ML16007A190

Catawba Nuclear Station, Units 1 and 2: Request for Additional Information Regarding License Amendment Request to Change the RCS Minimum Required Flow Rates (CAC Nos. MF6355 and MF6356)

ML16007A190
Person / Time
Site:	Catawba
Issue date:	01/20/2016
From:	Miller G E Plant Licensing Branch II
To:	Henderson K Duke Energy Carolinas
Miller G E
References
CAC MF6355, CAC MF6356
Download: ML16007A190 (9)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 Mr. Kelvin Henderson Site Vice President Catawba Nuclear Station Duke Energy Carolinas, LLC 4800 Concord Road York, NC 297 45 January 20, 2016

SUBJECT:

CATAWBA NUCLEAR STATION, UNITS 1 AND 2: REQUEST FOR ADDITIONAL INFORMATION REGARDING LICENSE AMENDMENT REQUEST TO CHANGE THE RCS MINIMUM REQUIRED FLOW RATES (TAC NOS. MF6355 AND MF6356)

Dear Mr. Henderson,

By letter dated June 12, 2015 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML 15168A009),

Duke Energy Carolinas, LLC (Duke Energy),

the licensee for Catawba Nuclear Station, Units 1 and 2, submitted a license amendment request (LAR) for changes to the Technical Specifications (TS). Specifically, the licensee proposed to modify TS Table 3.4.1-1, "RCS [Reactor Coolant System] DNB Parameters",

Parameter 3, "RCS Total Flow Rate." The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the licensee's submittal and determined that additional information is needed in order to complete the NRC staff's review. Enclosure 1 describes this request for additional information (RAI). On January 14, 2016, Mr. Lawrence Rudy of your staff agreed to respond within 45 days of this letter. If you have any questions, please call me at 301-415-2481.

Docket Nos. 50-413 and 50-414

Enclosure:

As stated cc w/encl: Distribution via Listserv Since;y . J (_:!)r,'11'""

G. Edward Miller, Project Manager Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation REQUEST FOR ADDITIONAL INFORMATION LICENSE AMENDMENT REQUEST TO SUPPORT THE MEASUREMENT UNCERTAINTY RECAPTURE POWER UPRATE DUKE ENERGY CAROLINAS.

LLC CATAWBA NUCLEAR STATION.

UNITS 1AND2 DOCKET NOS. 50-413 AND 50-414 TAC NOS. MF6355 AND MF6356 By letter dated June 12, 2015 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML 15168A009),

Duke Energy Carolinas, LLC (Duke Energy),

the licensee for Catawba Nuclear Station, Units 1 and 2, submitted a license amendment request (LAR) for changes to the Technical Specifications (TSs). Specifically, the licensee proposed to modify TS Table 3.4.1-1, "RCS [Reactor Coolant System] DNB Parameters",

Parameter 3, "RCS Total Flow Rate", Limit as follows:

For Unit 1: From "<:: 388,000 gpm and<:: the limit specified in the COLR (Unit 1 )", to"<:: 384,000 gpm and <::the limit specified in the COLR (Unit 1 )" For Unit 2: From"<::

390,000 gpm and<:: the limit specified in the COLR (Unit 2)", to"<:: 387,000 gpm and<:: the limit specified in the COLR (Unit 2)" Based on its review of this LAR, the NRC staff has determined the following additional information is necessary to continue its technical review. 1. Page 3 indicates that the reanalysis to support the TS changes used the methodologies documented in the topical reports (TR) as follows:

TR-1: DPC-NE-3001-P-A, "Multidimensional Reactor Transients and Safety Analysis Physics Parameter Methodology",

Revision Oa TR-2: DPC-NE-3002-A, "FSAR Chapter 15 System Transient Analysis Methodology",

Revision 4b TR-3: DPC-NE-2005-P-A, "Thermal Hydraulic Statistical Core Design Methodology",

Revision 4a TR-4: DPC-NE-3000-P-A, "Thermal-Hydraulic Transient Analysis Methodology",

Revision Sa Please provide TR-1 through TR-4, identify any differences from TRs originally approved for use in the Catawba licensing applications, and discuss how the Catawba reanalysis Enclosure satisfies the restrictions and conditions specified in the applicable SERs for TR-1 through TR-4. 2. Page 9 and page 15 indicate that the reanalysis used the calculated core bypass flow rates of 6.49 percent and 6.71 percent of the total reactor coolant system (RCS) flow for Unit 1 and Unit 2, respectively.

The core bypass flow rates are reduced from 8.5 percent for Unit 1, and 7.5 percent for Unit 2 assumed in the current analysis of record (AOR), resulting in a greater core flow rate for core heat removal.

Please discuss the conservatisms considered in the calculation of the core bypass flow and provide quantitative justification for the calculated bypass core flow of 6.49 percent and 6.71 percent for use in the reanalysis.

Also, please clarify if the current AOR for each of the transients and accident was incorporated in Chapter 15 of the updated final safety analysis report (UFSAR) for Catawba Units 1 and 2. 3. Pages 9 to 12 and pages 15 to 17 discuss the reanalysis and evaluation for Category-3 events to support the proposed TS changes reducing the RCS flow rates for Unit 1 and Unit 2, respectively.

Please clarify if the only change to the input parameter in the reanalysis compared with the AOR is the total RCS flow rates. Please justify any other changes in the input parameters, models, and methodologies used in the reanalysis.

4. Category-1 Events for Unit 1: Transients Bounded by Current RCS Flow Assumption Page 7 of Attachment 1 to the LAR lists six Category-1 events. The LAR indicates that for Category-1 events, the total RCS flow assumed in the current AOR is based on either the mechanical design flow of 420,000 gpm (where maximum RCS flow rates are conservative) or the thermal design flow of 382,000 gpm (where minimum RCS flow rates are conservative).

The LAR further states that the proposed minimum RCS total flow limit of 384,000 gpm has no impact on the analysis for this category events. The above quoted flow rates of 420,000 gpm and 382,000 gpm appear to be inconsistent with the values in FSAR Table 15.4 for two Category-1 events (Event 1 D and Event 1 E). The flow rates are 381,420 gpm for Event 1 D, the turbine trip analysis addressing the peak RCS pressure (UFSAR 15.2.3) and 373,596 gpm for Event 1 E, the analysis for the loss of non-emergency AC power to the station auxiliary (UFSAR 15.2.6),

respectively.

Please clarify the inconsistences discussed above and justify that the results of AOR for the above two events remain valid with the proposed lower RCS flow limit. Also, UFSAR 15.8 indicates that Event 1 F (for Unit 1 ), Anticipated Transients without Trip, is not analyzed.

Please explain why this event is classified as a Category-1 event that is defined by the licensee as an event that is bounded by AORs using current RCS flow assumptions.

Additionally, please address this question with respect to Event 41 for Unit 2. 5. Events 2G and 3N (Unit 1) and Event 5G (Unit 2) -Feedwater System Pipe Break (FLB, UFSAR 15.2.8, Short-Term)

For Events 2G and 3N (Unit 1) and Event 5G (Unit 2), the short-term FLB analysis is not reanalyzed at the proposed RCS flow rate, because the LAR indicates that the term-cooling results for the FLB analysis are bounded by the analysis for a loss of normal feedwater flow (LONF, UFSAR 15.2.7).

The above statement is apparently inconsistent with the statement discussed in the last paragraph of UFSAR 15.2. 8.2, which states that the short term cooling (DNBR) results for the FLB incident "is bounded by that of the complete loss of forced reactor coolant incident, thus, ensuring that the integrity of the core is maintained in the short term."1 Indicate where, in the UFSAR, is it stated that a FLB is not limiting.

I Additionally, please clarify the inconsistencies identified above regarding the minimum departure from nucleate boiling ratio (DNBR) results and justify that the cooling results for the FLB analysis meet the applicable acceptance criteria and are acceptable for cases with lower minimum RCS flow limits of 384,000 gpm and 387,000 gpm for Units 1 and 2, respectively.

6. Event 3K -Excessive Increase in Secondary Steam Flow (UFSAR 15.1.3) Page 10 indicates that the sensitivity analysis for Event 3K in UFSAR 15.1.3 showed that the results of the transient analysis are not sensitive to the RCS flow rate. UFSAR Table 15.2 indicates that for the increase in steam flow event, UFSAR Section 15.1.3 considered two cases: (1) manual rod control with the most negative moderator coefficient; and (2) automatic rod control with the most negative moderator coefficient.

Clarify if both cases were considered in the RCS flow rate sensitivity analysis.

7. Event 3L (Unit 1) and Event 6L (Unit 2) -Steam System Piping Failure (UFSAR 15.1.5) (a) Page 10 and page 16 indicate that event 3L for Unit 1 and Event 6L for Unit 2 were reanalyzed at a RCS flow rate of 384,000 gpm and 387,000 gpm, respectively.

UFSAR Table 15.2 indicates that for the steam line break (SLB) event, UFSAR 15.1.5 discussed the results of analysis for two cases: (1) an SLB event with offsite power maintained; and (2) an SLB event with offsite power lost. Please clarify if both cases were considered in the reanalysis for both Unit 1 and Unit 2. (b) The reanalysis of Event 3L and 6L indicate that DNB does not occur during the SLB event, since the calculated minimum DNBR is above the W-3S Critical Heat 1 The lined out portion of the question was included in the original Draft RAI. During a teleconference with the licensee, Duke staff indicated that the cited statement was not in the current UFSAR. Upon further review, the NRC staff identified that statement was removed in a previous revision to the UFSAR. Therefore, the NRC staff has modified the question accordingly. Flux (CHF) correlation limit of 1.45. Please indicate whether the use of W-3S correlation and associated DNBR limit of 1.45 in the SLB analysis for Catawba licensing applications has been previously reviewed and approved by the NRC. 8. Event 3M -Loss of Normal Feedwater (LONF) Analysis (UFSAR 15.2.7) For the long-term LONF analysis discussed for Event 3M, the AOR assumes an RCS flow of 388,000 gpm. Because a subcooling of at least 40 °F at the RCS hot-leg exists throughout the transient, the licensee states that "the proposed reduction in RCS flow rate to 384,000 gpm will have an inconsequential impact on this transient."

The quoted flow rate of 388,000 gpm appears to be inconsistent with the UFSAR Chapter 15 information:

UFSAR Table 15.2 indicates that for Unit 1, the LONF event (UFSAR 15.2. 7) is analyzed for the long-term cooling capability as Case 1. As indicated in UFSAR Table 15.4, Case 1 of the LONF event is analyzed with a total RCS flow of 381,420 gpm. Please clarify the apparent inconsistency for the RCS flow rates discussed in the information for Event 3M and UFSAR Table 15.4, and justify that the AOR Case 1 in UFSAR 15.2. 7 for the long-term LONF analysis remains valid with a lower minimum RCS flow limit for Unit 1. 9. Event 30 (Unit 1) and Event 6M (Unit 2) -Reactor Coolant Pump Shaft Seizure -Locked Rotor (UFSAR 15.3.3) Page 11 and page 16 indicate that Event 30 for Unit 1 and Event 6M for Unit 2 were reanalyzed at a RCS flow rate of 384,00 gpm and 387,00 gpm, respectively.

UFSAR Table 15.2 indicates that for the locked rotor event (Events 30 and 6M), UFSAR 15.3.3 considered three cases: (1) the worst peak pressure case; (2) the core cooling analysis with offsite power maintained; and (3) the core cooling analysis with offsite power lost. Please clarify if all three cases were considered in the updating analysis.

Also please provide justification for the cases that were not considered in the reanalysis for both Unit 1 and Unit 2. 10. Event 3P -Uncontrolled RCCA Bank Withdrawal from a Subcritical or Low Power Startup Condition (BWFS or BWALP, UFSAR 15.4.1) The information for Event 3P indicates that for BWFS or BWALP (UFSAR 15.4.1 ), Case 1 addressing adequacy of the core cooling assumes RCS flow with three reactor coolant pumps operational based on nominal flow of 388,000 gpm. The quoted flow rate of 388,000 gpm is not consistent with the value included in FASR Table 15.4 which indicates in the column designated as UFSAR Section 15.4.1 that the RCS flow rate used is 299,613 gpm for the Case 1 of the BWFS or BWALP analysis.

Please clarify the inconsistency discussed above and justify that Case 1 of the AOR in UFSAR 15.4.1 remains valid with the required minimum RCS flow reduced from 388,000 gpm to :)84,000 gpm. 11. Event 30 (Unit 1) and 60 (Unit 2) -Uncontrolled RCCA Bank Withdrawal at Power (RWDAP, UFSAR 15.4.2) Page 12 and page 17 indicate that Event 30 for Unit 1 and Event 60 for Unit 2 were reanalyzed at a RCS flow rate of 384,000 gpm and 387,000 gpm, respectively.

UFSAR Table 15.2 indicates that for the RWDAP event, UFSAR 15.4.2 considered five cases: ( 1) (2) (3) (4) (5) Bank withdrawal from 10 percent power core cooling; Bank withdrawal from 8 percent power peak RCS pressure; Bank withdrawal from 50 percent power core cooling; Bank withdrawal from 98 percent power core cooling; and Bank withdrawal from 100 percent power core cooling.

Please clarify if all five cases were considered in the reanalysis.

Provide justification for the cases that were not considered in the updating analysis for Unit 1 and Unit 2. 12. Events 3R (Unit 1) and 6P (Unit 2) -Startup of an Inactive RCP at an Incorrect Temperature (UFSAR 15.4.4) The information for Event 3R for Unit 1 and Event 6P for Unit 2 indicates that the current AOR is based on the calculated three-pump flow, starting from a nominal power and four pump flow of 388,000 gpm. The above quoted flow rate of 388,000 gpm is not consistent with the value of 272,747 gpm included in in FSAR Table 15.4 for UFSAR 15.4.4 case, the event of the startup of an inactive RCP at an incorrect temperature.

Please clarify the inconsistency for the flow rates discussed above and justify that the AOR in UFSAR 15.4.4 remains valid with a lower minimum RCS flow limit of 384,000 gpm and 387,000 gpm for Units 1 and 2, respectively.

13. Events 3S (Unit 1) and 60 (Unit 2) -Steam Generator Tube Rupture (SGTR, UFSAR 15.6.3) (a) Overfill analysis For the SGTR analysis discussed in the information for Event 3S (Unit 1 ), and 60 (Unit 2), the licensee indicates that "the overfill analysis determined the assumed RCS flow to be inconsequential."

Please provide analyses or other information to justify that the AOR overfill analysis is insensitive to the RCS flow and remains valid with the proposed RCS flow limit of 384,000 gpm, and 387,000 gpm for Units 1 and 2, respectively.

(b) Dose Input Analysis The information discussing Events 3S and 60 indicates that "the dose input analysis was performed at 390,000 gpm plus uncertainty."

The above quoted RCS flow rate is inconsistent with that for Case 1 shown in UFSAR Table 15.4, the dose input analysis, which is based on the flow rate of 373,599 gpm. Please clarify the above inconsistency for the flow rate and justify that the AOR dose input analysis in UFSAR 15.6.3 remains valid for lower required minimum RCS flow limits of 384,000 gpm, and 387,000 gpm for Units 1 and 2, respectively.

14. Events 3T (Unit 1) and 6R (Unit 2) -Loss-of-Coolant Accident (LOCA) (a) Large-Break LOCA (LBLOCA)

For the LBLOCA analysis discussed in the information for Event 3T (Unit 1) and Event 6R (Unit 2), the LAR indicates that a Westinghouse analysis determines that "the variations in the global model calculations are such that the 95th percentile peak clad temperature is not impacted."

Please provide a discussion of the "Westinghouse analysis" used to determine the effects of the RCS flow changes on the peak clad temperature (PCT) during LBLOCA conditions and address the acceptability of the "Westinghouse analysis" for supporting the TS changes in reducing the minimum required RCS flow limit. The requested information should include the methods and RCS flow rates used for the analysis, and the results of the analysis to support the licensee's position stating that the LBLOCA PCT is not affected by the variations of the RCS flow rate, which is 390,000 gpm (indicated in Note 16 of FSAR Table 15.4 for Case 1, UFSAR Section 15.6.5) used in the AOR for LBLOCA. (b) Small-Break LOCA (SBLOCA)

For the SBLCA analysis discussed in Events 3T and 6R, the licensee indicated that a RCS flow change would not significantly affect four significant factors dominating the SBLOCA analysis.

The factors discussed were decay heat, RCS mass, break flow, and ECCS delivery.

Please provide a discussion or analysis to justify that an RCS flow change would not significantly affect the four factors dominating the SBLOCA analysis.

As part of this discussion, address the consideration that the RCS flow rate will determine the values of the heat transfer coefficients and thus, the heat removal rate from the RCS primary to secondary side. The heat removal rate would determine the changes of the temperature,

pressure, and void fraction of the RCS and steam generator, which, in terms, could affect the RCS water level, RCS mass, break flow, and ECCS delivery, resulting in changes in the results of the SBLOCA analysis.

15. Category-1 Events for Unit 2: Transients Bounded by Current RCS Flow Assumption Page 13 of Attachment 1 to the LAR lists nine Category-1 events for Unit 2. The licensee indicates that for the Category-1 events, the total RCS flow assumed in the current AOR is based on either the mechanical design flow of 420,000 gpm (where maximum RCS low rates are conservative) or the thermal design flow of 382,000 gpm (where minimum RCS flow rates are conservative).

The licensee further states that the proposed minimum RCS total flow limit of 387,000 gpm has no impact on the analysis for this category events. The above quoted flow rates of 420,000 gpm and 382,000 gpm appear to be inconsistent with the values in UFSAR Table 15.4 for the following Category-1 events: Event o 40 (UFSAR 15.1.3)

• 4E (UFSAR 15.2.3)

• 4F (UFSAR 15.2.6)

• 4G (UFSAR 15.2.7)

• 4H (UFSAR 15.2.8) Flow Rate (gpm) 388,000 381,420 373,596 376,530 373,596 (Peak RCS Pressure case) (Long-Term Core Cooling case) (Long-Term Core Cooling case) Please clarify the inconsistences discussed above and justify that the results of AOR for each of the above five events remained valid with the total minimum RCS flow limit reduced from 390,000 gpm to 387,000 gpm. 16. Event 6N -Bank Withdrawal from a Subcritical or Low Power Startup Condition (UFSAR 15.4.1) The information discussing Event 6N indicates that the minimum DNBR for Case 1 AOR is 3.395 and peak RCS for Case 2 have a margin of 150 psi relative to the design value of 2735 psi. It does not provide the values of the RCS flow used in the AOR. In accordance with FSAR Table 15.4, it appears that the RCS flow rates used are 299,613 gpm and 375,669 gpm for Case 1 and Case 2, respectively.

Please verify that the AOR for Case 1 and Case 2 in FSAR 15.4.1 remains valid with the required minimum RCS flow reduced from 390,000 gpm to 387,000 gpm for Unit 2.

Mr. Kelvin Henderson Site Vice President Catawba Nuclear Station Duke Energy Carolinas, LLC 4800 Concord Road York, NC 29745 January 20, 2016

SUBJECT:

CATAWBA NUCLEAR STATION, UNITS 1 AND 2: REQUEST FOR ADDITIONAL INFORMATION REGARDING LICENSE AMENDMENT REQUEST TO CHANGE THE RCS MINIMUM REQUIRED FLOW RA TES (TAC NOS. MF6355 AND MF6356)

Dear Mr. Henderson,

By letter dated June 12, 2015 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML 15168A009),

Duke Energy Carolinas, LLC (Duke Energy),

the licensee for Catawba Nuclear Station, Units 1 and 2, submitted a license amendment request (LAR) for changes to the Technical Specifications (TS). Specifically, the licensee proposed to modify TS Table 3.4.1-1, "RCS [Reactor Coolant System] DNB Parameters",

Parameter 3, "RCS Total Flow Rate." The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the licensee's submittal and determined that additional information is needed in order to complete the NRC staff's review. Enclosure 1 describes this request for additional information (RAI). On January 14, 2016, Mr. Lawrence Rudy of your staff agreed to respond within 45 days of this letter. If you have any questions, please call me at 301-415-2481.

Sincerely,

/RA/ G. Edward Miller, Project Manager Plant Licensing Branch 11-1 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-413 and 50-414

Enclosure:

As stated cc w/encl: Distribution via Listserv DISTRIBUTION:

PUBLIC LPL2-1 R/F RidsNrrDorlLp12-1 Resource RidsNrrPMCatawba Resource RidsNrrLASFigueroa Resource RidsRgn2MailCenter Resource RidsNrrDeEmcb Resource RidsNrrSsScvb Resource RidsNrrDraAfpb Resource ADAMS Accession No. ML16007A190 OFFICE NRR/LPLl-1/PM NRR/LPL2-1/LA NRR/DSS/SRXB NAME GE Miller SFigueroa EOesterle DATE 01/12/16 01/11/16 01/12/16 OFFICIAL RECORD COPY RidsNrrDeEsgb Resource RidsNrrSsSrxb Resource RidsAcrs_MailCTR Resource NRR/LPL2-1/B MMarkley 01/20/16