RS-11-124, Plant Specific ECCS Evaluation Changes - 10 CFR 50.46 30-Day Report for Fuel Type GE14

Plant Specific ECCS Evaluation Changes - 10 CFR 50.46 30-Day Report for Fuel Type GE14

ML112093130
Person / Time
Site:	Dresden
Issue date:	07/28/2011
From:	Hansen J Exelon Generation Co, Exelon Nuclear
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
RS-11-124
Download: ML112093130 (9)

Text

Exelon Generation www.exeloncorp.com Exel6n 4300 Wir I Road N u c l ear L 60555 RS-11-124 10 CFR 50.46(a)(3)(ii)

July 28, 2011 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Dresden Nuclear Power Station, Unit 2 Renewed Facility Operating License No. DPR-19 NRC Docket No. 50-237

Subject:

Plant Specific ECCS Evaluation Changes - 10 CFR 50.46 30-Day Report for Fuel Type GE14

References:

1. Letter from J. L. Hansen (Exelon Generation Company, LLC(EGC)) to U. S. NRC, "Plant Specific ECCS Evaluation Changes - 10 CFR 50.46 Report," dated October 29, 2010

2. Letter from General Electric Hitachi Nuclear Energy (GEH) to EGC, "10 CFR 50.46 Notification Letter 2011-02 for Dresden (Units 2 & 3)," dated July 1, 2011

3. Letter from GEH to EGC, "10 CFR 50.46 Notification Letter 2011-03 for Dresden (Units 2 & 3)," dated July 6, 2011 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 this letter and its attachment to notify the NRC of changes or errors discovered in the Dresden Nuclear Power Station (DNPS), Unit 2 plant specific emergency core cooling system (ECCS) evaluation for Global Nuclear Fuel (GNF) GE14 fuel that have been determined to be significant. This submittal meets the requirements of 10 CFR 50.46(a)(3)(ii) for submittal of a report within 30 days.

In Reference 1, EGC provided the NRC with the annual 10 CFR 50.46 Report for DNPS, Units 2 and 3. On June 28, 2011, EGC received notification from GEH that errors had been discovered in the GEH methodology used to analyze the ECCS loss of coolant accident (LOCA) response for DNPS and Quad Cities Nuclear Power Station (QCNPS). The errors are associated with the way the GEH methodology distributes gamma energy deposition within GNF fuel. The DNPS, Unit 3 core does not contain GNF fuel, so these errors apply only to the GE14 fuel that remains in the DNPS, Unit 2 core. The errors reported in References 2 and 3 result in an increase in the analyzed PCT for GE14 fuel of 75°F and 10°F, respectively. Since the current GE14 licensing basis PCT is 21 10°F for DNPS, Unit 2, the revised licensing basis PCT,

July 28, 2011 U. S. Nuclear Regulatory Commission Page 2 accounting for these errors, is 2195°F. The revised PCT remains within the 2200 °F acceptance criterion of 10 CFR 50.46; however, since the absolute magnitude of the errors is greater than 50 °F, this report must be submitted to the NRC within 30 days of the notification in accordance with the requirements of 10 CFR 50.46(a)(3)(il).

The attachment to this letter provides updated information regarding the PCT value for the GE14 fuel in DNPS, Unit 2. Note 12 of the attachment provides details related to errors discussed above.

There are no commitments contained in this letter. If there are any questions concerning this letter, please contact Mitchel Mathews at (630) 657-2819.

Attachment:

Dresden Nuclear Power Station Unit 2 - 10 CFR 50.46 Report 30-Day Report for GE14 Fuel cc: Regional Administrator - NRC Region III NRC Senior Resident Inspector - Dresden Nuclear Power Station

Attachment Dresden Nuclear Power Station, Unit 2 10 CFR 50.46(a)(3)(ii) 30-Day Report for GE14 Fuel

Attachment Dresden Nuclear Power Station, Unit 2 10 CFR 50.46 30-Day Report for GE14 Fuel Page 1 of 6 PLANT NAME: Dresden Nuclear Power Station, Unit 2 ECCS EVALUATION MODEL: SAFER/GESTR-LOCA REPORT REVISION DATE: July 22, 2011 CURRENT OPERATING CYCLES: 22 ANALYSIS OF RECORD The GESTR-LOCA and SAFER Models for the Evaluation of the Loss-of-Coolant Accident, Evaluation Model: Volume III, SAFER/GESTR Application Methodology, NEDE-23785-1-PA, General Electric Company, Revision 1, October 1984.

SAFER/GESTR-LOCA Loss-of-Coolant Accident Analysis for Dresden Nuclear Station 2 and 3 and Calculation: Quad Cities Nuclear Station Units 1 and 2," NEDC-32990P, Revision 2, GE Nuclear Energy, September 2003.

Fuel Analyzed in Calculation: 9x9-2, ATRIUM-9B and GE14 Limiting Fuel Type: GE14 Limiting Single Failure: Diesel Generator Limiting Break Size and Location: 1.0 double-ended guillotine break in a recirculation suction pipe.

Reference Peak Cladding 2110 OF Temperature (PCT):

Attachment Dresden Nuclear Power Station, Unit 2 10 CFR 50.46 30-Day Report for GE14 Fuel Page 2 of 6 MARGIN ALLOCATION A. PRIOR LOSS OF COOLANT ACCIDENT (LOCA) MODEL ASSESSMENTS 10 CFR 50.46 report dated December 6, 2001 (See Note 1 ) OPCT = 0° F 10 CFR 50.46 report dated November 25, 2002 (See Note 2 ) APCT = 0° F 10 CFR 50.46 report dated November 25, 2003 (See Note 3 ) APCT = 0° F 10 CFR 50.46 report dated November 24, 2004 (See Note 4 ) OPCT = 0° F 10 CFR 50.46 report dated November 16, 2005 (See Note 5 ) OPCT = 0° F 10 CFR 50.46 report dated November 9, 2006 (See Note 6 ) APCT = 0° F 10 CFR 50.46 report dated October 31, 2007 (See Note 7) APCT = 0° F 10 CFR 50.46 report dated October 30, 2009 (See Note 10) APCT = 0° F 10 CFR 50.46 report dated October 29, 2010 (See Note 11) APCT = 0° F Net PCT 2110° F B. CURRENT LOCA MODEL ASSESSMENTS Gamma energy deposition error 1 (See Note 12) 75°F Gamma energy deposition error 2 (See Note 12) 10°F Total PCT change from current assessments EDPCT = 85°F Cumulative PCT change from current assessments APCT I = 85°F Net PCT 2195°F

Attachment Dresden Nuclear Power Station, Unit 2 10 CFR 50.46 30 -Day Report for GE14 Fuel Page 3 of 6 Assessment Notes

1. Prior LOCA Model Assessment The 50.46 letter dated December 6, 2001 reported a new LOCA analysis to support extended power uprate (EPU) and transition to GE14 fuel for Dresden Unit 2 Cycle 18.

The same report assessed impact of errors in Framatome ANP LOCA analysis model for Dresden Unit 3 Cycle 17 at pre-EPU power level.

[

Reference:

Letter from Preston Swafford (PSLTR: #01-0122) (Exelon) to USNRC, "Plant Specific ECCS Evaluation Changes - 10 CFR 50.46 Report," December 6, 2001.]

2. Prior LOCA Model Assessment Unit 3 implemented GE LOCA analysis and GE14 fuel with Dresden Unit 3 Cycle 18 startup on October 25, 2002. Therefore, both Dresden Units 2 and 3 are being maintained under the same LOCA analysis. In the referenced letter, the impact of GE LOCA error in the WEVOL code was reported for Dresden Units 2 and 3 and determined to be negligible.

[

Reference:

Letter from Robert J. Hovey (RHLTR: #02-0083) (Exelon) to USNRC, "Plant Specific ECCS Evaluation Changes - 10 CFR 50.46 Report," November 25, 2002.]

3. Prior LOCA Model Assessment The annual 50.46 report provided information on the LOCA model assessments for SAFER LevelNolume table error and Steam Separator pressure drop error. In the referenced letter, the impact of these two GE LOCA errors was reported to be negligible.

[

Reference:

Letter from Robert J. Hovey (RHLTR: #03-0077) (Exelon) to USNRC, "Plant Specific ECCS Evaluation Changes - 10 CFR 50.46 Report," November 25, 2003.]

4. Prior LOCA Model Assessment The referenced annual 50.46 report provided information on reload of GE14 fuel for Dresden Unit 2 Cycle 19 and the impact of postulated hydrogen-oxygen recombination on PCT. GE determined that there was no PCT impact due to the reload of GE14 fuel and the postulated hydrogen -oxygen recombination.

[

Reference:

Letter from Danny Bost (SVPLTR: #04-0075) (Exelon) to USNRC, "Plant Specific ECCS Evaluation Changes - 10 CFR 50.46 Report," November 24, 2004.]

Attachment Dresden Nuclear Power Station, Unit 2 10 CFR 50.46 30 -Day Report for GE14 Fuel Page 4 of 6

5. Prior LOCA Model Assessment The referenced letter provided the annual 50.46 report for Units 2 and 3. The letter reported the PCT impact of reload of GE14 fuel for D3C19. Also, the letter reported the GE LOCA evaluation for Unit 3, which implemented the lower sectional replacement and T-box clamp repairs. GE determined that there was no PCT impact due to the reload of GE14 fuel and the lower sectional replacement and T-box clamp repairs.

[

Reference:

Letter from Danny Bost (SVPLTR: #05-0044) (Exelon) to USNRC, "Plant Specific ECCS Evaluation Changes - 10 CFR 50.46 Report," November 16, 2005.]

6. Prior LOCA Model Assessment The referenced letter provided the annual 50.46 report for Units 2 and 3. The letter reported the PCT impact of the reload of GE14 fuel for D2C20. The letter also reported an evaluation of increased leakage of less than 5 gpm at pump runout conditions in the core spray line flow due to crack growth identified during the D2R19 outage.

Additionally, a GE evaluation of the small break for impact due to top-peak axial power shape was reported in this letter. The impact due to these changes on the licensing basis PCT was reported as zero.

[

Reference:

Letter from Danny Bost (SVPLTR: #06-0054) (Exelon) to USNRC, "Plant Specific ECCS Evaluation Changes - 10 CFR 50.46 Report," November 9, 2006.]

7. Prior LOCA Model Assessment The referenced letter provided the annual 10 CFR 50.46 report for Units 2 and 3. The letter reported D3C20 startup with the first reload of Westinghouse Optima2 fuel and implementation of the Westinghouse LOCA analysis. No error was reported for GE LOCA applicable to operation of GE14 fuel in the Unit 2 and Unit 3 cores.

[

Reference:

Letter from Danny Bost (SVPLTR: #07-0049) (Exelon) to USNRC, "Plant Specific ECCS Evaluation Changes - 10 CFR 50.46 Report," October 31, 2007.]

8. Prior LOCA Model Assessment (not applicable to this 30-day report)

The referenced letter provided the 30-day 10 CFR 50.46 report for Dresden unit 2. The 30-day 10 CFR 50.46 report was submitted for Dresden unit 2 due to the non-conservative modeling of Low Pressure Core Spray (LPCS) performance for Unit 2.

Dresden Unit 3 was not affected. Maximum Average Planar Linear Heat Generation Rate (MAPLHGR) limit reduction was implemented at Dresden Unit 2 in order to meet all 10 CFR 50.46 criteria while maintaining a PCT at or below the licensing basis value of 2150 OF for the entire Cycle 21 operation. This note only pertains to Westinghouse SVEA-96 Optima2 fuel.

Attachment Dresden Nuclear Power Station, Unit 2 10 CFR 50.46 30-Day Report for GE14 Fuel Page 5 of 6

[

Reference:

Letter from Jeffrey Hansen (RS-08-073) (Exelon) to USNRC, "Plant Specific ECCS Evaluation Changes - 10 CFR 50.46 30-Day Report for Fuel Type SVEA-96 Optima2," May 23, 2008.]

9. Prior LOCA Model Assessment (not applicable to this 30-day report)

The referenced letter provided the annual 10 CFR 50.46 report for Units 2 and 3. The letter reported implementation of Westinghouse revised LOCA report to document evaluation of the non-conservative modeling of Low Pressure Core Spray (LPCS) performance for Unit 2. Dresden Unit 3 was not affected by this error. This note only pertains to Westinghouse SVEA-96 Optima2 fuel.

[

Reference:

Letter from David Wozniak (SVPLTR: #08-0059 (Exelon) to USNRC, "Plant Specific ECCS Evaluation Changes - 10 CFR 50.46 Report," October 31, 2008.]

10. Prior LOCA Model Assessment The referenced letter provided the annual 10 CFR 50.46 report for Units 2 and 3. The letter updated the vessel leakage between the lower shroud and the downcomer.

Westinghouse evaluated this change and demonstrated that all 10 CFR 50.46 criteria were satisfied. This evaluation resulted in maximum PCT impact due to the change in vessel leakage of 2 OF for Optima2 fuel with the licensing basis PCT of 2152 IF. The vessel leakage was reported by GE to have an insignificant impact on the PCT transient portion of the LOCA event. Therefore, a PCT impact of 0°F is reported for GE14 fuel with the licensing basis PCT remaining at 2110 OF. Note: The new Westinghouse analysis is documented in Revision 5 of the Dresden LOCA Report and contains the same information as stated above and transmitted to the NRC in the Reference.

[

Reference:

Letter from Timothy Hanley (SVPLTR: # 09-0052 (Exelon) to USNRC, "Plant Specific ECCS Evaluation Changes - 10 CFR 50.46 Report," October 30, 2009.]

11. Prior LOCA Model Assessment The referenced letter provided the annual 10 CFR 50.46 report for Units 2 and 3.

The letter reported the replacement of core spray lower sectional piping in Dresden Unit 2 during D2R21. Both GEH and Westinghouse evaluated the core spray leakage due to this modification and concluded that the PCT impact was 0 OF. The letter also identified a change in input for modeling bypass hole flow coefficient in the Westinghouse LOCA analysis. The impact on PCT due to this change was determined by Westinghouse to be 12 IF. For D2C22, Westinghouse established a MAPLHGR limit for the fresh bundles to accommodate the change. For 10 CFR 50.46 reporting purposes, the PCT impact is conservatively applied to all bundle types including the fresh bundles. This PCT update

Attachment Dresden Nuclear Power Station, Unit 2 10 CFR 50.46 30-Day Report for GE14 Fuel Page 6 of 6 will remain in effect only until the MAPLHGR limits for all bundles in future Dresden Unit 2 and Unit 3 cores are evaluated for the change in bypass hole flow coefficient. The latter issue only pertains to Westinghouse SVEA-96 Optima2 fuel.

[

Reference:

Letter from Jeffrey Hansen (RS-10-191, Exelon) to USNRC, "Plant Specific ECCS Evaluation Changes - 10 CFR 50.46 Report", October 29, 2010.]

12. Current LOCA Model Assessment General Electric Hitachi Nuclear Energy (GEH) reported errors in the LOCA methodology associated with the GE14 fuel in Dresden Nuclear Power Station (DNPS),

Unit 2 (i.e., References 1 and 2). DNPS, Unit 3 is not affected because it does not have GNF fuel loaded in the core. GEH identified two errors. In Reference 1, 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 results in a PCT increase of 75 °F. In Reference 2, GEH reported an error related to the contribution of heat from gamma ray absorption by the fuel channel. The gamma ray absorption by the channel was found to have been minimized. Correcting this error results in a PCT increase of 10 F. The cumulative impact of the absolute values for both errors is 85 F.

When added to the prior licensing basis PCT, the revised ECCS-LOCA licensing basis becomes 2195 °F, which is less than the 10 CFR 50.46 acceptance criterion of 2200 F.

DNPS, Unit 2 has one batch of twice burned GE14 fuel remaining in the core. The GE14 fuel is scheduled to be discharged in the fall 2011 refueling outage (i.e., D2R22).

These errors apply only to the GE14 fuel in the DNPS, Unit 2 core. The LOCA analysis for the Westinghouse fuel in the DNPS, Unit 2 core is not affected by the errors discussed in this note.

References:

1. Letter from General Electric Hitachi Nuclear Energy (GEH) to Exelon Generation Company, LLC (EGC), "10 CFR 50.46 Notification Letter 2011-02 for Dresden (Units 2 & 3)," dated July 1, 2011

2. Letter from GEH to EGC, "10 CFR 50.46 Notification Letter 2011-03 for Dresden (Units 2 & 3)," dated July 6, 2011