-03 9.09E-03 9.09E-03 9.09E-03 LOCA/LOOP*

Calvert Cl iff s Units 1.SOE-08 1.51 E-08 1.SOE-08 1.52E-08 1&2-Normal/ Acc i dent** Calvert Cliffs Units 5.54E-06 5.62E-06 5.54E-06 5.63E-06 1 &2-LOCA/LOOP

• For the failure probability calculat i ons the mean flywhee l speed for normal/acciden t conditions is 1500 rpm; for LOCA/LOOP is it 3321 rpm. ** For the failure probability ca l cu l ations the mean flywheel speed for normal/accident conditions is 1125 rpm; for LOCA/LOOP i s it 1368 rpm. *** Selected as bounding value PWROG-17011-NP May 2018 Rev i sion 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-23 3.4.2 What are the Consequences?

The consequence evaluation is performed to identify the potential consequences from the failure of the RCP motor flywheel from an integrity standpoint.

The consequences are briefly discussed in Section 3.2. The consequence evaluation includes both direct effects and indirect effects of a flywheel failure. Direct effects are those effects associated directly with the component being evaluated , such as loss of process fluid flow. Indirect effects are those effects on surrounding equipment that may be impacted by mechanisms such as jet impingement , pipe whip , missiles , and flooding. The direct consequences are defined as failure of the RCP motor flywheel resulting in a failure of the RCP. If a failure of the RCP occurs , a reactor trip would result. The potent i al indirect or spatial effects associated with the postulated flywheel failure are associated with the potential missiles generated from the fragmented portions of the flywheel associated with a significant flywheel crack. For this evaluation, the conditional core damage probability associated with the failure of the flywheel will be assumed to be 1.0 (no credit for safety system actuation to mitigate the consequences of the failure). 3.4.3 Risk Calculation Th i s methodology is described in detail in WCAP-14572 , Revis i on 1-NP-A , Supplement 1 [9]. For failures that cause only an initiating event , the portion of the PRA model that is impacted is the initiating event and its frequency.

The core damage frequency from the failure is calculated by: CDF =IE* CCDP 1 E Where: CDF = Core Damage Frequency from a failure (events per year) CCDP 1 E = Conditiona l Core Damage Probabil i ty for the Initiator IE = In i tiating Event Frequency (in events per year) The initiating event frequency (in events per year) is obtained differently for the different cond i tions. For the normal operating mode , the init i ating event frequency is determined from the RCP motor flywheel failure probability model as described in Section 3.3. Because the model generates a probabil i ty , the probability must be transformed into a failure rate. The cumulative probability at a given t i me is divided by the number of years to end of operating license. In other words , IE= FP/EOL where: FP = Failure probability from fa i lure probability model (dimensionless)

PWROG-17011-NP May 2018 Revis i on 1

---

WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-24 EOL = Number of years used in the failure probability model (80 years used to cover an extended plant life). Between 40 and 80 years , the failure probability is relatively constant.

For the RCP motor flywheel failure following an overspeed event , the core damage frequency of associated with that event (initiating event with flywheel failure) is defined as: CDF =(IE* CFP)

• CCDP where: CDF = Core Damage Frequency from a failure (events per year) CCDP = Conditional Core Damage Probability for the initiator and flywheel failure IE = Initiating Event frequency (in events per year) CFP = Conditional Failure Probability of the flywheel by initiating event The frequencies of the initiating events for the different conditions were identified as follows: The initiating event frequency for a plant trip or non-LOCA transient is estimated as 1 event/year (plants on average experience 1 plant trip per year). The probability of a loss of offsite power or loss of power to the RCP following a plant trip was conservatively established from NUREG/CR-6890

[14) as 0.01. This value was based on the observation that the conditional LOOP probability had increased from 0.003 in the 1986-1996 time frame to 0.0053 based on 1997 to 2004 data. Furthermore , the authors noted that the conditional probability in the summer mont h s increase to 0.0091. The LOOP conditional on a LOCA event was estimated from Table 4.2 of NUREG/CR-6538

[13) as 1.4E-02 for PWR plants. LOCAs < 3 ft 2 and other plant transient events were conservatively combined, and the probability of a plant transient , concurrent with a LOOP, was conservatively represented by 0.014 and was used. The frequency of a large break LOCA events with break areas in excess of 3 tt2 (-23 inches in diameter) was estimated from NUREG-1829

[12). Mean failure rates of piping are presented in Table 7.19 of that reference. Using 25 and 40 year failure rates , failure rates provided in that table were linearly extrapolated to 60 years and 80 years and then interpolated to obtain a mean frequency of exceeding 3.0 ft 2 , Using this process the LOCA exceedance frequency for break areas > 3 ft 2 was estimated to be approximately 3.8E-07 per year. For this analysis , the LOCA IE was assigned a bounding value of 1 E-06 per year. Table 3-7 , Table 3-8, and Table 3-9 show the calculations that were used to estimate the frequency of the initiating event combined with the probability of the RCP motor flywheel failure. These calculations are also estimates of the core damage frequency given that the assumption of the CCDP is set to 1.0 (no credit taken for any safety systems). The resulting calculat i ons show that the change in CDF for flywheel Evaluation Group 1 is 1.33E-08/year/RCP , the change in the CDF for flywheel Evaluation Group 2 is 6.00E-09/year/RCP and the change in the CDF for the Calvert C l iffs flywheel is PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-25 1.30E-10/year/RCP. The RG-1.17 4 criteria for an acceptable change in risk for CDF are 1 E-06/year and for LERF is 1 E-07/year. These calculations show the change in risk from extending the inspection interval for the RCP motor flywheel continues to remain less than the acceptance criteria. PWROG-17011-NP May 2018 Revision 1 WES T INGHOUSE NON-PROPRIETARY CLASS 3 3-26 Table 3-7: Westinghouse RCP Motor Flywheel Evaluation Group 1 I n i tiating Condition Event Likelihood of RCP Motor Flywheel Frequency Failure (@80 years) (per year) With ISi after Without ISi after 10 Years 10 Years 1. Normal Operating Condition NIA 2.39E-07 2.52E-07 2. Failure of the RCP motor flywheel associated with a plant with NO loss 1 2.39E-07 2.52E-07 of electrical power to the RCP (1200 rpm peak speed)** 3. Failure of the RCP motor flywheel associated with a plant transient 1.40E-02 2.39E-07 2.52E-07 (including LOCA event (up to a 3 ft 2 break in the RCS loop piping)) with loss of electrical power to the RCP (1200 rpm peak speed)** 1.0 X (1.4E-02)

4. Failure of the RCP motor flywheel associated with a large LOCA (from 1.40E-08 9.87E-03 9.99E-03 a greater than 3 ft' break up to a DEGB of the RCS loop piping) coincident with an instantaneous power loss (e.g., loss of offsite power (LOOP) or loss of electrical power to the RCP) and therefore no electrical braking effects (3321 rpm peak speed) Totals Change in CDF for one Flywheel (per RCP risk) Change in CDF for 4 RCPs (4 Flywheels)

.... The peak speed is 1200 rpm , however , 1500 rpm is used for the failure probability calculations. PWROG-17011-NP Event with RCP Motor Flywheel Failure (and Core Damage Frequency, CCDP = 1.0) (per With IS After 10 Years 2.98E-09 2.39E-07 3.34E-09 1.38E-10 2.45E-07 year) Without ISi after 10 Years 3.15E-09 2.52E-07 3.52E-09 1.4E-10 2.588E-07 1.33E-08 5.32E-08 May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 Table 3-8: RCP Motor Flywheel Evaluation Group 2 Initiating Condition Event Likelihood of RCP Motor Flywheel Frequency Failure (@80 years) (per year) With ISi after Without ISi after 10 Years 10 Years 1. Normal Operating Condition N/A 1.29E-07 1.35E-07 2. Failure of the RCP motor flywheel associated with a plant with NO loss of 1 1.29E-07 1.35E-07 electrical power to the RCP (1200 rpm peak speed)** 3. Failure of the RCP motor flywheel associated with a plant transient 1.40E-02 1.29E-07 1.35E-07 (including LOCA event (up to a 3 ft 2 break in the RCS loop piping)) with loss of electrical power to the RCP (1200 rpm peak speed)** 1.0 x (1.4E-02)

4. Failure of the RCP motor flywheel associated with a large LOCA (from a 1.40E-08 9.09E-03 9.09E-03 greater than 3 ft' break up to a DEGB of the RCS loop piping) coincident with an instantaneous power loss (e.g., loss of offsite power (LOOP) or loss of electrical power to the RCP) and therefore no electrical braking effects (3321 rpm peak speed) Totals Change in CDF for one Flywheel (per RCP risk) Change in CDF for 4 RCPs (4 Flywheels)

• • The peak speed i s 1200 rpm , however , 1500 rpm is used for the failure probabil i ty ca lculations.

PWROG-17011

-NP 3-27 Event with RCP Motor Flywheel Failure (and Core Damage Frequency, CCOP = 1.0) (per With IS After 10 Years 1.61 E-09 1.29E-07 1.81 E-09 1.27E-10 1.33E-07 year) Without ISi after 10 Years 1.69E-09 1.35E-07 1.89E-09 1.273E-10 1.39E-07 6.00E-09 2.40E-08 May 2018 Revis i on 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-28 Table 3-9: Calvert Cliffs Units 1 and 2 RCP Motor Flywheel Evaluation Initiating Condition Event Likelihood of RCP Motor Flywheel Frequency Failure (@80 years) (per year) With 151 after Without 151 after 10 Years 10 Years 1. Normal Operating Condition N/A 1.50E-08 1.52E-08 2. Failure of the RCP motor flywheel associated with a plant with NO loss of 1 1.50E-08 1.52E-08 electrical power to the RCP (900 rpm peak speed)** 3. Failure of the RCP motor flywheel associated with a plant transient 1.40E-02 1.50E-08 1.52E-08 (including LOCA event (up to a 3 ft 2 break in the RCS loop piping)) with loss of electrical power to the RCP (900 rpm peak speed)** 1.0 x (1.4E-02)

4. Failure of the RCP motor flywheel associated with a large LOCA (from a 1.40E-08 5.54E-06 5.63E-06 greater than 3 ft' break up to a DEGB of the RCS loop piping) coincident with an instantaneous power loss (e.g., loss of offsite power (LOOP) or loss of electrical power to the RCP) and therefore no electrical braking effects (3321 rpm peak speed) Totals Change in CDF for one Flywheel (per RCP risk) Change in CDF for 4 RCPs (4 Flywheels)

• • The peak speed is 900 rpm , however , 1125 rpm is used for the failure probability calculations. PWROG-17011-NP Event with RCP Motor Flywheel Failure (and Core Damage Frequency, CCDP = 1.0) (per With 15 After 10 Years 1.88E-10 1.SOE-08 2.11E-10 7.76E-14 1.54E-08 year) Without 151 after 10 Years 1.90E-10 1.52E-08 2.12E-10 7.87E-14 1.557E-08 1.30E-10 5.20E-10 May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-29 3.5 CONSIDERATION OF UNCERTAINTY This section provides a discussion of uncertainties associated with the core damage risk assessment.

The discussion follows the general guidance of NUREG-1855

[15) in that the potential key model assumptions and uncertainties are identified and their impact is evaluated with respect to the current application.

The baseline risk assessment discussed in Section 3.4 includes several significant conservatisms which are intended to bias the results of the analysis in a conservative direction.

Specifically , these assumptions include: 1. All flywheel failure events result in both core damage and a large early release. This tacitly assumes that the missiles generated by the flywheel will result in both an unrecoverable LOCA and a loss in containment integrity sufficient to support a large re l ease of radionuclides. This is a highly unlikely sequence as events resulting from a reactor trip would have control rods inserted prior to the failure and the potential for flywheel fragments to render all safety injection flow paths unavailable is unlikely. Furthermore, there is virtually no likelihood that flywheel fragments could significantly impact the ability of the containment to perform its function or prevent containment isolation. 2. The f l ywheel failure probability is based on a bounding selection of rotational flywheel speeds. This assumption is intended to simplify the event grouping while upwardly biasing the flywheel failure probabilities. The flywheel failure probability model used to assess the failure probability has been developed as a realistic model. Details of that model are provided in [2] and a sensitivity study to typical input assumptions is provided in Section 3.2. 3. Non-LOCA plant events that could result in a LOOP were assigned a LOOP probability of 0.014. This value is representative of the conditional LOCNLOOP failure probability and as previously discussed overstates the LOOP potential for the more likely events. 4. The failure probabilities of flywheels are based on the cumulative failure probability over the lifetime of the flywheel.

This is conservative because the failure rates are observed to stabilize during the later years of operation. While these assumptions are intended to provide a bounding estimate of risk , uncertainty associated with other parameters may be of interest in understanding the potential risks of the risk evaluation. As discussed in Section 3.4 , the risk of the inspection interval extension to 80 years has three elements: the frequency of the initiating event, the probability of flywheel failure associated with an event, and the conditional probability of core damage associated with the failure. Sensitivity studies were performed to investigate the potential impact in changes to the risk assessment modeling assumptions. The results of these studies are included in Table 3-10. The uncertainty associated with each of these factors is discussed below. PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-30 3.5.1 Initiating Event Frequency As discussed in Table 3-7 through Table 3-9 the flywheel failure risks are assigned to four bins: normal operation, plant transient events w i thout a loss of off-site power , plant transient events (non-large LOCA) with a loss of off-site power and l arge LOCA events with a loss of offsite power. Normal operational events (for example RCP start-ups and shutdowns) are based on the flywheel operating life and a bounding number of start-up and shutdown cycles. This is a low contributor to flywhee l failure risks. Transient events are assumed to result in acceleration of the flywheel to design speeds. The risk assessment assumed that the plant will experience one transient event per year. A review of plant operation in the United States between 1988 and 2015 demonstrates that overall plant operation has improved and more typical plant failure probabil i ties are less than 0.80 per year 1 . The impact of the reduction in the plant trip frequency resu l ts in a 2.6E-09 per year per RCP reduction in CDF from the baseline value. The conditional LOOP probability contributes to the event frequencies for transient and LOCA events. Increasing the conditional LOOP probability from 0.014 to 0.05 only increases the incremental CDF by 5E-10 per year per RCP. Finally , the frequency of a large LOCA has a significant uncertainty attached to its mean value. In this study the large LOCA frequency (for breaks greater than 3 ft2) was increased an order of magnitude from 1 E-06 per year to 1 E-05 per year with no observable impact on plant r i sk. 3.5.2 Conditional Flywheel Failure Probability To simpl i fy analyses flywheel failure probabi l ities were based on 80 year end of life failure assumption and , with the exception of the large LOCA event , the assumption that the flywheel failure condition occurs at the plant design flywheel speed. For Westinghouse plants this was 1500 rpm. However , many plant transients are expected to result in events with lower flywheel speeds closer to that of nominal operation. Assuming flywheel failure probabilities associated with 1200 rpm operation , per RCP core damage frequency would reduce to 1 E-11 per year. 3.5.3 Conditional Core Damage/Large Early Release Probability Associated with a Flywheel Failure Event The baseline analysis assumes a conditional core damage probab i lity and a conditional large early release probability of 1.0. As discussed above , this is a limiting assumption and the actual values are expected to be much lower; therefore , the conditiona l LERP probabilities would be negligible. 1 I N/EXT-16-39534 , Initiating Event Rates at U.S. Nuclear Power Plants: 1988-2015 , INL , May 2016. PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-31 Table 3-10: CDF Sensitivity to Variations in PRA evaluation assumptions for RCP Flywheel Failure Risk Assessment for Extending 10-year inspection intervals to 80 years -(Flywheel Group 1) Incremental Change in CDF (per Year) Risk Impact of Single Risk impact of Flywheel Flvwheel Failure Failure (4 RCP Plant) Base l ine Change in CDF 1.33E-08 5.32E-08 PWR general and other transient 1.07E-08 4.28E-08 reduction to 0.8 per year Increase the Conditional LOOP 1.38E-08 5.51 E-08 probability to 0.05 Increase the LOCA frequency for 1.33E-08 5.33E-08 breaks >3 ft 2 to 1 E-05/year Flywheel Failure probability reduced for normal operation and the non-large 1.00E-11 4.01 E-11 LOCA transient based on 1200 rpm 3.5.4 Conclusion Regarding Treatment of Uncertainty The above sensitivity studies confirm that even for a relatively l arge increase in modeling parameters , the incremental CDF would continue to remain below the 1.0E-06 per year core damage and 1.0E-07 per year LERF criteria in [5] supporting the conclusion that this is a very small risk increase. This report assumes the incremental LERF and incremental CDF are equal. This is an extremely conseNative assumption. 3.6 RISK RESULTS AND CONCLUSIONS Given the extremely low failure probabilit i es for the RCP motor flywheel during normal/accident conditions and the extremely low probabil it y of LOCA/LOOP , and assuming a CCDP of 1.0 (complete failure of the safety systems), the CDF and change in risk would still not exceed the risk criteria in [5] (~CDF<1.0E-6 per year and ~LERF <1.0E-07 per year). Even consider i ng the uncertainties associated with this evaluation , the risk associated with the postulated failure of an RCP motor flywheel is significantly low. Even when all four RCP motor flywheels are considered in the bounding plant configuration case , the risk is still acceptably low. Because of the evaluation results for core damage frequency and the conseNative assumption that failure of the RCP motor flywheel results in core damage and a large early release, the calculations were not performed for the LERF. If detailed LERF analyses were performed , it is expected that the relative LERF contribution associated with these events would be significantly less than 20%. Regardless, this assessment assumes the calculated CDF is equal to LERF and that results are less than the LERF acceptance criterion (1 E-07/reactor year). PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 3-32 The key principles identified in RG-1.17 4 were also reviewed and the responses based on the evaluation are provided in Table 3-11. This evaluation , in conjunction with the previous deterministic calculations described throughout the report , concludes that the extension of the RCP motor flywheel examination from 10 to 20 years for RCP flywheels in operation up to 80 years would not be expected to result in a significant increase in risk; therefore , the proposed change is acceptable. Table 3-11: Evaluation with Respect to Regulatory Guide 1.17 4 (Key Pr i nciples) Key Principles Change meets current regulations unless it is explicitly related to a requested exemption or rule change Change is consistent with defense-in-depth philosophy Maintain sufficient safety marqins Proposed increases in CDF or risk are small and are consistent with the Commission's Safety Goal Policy Statement Use performance-measurement to monitor the change PWROG-17011-NP Evaluation Response No exemption or rule change is requested. This TR documents applicability of current ISi inspection i ntervals through 80 years of operation. The potential for failure of the RCP motor flywheel is negligible during normal accident conditions , and does not impact any plant structures , systems or components (SSCs). No safety analysis marqins are chanqed. The proposed increase in risk is estimated to be negligible. The RCS leakage exists prior to a LOCA (no core damage consequences are associated with the RCS leakage). No credit taken is taken for RCS leakaqe detection. NDE examinations are performed on a 20-year frequency for up to 80 years. Other indications of potential degradation of the RCP motor flywheel are available (e.g., pump vibration monitoring, and pump maintenance). May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 4-1 4 CONCLUSIONS The results and conclusions as summarized in WCAP-14535A

[1] remain valid and are reiterated below: 1. RCP flywheels are carefully designed and manufactured from excellent quality steel , which has a h i gh fracture toughness. 2. The RCP flywhee l overspeed i s the critical loading; however , LBB has limited the maximum speed to 1500 rpm. (Note , however , that LBB for LBLOCA was not considered in the risk assessment performed in WCAP-15666-A

[2}, which does consider the overspeed due to the LBLOCA.) 3. RCP flywheel inspections have been performed for over 20 years , with no service-induced flaws. 4. The RCP flywhee l integrity evaluations determined a very high flaw tolerance for the RCP flywheels. 5. Crack growth dur i ng service is negligible. 6. The structural re li ab i l i ty stud i es concluded that elim i nat i ng i nspect i ons will not change the probabi li ty of fa i lure. 7. The i nspections result in man-rem exposure and the potent i al for flywhee l damage during assembly and reassembly. The deterministic results as summarized in WCAP-15666-A

[2] remain applicable for 80 years of operation. The r i sk assessments are updated and presented in Sect i on 3 of th i s report. 1. The failure probab i lit i es for the RCP motor flywheels are small. 2. The change in risk i s less than the Regulatory Guide 1.174 CDF and LERF acceptance criteria.

3. The 20-year ISi frequency for the RCP motor flywheel , approved by the NRC in [2], remains applicab l e for 80 years of operat i on. PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 5-1 5 REFERENCES

1. Westinghouse Report , WCAP-14535A , Rev. 0 , " Topical Report on Reactor Coolant Pump Flywheel Inspection Elimination

," November 1996. 2. Westinghouse Report , WCAP-15666-A , Rev. 1 , " Extension of Reactor Coolant Pump Motor Flywheel Examination

," October 2003. 3. United States Nuclear Regulatory Commission , Office of Standards Development , Regulatory Guide 1.14 , Rev. 1 , " Reactor Coolant Pump F l ywheel Integr i ty ," August 1 975. 4. ASME Boiler and Pressure Vessel Code,Section XI , 2007 Edition with 2008 Addenda. 5. United States Nuclear Regulatory Commission , Regulatory Guide 1.174 , Rev. 2 , "An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis ," May 2011. 6. United States Nuclear Regulatory Commission NUREG-0800 , Standard Review Plan 19.0 , "Use of Probabilistic Risk Assessment in Plant Specific Risk-Informed Decision Making: General Guidance." 7. F. J. Witt , " Development and Applications of Probabilistic Fracture Mechanics for Critical Nuc l ear Reactor Components

," pages 55-70 , Advances in Probabilistic Fracture Mechanics , ASME PVP-Vol. 92 , 1984. 8. @RISK , Risk Analysis and Simulation add-In for Lotus 1-2-3 , Version 2.01 Users Guide , Palisade Corporation , Newfield , NY , February 6 , 1992. 9. Westinghouse Report , WCAP-14572 , Supplement 1, "Westinghouse Structural Reliability and Risk Assessment (SRRA) Model for Piping Risk-Informed lnservice Inspection

," Revision 1-NP-A , February 1999. 10. United States Nuclear Regulatory Commission NUREG/CR-5864 , Theoretical and User's Manual for pc-PRAISE, A Probabilistic Fracture Mechanics Computer Code for Piping Reliability Analysis, July 1992. 11. Documentation of Probabilistic Fracture Mechanics Codes Used for Reactor Pressure Vessels Subjected to Pressurized Thermal Shock Loading: Parts 1 and 2. Electric Power Research Institute , Palo Alto , CA: June 1995. TR-105001. 12. United States Nuclear Regulatory Commission NUREG-1829 , " Estimat i ng Coolant Accident (LOCA) Frequencies through the Elicitation Process ," Apr il 2008. 13. United States Nuclear Regulatory Commission NUREG/CR-6538 , "Evaluation of LOCA With Delayed Loop and Loop With Delayed LOCAAccident Scenarios," July 1997. 14. United States Nuclear Regulatory Commission NUREG/CR-6890 , " Reevaluation of Station Blackout Risk at Nuclear Power Plants: Analysis of Loss of Offsite Power Events," 1986-2004," December 2005. 15. United States Nuclear Regulatory Commission NUREG-1855 , Rev. " Guidance on the Treatment of Uncertainties Associated with PRAs in Risk-Informed Decisionmaking Final Report ," July , 2016. PWROG-17011-NP May 2018 Revision 1 r WESTINGHOUSE NON-PROPRIETARY CLASS 3 A-1 APPENDIX A: CALVERT CLIFFS UNIT 1 & 2 RCP MOTOR FLYWHEEL EVALUATIONS FOR EXTENSION OF ISi INTERVAL Background and Purpose WCAP-15666-A

[2] extended the ISi intervals for Westinghouse RCP motors from 10 to 20 years. Although Calvert Cliffs Units 1 and 2 are Combustion Engineering NSSS plants , they have Westinghouse RCP motors and flywheels; however , the motor operating speeds are different than those evaluated in WCAP-15666-A

[2]. A Calvert Cliffs plant-specific deterministic calculation and a probabilistic evaluation were performed using the methodology of [2] to justify 20-year ISi interval for 60 years of plant operation.

The probabilistic evaluations for Calvert Cliffs were updated in Section 3 of this report for 80 years of operation. The purpose of this Appendix is to evaluate and extend the applicability of [2] to 80-year plant operation for Calvert Cliffs Units 1 and 2. Ductile Failure Analysis As discussed in Section 2.3.2 of this report, the flywheel stresses are dependent on dimensions and rotation speed. Extending the operating period to 80 years does not affect the stress calculation.

Therefore , the current ductile failure analysis for 60 years remains valid for 80 years of operation. The ductile failure limiting speed was determined for the flywheel for two cases. Case 1 considered that no cracks were present but accounted for the reduced cross sectiona l area resulting from the keyway. Case 2 considered that a 10-inch radial crack existed emanating from the center of the keyway through the full thickness of the flywheel.

The calculated limiting speeds are: Case 1: 3219 rpm ( considering the keyway only , no crack) Case 2: 2856 rpm (considering the keyway and a 1 O" crack) Given the nominal operating speed of 900 rpm for Calvert Cliffs plants, criterion item f [3] is satisfied since this is lower than one half of the lowest calculated critical speed of 2856/2 = 1428 rpm , considering both no cracks present and a large crack (1 O") present. Given the LOCA over speed of 1368 rpm for the Calvert Cliffs plants, criterion item f [3] is satisfied because it is less than any calculated critical speeds considering both no cracks present and a large crack present. Non-ductile Failure Analysis As discussed in Section 2.3.3 of this report , extending the operating period to 80 years does not affect the K 1 calculations, and the flywheel fracture toughness, K ie would not change due to the 80 year extension. Therefore, the current non-ductile failure analysis for 60 years remains valid for 80 years of operation.

As in discussed in Section 2.3.3 , Table 2-5, RT N DT values of 0°F, 30°F and 60°F were used to calculate the critical flaw sizes shown in Table A-1. PWROG-17011-NP May 2018 Revision 1 WESTINGHOUSE NON-PROPRIETARY CLASS 3 A-2 Table A-1: Critical Crack Length in Inches and % Through Flywheel RT Nor 0°F 30°F 60°F Critica l Crack Length 18.5 8.8" 3.7 % Through the F l ywheel 52% 25% 10% Note: The % through the flywheel is calculated as CCL in the table div i ded by the rad i a l l eng t h from the maximu m r ad i al ke yw a y l ocat i on to the flyw heel ou t e r radius [CCL/ (41.0" -4.7 1 88" -0.93 7")]. Fatigue Crack Growth As discussed in Section 2.3.4 of this report , extending the operating period to 80 years does not affect the K , and .6.K, calculations. The 6000 design cycles of start and shutdown used for the FCG was determined to be bound i ng for 80 years of operat i on. However , the 6000 cycles for 80 years of operation must be confirmed for this TR to be applicable. The FCG of 0.025 inch after 80 years or 6000 cycles is negl i gible even when assuming a large i n i t i al crack length of 3.7 inches. Excessive Deformation Analysis As discussed in Section 2.3.5 of this report , the 80-year extension has no impact on the excess i ve deformation analysis of the flywheel.

The current deformat i on resu l ts for 60 years remain appl i cable to 80 years of operation. The change in the RCP flywheel bore radius and outer diameter at overspeed condition of 1368 rpm are: .6.a = the change in the flywheel bore radius at overspeed

= 0.003 i nch .6.b = the change in the flywheel outside radius at overspeed

= 0.006 inch Since .6. i s proportional to ol, this represents a 231% increase [(ro 05;ron)2 = (1368 / 900)2 = 2.31 = 231%] over the deformat i on at the normal ope r at i ng speed. This increase would not resu l t in any adverse cond i tions , such as excessive f l ywheel vibrational stresses that would result in crack propagation since the flywheel assemblies are interference fit to the flywheel shaft and the calculated deformations are small and insignificant.

It is noted that the deformation for Calvert Cliffs flywheels is less than the that of Westinghouse flywheels reported i n Section 2.3.5 of this report. Conclusion The current Calvert Cliffs evaluat i on and results for 60 years are applicable for 80 years of operation. The stress and fracture evaluation resu l ts for Calvert Cliffs flywheels are consistent with the flywheels evaluated in [3]. The probabilistic risk evaluation , in conjunction w i th the determ i nistic calculations described above , conc l uded that extension of the RCP motor flywheel ISi from 1 O to 20 years for flywheels in service up to 80 years is acceptable. PWROG-17011-NP May 2018 Rev i sion 1