ML14230A070

Submittal of 10 CFR 50.46 Annual Report Through August 16, 2013

ML14230A070
Person / Time
Site:	Peach Bottom
Issue date:	08/15/2014
From:	Jim Barstow Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML14230A070 (14)

Text

10 CFR 50.46 August 15, 2014 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Peach Bottom Atomic Power Station, Units 2 and 3 Renewed Facility Operating License Nos. DPR-44 and DPR-56 NRC Docket Nos. 50-277 and 50-278

Subject:

10 CFR 50.46 Annual Report

References:

1) Letter from James Barstow (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, 11 10 CFR 50.46 Annual Report, 11 dated August 16, 2013

2) Letter from GE Hitachi Nuclear Energy (GEH) to Exelon Generation 11 Company, LLC, 10 CFR 50.46 Notification Letter 2014-01, Peach Bottom Atomic Power Station (Unit 2 & 3)," dated May 21, 2014

3) Letter from GE Hitachi Nuclear Energy (GEH) to Exelon Generation Company, LLC, 11 10 CFR 50.46 Notification Letter 2014-02, Peach Bottom Atomic Power Station (Unit 2 & 3), 11 dated May 21, 2014

4) Letter from GE Hitachi Nuclear Energy (GEH) to Exelon Generation 11 Company, LLC, 10 CFR 50.46 Notification Letter 2014-03, Peach Bottom Atomic Power Station (Unit 2 & 3), 11 dated May 21, 2014

5) Letter from GE Hitachi Nuclear Energy (GEH) to Exelon Generation 11 Company, LLC, 10 CFR 50.46 Notification Letter 2014-04, Peach Bottom Atomic Power Station (Unit 2 & 3), 11 dated May 21, 2014 The purpose of this letter is to transmit the 10 CFR 50.46 reporting information for Peach Bottom Atomic Power Station (PBAPS), Units 2 and 3. The previous 50.46 report for PBAPS, Units 2 and 3, (Reference 1) provided the cumulative Peak Cladding Temperature (PCT) errors for the most recent fuel designs through August 16, 2013.

U.S. Nuclear Regulatory Commission Peach Bottom Atomic Power Station, Units 2 and 3 10 CFR 50.46 Annual Report August 15, 2014 Page 2 Since the referenced report was issued, four vendor notifications of an Emergency Core Cooling System (ECCS) model error/change applicable to PBAPS, Units 2 and 3, have been issued (References 2 thru 5). No ECCS-related changes or modifications have occurred at PBAPS, Units 2 and 3, that affect the assumptions of the ECCS analyses. The vendor notifications are summarized below.

1) Notification 2014-01: SAFER04A E4-Maintenance Update Changes (Reference 2)

Several accumulated observations were docketed on software control tracking tools which led to changes in the evaluation model SAFER04A. These changes are regarded as code maintenance items. Sensitivity calculations have demonstrated that these several items individually and collectively have an insignificant effect on calculated peak cladding temperature. GNF2 and GE14 PCTs are both unaffected by this notification.

2) Notification 2014-02: SAFER04A E4-Mass Non-Conservatism (Reference 3)

An error was discovered where there was an indication that the expected system mass diverges from the actual calculated system mass. This occurs when upper plenum liquid mass and core spray flow rate is low; system mass is gradually lost due to core spray being discarded, resulting in marginally less ECCS flow credited as reaching the core.

Correction of this error results in a PCT change of 10°F for both GNF2 and GE14.

3) Notification 2014-03: SAFER04A E4-Minimum Core DP Model (Reference 4)

Due to calculation of a non-physically low pressure differential (Llp) for droplet flow above a two-phase level in the core, an earlier version of the model imposed a minimum core Llp. It has been observed that for cores with greater voiding (more steam flow), this minimum Llp could be non-conservative, actually driving the steam flow slightly, and offering inappropriate steam cooling benefit above the core two-phase level. To correct this error, two changes were made to the code including removal of the imposition of the minimum core Llp and the addition of an explicit core Llp calculation without regard to droplet condition. Representative sensitivity calculations indicate a PCT change of -10°F for both GNF2 and GE14.

4) Notification 2014-04: SAFER04A E4-Bundle/Lower Plenum CCFL Head (Reference 5)

A counter current flow limitation (CCFL) is applied on the interface between the hot bundle and the lower plenum. The pressure head applied at that location is based on the liquid water level in the bundle. It was found, upon exercising the routine to define CCFL, the output would replace the pressure head with a value revised by that calculation, resulting in a representation of pressure head slightly different from that of the calculated water level in the bundle. The iteration scheme for CCFL has been fixed in the SAFER04A E4 model so that, consistently, the level head is applied whenever CCFL is calculated in that location. Representative sensitivity calculations indicate a PCT change of 5°F for both GNF2 and GE14.

U.S. Nuclear Regulatory Commission Peach Bottom Atomic Power Station, Units 2 and 3 10 CFR 50.46 Annual Report August 15, 2014 Page 3 Three (3) attachments are included with this letter that provide the current 10 CFR 50.46 status for PBAPS, Units 2 and 3.

If you have any questions, please contact Tom Loomis at 610-765-5510.

Respectfully, James Barstow Director, Licensing & Regulatory Affairs Exelon Generation Company, LLC Attachments: 1) Peach Bottom Unit 2 I SAFER/GESTR-LOCA I GE14/GNF2 Fuel 10 CFR 50.46 Report

2) Peach Bottom Unit 3 I SAFER/GESTR-LOCA I GE14/GNF2 Fuel 10 CFR 50.46 Report

3) Assessment Notes cc: USNRC Region I, Regional Administrator USNRC Senior Resident Inspector, PBAPS USNRC Senior Project Manager, PBAPS R. R. Janati, Bureau of Radiation Protection S. T. Gray, State of Maryland

ATTACHMENT 1 Peach Bottom Unit 2 I SAFER/GESTR-LOCA I GE14/GNF2 Fuel 10 CFR 50.46 Report

Peach Bottom Unit 2 I SAFER/GESTR-LOCA I GE14/GNF2 Fuel Attachment 1 10 CFR 50.46 Report Page 1of2 PLANT NAME: Peach Bottom Unit 2 ECCS EVALUATION MODEL: SAFER/GESTR-LOCA REPORT REVISION DATE: August 15, 2014 CURRENT OPERATING CYCLE: 20 ANALYSIS OF RECORD (AOR)

Evaluation Model:

1. NEDC-23785-1-PA, Rev. 1, 'The GESTR-LOCA and SAFER Models for the Evaluation of the Loss-of-Coolant Accident Volume II, SAFER - Long Term Inventory Model for BWR Loss-Of-Coolant Analysis, 11 October 1984.

2. NEDC-30996P-A, "SAFER Model for Evaluation of Loss-of-Coolant Accidents for Jet Pump and Non-jet Pump Plants, Volume I, SAFER - Long Term Inventory Model for BWR Loss-of-Coolant Analysis," October 1987.

3. NEDC-32950P, "Compilation of Improvements to GENE's SAFER ECCS-LOCA Evaluation Model, 11 January 2000.

4. NEDC-23785-1-PA, Rev. 1, 11 The GESTR-LOCA and SAFER Models for the Evaluation of the Loss-Of-Coolant Accident Volume Ill, SAFER/GESTR Application Methodology,"

October 1984. (Jet Pump Plant - SAFER)

Calculations:

1. NEDC-32163P, "Peach Bottom Atomic Power Station Units 2 and 3 SAFER/GESTR-LOCA Loss-of-Coolant Accident Analysis, 11 January 1993.

2. GENE-J11-03716-09-02P, "Peach Bottom Atomic Power Station ECCS-LOCA Evaluation for GE14," July 2000.

3. GENE-J11-03716-09-02P, "Errata and Addenda Sheet for Peach Bottom Atomic Power Station ECCS-LOCA Evaluation for GE14," October 2007.

4. 0000-0100-8531-R1, "Peach Bottom Atomic Power Station Units 2 & 3 GNF2 ECCS-LOCA Evaluation," March 2011.

Fuels Analyzed in Calculations and in Operation: GE14 and GNF2 Limiting Fuel Type: GNF2 Limiting Single Failure - GE14/GNF2: Battery Failure Limiting Break Size/Location - GE14: 0.08 ft 2 Small Break in a Recirculation Discharge Pipe Limiting Break Size/Location - GNF2: 0.06 ft2 Small Break in a Recirculation Discharge Pipe Reference PCT - GE14: 1450°F Reference PCT - GNF2: 1870°F

Peach Bottom Unit 2 I SAFER/GESTR-LOCA I GE14/GNF2 Fuel Attachment 1 10 CFR 50.46 Report Page 2 of 2 MARGIN ALLOCATION A. PRIOR LOCA MODEL ASSESSMENTS:

GE14 ilPCT=55°F GE14 ilPCT=45°F GE14 ilPCT=0°F GE14 ilPCT=0°F GE14 ilPCT=150°F GE14 ilPCT=0°F GE14 ilPCT=0°F GE14 ilPCT=15°F GE14 ilPCT=0°F GE14 ilPCT=50°F GNF2 ilPCT=50°F Annual 10 CFR 50.46 Report dated August 17, 2012 (See Note 11) GE14 ilPCT=0°F GNF2 ilPCT=0°F Annual 10 CFR 50.46 Report dated August 16, 2013 (See Note 12) GE14 ilPCT=30°F GNF2 ilPCT=0°F Net PCT GE14 1795°F Net PCT GNF2 1920°F B. CURRENT LOCA MODEL ASSESSMENTS:

Impact of SAFER04A E4-Maintenance Update Changes (See Note GE14 ilPCT=0°F

13)  :

GNF2 ilPCT=0°F Impact of SAFER04A E4-Mass Non-Conservatism Update Changes GE14 ilPCT=10°F (See Note 13) GNF2 ilPCT=10°F Impact of SAFER04A E4-Minimum Core DP Model Update Changes GE14 ilPCT=-10°F (See Note 13) GNF2 ilPCT=-10°F Impact of SAFER04A E4-Bundle/Lower Plenum CCFL Head Update GE14 ilPCT=5°F Chanqes (See Note 13) GNF2 ilPCT=5°F Total PCT change from current assessments (GE14) I:ilPCT=5°F Total PCT change from current assessments (GNF2) I:ilPCT=5°F Cumulative PCT chanqe from current assessments (GE14) I:lilPCTl=25°F Cumulative PCT chanqe from current assessments (GNF2) I:lilPCTl=25°F Net PCT (GE14) 1800°F Net PCT (GNF2) 1925°F

ATTACHMENT 2 Peach Bottom Unit 3 I SAFER/GESTR-LOCA I GE14/GNF2 Fuel 10 CFR 50.46 Report

Peach Bottom Unit 3 I SAFER/GESTR-LOCA I GE14/GNF2 Fuel Attachment 2 10 CFR 50.46 Report Page 1of2 PLANT NAME: Peach Bottom Unit 3 ECCS EVALUATION MODEL: SAFER/GESTR-LOCA REPORT REVISION DATE: August 15, 2014 CURRENT OPERATING CYCLE: 20 ANALYSIS OF RECORD (AOR)

Evaluation Model:

1. NEDC-23785-1-PA, Rev. 1, "The GESTR-LOCA and SAFER Models for the Evaluation of the Loss-of-Coolant Accident Volume II, SAFER - Long Term Inventory Model for 11 BWR Loss-Of-Coolant Analysis, October 1984.

2. NEDC-30996P-A, "SAFER Model for Evaluation of Loss-of-Coolant Accidents for Jet Pump and Non-jet Pump Plants, Volume I, SAFER - Long Term Inventory Model for BWR Loss-of-Coolant Analysis," October 1987.

3. NEDC-32950P, "Compilation of Improvements to GENE's SAFER ECCS-LOCA Evaluation Model, 11 January 2000.

4. NEDC-23785-1-PA, Rev. 1, "The GESTR-LOCA and SAFER Models for the Evaluation of the Loss-Of-Coolant Accident Volume Ill, SAFER/GESTR Application Methodology,"

October 1984. (Jet Pump Plant - SAFER)

Calculations:

1. NEDC-32163P, "Peach Bottom Atomic Power Station Units 2 and 3 SAFER/GESTR-LOCA Loss-of-Coolant Accident Analysis," January 1993.

2. GENE-J11-03716-09-02P, "Peach Bottom Atomic Power Station ECCS-LOCA Evaluation for GE14," July 2000.

3. GENE-J11-03716-09-02P, 11 Errata and Addenda Sheet for Peach Bottom Atomic Power Station ECCS-LOCA Evaluation for GE14," October 2007.

4. 0000-0100-8531-R1, "Peach Bottom Atomic Power Station Units 2 & 3 GNF2 ECCS-LOCA Evaluation," March 2011.

Fuels Analyzed in Calculations and in Operation: GE14 and GNF2 Limiting Fuel Type: GNF2 Limiting Single Failure - GE14/GNF2: Battery Failure Limiting Break Size/Location - GE14: 0.08 ft 2 Small Break in a Recirculation Discharge Pipe Limiting Break Size/Location - GNF2: 0.06 ft2 Small Break in a Recirculation Discharge Pipe Reference PCT - GE14: 1450°F Reference PCT- GNF2: 1870°F

Peach Bottom Unit 3 I SAFER/GESTR-LOCA I GE14/GNF2 Fuel Attachment 2 10 CFR 50.46 Report Page 2 of 2 MARGIN ALLOCATION A. PRIOR LOCA MODEL ASSESSMENTS:

30-Day 10 CFR 50.46 Report dated June 4, 2001 (See Note 1) GE14 LiPCT=55°F Annual 10 CFR 50.46 Report dated December 18, 2002 (See Note 2) GE14 LiPCT=45°F Annual 10 CFR 50.46 Report dated December 3, 2004 {See Note 3) GE14 LiPCT=0°F Annual 10 CFR 50.46 Report dated December 1, 2005 {See Note 4) GE14 LiPCT=0°F 0U-Uav I u vFR 50.46 Report dated August 22, 2006 (See Note 5) GE14 LiPCT -150°F

• I'"'\

Annual 10 CFR 50.46 Report date *

• GE14 LiPCT 0°F Annual 10 CFR 50.46 Report dated August 22, 2008 {See Note 7) GE14 LiPCT=0°F Annual 10 CFR 50.46 Report dated Auaust 21, 2009 {See Note 8) GE14 LiPCT =15°F nual 10 CFR 50.46 Report dated August 20, 2010 {See Note 9) GE14 LiPCT=0°F Annual 10 CFR 50.46 Report dated August 19, 2011 {See Note 10) GE14 LiPCT=50°F Annual 10 CFR 50.46 Report dated August 17, 2012 (See Note 11) GE14 LiPCT=0°F GNF2 LiPCT=50°F Annual 10 CFR 50.46 Report dated August 16, 2013 (See Note 12) GE14 LiPCT=30°F GNF2 LiPCT=0°F Net PCT (GE14) 1795°F Net PCT (GNF2) 1920°F B. CURRENT LOCA MODEL ASSESSMENTS:

Impact of SAFER04A E4-Maintenance Update Changes (See Note GE14 LiPCT=0°F

13) GNF2 LiPCT=0°F Impact of SAFER04A E4-Mass Non-Conservatism Update Changes GE14 LiPCT=10°F (See Note 13) GNF2 LiPCT=10°F Impact of SAFER04A E4-Minimum Core DP Model Update Changes GE14 LiPCT=-10°F

{See Note 13) GNF2 LiPCT=-10°F Impact of SAFER04A E4-Bundle/Lower Plenum CCFL Head Update GE14 LiPCT=5°F Changes {See Note 13) GNF2 LiPCT=5°F Total PCT chanae from current assessments {GE14) LLiPCT=5°F Total PCT change from current assessments {GNF2) LLiPCT=5°F Cumulative PCT change from current assessments (GE14) LILiPCTl=25°F Cumulative PCT change from current assessments {GNF2) LILiPCTl=25°F Net PCT (GE14) 1800°F Net PCT (GNF2) 1925°F

ATTACHMENT 3 Assessment Notes

Assessment Notes Attachment 3 Peach Bottom, Units 2 and 3 Page 1of4

1. Prior LOCA Assessment The referenced letter reported two GE LOCA errors related to a SAFER condensation error and a SAFER pressure rate error. The PCT impact for the new errors was determined to be 45°F and 10°F, respectively. These PCT errors applied to all fuel types.

This letter constituted a 30-Day Report. The total PCT impact of these errors on GE14 fuel was determined to be 55°F.

[

Reference:

Letter from James A. Hutton (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, 11 Peach Bottom Atomic Power Station, Units 2 and 3 10 CFR 50.46 Reporting Requirements, 11 dated June 4, 2001.]

2. Prior LOCA Assessment The referenced letter provided the Annual 50.46 Report for Units 2 and 3. This letter reported GE LOCA errors related to a SAFER core spray sparger elevation error and a SAFER bulk water level error. The PCT impact for the new errors was determined to be 40°F and 5°F, respectively. These PCT errors applied to all fuel types. The total PCT impact of these errors on GE14 fuel was determined to be 45°F.

[

Reference:

Letter from Michael P. Gallagher (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "10 CFR 50.46 Reporting Requirements," dated December 18, 2002.]

3. Prior LOCA Assessment The referenced letter provided the Annual 50.46 Report for Units 2 and 3. This letter reported GE LOCA errors related to a GESTR file interpolation error, a SAFER computer platform change, a WEVOL S1 volume error, a SAFER level/volume table error, a SAFER separator pressure drop error and a new heat source. The PCT impact for the new errors was determined to be 0°F for each error. The total PCT impact of these errors on GE14 fuel was determined to be 0°F.

[

Reference:

Letter from Michael P. Gallagher (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report," dated December 3, 2004.]

4. Prior LOCA Assessment The referenced letter provided the Annual 50.46 Report for Units 2 and 3. This letter reported that no vendor 50.46 change/error notifications had been received since the last annual report. Therefore, the annual PCT change for GE14 fuel was reported as 0°F.

[

Reference:

Letter from Pamela B. Cowan (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, 11 10 CFR 50.46 Annual Report," dated December 1, 2005.]

Assessment Notes Attachment 3 Peach Bottom, Units 2 and 3 Page 2 of 4 Prior LOCA Assessment The referenced letter provided a 30-Day 50.46 Report for Units 2 and 3. This letter reported a newly discovered sensitivity to the assumed axial power shape for small break LOCA cases. This sensitivity may result in higher calculated PCT values for top-peaked axial power shapes. Due to this sensitivity, the calculated PCT for Peach Bottom was higher than the previously calculated value. The PCT impact was determined to be 150°F for GE14 fuel. The 0.08 ft 2 Small Break in a Recirculation Discharge Pipe is the Licensing Basis PCT event for Peach Bottom for GE14 fuel.

[

Reference:

Letter from Pamela B. Cowan (Exelon Generation Company, LLC) to U.S.

11 Nuclear Regulatory Commission, 10 CFR 50.46 30-Day Report," dated August 22, 2006.]

6. Prior LOCA Assessment The referenced letter provided the Annual 50.46 Report for Units 2 and 3. This letter reported that no vendor 50.46 change/error notifications had been received since the last annual report. Therefore, the annual PCT change for GE14 fuel was reported as 0°F.

[

Reference:

Letter from David P. Helker (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report," dated August 22, 2007.]

7. Prior LOCA Assessment The referenced letter provided the Annual 50.46 Report for Units 2 and 3. This letter reported that no vendor 50.46 change/error notifications had been received since the last annual report. Therefore, the annual PCT change for GE14 fuel was reported as 0°F.

[

Reference:

Letter from David P. Helker (Exelon Generation Company, LLC) to U.S.

11 Nuclear Regulatory Commission, 10 CFR 50.46 Annual Report," dated August 22, 2008.]

8. Prior LOCA Assessment The referenced letter provided the Annual 50.46 Report for Units 2 and 3. This letter reported that GE/GNF identified a Steam Flow Induced Error (SFIE, or Bernoulli Error) where water level could reach the bottom of the dryer and allow steam to bypass to the annulus. This bypass affects the L3 water level measurement, which relies on pressure taps in the annulus. Scram from the L3 level indication is conservatively modeled in the Small Break ECCS-LOCA analyses assuming Appendix K requirements. The OBA (large break) analyses are confirmed to be unaffected by the SFI E because the modeling relies on signals other than L3 for scram and ECCS response. The PCT impact for PBAPS GE14 fuel (small break limited) due to the SFIE was reported as 15°F.

[

Reference:

Letter from David P. Helker (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, 11 10 CFR 50.46 Annual Report," dated August 21, 2009.]

9. Prior LOCA Assessment The referenced letter provided the Annual 50.46 Report for Units 2 and 3. This letter reported that no vendor 50.46 change/error notifications had been received since the last annual report. Therefore, the annual PCT change for GE14 fuel was reported as 0°F.

Assessment Notes Attachment 3 Peach Bottom, Units 2 and 3 Page 3 of 4

[

Reference:

Letter from David P. Helker (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report," dated August 20, 2010.]

10. Prior LOCA Assessment The referenced letter reported that the GNF2 fuel design had been introduced into the Peach Bottom Unit 2 core since the previous cycle. The assessment notes above are not applicable to GNF2 fuel. The referenced letter also reported that two vendor notifications of Emergency Core Cooling System (ECCS) model error/changes that were applicable to Peach Bottom were issued. No ECCS-related changes or modifications had occurred at Peach Bottom that affected the assumptions of the ECCS analyses. The errors/changes are summarized below:

The error identified in Reference 2 of the referenced letter involved the way input coefficients were used to direct the deposition of gamma radiation energy produced by the fuel. Correction of this error resulted in a PCT increase of 45°F for both the GE14 fuel and GNF2 fuel.

The error identified in Reference 3 of the referenced letter involved the contribution of heat from gamma ray absorption by the channel. The gamma ray absorption by the channel was found to have been minimized. Correction of this error resulted in a PCT increase of 5°F for both the GE14 fuel and GNF2 fuel.

[

Reference:

Letter from Michael D. Jesse (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report," dated August 19, 2011.]

11. Prior LOCA Assessment The referenced letter reported that the GNF2 fuel design had been introduced into the Peach Bottom Unit 3 core since the last annual report. The Emergency Core Cooling System (ECCS) model error/changes discussed in Note 10 were applied to the GNF2 fuel in the Peach Bottom Unit 3 core which resulted in a PCT increase of 50°F, identical to the GNF2 fuel in the Unit 2 core.

[

Reference:

Letter from Michael D. Jesse (Exelon Generation Company, LLC) to U.S.

Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report," dated August 17, 2012.]

12. Prior LOCA Assessment To address inaccuracies in thermal conductivity degradation (TCD), GEH replaced the GESTR-LOCA model with a newer model, PRIME. The most dominant effect impacting PCT is from the way the PRIME fuel properties treat thermal conductivity, which results in a higher fuel stored energy. The PCT impact identified in the referenced letter reflects the difference between the existing GESTR analysis PCT and a conservatively postulated PCT if the analysis were performed with the PRIME model. The ECCS-LOCA analysis methodology remains GESTR based and will not be PRIME based until the ECCS-LOCA analysis is re-performed using PRIME. The notification resulted in a 0°F PCT impact to GNF2 fuel and a 30°F PCT impact to GE14 fuel.

Assessment Notes Attachment 3 Peach Bottom, Units 2 and 3 Page 4 of 4

[

Reference:

Letter from ..;onoro*rif'\n Company, LLC) to U.S.

Nuclear August 16, 2013.]

Note 12), four vendor notifications were

.-:1r1 1""tro,c-~~~~ accumulated updates to fY\Olr"l'ti"lr"IOlnl"'O changes have an individually and cladding temperature. The second a error been isolated, occurring with an exc>ec*tea system mass diverges from the calculated actual mass. This error affects the flow credited as reaching the core. Correction of this error results in a 10°F PCT change to both GE14 and GNF2. The third notification (Reference 3) addresses an error with imposed minimum pressure differential (Lip) for droplet flow above a two-phase level in the core. This error can offer an inappropriate steam cooling benefit above the core two-phase level. To correct this error, an explicit core Lip calculation is applied without regard to droplet condition resulting in a PCT of -10°F to both GE14 and GNF2. The fourth notification (Reference 4) addresses an incorrect pressure head representation when defining the counter current flow limitation (CCFL). Correction of this error results in a PCT change to both GE14 and GNF2.

[Reference 1: Letter from GE Hitachi Nuclear Energy (GEH) to Exelon Generation Company, LLC, 11 10 CFR 50.46 Notification 2014-01, Peach Bottom Atomic Power Station (Unit 2 & 3)," dated May 21 2014.]

[Reference 2: Letter from GE Hitachi Nuclear Energy (GEH) to Exelon Generation Company, LLC, 11 10 CFR 50.46 Notification 2014-02, Peach Bottom Atomic Power Station (Unit 2 & 3), 11 dated May 21, 2014.]

[Reference 3: Letter from GE Hitachi Nuclear Energy (GEH) to Exelon Generation Company, LLC, 11 10 CFR 50.46 Notification 2014-03, Peach Bottom Atomic Power Station (Unit 2 & 3)," dated May 21, 2014.]

[Reference 4: Letter from GE Hitachi Nuclear Energy (GEH) to Exelon Generation Company, LLC, 11 10 CFR 50.46 Notification 2014-04, Peach Bottom Atomic Power Station (Unit 2 & 3), 11 dated May 21, 2014.]