RA-19-0241, Response to Request for Additional Information Regarding Advanced Framatome Methodologies License Amendment Request

Response to Request for Additional Information Regarding Advanced Framatome Methodologies License Amendment Request

ML19169A033
Person / Time
Site:	Brunswick
Issue date:	06/18/2019
From:	William Gideon Duke Energy Progress
To:	Document Control Desk, Office of Nuclear Reactor Regulation
Shared Package
ML19169A032	List: RA-19-0241, Response to Request for Additional Information Regarding Advanced Framatome Methodologies License Amendment Request
References
EPID L-2018-LLA-0273, RA-19-0241 ANP-3782NP, Rev 2
Download: ML19169A033 (157)

Text

William R. Gideon Vice President Brunswick Nuclear Plant P.O. Box 10429 Southport, NC 28461 Enclosure 1 Contains Proprietary Information o: 910.832.3698 Withhold in Accordance with 10 CFR 2.390 June 18, 2019 Serial: RA-19-0241 10 CFR 50.90 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001

Subject:

Brunswick Steam Electric Plant, Unit Nos. 1 and 2 Renewed Facility Operating License Nos. DPR-71 and DPR-62 Docket Nos. 50-325 and 50-324 Response to Request for Additional Information Regarding Advanced Framatome Methodologies License Amendment Request

Reference:

1. Letter from William R. Gideon (Duke Energy) to the U.S. Nuclear Regulatory Commission Document Control Desk, Request for License Amendment Regarding Application of Advanced Framatome Methodologies, dated October 11, 2018, ADAMS Accession Number ML18284A395.

2. NRC E-mail Capture, Brunswick Unit 1 and Unit 2 Request for Additional Information Related to Transition to Framatome ATRIUM-11 Fuel (EPID: L-2018-LLA-0273), dated May 9, 2019, ADAMS Accession Number ML19135A307.

3. Letter from William R. Gideon (Duke Energy) to the U.S. Nuclear Regulatory Commission Document Control Desk, Response to Request for Additional Information Regarding Advanced Framatome Methodologies License Amendment Request, dated May 29, 2019, ADAMS Accession Number ML19149A319.

Ladies and Gentlemen:

By letter dated October 11, 2018 (i.e., Reference 1), Duke Energy Progress, LLC (Duke Energy), submitted a license amendment request (LAR) for the Brunswick Steam Electric Plant (BSEP), Unit Nos. 1 and 2. The proposed license amendment revises Technical Specification 5.6.5.b to allow application of Advanced Framatome Methodologies for determining core operating limits in support of loading Framatome fuel type ATRIUM 11.

On May 9, 2019, by electronic mail (i.e., Reference 2), the NRC provided a request for additional information (RAI) regarding the LAR. Duke Energy provided the first set of RAI responses on May 29, 2019 (i.e., Reference 3). This letter provides the second and final set of RAI responses addressing all outstanding RAIs. contains information considered proprietary to Framatome. The proprietary information in this enclosure has been denoted by brackets. As owner of the proprietary

U.S. Nuclear Regulatory Commission Page 3 of 3 cc (with all Enclosures):

U. S. Nuclear Regulatory Commission, Region II ATTN: Ms. Catherine Haney, Regional Administrator 245 Peachtree Center Ave, NE, Suite 1200 Atlanta, GA 30303-1257 U. S. Nuclear Regulatory Commission ATTN: Mr. Gale Smith, NRC Senior Resident Inspector 8470 River Road Southport, NC 28461-8869 U. S. Nuclear Regulatory Commission ATTN: Mr. Andrew Hon 11555 Rockville Pike Rockville, MD 20852-2738 U.S. Nuclear Regulatory Commission ATTN: Mr. Dennis J. Galvin 11555 Rockville Pike Rockville, MD 20852-2738 cc (with Enclosures 2 and 3 only):

Chair - North Carolina Utilities Commission (Electronic Copy Only) 4325 Mail Service Center Raleigh, NC 27699-4300 swatson@ncuc.net Mr. W. Lee Cox, III, Section Chief (Electronic Copy Only)

Radiation Protection Section North Carolina Department of Health and Human Services 1645 Mail Service Center Raleigh, NC 27699-1645 lee.cox@dhhs.nc.gov

RA-19-0241 Enclosure 2 ANP-3782NP, Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information, Revision 2

Controlled Document Brunswick ATRIUM 11 Advanced ANP-3782NP Revision 2 Methods Response to Request for Additional Information June 2019

© 2019 Framatome Inc.

Controlled Document ANP-3782NP Revision 2 Copyright © 2019 Framatome Inc.

All Rights Reserved

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page i Nature of Changes Section(s)

Item or Page(s) Description and Justification.

1 Page v - vii Added nomenclature page.

2 Introduction Added discussion of revision.

3 Section 2 Added RAI-1 and response.

4 Section 4 Inserted a new section with the LOCA related RAIs 11 to 22 and responses.

5 Section 5 Added BEO-III related RAIs 25 to 29 and responses.

6 Section 7 Added References 3 to 7 and ordered by occurrence.

7 All Reference numbers adjusted due to the addition of new references.

8 Page 5-2 Added an additional pointer to the LAR.

9 Appendix A Added Appendix A.

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page ii Contents Page

1.0 INTRODUCTION

............................................................................................... 1-1 2.0 ANTICIPATED TRANSIENT WITHOUT SCRAM WITH INSTABILITY (ATWS-I) ..................................................................................... 2-1 3.0 ANTICIPATED OPERATING EVENT (AOO) AND ATWS ................................. 3-1 4.0 LOSS-OF-COOLANT ACCIDENT (LOCA) ........................................................ 4-1 5.0 BEST ESTIMATE ENHANCED OPTION-III (BEO-III) WITH CONFIRMATION DENSITY ALGORITHM (CDA) ............................................. 5-1 6.0 CONTAINMENT ................................................................................................ 6-1

7.0 REFERENCES

.................................................................................................. 7-1 APPENDIX A GENERIC ATWS-I RAI RESPONSES .................................................. A-1

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page iii List of Tables Table 2-1 ATRIUM 11 Gap Conductance Sensitivity Study .................................... 2-2 Table 9-1 Brunswick ATRIUM 11 Disposition of Events ......................................... 3-2 Table 18-1 Disposition of Operating Domains ........................................................ 4-10 Table 20-1 Grid Spacer Location Sensitivity ........................................................... 4-13 Table 21-1 Sensitivity of (( )) .......................................... 4-14 Table 22-1 Brunswick and (( )) ........................................... 4-16 Table 24-1 BEO-III Time Step Criteria ...................................................................... 5-3 Table 24-2 Time Step Control Parameters for Sensitivity Studies ............................ 5-3 Table 24-3 Reactor Benchmark Sensitivity to Time Steps ........................................ 5-4 Table 24-4 BEO-III MELLLA+ FoM Sensitivity to Time Steps ................................... 5-4 Table 24-5 Reactor Benchmark Sensitivity to Vessel Nodalization ........................... 5-5 Table 24-6 BEO-III MELLLA+ FoM Sensitivity to Vessel Nodalization ...................... 5-5 Table 26-1 BEO-III MELLLA+ Sensitivity to (( )) .... 5-9 Table 26-2 BEO-III MELLLA+ FoM Sensitivity to (( )) ....................... 5-10 Table 29-1 BEO-III MELLLA+ FoM Sensitivity to (( )) ... 5-19 Table 29-2 BEO-III MELLLA+ (( )) .................. 5-20 Table 31-1 Decay Heat Evaluation ........................................................................... 6-3

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page iv List of Figures Figure 2-1 ATRIUM 11 PCT versus Gap Conductance Sensitivity........................... 2-2 Figure 7-1 (( )) ........................................... 2-7 Figure 12-1 Cladding Temperature for a (( )) ...................... 4-3 Figure 13-1 Break (( )) .............................................................. 4-4 Figure 13-2 Break (( )) ............................................................... 4-5 Figure 15-1 Local Cladding Oxidation versus Exposure ............................................ 4-7 Figure 16-1 (( )) ............................... 4-8 Figure 16-2 (( )) Sensitivity ................................... 4-9 Figure 22-1 Peak Cladding Temperatures for (( )) ........... 4-15 Figure 22-2 Void Fraction for (( )) .................................... 4-16 Figure 22-3 Quality for (( )) .............................................. 4-17 Figure 22-4 Heat Flux for (( )) .......................................... 4-17 Figure 22-5 Critical Heat Flux for (( )) .............................. 4-18 Figure 22-6 Pressure for (( )) ........................................... 4-18 Figure 25-1 (( )) .................................................................. 5-7 Figure 25-2 Core Pressure Drop by Stage ................................................................. 5-8 Figure 26-1 Pump Coastdown ................................................................................. 5-12 Figure 26-2 Limiting MELLLA+ MCPR ..................................................................... 5-12 Figure 26-3 Limiting MELLLA+ (( )) ..................................... 5-13 Figure 27-1 Mode Observations Versus Exposure................................................... 5-16 Figure 27-2 Average Phase Lag Versus Exposure .................................................. 5-16 Figure 27-3 Terminal Operating Conditions ............................................................. 5-17 Figure 27-4 Oscillation Periods for MELLLA+ Pump Trip Scenarios ........................ 5-17

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page v Nomenclature Acronym Definition ABSP Automatic Backup Stability Protection ACCH Maximum Truncation Error ADS Automatic Depressurization System AOO Anticipated Operational Occurrence APRM Average Power Range Monitor ATWS Anticipated Transients Without Scram ATWS-I Anticipated Transients Without Scram With Instability BEO-III Best-estimate Enhanced Option-III BATT Battery BOC Beginning of Cycle BSP Backup Stability Protection BWR Boiling Water Reactor CDA Confirmation Density Algorithm CFR Code of Federal Regulations CHF Critical Heat Flux CPR Critical Power Ratio DEG Double-Ended Guillotine DIVOM Delta CPR (critical power ratio) over Initial CPR Versus Oscillation Magnitude DMH Direct Moderator Heating

(( ))

DR Decay Ratio ECCS Emergency Core Cooling System ECPR Experimental Critical Power Ratio EOC End of Cycle EOOS Equipment out-of-service EPU Extended Power Uprate F/I MCPR Final over Initial Minimum Critical Power Ratio

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page vi FoM Figure of Merit F2OMAX (( ))

GDC General Design Criteria GE General Electric HTC Heat Transfer Coefficient HMIN Minimum Time Step ICF Increased Core Flow ICO Independent Channel Oscillation KATHY Karlstein Thermal Hydraulic Test Facility LAR License Amendment Request LHGR Linear Heat Generation Rate LOCA Loss of Coolant Accident LPCI Low Pressure Coolant Injection LPRM Local Power Range Monitor LTR Licensing Topical Report LTSS Long-Term Stability Solution MAPLHGR Maximum Average Planar Linear Heat Generation Rate MCPR Minimum Critical Power Ratio MELLLA+ Maximum Extended Load Line Limit Analysis Plus MSIV Main Steam Isolation Valve NRC Nuclear Regulatory Commission OLMCPR Operating Limit Minimum Critical Power Ratio OPRM Oscillating Power Range Monitor PBA Period Based Algorithm PCI Pellet Clad Interaction PCT Peak Cladding Temperature PHE Peak Hot Excess

(( ))

RDIV Recirculation Discharge Isolation Valve FSAR Final Safety Analysis Report RSAR Reload Safety Analysis Report

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page vii SF Single Failure SLO Single Loop Operation SRV Safety Relief Valve SS Steady-State STP Simulated Thermal Power TR Topical Report TTWB Turbine Trip With Bypass TTNB Turbine Trip No Bypass 1RPT (1PT) One Recirculation Pump Trip 2RPT (2PT) Two Recirculation Pump Trip

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 1-1

1.0 INTRODUCTION

By letter dated October 11, 2018, Duke Energy submitted a license amendment request for Brunswick Steam Electric Plant, Units 1 and 2 (Brunswick) to allow application of the Framatome analysis methodologies necessary to support a planned transition to ATRIUM 11 fuel under the currently licensed Maximum Extended Load Line Limit Analysis Plus (MELLLA+) operating domain, Reference 1 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML18284A395). Upon review of the submittal, the NRC staff provided requests for additional information (RAIs) in an email dated 5/9/19 (ML19135A307, Reference 2). Responses to NRC RAIs 1-10, 23, 24, 28, and 30-32 were provided by Reference 3. This Revision provides responses to the remaining RAIs. In addition, Appendix A provides additional pertinent information related to the Brunswick Specific ATWS-I Methodology (i.e., ANP-3694P) and is being provided to aid the NRC in their review of the subject LAR.

The proprietary information in this document is marked with double brackets such as

(( )).

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 2-1 2.0 ANTICIPATED TRANSIENT WITHOUT SCRAM WITH INSTABILITY (ATWS-I)

NRC RAI 1. Justify the use of a feedwater temperature reduction rate of 1.3°F/s, as well as the initial delay time (if any) before feedwater temperature reduction begins in the ATWS-I analysis.

Response 1:

The response to this RAI was provided in Enclosure 3 of Reference 3.

NRC RAI 2. Discuss how the gap conductance sensitivity will be addressed when fuel design changes occur and provide results for ATRIUM-11 fuel.

Response 2:

An ATRIUM 11 gap sensitivity study has been performed. For this study, ((

))

In the future, if a fuel design beyond ATRIUM 11 is introduced, the gap conductance for the new fuel design will either be justified to be sufficiently similar to the ATRIUM 11 (i.e.

minimal rod changes) or a new gap conductance sensitivity will be performed.

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 2-2 Table 2-1 ATRIUM 11 Gap Conductance Sensitivity Study Figure 2-1 ATRIUM 11 PCT versus Gap Conductance Sensitivity

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 2-3 NRC RAI 3. Confirm that the steam line and valve modeling options accurately capture the expected plant-specific system performance during ATWS-I events.

Response 3:

The steam line and SRVs were modeled consistent with expected performance.

((

))

It is also noted that the modeling of these valve characteristics can have a noticeable effect on the onset of instability which can impact the timing of the event. For Brunswick, ((

)) The overall impact on the PCT for Brunswick due to the cycling of the valves is minimal ((

)).

NRC RAI 4. Provide a justification that the ATWS-I analyses based on the reference core will bound all expected future core designs. As part of this discussion, address transition cores and core design specific considerations that may affect local stability characteristics, such as nodal variations, control rod patterns, and operating strategies.

Response 4:

For ATWS-I analyses the most conservative result will occur when ((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 2-4

((

))

Therefore, the ATRIUM 11 ATWS-I analysis for Brunswick contains sufficient conservatism to bound follow-on cycles.

NRC RAI 5. Two events are considered potentially limiting in the ATWS-I transient scenario: two reactor pump trip (2RPT) and turbine trip with bypass (TTWB). Brunswick analyzed the TTWB event and, since instability and dryout/rewet occurred, the 2RPT event was unanalyzed per the Calculational Procedure in Section 8.0 of the submittal. In order to assure the limiting event was analyzed, provide results for the 2RPT ATWS-I event, with justification given for the operator action time assumptions used. Certain changes in plant design or operation may affect stability behavior for these events. Discuss how the TTWB event will be confirmed to remain limiting relative to the 2RPT event if changes are made to the plant design or operation that may affect stability behavior during anticipated transient without scram (ATWS), such as: turbine bypass capability, fraction of steam-driven feedwater pumps, and changes expected to increase core inlet subcooling during ATWS events.

Response 5:

Section 7 of ANP-3694P (Attachment 14a of the subject LAR) provides Brunswick TTWB and 2RPT results for ATRIUM 10XM. A review of the results shows ((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 2-5

((

))

NRC RAI 6. Justify that the selected settings and modeling options are appropriate, including core and vessel nodalization, time step control parameters, and noise parameters. Discuss how the modeling is consistent with the characteristics of Brunswick and the validation basis for the proposed RAMONA5-FA ATWS-I methodology.

Response 6:

All benchmarks and analyses provided in ANP-3694P utilized consistent vessel nodalization and time step control parameters. Since these values were used in the benchmarking of the code, and the benchmarks showed good agreement with the data, then these values are appropriate.

The noise parameters were ((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 2-6 NRC RAI 7. Understanding that both ((

))

Response 7:

((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 2-7 Figure 7-1 (( ))

((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 2-8 NRC RAI 8. Tables 7-1 and F-1 of ANP-3694P indicate a trend of ((

)). Provide an explanation for this observed trend.

Response 8:

((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 3-1 3.0 ANTICIPATED OPERATING EVENT (AOO) AND ATWS NRC RAI 9. ANP-3702P provides a subset of the events analyzed in the Brunswick Chapter 15 Updated Final Safety Analysis Report (UFSAR) and covered by the AURORA-B AOO/ATWS methodology. To ensure the methodology is implemented appropriately for the events not covered in ANP-3702P and to ensure that the analysis of these events is sufficient to meet GDCs 10, 13, 15, 20, 25, and 26 and ATWS acceptance criteria, provide the following:

a. Describe how each Chapter 15 UFSAR event (that is covered by the AUORAB-AOO/ATWS methodology) will be analyzed in the AURORA B AOO methodology framework (e.g., a table identifying FSAR Section/Event Name/Disposition)

b. Describe how the methodology is implemented (including steps prior to the execution of the uncertainty analysis) to ensure there is appropriate coverage of operational power/flow statepoints, equipment-out-of-service conditions, time-in-cycle, etc.

Response 9 a.:

A disposition of events is created for a reactor to establish or re-establish the licensing basis in situations like vendor transitions, fuel transitions, and significant plant configuration modifications (i.e., extended power uprate (EPU) or MELLLA+). For each transient event in the final safety analysis report (FSAR) this disposition identifies which events 1) require cycle-specific analyses, 2) are analyzed for the initial reload, and 3) are non-limiting based on first principles. The Chapter 15 disposition of events for the transition to ATRIUM 11 is given in Table 9-1.

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 3-2 Table 9-1 Brunswick ATRIUM 11 Disposition of Events FSAR Section Event Name Disposition Status Comments 15.1.1 Loss of Feedwater Heater Address each reload Potentially limiting AOO.

(LFWH) 15.1.2 Feedwater Controller Failure Address each reload Potentially limiting AOO.

(FWCF) - Maximum Demand 15.1.3 Inadvertent HPCI or RCIC No further analysis Consequences bound by the FWCF.

Pump Start required 15.1.4 Pressure Regulator Failure No further analysis The PRFO event causes no Open (PRFO) required significant threat to the fuel thermal margins. The peak heat flux and fuel surface heat flux do not exceed the initial power and no fuel damage occurs.

This event can result in a turbine trip and the resulting core pressurization and reactor scram. While the steam flow at the time of the TSV closure may be higher than the initial steam flow, the turbine bypass valves are open prior to the turbine trip and will therefore remain open to provide some pressure relief during the turbine trip. The consequences of this event are bound by the TTNB.

15.1.5 Inadvertent Opening of a No further analysis The event causes a mild Relief Valve or Safety Valve required depressurization. The peak heat flux and fuel surface heat flux do not exceed the initial power and no fuel damage occurs. This event is benign.

15.1.6 Inadvertent RHR Shutdown No further analysis This is a benign event without fuel Cooling Operation required damage and without any measurable nuclear system pressure increase.

15.2.1 Generator Load Rejection Address each reload Potentially limiting AOO with bypass with and without bypass inoperable.

(LRNB) Below 50% power, the effects of the PLU device need to be addressed.

15.2.2 Turbine Trip with and without Address for initial Potentially bound by LRNB.

bypass (TTNB) reload

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 3-3 Table 9-1 Brunswick ATRIUM 11 Disposition of Events (continued)

FSAR Section Event Name Disposition Status Comments 15.2.3 Main Steam Isolation Valve No further analyses The fuel thermal transient resulting (MSIV) Closure required from this event is bounded by other more limiting pressurization events, such as the LRNB or TTNB event which have a much faster valve closure time.

15.2.4 Loss of Condenser Vacuum No further analyses In the most extreme case of an required instantaneous loss of vacuum, this transient is equivalent to a TTNB.

Therefore, this transient is bounded by the TTNB and LRNB and no further analysis is required.

15.2.5 Loss of Auxiliary Power No further analyses The loss of auxiliary power long-required term water level response is bound by the loss of feedwater flow event.

If complete connection with the external grid is lost, the reactor will experience a generator load rejection. The coastdown of the recirculation and feedwater pumps will reduce the severity of the event compared to the generator load rejection event, by reducing core power. Therefore consequences are bound by the LRNB event.

15.2.6 Loss of Feedwater Flow No further analysis This event does not pose any direct required threat to the fuel in terms of a thermal power increase from the initial conditions. The fuel will be protected provided the water level inside the shroud does not drop below the TAF. Previous evaluations for a different fuel design showed that the lowest level following a loss of feedwater event remained above Low Level 3.

Based on this, MSIV closure, ADS timer start and Low Pressure ECCS initiation are not expected. The long term water level transient is dependent upon the decay heat which is ((

)). This is a benign event.

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 3-4 Table 9-1 Brunswick ATRIUM 11 Disposition of Events (continued)

FSAR Section Event Name Disposition Status Comments 15.2.7 Loss of RHR Shutdown No further analyses Benign event.

Cooling required 15.2.8 Pressure Regulator Failure- No further analyses If the controlling regulator fails in a Closed required closed direction, the backup regulator takes over control of the turbine control valves preventing a serious transient. The disturbance is mild, similar to a pressure setpoint change and no significant thermal margin reductions occur. This is a benign event.

15.3.1 Recirculation Pump Trip No further analyses The reduction in core flow is required accompanied by an increase in core voiding and a decrease in core power. While the decrease in core flow can result in a degradation of the thermal margins, the decrease in core power helps to mitigate that effect. This is a benign event.

15.3.2 Recirculation Flow Control No further analyses Benign event and bound by single Failure - Decreasing Flow required pump trip.

15.3.3 Recirculation Pump Seizure No further analyses Consequences of the pump seizure required event are bound by other limiting rated power AOO events.

15.4.1 Rod Withdrawal Error during No further analyses Benign event.

Low Power Operation required 15.4.2 Rod Withdrawal Error at Address each reload Potentially limiting AOO.

Power 15.4.3 Startup of Idle Recirculation No further analyses The consequences of the idle loop Loop required startup event are benign and non-limiting compared to other AOO events.

15.4.4 Recirculation Flow Control No further analyses The event is non-limiting relative to Failure - Increasing Flow required the slow flow runup.

15.4.5 Fuel Assembly Error during No further analyses Non-limiting or benign event.

Refueling required

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 3-5 Table 9-1 Brunswick ATRIUM 11 Disposition of Events (continued)

FSAR Section Event Name Disposition Status Comments 15.4.6 Control Rod Drop Accident Address each reload Potentially limiting event.

Verification that deposited enthalpy is less than 230 calories per gram and to determine the number of rods exceeding the PCMI and high temperature failure thresholds for the given fuel cladding. (It is assumed that criteria similar to that in DG-1327 will be applied for the ATRIUM 11 fuel.)

Evaluation of ATRIUM 11 with AST is required.

15.6.3 Main steam line break No additional analysis The consequences of a large main accident required steam line break are non-limiting with respect to 10 CFR 50.46 acceptance criteria. Although a main steam line break may be limiting with respect to reactor vessel, containment, or radiological limits, current evaluations are not significantly impacted by fuel or core design characteristics. The consequences of a main steam line break on the core and fuel are bound by the recirculation line break analyses.

15.6.4 Loss of Coolant Accident Address for initial Potentially limiting accident. The (LOCA) reload break spectrum analysis needs to be addressed for the initial reload of ATRIUM 11 with the AURORA-B LOCA method.

Evaluation of ATRIUM 11 with AST is required.

15.7.1 Refueling Accident Address for initial Potentially limiting accident.

reload Evaluation of ATRIUM 11 with AST is required.

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 3-6 Table 9-1 Brunswick ATRIUM 11 Disposition of Events (continued)

FSAR Section Event Name Disposition Status Comments 15.8 Anticipated Transient Without Address each reload Peak pressure evaluation needs to Scram be addressed each reload.

Long term ATWS evaluations for suppression pool temperature and containment pressure requires

((

)).

PCT and MWR are bound by other analyses.

For MELLLA+, ATWS with core instability evaluations will be needed at least for the initial reload.

15.9 Analytical Methods for Address for initial Evaluation of ATRIUM 11 with AST Evaluating Radiological reload is required.

Effects with Alternative Source Term Response 9 b.:

Once the disposition of events has been completed, a calculation plan is constructed.

The calculation plan defines the minimum analysis set required to license a given cycle.

The events to be analyzed are defined by the disposition of events. The calculation plan will also define all operational flexibility options that are to be supported. These include items such as equipment out-of-service options (EOOS) and exposure windows.

The calculation plan is generated on a cycle specific basis and is reviewed and approved by Duke. Note that the calculation plan defines the minimum set of analyses required to license a cycle. Additional analyses may be added during the evaluation process if unexpected trends arise. These are added on an as-needed basis to ensure that the limits are appropriately conservative.

The statepoints to be analyzed are also defined in the calculation plan. The initial transition to AURORA-B methods will include ((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 3-7

((

))

NRC RAI 10. To ensure there is appropriate coverage of the parameters used in the uncertainty analysis and to ensure there is no significant trends with respect to the uncertainty parameters in the results such that the Brunswick implementation of the AURORA-B methodology is sufficient to meet GDCs 10, 13, 15, 20, 25, and 26 and ATWS acceptance criteria, provide the following for the load rejection no bypass (LRNB) event at 100% power / 104.5% flow and main steam isolation valve (MSIV) closure ATWS event at 100% power and 85% flow:

a. The sampled values of the uncertainty parameters for all cases executed in the set

b. The figure of merit (FoM) results for all cases executed in the set Response 10:

Files containing the requested data have been provided. CKSUM identification is provided below.

2647460735 46730 100P104F_EOC_LRNB.xlsx 4082081760 46164 100P85F_BOC_ATWS.xlsx

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 4-1 4.0 LOSS-OF-COOLANT ACCIDENT (LOCA)

The RAI responses in this section are based on ANP-3674P, Revision 1 (i.e. 3a of the subject LAR). As discussed in Reference 4, a revision to ANP-3674P will be provided by Duke Energy. While the numerical results will change in Revision 2, the general conclusions provided by these RAI responses will remain applicable.

NRC RAI 11. Please justify the statement on page 1-2 of ANP-3674P that the limiting break will not change with exposure or nuclear fuel design. Although the NRC staffs safety evaluation on ANP-10332P found that the AURORA-B LOCA evaluation model may ((

)). Hence, the requested information is necessary to justify satisfaction of the requirement in 10 CFR 50.46(a)(1)(i) that a sufficient number of postulated scenarios has been considered to provide assurance that the most severe postulated loss-of-coolant accident has been calculated.

Response 11:

The statement refers to the ((

)) as discussed in the topical report. The clause or nuclear fuel design should be excluded from the sentence, since the discussion relates to exposure. This change will be incorporated into ANP-3674P, Revision 2.

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 4-2 NRC RAI 12. Please justify the conclusion in ANP-3674P that postulated breaks in the reactor water cleanup system and instrument lines ((

)). Hence, the requested information is necessary to justify satisfaction of the requirement in 10 CFR 50.46(a)(1)(i) that a sufficient number of postulated scenarios has been considered to provide assurance that the most severe postulated loss-of-coolant accident has been calculated.

Response 12:

Instrument lines ((

)).

The (( )) from the reactor water cleanup system ((

)).

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 4-3 Figure 12-1 Cladding Temperature for a (( ))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 4-4 NRC RAI 13. Although figures of merit are provided for limiting scenarios, ANP-3674P does not demonstrate that the AURORA-B LOCA evaluation model ((

)).

The requested information is necessary to justify satisfaction of the requirement in 10 CFR 50.46(a)(1)(i) that a sufficient number of postulated scenarios has been considered to provide assurance that the most severe postulated loss-of-coolant accident has been calculated.

Response 13:

Figure 13-1 and Figure 13-2 show the break ((

)).

Figure 13-1 Break (( ))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 4-5 Figure 13-2 Break (( ))

NRC RAI 14. The predicted peak cladding temperature for the SF-BATT single failure

((

)). The requested information is necessary to justify a conservative calculation of the figures of merit in demonstrating satisfaction of the relevant acceptance criteria specified in 10 CFR 50.46(b).

Response 14:

(( )) for the SF-BATT single failure ((

)).

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 4-6 NRC RAI 15. Table 9.1 of ANP-3674P shows that the calculated maximum local cladding oxidation ((

)). The requested information is necessary to justify satisfaction of the acceptance criterion for local cladding oxidation (i.e., total oxidation) specified in 10 CFR 50.46(b)(2).

Response 15:

This is due to a ((

)).

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 4-7 Figure 15-1 Local Cladding Oxidation versus Exposure NRC RAI 16. Limitation and Condition 15 from the NRC staffs draft safety evaluation on ANP-10332P requested that licensees ((

)). ANP-3674P does not provide sufficient information to ((

)). The requested information is necessary to justify satisfaction of the relevant acceptance criteria specified in 10 CFR 50.46(b).

Response 16:

BWR fuel rods are ((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 4-8

((

)).

Figure 16-1 (( ))

A code version was created that ((

)).

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 4-9 Figure 16-2 (( )) Sensitivity NRC RAI 17. Please demonstrate that either (1) the calculations performed for Brunswick either directly satisfy Limitation and Condition 19 from the NRC staffs draft safety evaluation on ANP-10332P or (2) the predicted results for Brunswick presented in ANP-3674P would provide more conservative results than simulations that directly satisfy Limitation and Condition 19.

The requested information is necessary to justify satisfaction of paragraph I.C.4.e of Appendix K to 10 CFR 50.

Response 17:

A sensitivity calculation was performed for the limiting case with the ((

)).

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 4-10 NRC RAI 18. Please identify each operating domain for which Brunswick is currently licensed (e.g., expanded operating domains on power-to-flow map, equipment-out-of-service conditions). Please clarify whether each licensed operating domain has been analyzed explicitly for the LOCA event, or whether it has been dispositioned based upon qualitative factors.

For each licensed operating domain, provide the analytical results or qualitative rationale demonstrating the condition is non-limiting. The requested information is necessary to justify satisfaction of the requirement in 10 CFR 50.46(a)(1)(i) that a sufficient number of postulated scenarios has been considered to provide assurance that the most severe postulated loss-of-coolant accident has been calculated.

Response 18:

Table 18-1 summarizes the disposition of the operating domains and equipment out-of-service (OOS) conditions applicable to LOCA presented in ANP-3674P, Rev. 1.

Table 18-1 Disposition of Operating Domains Operating Disposition Result or Rationale Domain MELLLA Analyzed ((

))

MELLLA+ Analyzed ((

))

SLO Analyzed ((

))

ADSOOS Analyzed All analyses assume one ADS valve out of service (OOS) ((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 4-11 Operating Disposition Result or Rationale Domain MSIVOOS Dispositioned Operation with an MSIVOOS is limited to two-loop operation and power levels below 70% where a LHGR reduction is applied and LOCA results are non-limiting.

One MSIVOOS can result in a higher reactor pressure at the initiation of the LOCA and slightly higher break flow; ((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 4-12 NRC RAI 19. As described in ANP-3674P, the LOCA analysis performed for Brunswick considered a ((

)).

The requested information is necessary to justify satisfaction of the requirement in 10 CFR 50.46(a)(1)(i) that a sufficient number of postulated scenarios has been considered to provide assurance that the most severe postulated loss-of-coolant accident has been calculated.

Response 19:

Thermal-hydraulic ((

)).

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 4-13 NRC RAI 20. Please show that Limitation and Condition 35 from the NRC staffs draft safety evaluation on ANP-10332P has been satisfied by providing ((

)). The requested information is necessary to justify satisfaction of the relevant acceptance criteria specified in 10 CFR 50.46(b) and the requirements of Paragraph II.3 of Appendix K to 10 CFR 50.

Response 20:

((

)).

Table 20-1 Grid Spacer Location Sensitivity NRC RAI 21. Please show that Limitation and Condition 37 from the NRC staffs draft safety evaluation on ANP-10332P has been satisfied by providing ((

)). The requested information is necessary to justify satisfaction of the relevant acceptance criteria specified in 10 CFR 50.46(b) and the requirements of Paragraph II.3 of Appendix K to 10 CFR 50.

Response 21:

The break spectrum for the ((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 4-14

((

)).

Table 21-1 Sensitivity of (( ))

NRC RAI 22. The NRC staffs review of the results presented in ANP-3674P observed notable differences relative to ((

)). Please clarify the basis for these observed differences. The requested information is necessary to justify satisfaction of the relevant acceptance criteria specified in 10 CFR 50.46(b).

Response 22:

The ((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 4-15

((

)).

Figure 22-1 Peak Cladding Temperatures for (( ))

Brunswick and the ((

)) the key differences summarized in Table 22-1

((

)) are plotted in Figure 22-2 to Figure 22-5.

The earlier ((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 4-16

((

)).

Table 22-1 Brunswick and (( ))

Figure 22-2 Void Fraction for (( ))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 4-17 Figure 22-3 Quality for (( ))

Figure 22-4 Heat Flux for (( ))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 4-18 Figure 22-5 Critical Heat Flux for (( ))

Figure 22-6 Pressure for (( ))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 5-1 5.0 BEST ESTIMATE ENHANCED OPTION-III (BEO-III) WITH CONFIRMATION DENSITY ALGORITHM (CDA)

NRC RAI 23. For cycle operation that differs significantly from the original cycle design, describe and justify the process for evaluating whether the analysis continues to bound actual plant operation or whether additional analysis is necessary.

Response 23:

Cycle operation can differ from the final core design for a variety of reasons. The primary concern of these variations is that the actual cycle operations drifts to the point that the computed operating limits are no longer supported. A process exists between Duke and Framatome in the event there are major modifications such as changes to the licensed core loading pattern or implementation of suppression rods where comparison results are provided to Framatome to evaluate the impact on the reload licensing. With this information, Framatome will either determine the change is minor and has negligible impact or decide to rerun (( )). For smaller changes, the RSAR identifies a target end-of-cycle axial power distribution that supports the plant operating limits, such that the integrated impact of minor modifications to rod patterns or operating conditions throughout the cycle can be assessed to determine if the changes invalidate the cycle licensing limits.

To support the evaluation of cycle design deviations, Duke regularly performs projections of plant operation to the end-of-full power cycle exposure to ensure that the RSAR axial power distribution remains bounding. In addition, Duke procedures require this check to be performed in the event that there is a substantial change in the rod pattern from a previously analyzed depletion before the control rod pattern can be implemented at the plant. In the event that a disposition becomes necessary (i.e. RSAR axial power shape no longer bounding), Duke provides Framatome with an up-to-date core follow and depletion to end of full power exposure using appropriate rod patterns.

This new target step-through is used to determine ((

))

In the event that either the major changes or accumulated minor deviations no longer support the established operating limits, Framatome uses the historic operating data

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 5-2 and projected depletion steps to end-of-cycle and establishes new operating limits as appropriate.

NRC RAI 24. Provide sensitivity studies on timestep size and vessel nodalization to demonstrate that potential perturbations to discretization would not have an undue impact on calculated figures of merit or change the sensitivities to statistical parameters.

Response 24:

Sensitivity studies were performed on both the time step size and vessel nodalization consistent with the studies performed for the ATWS-I methodology (Reference 8). Both sensitivity studies examined the impact on the linear reactor benchmarks and the 95/95 core MCPR and (( )) for the MELLLA+ BEO-III analyses reported in ANP-3703P (Attachment 15a of the subject LAR).

((

)) The combinations of

(( )) used for the sensitivity are provided in Table 24-2. The reactor benchmarking sensitivities to variations in the time step control parameters are provided in Table 24-3. The variations of key parameters for the Brunswick MELLLA+ BEO-III analyses are presented in Table 24-4. In both the reactor benchmarks and BEO-III analyses there is ((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 5-3

((

))

The sensitivities to variations in the vessel nodalization are (( )) than the time step sensitivities. The base nodalization for the reactor benchmarks and BEO-III analyses was increased by ((

)) The sensitivities to the finer vessel nodalization are presented in Table 24-5 and Table 24-6 for the benchmarks and MELLLA+ BEO-III analyses, respectively.

((

)) and therefore the discretization is considered acceptable.

Table 24-1 BEO-III Time Step Criteria Table 24-2 Time Step Control Parameters for Sensitivity Studies

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 5-4 Table 24-3 Reactor Benchmark Sensitivity to Time Steps Table 24-4 BEO-III MELLLA+ FoM Sensitivity to Time Steps

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 5-5 Table 24-5 Reactor Benchmark Sensitivity to Vessel Nodalization Table 24-6 BEO-III MELLLA+ FoM Sensitivity to Vessel Nodalization NRC RAI 25. Provide the following clarifications for the (( )) BEO-III analysis:

a. How is the duration of the ((

))

b. What method is used to calculate the (( )) from the RAMONA5-FA time-dependent results?

c. How is the perturbation amplitude (( ))

determined?

d. Explain why the ((

)).

e. Provide plot of core pressure drop ((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 5-6 Response 25 a.:

((

))

Response 25 b.:

((

))

Response 25 c.:

((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 5-7

((

))

Response 25 d.:

((

))

Figure 25-1 (( ))

Response 25 e:

Figure 25-2 presents the core pressure drop as a function of time. ((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 5-8 Figure 25-2 Core Pressure Drop by Stage NRC RAI 26. Address the impact of including medium-importance phenomena in the calculation of relevant figures of merit. Perform an updated BEO-III statistical analysis including all medium-importance phenomena, or justify the exclusion of any particular medium-importance phenomena.

Response 26:

There were seven phenomena identified as medium importance in the PIRT. Each is discussed below:

((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 5-9

((

))

Table 26-1 BEO-III MELLLA+ Sensitivity to (( ))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 5-10

((

))

Table 26-2 BEO-III MELLLA+ FoM Sensitivity to (( ))

((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 5-11

((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 5-12 Figure 26-1 Pump Coastdown Reanalysis of the MELLLA+ 2PT event: The MELLLA+ 2PT event analyzed with the additional medium ranked phenomena discussed above results in ((

))

Figure 26-2 Limiting MELLLA+ MCPR

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 5-13 Figure 26-3 Limiting MELLLA+ (( ))

NRC RAI 27. The capability to characterize the oscillation mode (i.e., as in-phase or out-of-phase) for a predicted instability condition may provide information that is relevant to (1) understanding the physical behavior of the reactor, (2) assessing code predictions against a priori expectation, and (3) assuring that uncertainty characterizations are appropriate.

a. Please clarify whether the plant-specific BEO-III methodology is capable of characterizing the predicted oscillation mode. If such capability exists, please describe and justify the approach used to perform this characterization.

b. Please clarify whether any parameters and phenomena considered in the uncertainty analysis (including any medium-importance phenomena incorporated to address RAI NRC RAI 26) may have a significantly different impact on predicted figures of merit, depending on whether the oscillation mode for the cases analyzed tends to be in-phase or out-of-phase.

c. Provide an assessment of which oscillation modes were observed in the BEO-III analysis for Brunswick and to what degree this impacted the sensitivity to these parameters. Additionally, provide an assessment of the degree to which the statistically-sampled values influenced the calculated oscillation mode.

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 5-14 Response 27 a.:

The RAMONA5-FA code is capable of resolving the oscillation mode given the model fidelity and level of details where ((

))

Response 27 b.:

((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 5-15

((

))

Response 27 c.:

((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 5-16 Figure 27-1 Mode Observations Versus Exposure Figure 27-2 Average Phase Lag Versus Exposure NRC RAI 27. Perform plant-specific BEO-III calculations for the 100%-power / 85%-flow single-recirculation-pump-trip event and provide results including the calculated values for oscillation period, to ensure that all anticipated oscillations remain within the period detection bounds for the Brunswick CDA implementation.

Response 27:

The single pump trip event from the MELLLA+ corner at 100% power and 85% flow was performed with the expanded parameter sampling identified in the response to RAI 26.

((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 5-17

((

))

Figure 27-3 Terminal Operating Conditions Figure 27-4 Oscillation Periods for MELLLA+ Pump Trip Scenarios

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 5-18 NRC RAI 28. Particular statistical cases were ((

))

Response 28:

The response to this RAI was provided in Enclosure 3 of Reference 3.

NRC RAI 29. Justify the dispositioning of the following phenomena as Low Importance in the BEO-III phenomena identification and ranking table (PIRT), given their potential significance for stability and, in some cases, their inclusion in the AURORA-B AOO (ANP-10300P, Rev 1) statistical sampling for non-pressurization transients:

• ((

• ))

Response 29:

((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 5-19

((

))

Table 29-1 BEO-III MELLLA+ FoM Sensitivity to (( ))

((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 5-20

((

))

Table 29-2 BEO-III MELLLA+ (( ))

NRC RAI 30. In Stage 3 of the multistage analysis, ((

))

Response 30

((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 6-1 6.0 CONTAINMENT NRC RAI 31. In section 7.3 of ANP-3705P, the licensee states that fuel design differences may impact the power and pressure excursion experienced during an ATWS event. The licensee further states that ATRIUM-10XM analysis bounds the ATRIUM-11 fuel because ((

))

a. Describe the analysis done to justify that ((

))?

b. Provide quantitative results for the containment pressure and suppression pool temperature response changes due to the change in fuel type. Describe the analyses performed to confirm the ATRIUM-10XM analysis bounds the ATRIUM-11 fuel transition.

c. Containment heatup is directly impacted by the stored energy within the fuel and the decay heat. Provide a quantitative comparison of the decay heat between the ATRIUM-10XM and ATRIUM-11 fuel.

Response 31 a.:

Analysis to confirm that ((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 6-2 Response 31 b.:

The Framatome description of the approach for evaluating containment impacts and results of that evaluation are described in Section 7.3 of Reference 10. This approach is based on (( )). A review of the current licensing basis for Brunswick ATWS containment shows that peak suppression pool temperature for MELLLA+ was 174 °F and the peak containment pressure was 8.4 psig, Section 9.3.1 of Reference 11. ((

))

Response 31 c.:

In general, the decay heat results are ((

))

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 6-3 Table 31-1 Decay Heat Evaluation

((

))

NRC RAI 32. Regulatory Basis - 10 CFR 50 GDCs 16, 38, and 50 No additional events were listed in the application as having had an impact from the transition to ATRIUM-11 fuel. Explain any changes that were made to any analyses which impact the mass and energy release during an accident or a special event (station blackout or fire event).

Response 32:

((

)) No other plant design changes are planned during this transition to ATRIUM 11 fuel. Therefore the analysis of record is not impacted by the introduction of ATRIUM 11 fuel. In the future, plant modifications will be dispositioned for their impact on the licensing basis events and analyses will be updated as necessary.

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 7-1

7.0 REFERENCES

1. William R. Gideon (Duke Energy) to U.S. Nuclear Regulatory Commission, Brunswick Steam Electric Plant, Unit Nos. 1 and 2 Renewed Facility Operating License Nos. DPR-71 and DPR-62 Docket Nos. 50-325 and 50-324 Request for License Amendment Regarding Application of Advanced Framatome Methodologies, ML18284A395, October 11, 2018.

2. Email, Andrew Hon (USNRC) to Stephen Yodersmith (Duke Energy), Brunswick Unit 1 and Unit 2 Request for Additional Information related Transition to Framatome ATRIUM-11 Fuel (EPID:L-2018-LLA-0273), ML19135A307, May 9, 2019.

3. William R. Gideon (Duke Energy) to U.S. Nuclear Regulatory Commission, Brunswick Steam Electric Plant, Unit Nos. 1 and 2 Renewed Facility Operating License Nos. DPR-71 and DPR-62 Docket Nos. 50-325 and 50-324 Response to Request for Additional Information Regarding Advanced Framatome Methodologies License Amendment Request, ML19149A319, May 29, 2019.

4. William R. Gideon (Duke Energy) to U.S. Nuclear Regulatory Commission, Brunswick Steam Electric Plant, Unit Nos. 1 and 2 Renewed Facility Operating License Nos. DPR-71 and DPR-62 Docket Nos. 50-325 and 50-324 Supplement to Request for License Amendment Regarding Application of Advanced Framatome Methodologies, ML19135A029, May 14, 2019.

5. ANP-10332Q1P Revision 1, AURORA-B: An Evaluation Model for Boiling Water Reactors; Application to Loss of Coolant Accident Scenarios Response to NRC Request for Additional Information, October 2018.

6. XN-NF-82-07(P)(A) Revision 1, Exxon Nuclear Company ECCS Cladding and Swelling and Rupture Model, October 1982.

7. ANP-3644(P) Revision 0, Brunswick Unit 2 Thermal-Hydraulic Design Report for ATRIUM 11 Fuel Assemblies, August 2018.

8. ANP-10346Q1P Revision 0, ATWS-I Analysis Methodology for BWRs Using RAMONA5-FA Response to NRC Request for Additional Information, ML19071A274, March 2019.

9. ANP-10300P-A Revision 1, AURORA-B: An Evaluation Model for Boiling Water Reactors; Application to Transient and Accident Scenarios, January 2018.

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page 7-2

10. ANP-3705P Revision 1, Applicability of Framatome BWR Methods to Brunswick with ATRIUM 11, Framatome Inc., November 2018.

11. DUKE-OB21-1104-000(NP), Safety Analysis Report For Brunswick Steam Electric Plant Units 1 and 2 Maximum Extended Load Line Limit Analysis Plus, ML16257A411, July 31, 2016.

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-1 Appendix A Generic ATWS-I RAI Responses BACKGROUND This document comprises Framatomes response to the Nuclear Regulatory Commission (NRCs) Request for Additional Information (RAIs) for the Licensing Topical Report (LTR) ANP-10346, ATWS-I Analysis Methodology for BWRs Using RAMONA5-FA. These RAIs are being provided to aid the NRC in their review of the Brunswick Advanced Methods LAR (i.e., ML18284A395). These generic RAI responses are applicable to the Plant Specific methodology presented in ANP-3694P (i.e., Attachment 14a of ML18284A395).

The specific regulatory requirements associated with anticipated transient without scram (ATWS) events are contained in Title 10 of the Code of Federal Regulations (10 CFR)

Part 50.62, "Requirements for reduction of risk from anticipated transients without scram (ATWS) events for light-water-cooled nuclear power plants," and 10 CFR 50.46, "Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors," as well as General Design Criteria (GDC) 12, "Suppression of Reactor Power Oscillations," 14, "Reactor Coolant Pressure Boundary," 16, "Containment Design," 35, "Emergency Core Cooling," 38, "Containment Heat Removal," and 50, "Containment Design Basis," which are contained in Appendix A to 10 CFR 50.

Of those requirements, GDCs 12 and 35 are the most relevant, in that the intent of the ATWS with-instability (ATWS-I) analyses is to demonstrate that: (1) power oscillations that arise due to instability in the core are adequately mitigated by appropriate operator actions and/or automatic system responses, and (2) adequate cooling of the fuel is maintained, such that the maximum cladding temperature does not reach thresholds where significant fuel/cladding damage or metal-water reactions are expected to occur.

The NRC guidance related to the boiling water reactor (BWR) ATWS-I event is presented in the Standard Review Plan, Section 15.8. During review of Topical Report (TR), ANP-10346P, Revision 0, "ATWS-I Analysis Methodology for BWRs Using RAMONA5-FA," the NRC staff identified some information that would be necessary to

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-2 establish adequate technical bases to make a safety determination based on the above regulatory requirements. In particular, this information directly affects the calculation of the three figures of merit (FoMs) that the demonstration of regulatory compliance are based on-the oscillation inception (i.e., how much time operators have to act), limit cycle amplitude (i.e., worst case oscillation), and post-dryout (i.e., peak cladding temperature (PCT)).

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-3

RAI-1

The Framatome 3-dimensional core physics simulator code, MICROBURN-B2, is used to produce data transfer files which pass condensed versions of relevant information for use in the RAMONA5-FA neutron kinetics solution [

]. Therefore, the NRC staff requests the following information:

1. What [ ] information is passed from MICROBURN-B2 to the RAMONA5-FA ATWS-I calculation? What process and/or criteria, if any, is used to ensure that [

]?

Framatome Response RAI-1:

[

]. These include:

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-4

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-5

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-6

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-7 The RAMONA5-FA code incorporates several models to capture specific phenomena of interest for the ATWS-I event. These models are typically constructed from empirical correlations developed based on a combination of theoretical principles and experimental data analysis. In order for the models to capture the phenomena of interest throughout the ranges of interest for key analysis parameters, the appropriate dependencies must be accurately captured in the models. To do so, the models must consider all relevant parameters, and the empirical correlations must be based on an appropriate analysis of the available data (including any gaps or limitations). Therefore, the NRC staff requests the following information

RAI-2

The NRC staff has the following questions regarding the fitting of model parameters to measured data:

a. For models such as the dryout-rewet model and gap conductance model which contain multiple fitting parameters, how were values for these parameters inferred in cases where direct experimental validation for each parameter is not possible or not available?

b. For the gap conductance model, the TR states that [

]. Describe this approach in additional detail, including how this adjustment was performed and how these values compare to similar values used in other Framatome methodologies.

Framatome Response RAI-2-a:

The fitting of coefficients depends not only on experimental data but also on assumptions that are based on first principles and reasonable engineering judgment.

These must be applied on a case by case basis.

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-8 Framatome Response RAI-2-b:

[

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-9

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-10

RAI-3

Justify the [

] used in the TR methodology. Include data for the [

].

Framatome Response RAI-3:

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-11

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-12 Figure 1 [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-13 Figure 2 [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-14 Figure 3 [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-15 Figure 4 [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-16 Figure 5 [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-17 Figure 6 [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-18 Figure 7 [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-19 Figure 8 Dry [ ]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-20

RAI-4

Since the [ ] was not part of the KATHY dryout-rewet experimental validation, justify that the models are a reasonable and accurate representation of [ ] during ATWS-I.

Framatome Response RAI-4:

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-21

RAI-5

The [

]. How is the model ensured to give reasonable and accurate behavior under such conditions during ATWS-I?

Framatome Response RAI-5:

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-22 h p h

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-23 Figure 9 Illustration of [

]

[

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-24 Figure 10 Illustration of [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-25 Figure 11 Illustration of [

]

[

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-26 Figure 12 Illustration of [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-27 Figure 13 Illustration of the [

]

[

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-28 Figure 14 Illustration of [

]

[

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-29 Figure 15 Illustration of [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-30 Once all of the models and coupling equations were combined into an unified analysis methodology within RAMONA5-FA to calculate the thermal hydraulic and neutron kinetics response during an ATWS-I event, Framatome validated the overall methodology by comparing calculational results to independent benchmarks. By demonstrating that RAMONA5-FA can independently reproduce key parameters for applicable benchmarks, reasonable assurance is provided that RAMONA5-FA will reproduce the same parameters for a postulated ATWS-I event. The key comparison results are presented in the TR, but some additional detail is needed to confirm that the benchmarks, and information used in the benchmarking calculations, are applicable to the intended use of RAMONA5-FA. Therefore, the NRC staff requests the following information:

RAI-6

The NRC staff has the following questions regarding the linear stability benchmarks provided in the TR:

a. Provide a table showing the following operating conditions and calculated conditions for each linear stability benchmark case: core power, core flow rate, core inlet subcooling, axial peaking factor, peak axial power location, and radial peaking factor.

b. What fuel type(s) were present in the core for each of the linear stability benchmarks? Were all data and specifications available for these fuel types? What data and specifications required by RAMONA5-FA ATWS-I were not available, if any?

c. What neutronic and thermal hydraulic data were used from each plant in these benchmarks?

Framatome Response RAI-6-a:

The range of operating conditions for the various linear stability reactor benchmarks are shown in Table 1.

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-31 Table 1 Operating conditions of the linear reactor benchmarks Framatome Response RAI-6-b:

The linear stability benchmarks were all taken from the approved STAIF (Reference 5) and RAMONA5-FA (Reference 6) benchmarking suites. For these benchmarks the majority of fuel inputs were already available. In some cases, [

].

[

].

Framatome Response RAI-6-c:

The neutronics and thermal-hydraulics data for these benchmarks was taken directly from the approved STAIF (Reference 5) and RAMONA5-FA (Reference 6) benchmarking suite. No additional neutronics or thermal-hydraulics data was required.

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-32

RAI-7

The NRC staff has the following questions regarding the nonlinear stability benchmarks provided in the TR:

a. What fuel type(s) were present in the core for each of the nonlinear stability benchmarks? Were all data and specifications available for these fuel types? What data and specifications required by RAMONA5-FA ATWS-I were not available, if any?

b. What deviations, if any, were made in the boundary conditions or other modeling assumptions for these cases relative to measured data and/or available benchmark specifications?

Framatome Response RAI-7-a:

The Oskarshamn-2 benchmark consisted of [

].

Framatome Response RAI-7-b:

For the Oskarshamn-2 benchmark, the initial power, core flow and inlet subcooling were all input as the initial measured conditions. The feedwater flow versus time was decreased from the measured data to ensure reasonable water level calculation. This was necessary to restore correct mass balance as the calculated steam flow underpredicted the measured steam flow which would have led to an upward drift in water level. Modifying the feedwater flow versus time to better control water level is also consistent with the application of the method which utilizes a feedwater control system for the same purpose. The feedwater temperature versus time was taken directly from the benchmark specifications and includes the adjustment to the temperature function that accounts for instrumentation delay due to pipe heat conduction. The pressure was set to the measured value versus time. The control rod

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-33 insertions were modeled as they occurred in the event. Two sets of runs were made for pump speed. In one case, the measured pump speed versus time was prescribed.

Reviewing the output of this run, it was observed that the core flow just prior to oscillation inception is overpredicted when compared to measurements. To investigate this effect, a second run was made with a pump speed that was modified to provide a core flow close to the measured values. Both cases were presented in the topical report.

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-34 The TR includes guidance for nodalization of the plant models used in executing the RAMONA5-FA ATWS-I calculations. The nodalization selected in a model is generally a balance between managing the time required to complete a calculation, maintaining calculational stability, and resolving the time/spatial distribution of parameters to a sufficiently fine level for accuracy. In general, the testing performed by Framatome can be expected to ensure that the computational time and stability are acceptable, but the NRC staff needs to verify that the nodalization recommendations are adequate to provide reasonable accuracy in the calculations. Therefore, the NRC staff requests the following information:

RAI-8

Justify that the RAMONA5-FA ATWS-I axial nodalization scheme in the core region provides sufficient numerical fidelity for the ATWS-I calculations, including considerations of numerical diffusion and resolution of the axial void distribution.

In particular, prior studies by the NRC staff and contractors have shown that the axial void distribution may need to be captured at a sufficiently high resolution to result in an accurate calculation of the axial power profile, and thus accurate calculation of stability behavior (e.g. decay ratio), in some codes. This effect has been shown to be separate from that of numerical diffusion, so provide a discussion regarding whether the average void fraction for each node is accurate enough to correctly capture the axial power distribution for stability calculations.

For example, would an increase in the number of thermal hydraulic nodes lead to a significant change in the locally-averaged void fraction across the coupled neutronic nodes due to the higher resolution of the void fraction distribution, and would this significantly affect the RAMONA5-FA ATWSI calculations?

Framatome Response RAI-8:

A theoretical discussion of the numerical fidelity of the algorithms used for BWR stability must come with a disclaimer pointing to the wide opinions promulgated in the nuclear industry where no studies can claim completeness or generality of applicability to all codes. While a discussion is provided here, the ultimate support for the RAMONA5-FA code numerical fidelity rests on the empirical proof afforded by good agreement with a wide variety of experimental data forming a benchmarking database, and stressing the code with numerical experiments and sensitivity studies.

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-35 Numerical diffusion and damping Numerical diffusion results from the residuals of finite differencing (or finite volume) approximations of transport differential equations. Neglected higher order terms resemble diffusion operators acting on the transported property, e.g. temperature moving in a 1-D pipe. In the ideal example of a step change in temperature of a fluid moving through a pipe, the exact solution maintains the same step function shape which moves along the pipe at the flow speed. Physical or numerical diffusion causes the sharp step change to diffuse and the temperature distribution spreads increasingly with time. This numerical diffusion is a kinematic aspect as it does not involve forces or momenta. The effect of diffusion (spread) of various flow variables on the momentum is not discussed in the available literature beyond numerical experiments demonstrating a damping effect of the perturbations as functions of time; the connection between the spatial diffusion and temporal damping is implied but only as a qualitative trend without proof. An attempt to make this dynamic connection in the context of density waves is presented here. [

] Another possible effect of diffusion is increasing the attenuation of the flow perturbations as they travel from the inlet to higher elevations. In this case, the magnitude of the pressure drop near the exit would be reduced relative to that of the inlet which has a dampening effect. A third possible effect is related to how the momentum balance equations are formulated where either nodal momentum equations are used or a single integrated momentum equation is formulated per boiling channel.

The effect of increased attenuation of the flow perturbations as they travel up the boiling channel has been shown [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-36

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-37

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-38 magnitude cases, the increased nodalization also produced larger oscillations that

[

].

Figure 16 Calculated Versus Measured Decay Ratio for [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-39 Figure 17 Calculated Versus Measured Frequency for [

]

[

].

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-40 Table 2 Linear reactor benchmarks [

]

[

].

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-41 Figure 18 [

]

[

].

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-42 Figure 19 [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-43 Figure 20 [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-44 Figure 21 [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-45 Figure 22 [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-46 Figure 23 [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-47 Table 3 provides a comparison between the results of the Brunswick ATWS-I sample base case with standard nodalization and the doubled core nodalization case.

Table 3 Comparison between Brunswick sample case results with standard and doubled core nodalization Parameter Base Case Doubled Nodalization Time of oscillation inception (sec) 113 92 Time of failure to rewet excursion (sec) 117 97 Time of peak bundle power (sec) 117.2 143.3 Peak bundle power (MW) 5.74 5.69 Time of maximum core inlet subcooling (sec) 147.1 151.5 Maximum core inlet subcooling (kJ/kg) 195.8 205.5 Time of peak clad temperature (sec) 140.7 143.5 Peak clad temperature (oC) 656 677

[

].

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-48

RAI-9

Justify that the vessel nodalization used for RAMONA5-FA ATWS-I is sufficient to provide a reasonable and accurate prediction of PCT during ATWS-I events.

Framatome Response RAI-9:

The Brunswick test case for ATWS-I was rerun with the nodalization in the vessel

[

].

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-49 Figure 24 Brunswick sample problem showing effect on [

] due to vessel nodalization

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-50 Figure 25 Brunswick sample problem showing effect on [

] due to vessel nodalization

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-51 Figure 26 Brunswick sample problem showing effect on [

] due to vessel nodalization

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-52 Figure 27 Brunswick sample problem showing effect on [

] due to vessel nodalization For the same calculation where the operator actions are omitted (unmitigated case), the core inlet subcooling varies towards the end of the run due to the effect of the power and flow oscillations in the core which become highly nonlinear and chaotic fluctuations are expected. [

].

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-53 Table 5 Unmitigated Brunswick sample problem PCT results with different vessel nodalization Figure 28 Unmitigated Brunswick sample problem showing effect on

[ ] due to vessel nodalization

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-54 Figure 29 Unmitigated Brunswick sample problem showing effect on

[ ] due to vessel nodalization

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-55

RAI-10

Provide an example(s) of the calculated time-dependent behavior of the [

] during large-amplitude oscillations with flow reversal. In the cases presented in the TR, did sufficient flow reversal occur such that [ ]? If such a circumstance occurs, justify that the RAMONA5-FA ATWS-I methodology treats this circumstance in a reasonable and/or conservative way, with respect to the ATWS acceptance criteria.

Framatome Response RAI-10:

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-56 Figure 30 [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-57 Several inputs to the ATWS-I calculation are described in the TR, with specific recommendations provided. In some cases, the parameters of interest may be determined to be insensitive to specific inputs based on engineering judgment or sensitivity studies. In other cases, the parameters of interest are adjusted to achieve desired results. In all cases, the recommendations must ensure that the results from the ATWS-I calculations are accurate or conservative. In order to verify this, the NRC staff requests the following information:

RAI-11

Provide sensitivity results for one or more linear stability benchmark cases and a simulated ATWS-I event (either a nonlinear benchmark problem or a sample full-core case) by adjusting the gap conductance values. Show time-dependent results for power, PCT, and other relevant results.

Framatome Response RAI-11:

The effect of gap conductance on the reactor benchmarks is given in Table 5, [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-58 Table 5 Effect of gap conductance [ ]

linear reactor stability benchmarks

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-59 Figure 31 [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-60 Figure 32 [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-61 Figure 33 [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-62 Figure 34 [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-63

RAI-12

The NRC staff has the following questions regarding time step control:

a. What input parameters are provided by RAMONA5-FA ATWS-I to control the timestep size? What are the recommended values for use?

b. What values for these parameters were used for the nonlinear stability benchmarks and the sample problem provided in the TR?

c. Provide a set of sensitivity results for timestep size, similar to the sensitivity study provided for RAI11.

Framatome Response RAI-12-a:

Framatome Response RAI-12-b :

The values are provided in Table 6 and are common between the benchmarks and the sample problem.

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-64 Table 6 Time Step Criteria Framatome Response RAI-12-c:

Time step control parameters were varied to generate the time step sensitivity for several cases including the reactor benchmarks and the sample Brunswick ATWS-I run.

[

]. An example of the time step variation will be provided.

Table 7 Control parameters for time step sensitivity The reactor benchmarking results using these time step control parameters are provided in Table 8, [

].

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-65 Table 8 Linear reactor benchmark results with variations of time step controls listed in Table 7 The results of the Brunswick sample run for different time step controls are plotted together. [

].

Table 9 Peak clad temperature results for the Brunswick sample case with varied time step control parameters

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-66 Figure 35 Brunswick sample problem with varied time step control parameters showing [ ]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-67 Figure 36 Brunswick sample problem with varied time step control parameters showing [ ]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-68 Figure 37 Brunswick sample problem with varied time step control parameters showing [ ]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-69 Figure 38 Brunswick sample problem with varied time step control parameters showing [ ]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-70 Figure 39 Brunswick sample problem with varied time step control parameters showing [ ]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-71

RAI-13

What spatial distribution is used for the [

]? Justify that the modeling approach for [

].

Framatome Response RAI-13 :

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-72 Figure 40 Oskarshamn Core Power Results, [ ]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-73 Figure 41 Oskarshamn Core Power Zoomed Results, [

]

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-74

RAI-14

Justify that the [

].

Framatome Response RAI-14:

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-75

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-76 The TR provides a brief procedure that would be used to perform the ATWS-I analysis and determine whether acceptance criteria are met. [

]. Therefore, the NRC staff requests the following information:

RAI-15

[

]

Framatome Response RAI-15:

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-77

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-78

RAI-16

For the process described in RAI 15, discuss how the various modeling and input assumptions remain appropriate when considering their effect on the time of oscillation onset.

Framatome Response RAI-16:

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-79 Additional Information In the topical report ANP-10346P, Section 8.0 (Calculation Procedure), Steps 3a and 3b are inconsistent.

Step 3a contains the following statement:

A corrected page 8-2 has been added below to reflect this change.

Controlled Document Framatome Inc. ANP-3694NP Revision 0 ATWS-I Analysis Methodology for Brunswick Using RAMONA5-FA Page 8-2

Controlled Document Framatome Inc. ANP-3782NP Revision 2 Brunswick ATRIUM 11 Advanced Methods Response to Request for Additional Information Page A-81 References

1. Y. M. Farawila and M. R. Billaux, XEDOR -- Reduced Order Stress Model for Interactive Maneuvering of Boiling Water Reactors, Proceedings of the International LWR Fuel Performance Top Fuel Meeting, San Francisco, September 30 - October 3 2007, Paper 1059.

2. Y. M. Farawila, K. Wei, and R. G. Grummer, "XEDOR Evaluation of PCI Risk due to Loss of Feedwater Heating in Boiling Water Reactors," Proceedings of the 2008 Water Reactor Fuel Performance Meeting, Seoul Korea, October 19-23, Paper 8142.

3. J. March-Leuba, C. G. Thurston and T. L. Huang, "Time-space nodalization issues in BWR stability calculations," in NURETH-15, Pisa, Italy, 2013.

4. Aaron J. Wysocki, Investigation of Limit Cycle Behavior in BWRs with Time-Domain Analysis, PhD Thesis, University of Michigan, 2015.

5. EMF-CC-074(P)(A) Volume 4 Revision 0, BWR Stability Analysis: Assessment of STAIF with Input from MICROBURN-B2, August 2000.

6. BAW-10255PA Revision 2, Cycle-Specific DIVOM Methodology Using the RAMONA5-FA Code, May 2008.

7. P. Yarsky, Sensitivity to Tmin In Trace/Parcs Analysis of ATWS with Instability, NURETH-16, Chicago, IL, August 30-September 4, 2015

8. Yousef M. Farawila, Fuel Design Concept to Stabilize Boiling Water Reactors, Top Fuel 2016, Boise, ID, September 11-15, 2016

9. Letter, Jonathan G. Rowley (NRC) to Gary Peters (Framatome), Request for Additional Information Regarding Framatome Inc. Topical Report ANP-10346P Revision 0, ATWS-I Analysis Methodology for BWRs Using RAMONA5-FA (EPID:

L-2017-TOP-0067), September 21, 2018.

RA-19-0241 Enclosure 3 Affidavit for ANP-3782P, Revision 2