RS-11-168, Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors

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

ML113010206
Person / Time
Site:	Clinton
Issue date:	10/28/2011
From:	Gullott D Exelon Generation Co, Exelon Nuclear
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
RS-11-168
Download: ML113010206 (7)

Text

Exelon Generation Company, LLC www.exeloncorp.com 4300 Winfield Road Warrenville, I L 60555 clear RS-11-168 10 CFR 50.46(a)(3)(ii)

October 28, 2011 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 30, 2010, through October 28, 2011.

There are no regulatory commitments contained in this letter. Should you have any questions concerning this letter, please contact Mr. Mitchel A. Mathews at (630) 657-2819.

Respectfully, David M. Gullott Manager - Licensing Attachments:

1. 10 CFR 50.46 Report

2. 10 CFR 50.46 Report Assessment Notes

Attachment 1 Clinton Power Station, Unit 1 10 CFR 50.46 Report Page 1 of 2 PLANT NAME: Clinton Power Station, Unit 1 ECCS EVALUATION MODEL: SAFER/GESTR - LOCA REPORT REVISION DATE: 10/28/2011 CURRENT OPERATING CYCLE: 13 ANALYSIS OF RECORD Evaluation Model Methodology: The GESTR-LOCA and SAFER Models for the Evaluation of the Loss-of-Coolant Accident; Volume III, SAFER/GESTR Application Methodology, NEDC-23785-1-PA, Revision 1, General Electric Company, October 1984.

Calculation: Clinton Power Station, SAFER/GESTR-LOCA Analysis Basis Documentation, NEDC-32974P, GE Nuclear Energy, October 2000.

Fuel: GE 14 Limiting Fuel: GE 14 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):

Attachment 1 Clinton Power Station, Unit 1 10 CFR 50.46 Report Page 2 of 2 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) OPCT = 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) OPCT = 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) OPCT = 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) OPCT = -15°F Net PCT 1586°F B. CURRENT LOCA MODEL ASSESSMENTS None (Note 14) APCT = 0°F Total PCT change from current assessments F,APCT = 0°F Cumulative PCT change from current assessments ( APCT ( = 0°F Net PCT 1586°F

Attachment 2 Clinton Power Station, Unit 1 10 CFR 50.46 Report Assessment Notes Page 1 of 4 NOTES:

1. Prior Loss of Coolant Accident (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 (EGC)) 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 (EGC) 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 (EGC) to U. S. NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated November 5, 2003.]

Attachment 2 Clinton Power Station, Unit 1 10 CFR 50.46 Report Assessment Notes Page 2 of 4

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 (EGC) 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 (EGC) 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 (EGC) 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 uncovery. The effect has been conservatively assessed to increase the PCT for the limiting LOCA by less than 6 OF.

[

Reference:

Letter from Patrick R. Simpson (EGC) 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.]

Attachment 2 Clinton Power Station, Unit 1 10 CFR 50.46 Report Assessment Notes Page 3 of 4

9. Prior COCA 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 CPS LOCA analysis.

[

Reference:

Letter from Jeffrey L. Hansen (EGC) 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 COCA 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 CPS LOCA analysis.

[

Reference:

Letter from Jeffrey L. Hansen (EGC) 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 COCA Model Assessments In the referenced letter, Exelon submitted to the NRC the annual 10CFR 50.46 report for 2009. There was no LOCA model assessment for the CPS LOCA analysis.

[

Reference:

Letter from Jeffrey L. Hansen (EGC) 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 COCA Model Assessments In the referenced letter, Exelon submitted to the NRC the annual 1 OCFR 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 (EGC) to U. S. NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated October 29, 2010.]

Attachment 2 Clinton Power Station, Unit 1 10 CFR 50.46 Report Assessment Notes Page 4 of 4

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 CPS core were reported. GEH reported an error related to the way input coefficients are used to direct the deposition of gamma radiation energy produced by the fuel. Accounting for this error resulted in a PCT increase of 25 OF. 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 OF. The cumulative impact of these errors resulted in a 15 OF decrease in the licensing basis PCT.

[

Reference:

Letter from David M. Gullott (EGC) to U. S. NRC, "Plant Specific ECCS Evaluation Changes - 10 CFR 50.46 30-Day Report for Fuel Type GE14," dated August 10, 2011.]

14. Current LOCA Model Assessment Since the last 10 CFR 50.46 report (i.e., as discussed in Note 13 above), no vendor notifications of Emergency Core Cooling System (ECCS) model errors/changes applicable to CPS have been issued. No ECCS related changes or modifications have occurred at CPS that affect the assumptions in the LOCA analysis of record.