ML12114A003

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CFR 50.46 30-Day and Annual Report
ML12114A003
Person / Time
Site: Browns Ferry  Tennessee Valley Authority icon.png
Issue date: 04/18/2012
From: James Shea
Tennessee Valley Authority
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML12114A003 (9)
v • d • e


Text

Tennessee Valley Authority, 1101 Market Street, Chattanooga, Tennessee 37402-2801 April 18, 2012 10 CFR 50.4 10 CFR 50.46 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Browns Ferry Nuclear Plant, Units 2 and 3 Facility Operating License Nos. DPR-52 and DPR-68 NRC Docket Nos. 50-260 and 50-296

Subject:

10 CFR 50.46 30-Day and Annual Report for Browns Ferry Nuclear Plant, Units 2 and 3

Reference:

TVA Letter to NRC, "10 CFR 50.46 Annual Report," dated June 3, 2011 The purpose of this letter is to provide a report of changes or errors discovered in the Emergency Core Cooling System (ECCS) evaluation model for Browns Ferry Nuclear Plant, Units 2 and 3. In accordance with 10 CFR 50.46, "Acceptance Criteria for ECCS for Light-Water Nuclear Power Reactors," paragraph (a)(3)(ii), Enclosures 1 and 2 describe the nature and the estimated effect on the limiting ECCS analysis of changes or errors discovered since submittal of the reference letter for Browns Ferry Nuclear Plant, Units 2 and 3, respectively. As a result of the changes described in Enclosures 1 and 2, the Tennessee Valley Authority (TVA) will submit the revised Loss of Coolant Accident (LOCA) Analysis for Browns Ferry Nuclear Plant, Units 2 and 3, to the NRC for review and approval by June 30, 2012, as documented in Enclosure 3.

This report serves as both the 30-day report for a significant change and the annual report for Browns Ferry Nuclear Plant, Units 2 and 3. The significant Peak Cladding Temperature (PCT) changes discussed in the enclosures were initially reported to TVA by AREVA in May 2011, with revisions in July and December of 2011. These changes were created to support an operability assessment to address issues with the applicability of the EXEM BWR-2000 LOCA methodology identified during the NRC acceptance review of the BFN, Unit 1, ATRIUMTM-10 fuel transition License Amendment Request. TVA did not immediately recognize thatthe operability assessment that determined the PCT change constituted a Printed on recycled paper d

U.S. Nuclear Regulatory Commission Page 2 April 18, 2012 change to the evaluation model. Thus, the PCT change was not promptly identified for 10 CFR 50.46 reporting. TVA's failure to report the significant PCT change in accordance with 10 CFR 50.46 requirements is being addressed by TVA's Corrective Action Program.

There is one regulatory commitment in this letter as reflected in Enclosure 3. Please direct questions concerning this issue to Tom Hess at (423) 751-3487.

Res e ully, j W; Shea an ger, Corporate Nuclear Licensing

Enclosures:

1. 10 CFR 50.46 30-Day and Annual Report for Browns Ferry Nuclear Plant, Unit 2
2. 10 CFR 50.46 30-Day and Annual Report for Browns Ferry Nuclear Plant, Unit 3
3. Regulatory Commitment cc (Enclosures): NRC Regional Administrator - Region II NRC Senior Resident Inspector - Browns Ferry Nuclear Plant

ENCLOSUREI 10 CFR 50.46 30-DAY AND ANNUAL REPORT FOR BROWNS FERRY NUCLEAR PLANT, UNIT 2 The Browns Ferry Nuclear Plant (BFN), Unit 2, reactor core currently contains only the ATRIUM TM-10 fuel design.

Description of Changes or Errors Relative to the Previous Report The previous 10 CFR 50.46 report for BFN, Unit 2, was submitted in June 2011. This report referenced ANP-2910 Revision 0 (Reference 2) as a reference document, with a baseline Peak Cladding Temperature (PCT) of 1990 OF. Reference 3 is a revision to Reference 2, which includes the new limiting lattice that was reported as a 2 OF change in the June 2011 report, resulting in a revised baseline PCT of 1992 °F.

As part of the acceptance review of the BFN, Unit 1, ATRIUMTM-10 fuel transition License Amendment Request (LAR), the NRC questioned the applicability of the EXEM BWR-2000 LOCA methodology to analyze the unique BFN configuration that resulted in the limiting Loss of Coolant Accident (LOCA) event. The NRC position is that the limiting event in Reference 1 (i.e.,

a single failure resulting in failure of automatic initiation of the Automatic Depressurization System (ADS)) results in an event outside of the typical 10 CFR 50 Appendix K assumed event progression. Consequently, the NRC concluded the EXEM BWR-2000 methodology is being applied outside its Safety Evaluation Report basis for the as-analyzed limiting event in ANP-2908(P). Technical details regarding the NRC concerns and the modeling changes made by AREVA to address those concerns are available in the October 7, 2011, TVA response to "NRC Request for Additional Information" (Reference 8).

AREVA has developed a modified analysis methodology that addresses the concerns of the NRC and has performed an evaluation of the limiting LOCA event for BFN. The results of this conservative evaluation show that a PCT less than 2200 OF can be attained, provided that thermal limit (Maximum Average Planar Linear Heat Generation Rate (MAPLHGR)) penalties are applied as specified in Reference 4.

Reference 5 details the PCT changes due to the revised methodology and thermal limit changes. The revised methodology results in a PCT increase due to the conservative changes that were made. The thermal limit penalties change the initial conditions of the analysis, resulting in a decrease in PCT. Different thermal limit penalties have been applied for BFN, Units 2 and 3, resulting in different impacts on PCT for each unit.

A modification to the ADS is planned for the spring 2013 refueling outage, which will restore the automatic initiation capability of the ADS in the event of a single failure and return BFN, Unit 2, to a more typical 10 CFR 50 Appendix K event progression. A new baseline LOCA analysis (References 6 and 7), which also assumes the ADS modification is implemented, has been submitted to the NRC as part of the BFN, Unit 1, ATRIUMTM-10 fuel transition LAR. This revised LOCA analysis will be submitted to the NRC for application to BFN, Unit 2, by June 30, 2012. TVA will continue to treat this issue as a degraded/nonconforming condition until it is resolved by modification of the ADS and NRC approval of the revised LOCA analysis.

El -I of 3

ENCLOSURE 1 10 CFR 50.46 30-DAY AND ANNUAL REPORT FOR BROWNS FERRY NUCLEAR PLANT, UNIT 2 Cumulative Effect of PCT Changes - BFN, Unit 2 Baseline PCT (Reference 3) 19920 F Revised HUXY numerical view factor treatment analysis (reported in the +1 OF June 3, 2011, 10 CFR 50.46 Annual Report)

Modification to methodology to address NRC concerns regarding +322 0 F 10 CFR 50 Appendix K event progression Change in initial conditions for analysis (MAPLHGR reduction) -221 OF Accumulated changes since baseline analysis +102 0 F Absolute value of accumulated changes 544 0F Current PCT 2094°F El -2 of 3

ENCLOSURE I 10 CFR 50.46 30-DAY AND ANNUAL REPORT FOR BROWNS FERRY NUCLEAR PLANT, UNIT 2 References

1. ANP-2908(P) Revision 0, "Browns Ferry Units 1, 2, and 3 105% OLTP LOCA Break Spectrum Analysis," AREVA NP Inc., March 2010.
2. ANP-2910(P) Revision 0, "Browns Ferry Units 1, 2, and 3 105% OLTP LOCA-ECCS Analysis MAPLHGR Limit for ATRIUM TM-10 Fuel," AREVA NP Inc., March 2010.
3. ANP-2910(P) Revision 1, "Browns Ferry Units 1, 2, and 3 105% OLTP LOCA-ECCS Analysis MAPLHGR Limit for ATRIUMTM-1 0 Fuel," AREVA NP Inc., November 2010.
4. FAB1 1-2533, "Transmittal of Browns Ferry BFE2-17 and BFE3-15 Operability Assessment Revision 4," AREVA NP Inc., December 2011.
5. FAB12-2132, "Transmittal of TVA Requested 10 CFR 50.46 PCT Error Reporting for Browns Ferry Unit 2 Cycle 17 and Unit 3 Cycle 15 Summary," AREVA NP Inc., April 2012.
6. ANP-3015(P) Revision 0, "Browns Ferry Units 1, 2, and 3 LOCA Break Spectrum Analysis,"

AREVA NP Inc., September 2011.

7. ANP-3016(P) Revision 0, "Browns Ferry Units 1, 2, and 3 LOCA-ECCS MAPLHGR Limit for ATRIUMTM-10 Fuel," AREVA NP Inc., December 2011.
8. TVA Letter to NRC, "Response to NRC Request for Additional Information Regarding Amendment Request to Transition to AREVA Fuel (TAC NO. ME3775)," October 7, 2011.

El - 3 of 3

ENCLOSURE2 10 CFR 50.46 30-DAY AND ANNUAL REPORT FOR BROWNS FERRY NUCLEAR PLANT, UNIT 3 The Browns Ferry Nuclear Plant (BFN), Unit 3, reactor core currently contains only the ATRIUM TM-10 fuel design.

Description of Changes or Errors Relative to the Previous Report The previous 10 CFR 50.46 report for BFN, Unit 3, was submitted in June 2011. This report referenced ANP-2910 Revision 0 (Reference 2) as a reference document, with a baseline Peak Cladding Temperature (PCT) of 1990 OF. Reference 3 is a revision to Reference 2, which includes the new limiting lattice that was reported as a 2 OF change in the June 2011 report, resulting in a revised baseline PCT of 1992 OF.

As part of the acceptance review of the BFN, Unit 1, ATRIUMTM-10 fuel transition License Amendment Request (LAR), the NRC questioned the applicability of the EXEM BWR-2000 LOCA methodology to analyze the unique BFN configuration that resulted in the limiting Loss of Coolant Accident (LOCA) event. The NRC position is that the limiting event in Reference 1 (i.e.,

a single failure resulting in failure of automatic initiation of the Automatic Depressurization System (ADS)) results in an event outside of the typical 10 CFR 50 Appendix K assumed event progression. Consequently, the NRC concluded the EXEM BWR-2000 methodology is being applied outside its Safety Evaluation Report basis for the as-analyzed limiting event in ANP-2908(P). Technical details regarding the NRC concerns and the modeling changes made by AREVA to address those concerns are available in the October 7, 2011, TVA response to "NRC Request for Additional Information" (Reference 8).

AREVA has developed a modified analysis methodology that addresses the concerns of the NRC and has performed an evaluation of the limiting LOCA event for BFN. The results of this conservative evaluation show that a PCT less than 2200 OF can be attained, provided that thermal limit (Maximum Average Planar Linear Heat Generation Rate (MAPLHGR) and Minimum Critical Power Ratio (MCPR)) penalties are applied as specified in Reference 4.

Reference 5 details the PCT changes due to the revised methodology and thermal limit changes. The revised methodology results in a PCT increase due to the conservative changes that were made. The thermal limit penalties change the initial conditions of the analysis, resulting in a decrease in PCT. Different thermal limit penalties have been applied for BFN, Units 2 and 3, resulting in different impacts on PCT for each unit.

A modification to the ADS is planned for the spring 2012 refueling outage, which will restore the automatic initiation capability of the ADS in the event of a single failure and return BFN, Unit 3, to a more typical 10 CFR 50 Appendix K event progression. A new baseline LOCA analysis (References 6 and 7), which also assumes the ADS modification is implemented, has been submitted to the NRC as part of the BFN, Unit 1, ATRIUMTM-10 fuel transition LAR. This revised LOCA analysis will also be submitted to the NRC for application to BFN, Unit 3, by June 30, 2012. TVA will continue to treat this issue as a degraded/nonconforming condition until it is resolved by the modification of the ADS and NRC approval of the revised LOCA analysis.

E2 -1 of 3

ENCLOSURE2 10 CFR 50.46 30-DAY AND ANNUAL REPORT FOR BROWNS FERRY NUCLEAR PLANT, UNIT 3 Cumulative Effect of PCT Changes - BFN, Unit 3 Baseline PCT (Reference 3) 1992 0 F Revised HUXY numerical view factor treatment analysis (reported in the +1 0 F June 3, 2011, 10 CFR 50.46 Annual Report)

Increased core spray leakage from lower sectional replacement hardware modification analysis (reported in the April 30, 2010, 10 CFR 50.46 Annual +190 F Report)

Modification to methodology to address NRC concerns regarding +322 0 F 10 CFR 50 Appendix K event progression Change in initial conditions for analysis (MAPLHGR reduction and MCPR -241 OF increase)

Accumulated changes since baseline analysis +101 °F Absolute value of accumulated changes 5830 F Current PCT 2093°F E2 - 2 of 3

ENCLOSURE 2 10 CFR 50.46 30-DAY AND ANNUAL REPORT FOR BROWNS FERRY NUCLEAR PLANT, UNIT 3 References

1. ANP-2908(P) Revision 0, "Browns Ferry Units 1, 2, and 3 105% OLTP LOCA Break Spectrum Analysis," AREVA NP Inc., March 2010.
2. ANP-2910(P) Revision 0, "Browns Ferry Units 1, 2, and 3 105% OLTP LOCA-ECCS Analysis MAPLHGR Limit for ATRIUM TM-10 Fuel," AREVA NP Inc., March 2010.
3. ANP-2910(P) Revision 1, "Browns Ferry Units 1, 2, and 3 105% OLTP LOCA-ECCS Analysis MAPLHGR Limit for ATRIUM TM-10 Fuel," AREVA NP Inc., November 2010.
4. FAB1 1-2353, "Transmittal of Browns Ferry BFE2-17 and BFE3-15 Operability Assessment Revision 3," AREVA NP Inc., July 2011.
5. FAB12-2132, "Transmittal of TVA Requested 10 CFR 50.46 PCT Error Reporting for Browns Ferry Unit 2 Cycle 17 and Unit 3 Cycle 15 Summary," AREVA NP Inc., April 2012.
6. ANP-3015(P) Revision 0, "Browns Ferry Units 1, 2, and 3 LOCA Break Spectrum Analysis,"

AREVA NP Inc., September 2011.

7. ANP-3016(P) Revision 0, "Browns Ferry Units 1, 2, and 3 LOCA-ECCS MAPLHGR Limit for ATRIUMTM-10 Fuel," AREVA NP Inc., dated December 2011.
8. TVA Letter to NRC, "Response to NRC Request for Additional Information Regarding Amendment Request to Transition to AREVA Fuel (TAC NO. ME3775)," October 7, 2011.

E2 - 3 of 3

ENCLOSURE 3 REGULATORY COMMITMENT The Tennessee Valley Authority will submit the revised Loss of Coolant Accident (LOCA)

Analysis for Browns Ferry Nuclear Plant, Units 2 and 3, to the NRC for review and approval by June 30, 2012.

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