RS-14-307, Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors

Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors

ML14297A109
Person / Time
Site:	Clinton
Issue date:	10/24/2014
From:	Simpson P Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RS-14-307
Download: ML14297A109 (11)

Text

Adore 4300 WinfieIci Road Warrenvilie. R. 60555 Generation 630 657 2000 Office RS-14-307 10 CFR 50.46(a)(3)(ii)

October 24, 2014 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Clinton Power Station, Unit 1 Facility Operating License No. NPF-62 NRC Docket No. 50-461

Subject:

Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station In accordance with 10 CFR 50.46, "Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors," paragraph (a)(3)(ii), Exelon Generation Company, LLC (EGC) is submitting the annual report of the Emergency Core Cooling System (ECCS)

Evaluation Model changes and errors for Clinton Power Station, Unit 1 (CPS). This report covers the period from October 25, 2013, through October 24, 2014.

There are no regulatory commitments contained in this letter. Should you have any questions concerning this letter, please contact Mr. Timothy A Byam at (630) 657-2818.

Respectfully, Patrick R. Simpson Manager Licensing Attachments:

1. 10 CFR 50.46 Report (GE14 Fuel)

2. 10 CFR 50.46 Report (GNF2 Fuel)

3. 10 CFR 50.46 Report Assessment Notes

October 24, 2014 U. S. Nuclear Regulatory Commission Page 2 cc: Regional Administrator NRC Region ill NRC Senior Resident Inspector Clinton Power Station Illinois Emergency Management Agency Division of Nuclear Safety

Attachment 1 Clinton Power Station, Unit 1 10 CFR 50.46 Report (GE14 Fuel)

PLANT NAME: Clinton Power Station, Unit 1 ECCS EVALUATION MODEL: SAFER/GESTR - LOCA REPORT REVISION DATE: October 24, 2014 CURRENT OPERATING CYCLE: 15 ANALYSIS OF RECORD Evaluation Model Methodology: NEDC-23785-1-PA Rev. 1, "The GESTR-LOCA and SAFER Models for the Evaluation of the Loss-Of-Coolant Accident Volume III, SAFER/GESTR Application Methodology," October 1984.

Calculation: NEDC-32974P, "Clinton Power Station SAFER/GESTR-LOCA Analysis Basis Documentation,"

October 2000.

Fuel: GE14 Limiting Fuel: GNF2 Limiting Single Failure: High Pressure Core Spray (HPCS) Diesel Generator Limiting Break Size and Location: 1.0 Double Ended Guillotine of Recirculation Pump Suction Piping Reference Peak Cladding 1550°F Temperature (PCT):

Page 1 of 2

Attachment 1 Clinton Power Station, Unit 1 10 CFR 50.46 Report (GE14 Fuel)

MARGIN ALLOCATION A. PRIOR LOSS OF COOLANT ACCIDENT LOCA MODEL ASSESSMENTS 10 CFR 50.46 report dated November 13, 2000 (See Note 1) APCT = 0°F 10 CFR 50.46 report dated November 08, 2001 (See Note 2) APCT = 5°F 10 CFR 50.46 report dated November 05, 2002 (See Note 3) APCT = 35°F 10 CFR 50.46 report dated November 05, 2003 (See Note 4) APCT = 5°F 10 CFR 50.46 report dated November 05, 2004 (See Note 5) APCT = 0°F 10 CFR 50.46 report dated November 04, 2005 (See Note 6) APCT = 0°F 10 CFR 50.46 report dated November 03, 2006 (See Note 7) APCT = 0°F 10 CFR 50.46 report dated April 19, 2007 (See Note 8) APCT = 6°F 10 CFR 50.46 report dated November 02, 2007 (See Note 9) APCT = 0°F 10 CFR 50.46 report dated October 31, 2008 (See Note 10) APCT = 0°F 10 CFR 50.46 report dated October 30, 2009 (See Note 11) APCT = 0°F 10 CFR 50.46 report dated October 29, 2010 (See Note 12) APCT = 0°F 10 CFR 50.46 report dated August 10,2011 (See Note 13) APCT = -15°F 10 CFR 50.46 report dated October 28, 2011 (See Note 14) APCT = 0°F 10 CFR 50.46 report dated October 26, 2012 (See Note 15) APCT = 0°F 10 CFR 50.46 report dated October 25, 2013 (See Note 16) APCT = 10°F Net PCT 1596°F B. CURRENT LOCA MODEL ASSESSMENTS Impact of SAFERO4A E4-Maintenance Update Changes (See Note 17) APCT= 0°F Impact of SAFERO4A E4-Mass Non-Conservatism (See Note 17) APCT= 0°F Impact of SAFERO4A E4-Minimum Core DP Model (See Note 17) APCT= -15°F Impact of SAFERO4A E4-Bundle/Lower Plenum CCFL Head (See Note 17) APCT= 0°F Total PCT change from current assessments EAPCT = -15°F Cumulative PCT change from current assessments E I APCT I = 15°F Net PCT 1581°F Page 2 of 2

Attachment 2 Clinton Power Station, Unit 1 10 CFR 50.46 Report (GNF2 Fuel)

PLANT NAME: Clinton Power Station, Unit 1 ECCS EVALUATION MODEL: SAFER/GESTR - LOCA REPORT REVISION DATE: October 24, 2014 CURRENT OPERATING CYCLE: 15 ANALYSIS OF RECORD Evaluation Model Methodology: NEDC-23785-1-PA Rev. 1, "The GESTR-LOCA and SAFER Models for the Evaluation of the Loss-Of-Coolant Accident Volume III, SAFER/GESTR Application Methodology," October 1984.

Calculation: GEH Report 0000-0121-9100-RO, Clinton Power Station, GNF2 ECCS-LOCA Evaluation, October 2011.

Fuel: GNF2 Limiting Fuel: GNF2 Limiting Single Failure: High Pressure Core Spray (HPCS) Diesel Generator Limiting Break Size and Location: 1.0 Double Ended Guillotine of Recirculation Pump Suction Piping Reference Peak Cladding 1880°F Temperature (PCT):

MARGIN ALLOCATION A. PRIOR LOSS OF COOLANT ACCIDENT LOCA MODEL ASSESSMENTS 10 CFR 50.46 report dated October 26, 2012 (See Note 15) APCT = 0°F 10 CFR 50.46 report dated October 25, 2013 (See Note 16) APCT = 40°F Net PCT 1920°F Page 1 of 2

Attachment 2 Clinton Power Station, Unit 1 10 CFR 50.46 Report (GNF2 Fuel)

B. CURRENT LOCA MODE ASSESSMENTS Impact of SAFER04A E4-Maintenance Update Changes (See Note 17) APCT= 0°F Impact of SAFERO4A E4-Mass Non-Conservatism (See Note 17) APCT= 0°F Impact of SAFERO4A E4-Minimum Core DP Model (See Note 17) APCT= -15°F Impact of SAFERO4A E4-Bundle/Lower Plenum CCFL Head (See Note 17) APCT= 0°F Total PCT change from current assessments EAPCT = -15°F Cumulative PCT change from current assessments E I APCTI. 15°F Net PCT 1905°F Page 2 of 2

Attachment 3 Clinton Power Station, Unit 1 10 CFR 50.46 Report Assessment Notes

1. Prior LOCA Model Assessments The referenced letter reported a new analysis of record for Clinton Power Station (CPS).

[

Reference:

Letter from M. A. Reandeau (AmerGen Energy Company) to U.S. NRC, "Report of a Change to the ECCS Evaluation Model Used for Clinton Power Station (CPS)," dated November 13, 2000.]

2. Prior LOCA Model Assessments An inconsistent core exit steam flow was used in the pressure calculation in the SAFER code when there is a change in the two-phase level. The incorrect calculated pressure may result in premature termination of ECCS condensation and will impact the second peak clad temperature (PCT). GE evaluated the impact of this error and determined that the impact is an increase of 5°F in the PCT. This error was reported to the NRC in the referenced letter.

[

Reference:

Letter from K. A. Ainger (Exelon Generation Company) to U.S. NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated November 8, 2001.]

3. Prior LOCA Model Assessments In the referenced letter to the NRC, the impact of the Low Pressure Coolant Injection (LPCI) and Low Pressure Core Spray (LPCS) minimum flow valve flow diversion was reported and was found to have a 0°F impact. Also in the referenced letter GE LOCA errors were reported all of which had a 0°F PCT increase except for a SAFER Core Spray sparger injection elevation error that resulted in a 15°F increase in the PCT.

The Extended Power Uprate (EPU) has resulted in an increase of 20°F in the PCT.

The EPU was implemented in Cycle 9 Reload.

[

Reference:

Letter from Patrick R. Simpson (Exelon Generation Company) to U.S.

NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated November 5, 2002.]

4. Prior LOCA Model Assessments In the referenced letter to the NRC, the impact of an error found in the initial level/volume table for SAFER was reported. The level/volume tables were generated with incorrect initial water levels. This resulted in an incorrect volume split in the nodes above and below the water surface, and incorrect initial liquid mass. This error resulted in a 5°F increase in the PCT for all fuel types (i.e., GE 10 & GE14).

[

Reference:

Letter from Patrick R. Simpson (Exelon Generation Company) to U.S.

NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated November 5, 2003.]

Page 1 of 5

Attachment 3 Clinton Power Station, Unit 1 10 CFR 50.46 Report Assessment Notes

5. Prior LOCA Model Assessments In the referenced letter to the NRC, the impact of a GE postulated new heat source applicable to the LOCA event was reported. This heat source is due to recombination of hydrogen and excess oxygen drawn into the vessel from containment during core heatup. The PCT impact for all fuel types was 0°F and the effect on local oxidation was negligible.

[

Reference:

Letter from Patrick R. Simpson (Exelon Generation Company) to U.S.

NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated November 5, 2004.]

6. Prior LOCA Model Assessments In the referenced letter to the NRC, the impact of the 24-month cycle operation was reported. The evaluation determined that the LOCA analysis of record was performed with bounding assumptions and hence is not impacted with the 24-month cycle. A 0°F PCT impact was assigned.

[

Reference:

Letter from Patrick R. Simpson (Exelon Generation Company) to U.S.

NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated November 4, 2005.]

7. Prior LOCA Model Assessments In the referenced letter to the NRC, the impact of the top peak axial power shape on the small break LOCA was reported. The impact of the top peak axial power shape on the licensing basis PCT was 0°F for GE 14 Fuel for CPS.

[

Reference:

Letter from Kenneth M. Nicely (Exelon Generation Company) to U.S.

NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated November 3, 2006.]

8. Prior LOCA Model Assessments In the referenced letter, the impact of the core shroud repair on the PCT was reported to the NRC. The leakage flows through the repair holes result in slightly increased time to core recovery, following core uncovering. The effect has been conservatively assessed to increase the PCT for the limiting LOCA by less than 6°F.

[

Reference:

Letter from Patrick R. Simpson (Exelon Generation Company) to U.S.

NRC, "Updated Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated April 19, 2007.]

9. Prior LOCA Model Assessments In the referenced letter, Exelon submitted to the NRC the annual 10 CFR 50.46 report for 2007. There was no LOCA model assessment for the Clinton LOCA analysis.

Page 2 of 5

Attachment 3 Clinton Power Station, Unit 1 10 CFR 50.46 Report Assessment Notes

[

Reference:

Letter from Jeffrey L. Hansen (Exelon Generation Company) to U.S.

NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated November 2, 2007.]

10. Prior LOCA Model Assessments In the referenced letter, Exelon submitted to the NRC the annual 10 CFR 50.46 report for 2008. There was no LOCA model assessment for the Clinton LOCA analysis.

[

Reference:

Letter from Jeffrey L. Hansen (Exelon Generation Company) to U.S.

NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated October 31, 2008.]

11. Prior LOCA Model Assessments In the referenced letter, Exelon submitted to the NRC the annual 10 CFR 50.46 report for 2009. There was no LOCA model assessment for the Clinton LOCA analysis.

[

Reference:

Letter from Jeffrey L. Hansen (Exelon Generation Company) to U.S.

NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated October 30, 2009.]

12. Prior LOCA Model Assessments In the referenced letter, Exelon submitted to the NRC the annual 10 CFR 50.46 report for 2010. Eight Isotope Test Assemblies (GE14i ITA) were loaded in to the cycle 13 core, all the GE14 10 CFR 50.46 errors are applicable to the GE14i ITA and the PCT for GE14 fuel remain applicable for GE14i ITAs.

[

Reference:

Letter from Jeffrey L. Hansen (Exelon Generation Company) to U.S.

NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated October 29, 2010.]

13. Prior LOCA Model Assessment In the referenced letter, the impact of two General Electric Hitachi Nuclear Energy (GEH) errors in the LOCA methodology associated with the GE14 fuel in the Clinton Power Station core were reported. GEH reported an error related to the way input coefficients were used to direct the deposition of gamma radiation energy produced by the fuel. Accounting for this error resulted in a PCT increase of 25°F. GEH also reported an error related to the contribution of heat from gamma ray absorption by the channel. Accounting for this error resulted in a PCT decrease of 40°F. The cumulative impact of these errors resulted in a 15°F decrease in the licensing basis PCT.

[

Reference:

Letter from David M. Gullott (Exelon Generation Company, LLC (EGG))

to U. S. NRC, "Plant Specific EGGS Evaluation Changes 10 CFR 50.46 30-Day Report for Fuel Type GE14," dated August 10, 2011.1 Page 3 of 5

Attachment 3 Clinton Power Station, Unit 1 10 CFR 50.46 Report Assessment Notes

14. Prior LOCA Model Assessment In the referenced letter, Exelon submitted to the NRC the annual 10 CFR 50.46 report for 2011. There were no ECCS related changes or modifications that occurred which affected the assumptions in the Clinton Power Station LOCA analysis of record.

[

Reference:

Letter from David M. Gullott (Exelon Generation Company, LLC (EGG))

to U. S. NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated October 28, 2011]

15. Prior LOCA Model Assessment In the referenced letter, it was reported that the GNF2 fuel design had been introduced into the Clinton Unit 1 core during the Reload 13 (Cycle 14) outage. The assessment notes above (Notes 1-14) were not applicable to the GNF2 fuel. There were no ECCS related changes or modifications that occurred which affected the assumptions in the CPS LOCA analysis of record.

[

Reference:

Letter from Patrick R. Simpson (Exelon Generation Company, LLC (EGC)) to U. S. NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated October 26, 2012.]

16.Prior LOCA Model 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 10°F PCT impact to GE14 fuel and a 40°F PCT impact to GNF2 fuel.

[

Reference:

Letter from Patrick R. Simpson (Exelon Generation Company, LLC (EGG)) to U. S. NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated October 25, 2013.]

Page 4 of 5

Attachment 3 Clinton Power Station, Unit 1 10 CFR 50.46 Report Assessment Notes

17. Current LOCA Assessment Subsequent to the 2013 Annual 50.46 report (see note 16) four vendor notifications were received. The first notification addressed several accumulated updates to the SAFERO4A model. These code maintenance changes have an individually and collectively insignificant effect on calculated peak cladding temperature. The second notification corrected a logic error that has been isolated, occurring with an indication that the expected system mass diverges from the calculated actual system mass.

This error affects the ECCS flow credited as reaching the core. Correction of this error did not impact the PCT for 0E14 or GNF2 fuel. The third notification addressed an error with the imposed minimum pressure differential (4) 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 -15°F to both GE14 and GNF2. The fourth notification addressed an incorrect pressure head representation when defining the counter current flow limitation (CCFL). Correction of this error did not impact the PCT for GE14 or GNF2 fuel.

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