ML12340A010
| ML12340A010 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 11/29/2012 |
| From: | Price J Dominion, Dominion Nuclear Connecticut |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 12-705 | |
| Download: ML12340A010 (8) | |
Text
Dominion Nuclear 5000 Dominion Connecticut, Boulevard, Inc.Dmnin Glen Allen, VA 23060 Dominion Web Address: www.dom.com November 29, 2012 U.S. Nuclear Regulatory Commission Serial No.12-705 Attention: Document Control Desk NL&OS/MAE RO Washington, DC 20555 Docket No. 50-423 License No. NPF-49 DOMINION NUCLEAR CONNECTICUT. INC.
MILLSTONE POWER STATION UNIT 3 30-DAY REPORT OF EMERGENCY CORE COOLING SYSTEM (ECCS) MODEL CHANGES PURSUANT TO THE REQUIREMENTS OF 10 CFR 50.46 In accordance with 10 CFR 50.46(a)(3)(ii), Dominion Nuclear Connecticut, Inc. (DNC) hereby submits information regarding an evaluation of fuel pellet thermal conductivity with fuel burnup in the Westinghouse Best-Estimate Large Break Loss of Coolant Accident (LBLOCA) analysis methodology for Millstone Power Station Unit 3 (MPS3) and its effect on peak cladding temperature (PCT). MPS3 uses the Westinghouse Automated Statistical Treatment of Uncertainty Method (ASTRUM) LBLOCA evaluation model (EM) documented in WCAP-16009-P-A (Reference 1). describes the evaluation to determine the estimated PCT effects of fuel pellet thermal conductivity degradation (TCD) and peaking factor burndown. The methodology for estimating the PCT effect is described in Reference 2, which was provided to the NRC by Westinghouse. A revised LBLOCA PCT margin utilization sheet is provided in Attachment
- 2. The peaking factor burndown used in the TCD evaluation described in Attachments 1 and 2 is conservative for the current cycle and will be added to the MPS3 reload design process for validation. DNC has reviewed the information provided by Westinghouse and determined that the adjusted LBLOCA PCT values and the manner in which they were derived continue to comply with the requirements of 10 CFR 50.46.
The estimated impact from fuel pellet TCD on the Millstone 3 ASTRUM LBLOCA EM is
+2220 F. Since the magnitude of the change in PCT is greater than 50 0 F, the evaluation of fuel pellet TCD represents a significant change in PCT as defined in 10 CFR 50.46(a)(3)(i). Accordingly, DNC has evaluated the requirement for reanalysis specified in 10 CFR 50.46(a)(3)(ii) and hereby proposes the following schedule for reanalysis.
Prior to November 30, 2017, DNC plans to submit to the NRC for review and approval, a LBLOCA analysis that applies NRC-approved methods that include the effects of fuel TCD. The date for the analysis submittal is based on the following milestones, which must be completed in order to perform a revised licensing basis LBLOCA analysis with an NRC-approved ECCS EM that explicitly accounts for TCD:
- 1. Obtain prior NRC approval of a fuel performance analysis methodology that includes the effects of TCD. The new methodology would replace the current licensing basis methodology in WCAP-1 5063-P-A, Revision 1 (Reference 3), which is referenced in Section 4.2.3.3 of the MPS3 Final AJg Serial No.12-705 Docket No. 50-423 ECCS Model Changes Page 2 of 3 Safety Analysis Report (FSAR), to develop inputs to the LBLOCA Evaluation Model.
- 2. Obtain prior NRC approval of a LBLOCA EM that includes the effects of TCD and accommodates the ongoing 10 CFR 50.46(c) rulemaking process.
The new methodology would replace the current licensing basis methodology in WCAP-16009-P-A (Reference 1) which is referenced in Section 15.6.5.2 of the MPS3 FSAR.
If you have any further questions regarding this submittal, please contact Mr. William Bartron at (860) 444-4301.
Sincerely, J. Alan Price Vice President - Nuclear Engineering Commitments made in this letter: None Attachments:
- 1. Impact of Thermal Conductivity Degradation and Peaking Factor Burndown on Westinghouse Large Break LOCA ECCS Evaluation Model - Millstone Power Station Unit 3.
- 2. 30-Day Reporting of 10 CFR 50.46 Margin Utilization - Millstone Power Station Unit 3.
References:
- 1. WCAP-16009-P-A, "Realistic Large-Break LOCA Evaluation Methodology Using the Automated Statistical Treatment Of Uncertainty Method (ASTRUM)," January 2005.
- 2. PWR Owners Group Letter OG-12-386, "For Information Only - Input Supporting the PWROG LBLOCA Program Regarding Nuclear Fuel Thermal Conductivity Degradation (PA-ASC-1073, Revision 0) (Proprietary/Non-Proprietary),"
September 18, 2012.
- 3. WCAP-15063-P-A, Revision 1 with Errata, "Westinghouse Improved Performance Analysis and Design Model (PAD 4.0)," July 2000.
Serial No.12-705 Docket No. 50-423 ECCS Model Changes Page 3 of 3 cc: U.S. Nuclear Regulatory Commission Region I 2100 Renaissance Blvd.
Suite 100 King of Prussia, PA 19406-2713 J. S. Kim Project Manager - Millstone Power Station U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 08 C2A Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station
Serial No.12-705 Docket No. 50-423 ATTACHMENT 1 IMPACT OF THERMAL CONDUCTIVITY DEGRADATION AND PEAKING FACTOR BURNDOWN ON WESTINGHOUSE LARGE BREAK LOCA ECCS EVALUATION MODEL MILLSTONE POWER STATION UNIT 3 DOMINION NUCLEAR CONNECTICUT, INC.
Serial No.12-705 Docket No. 50-423 ECCS Model Changes Attachment 1, Page 1 of 2
Background
Fuel pellet thermal conductivity degradation (TCD) and peaking factor burndown were not explicitly considered in the Millstone Power Station Unit 3 (MPS3) Best Estimate Large Break Loss-of-Coolant Accident (BE LBLOCA) Analysis of Record (AOR).
Nuclear Regulatory Commission (NRC) Information Notice 2011-21 (Reference 1) notified addressees of recent information obtained concerning the impact of irradiation on fuel thermal conductivity and its potential to cause significantly higher predicted peak cladding temperature (PCT) results in realistic emergency core cooling system (ECCS) evaluation models. This evaluation provides an estimated effect of fuel pellet TCD and peaking factor burndown on the PCT calculation for the MPS3 BE LBLOCA AOR. This change represents a Non-Discretionary Change in accordance with Section 4.1.2 of WCAP-13451 (Reference 2).
Affected Evaluation Model 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect A quantitative evaluation, as discussed in Reference 3, was performed to assess the PCT effect of fuel pellet TCD and peaking factor burndown on the MPS3 BE LBLOCA analysis and concluded that the estimated PCT impact is 222'F for 10 CFR 50.46 reporting purposes. The peaking factor burndown included in the evaluation is provided in Table 1 and is conservative for the current cycle. Dominion Nuclear Connecticut, Inc.
and its vendor, Westinghouse Electric Company LLC, use processes which ensure that the LOCA analysis input values conservatively bound the as-operated plant values for those parameters and will be validated as part of the reload design process.
Table 1: Peaking Factors Assumed in the Evaluation of TCD Fuel Rod Burnup (MWD/ FdH(1)(2 ) FQ Transient(1 ) FQ Steady-MTU) State 0 1.650 2.60 2.000 30,000 1.650 2.60 2.000 60,000 1.400 2.08 1.600 62,000 1.400 2.08 1.000 (1) Includes uncertainties.
(2) Hot assembly average power follows the same burndown, since it is a function of FdH.
Serial No.12-705 Docket No. 50-423 ECCS Model Changes Attachment 1, Page 2 of 2 Conclusion DNC has performed an evaluation of PCT for comparison to 10 CFR 50.46 requirements. The analysis of record PCT for MPS3 is 1781°F. Considering the current PCT changes, the licensing basis LBLOCA PCT is 2003OF for MPS3. The LBLOCA results have sufficient margin to the 2200°F limit specified in 10 CFR 50.46(b)(1). The current PCT assessment of 222 0 F is greater than the 50°F limit for reporting as defined in 10 CFR 50.46(a)(3)(i); hence, the change is significant and submittal of this 30-day report to the NRC is required.
References
- 1. NRC Information Notice 2011-21, McGinty, T. J., and Dudes, L. A., "Realistic Emergency Core Cooling System Evaluation Model Effects Resulting From Nuclear Fuel Thermal Conductivity Degradation," December 13, 2011. (ML113430785)
- 2. WCAP-1 3451, "Westinghouse Methodology for Implementation of 10 CFR 50.46 Reporting," October 1992.
- 3. OG-12-386, "For Information Only- Input Supporting the PWROG LBLOCA Program Regarding Nuclear Fuel Thermal Conductivity Degradation (PA-ASC-1073, Revision 0) (Proprietary/Non-Proprietary)," September 18, 2012.
Serial Number 12-705 Docket No. 50-423 ATTACHMENT 2 30-DAY REPORTING OF 10 CFR 50.46 MARGIN UTILIZATION MILLSTONE POWER STATION UNIT 3 DOMINION NUCLEAR CONNECTICUT, INC.
Serial Number 12-705 Docket No. 50-423 ECCS Model Changes Attachment 2, Page 1 of 1 10 CFR 50.46 MARGIN UTILIZATION - LARGE BREAK LOCA Plant Name: Millstone Power Station, Unit 3 Utility Name: Dominion Nuclear Connecticut, Inc.
Analysis Information EM: ASTRUM (2004) Limiting Break Size: Guillotine Analysis Date: 04/17/07 Vendor: Westinghouse FQ: 2.6 FdH: 1.65 Fuel: RFA-2 SGTP (%): 10 Notes: None Clad Temp (OF)
LICENSING BASIS Analysis of Record PCT 1781 PCT ASSESSMENTS (Delta PCT)
A. Prior ECCS Model Assessments
- 1. HOTSPOT Burst Temperature Logic Errors 0
- 2. CCFL Global Volume Error 0
- 3. HOTSPOT Gap Heat Transfer Logic 0
- 4. Discrepancy in Metal Masses Used From Drawings 0
- 5. Error in ASTRUM Processing of Average Rod Burnup and Rod Internal Pressure 0
- 6. Treatment of Vessel Average Temperature Uncertainty 0
- 7. Error in ASTRUM Processing of Average Rod Burnup 0
- 8. PBOT and PMID Evaluation 0 B. Planned Plant Modification Evaluations
- 1. None 0 C. 2012 ECCS Model Assessments
- 1. Evaluation of Fuel Pellet Thermal Conductivity Degradation and Peaking Factor Burndown 222 D. Other