ML20127H672

CFR 50.46 Annual Report

ML20127H672
Person / Time
Site:	Crane
Issue date:	05/06/2020
From:	David Helker Exelon Generation Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
TMI-20-18
Download: ML20127H672 (11)

Text

200 Exelon Way Kennett Square, PA 19348 www.exeloncorp.com Kennett Square, PA 19348 10 CFR 50.46 TMI-20-18 May 6, 2020 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Three Mile Island Nuclear Station, Unit 1 Renewed Facility License No. DPR-50 NRC Docket No. 50-289

Subject:

10 CFR 50.46 Annual Report

Reference:

1)

Letter from David P. Helker (Exelon Generation Company, LLC) to U.S. Nuclear Regulatory Commission, "10 CFR 50.46 Annual Report,"

dated May 6, 2019

2) FS1-0049426-2.0, "Transmittal of Input for TMI 50.46 Report for 2019, dated April 24, 2020

3) FS1-0038707, Rev. 1, "TMI-1 LBLOCA Summary Report," November 27, 2018

4) TMI-19-095, Letter from Michael P. Gallagher, Exelon Generation Company, LLC, to U.S. Nuclear Regulatory Commission, "Certification of Permanent Removal of Fuel from the Reactor Vessel for Three Mile Island Nuclear Station, Unit 1," dated September 26, 2019.

The purpose of this letter is to submit the 10 CFR 50.46 reporting information for Three Mile Island Nuclear Station, Unit 1 (TMI-1). The most recent annual 50.46 Report for TMI-1, (Reference 1), provided the cumulative Peak Cladding Temperature (PCT) errors for the most recent fuel designs.

Reference 2 documented Framatome's deliverable to Exelon to support the 10 CFR 50.46 annual report. The new LBLOCA (Reference 3) followed the methodology from the supplement to topical BAW-10192PA-00, approved by the NRC to adequately account for the effects of Thermal Conductivity Degradation (TCD) on volume average fuel temperatures later in life. The approval of the topical report does not affect TMI-1's LBLOCA Analysis of Record (AOR) at the time of final shutdown and only applies to the new LBLOCA. The new LBLOCA analysis has not been implemented and will not be implemented due to transition to decommissioning at the end of Cycle 22 (Fall 2019).

U.S. Nuclear Regulatory Commission 10 CFR 50.46 Annual Report May 6, 2020 Page 2 As of September 26, 2019, TM 1-1 certified that all fuel was permanently removed from the TM 1-1 reactor vessel (Reference 4). Pursuant to 10 CFR 50.82{a)(2) TMl-1 is no longer authorized to operate the reactor or place or retain fuel in the reactor vessel. Therefore, this annual report covers the period from the issuance of the last report (Reference 1) until all fuel was permanently removed from the TMl-1 reactor vessel on September 26, 2019.

Two attachments are included with this letter that provide the current TMI, Unit 1, 10 CFR 50.46 status. Attachment 1 ("Peak Cladding Temperature Rack-Up Sheets")

provides updated information regarding the PCT for the limiting SBLOCA and LBLOCA analyses. Attachment 2 ("Assessment Notes") contains a detailed description for each change or error reported.

No new regulatory commitments are established in this submittal.

If any additional information is needed, please contact Frank Mascitelli at (610) 765-5512.

Respectfully, David P. Helker Sr. Manager, Licensing and Regulatory Affairs Exelon Generation Company, LLC Attachments: 1) Peak Cladding Temperature Rack-Up Sheets

2) Assessment Notes cc:

USNRC Administrator, Region I Regional Decommissioning Inspector - TMl-1 USNRC Project Manager, TMl-1 R. R. Janati, Pennsylvania Bureau of Radiation Protection

U.S. Nuclear Regulatory Commission 10 CFR 50.46 Annual Report May 6, 2020 Page 3 bcc:

w/o Attachment Senior Vice President-Mid-Atlantic Operations Vice President - Licensing & Regulated - KSA Site Decommissioning Director - Three Mile Island Manager, Site Engineering - Three Mile Island Director, Licensing - KSA w/ Attachment Site Decommissioning Regulatory Assurance Lead - Three Mile Island Sr. Manager, Licensing - KSA Licensing Records - KSA Commitment Coordinator - KSA N. S. Cole - KSA J. Massari - KSA

ATTACHMENT 1 10 CFR 50.46 Acceptance Criteria for Emergency Core Cooling Systems for Light-Water Nuclear Power Reactors Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments Assessments as of May 6, 2020 Peak Cladding Temperature Rack-Up Sheets TMI, Unit 1

Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of May 6, 2020 Peak Cladding Temperature Rack-Up Sheet Page 1 of 2 PLANT NAME:

Three Mile Island Unit 1 ECCS EVALUATION MODEL:

Small Break Loss of Coolant Accident (SBLOCA)

REPORT REVISION DATE:

5/06/2020 CURRENT OPERATING CYCLE:

N/A ANALYSIS OF RECORD (AOR)

Evaluation Model: BWNT1 Calculation: AREVA NP, 86-9111507-000, August 2009 (Mark-B-HTP with Enhanced Once-Through Steam Generators (EOTSGs))

Fuel: Mark-B-HTP Limiting Fuel Type: Mark-B-HTP Limiting Single Failure: Loss of One Train of ECCS Limiting Break Size and Location: 0.07 ft2 Break in Cold Leg Pump Discharge Piping Reference Peak Cladding Temperature (PCT)

PCT = 1444.0°F MARGIN ALLOCATION A. PRIOR LOSS OF COOLANT ACCIDENT (LOCA) MODEL ASSESSMENTS Annual 10 CFR 50.46 Report dated May 16, 2007 (See Note 1)

PCT = 0 °F Annual 10 CFR 50.46 Report dated May 15, 2009 (See Note 3)

PCT = 0 °F Annual 10 CFR 50.46 Report dated May 14, 2010 (See Note 4)

PCT = 0 °F 30-Day 10 CFR 50.46 Report dated September 7, 2010 (See Note 5)

PCT = 225°F Annual 10 CFR 50.46 Report dated May 13, 2011 (See Note 6)

PCT = 0 °F 30-Day 10 CFR 50.46 Report dated March 21, 2012 (See Note 7)

PCT = 0 °F Annual 10 CFR 50.46 Report dated May 11, 2012 (See Note 8)

PCT = 0 °F Annual 10 CFR 50.46 Report dated May 10, 2013 (See Note 9)

PCT = 0 °F Annual 10 CFR 50.46 Report dated May 9, 2014 (See Note 10)

PCT = 0 °F 30-Day 10 CFR 50.46 Report dated December 22, 2014 (See Note 11) PCT = 0°F Annual 10 CFR 50.46 Report dated May 8, 2015 (See Note 12)

PCT = 0°F Annual 10 CFR 50.46 Report dated May 6, 2016 (See Note 13)

PCT = 0°F Annual 10 CFR 50.46 Report dated May 5, 2017 (See Note 14)

PCT = 0°F Annual 10 CFR 50.46 Report dated May 4, 2018 (See Note 15)

PCT = 0°F Annual 10 CFR 50.46 Report dated May 6, 2019 (See Note 16)

PCT = 0°F NET PCT PCT = 1669.0°F B. CURRENT LOCA MODEL ASSESSMENTS Two Documentation Errors in BAW-10227PA-01 (See Note 17)

PCT = 0°F SBLOCA Homogeneous LOCA Hole EM Model Change (See Note 17) PCT = 0°F Total PCT change from current assessments PCT = 0°F Cumulative PCT change from current assessments PCT = 0°F NET PCT PCT = 1669.0°F 1 The BWNT EM is based on RELAP5/MOD2-B&WCURRENT LOCA MODEL ASSESSMENTS

Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of May 6, 2020 Peak Cladding Temperature Rack-Up Sheet Page 2 of 2 PLANT NAME:

Three Mile Island Unit 1 ECCS EVALUATION MODEL:

Large Break Loss of Coolant Accident (LBLOCA)

REPORT REVISION DATE:

5/06/2020 CURRENT OPERATING CYCLE:

N/A ANALYSIS OF RECORD (AOR)

Evaluation Model: BWNT 2

Calculation: AREVA NP, 86-9111507-000, August 2009 (Mark-B-HTP with EOTSGs) Fuel: Mark-B-HTP Limiting Fuel Type: Mark-B-HTP Limiting Single Failure: Loss of One Train of ECCS Limiting Break Size and Location: Guillotine Break in Cold Leg Pump Discharge Piping Reference Peak Cladding Temperature (PCT)

PCT =

1890°F MARGIN ALLOCATION A. PRIOR LOCA MODEL ASSESSMENTS Annual 10 CFR 50.46 Report dated May 16, 2007 (See Note 1)

PCT = 0°F Annual 10 CFR 50.46 Report dated May 15, 2008 (See Note 2)

PCT = 0°F Annual 10 CFR 50.46 Report dated May 15, 2009 (See Note 3)

PCT = 0°F Annual 10 CFR 50.46 Report dated May 14, 2010 (See Note 4)

PCT = 0°F Annual 10 CFR 50.46 Report dated May 13, 2011 (See Note 6)

PCT = 0°F 30-Day 10 CFR 50.46 Report dated March 21, 2012 (See Note 7)

PCT = 0 °F Annual 10 CFR 50.46 Report dated May 11, 2012 (See Note 8)

PCT = 0 °F Annual 10 CFR 50.46 Report dated May 10, 2013 (See Note 9)

PCT = 0 °F Annual 10 CFR 50.46 Report dated May 9, 2014 (See Note 10)

PCT = 0 °F 30-Day 10 CFR 50.46 Report dated December 22, 2014 (See Note 11)

PCT = +18°F Annual 10 CFR 50.46 Report dated May 8, 2015 (See Note 12)

PCT = 0°F Annual 10 CFR 50.46 Report dated May 6, 2016 (See Note 13)

PCT = 0°F Annual 10 CFR 50.46 Report dated May 5, 2017 (See Note 14)

PCT = 0°F Annual 10 CFR 50.46 Report dated May 4, 2018 (See Note 15)

PCT = 0°F Annual 10 CFR 50.46 Report dated May 6, 2019 (See Note 16)

PCT = 0°F NET PCT PCT = 1908°F B. CURRENT LOCA MODEL ASSESSMENTS Two Documentation Errors in BAW-10227PA-01 (See Note 17)

PCT = 0°F Total PCT change from current assessments PCT = 0°F Cumulative PCT change from current assessments PCT = 0°F NET PCT PCT = 1908°F 2 The BWNT EM is based on RELAP5/MOD2-B&W

ATTACHMENT 2 10 CFR 50.46 Acceptance Criteria for Emergency Core Cooling Systems for Light-Water Nuclear Power Reactors Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments Assessments as of May 6, 2020 Peak Cladding Temperature Rack-Up Sheets TMI, Unit 1 Assessment Notes

Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of May 6, 2020 Assessment Notes Page 1 of 4

1. Prior LOCA Model Assessment The 10 CFR 50.46 report dated May 16, 2007 reported an evaluation for a LOCA model change which resulted in a 0 °F PCT change. The reported evaluation considered the effect on the containment pressure response for LOCA due to GSI-191 related reactor building sump screen replacement. The evaluation resulted in 0 °F impact for LBLOCA and SBLOCA PCTs.

2. Prior LOCA Model Assessment The 10 CFR 50.46 report dated May 15, 2008 reported an evaluation for LOCA model change which resulted in a 0 °F PCT change. Reported change included the impact of an energy deposition factor error which resulted in a LBLOCA PCT impact of 0 °F.

3. Prior LOCA Model Assessment The 10 CFR 50.46 report dated May 15, 2009 reported no evaluations or PCT penalties for either SBLOCA or LBLOCA.

4. Prior LOCA Model Assessment The 10 CFR 50.46 report dated May 14, 2010 reported a change to the reference PCT value for LBLOCA due to the final discharge of all Mark-B9 fuel.

Also identified in this report was a new SBLOCA analysis, implemented beginning with the Cycle 18 operation. This SBLOCA analysis was evaluated with the mixed core of Mark-B12 and Mark-B-HTP and a new PCT of 1444°F was calculated for the limiting Mark-B-HTP fuel type, which bounds the Mark-B12 fuel type. This analysis also includes consideration of the effect of reduced EDW wetting associated with the Enhanced Once-Through Steam Generators (EOTSGs).

5. Prior LOCA Model Assessment The 10 CFR 50.46 report dated September 7, 2010 reported an evaluation for the SBLOCA analysis due to a non-bounding axial power shape from middle-of-cycle to end-of-cycle conditions. This resulted in a PCT increase of 225°F. The large break LOCA is not affected in this report.

6. Prior LOCA Model Assessment The 10 CFR 50.46 report dated May 13, 2011 reported no evaluations or PCT penalties for either SBLOCA or LBLOCA.

7. Prior LOCA Model Assessment The 10 CFR 50.46 report dated March 21, 2012 reported two changes to the TMI LOCA model. One consisted of an error in the ECCS Bypass Calculation that affected the LBLOCA analysis. The second change consisted of correcting the Upper Plenum Column

Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of May 6, 2020 Assessment Notes Page 2 of 4 Weldment Model which affected both the SBLOCA and LBLOCA analysis. The results of both of these changes were a 0°F PCT impact for both SBLOCA and LBLOCA.

8. Prior LOCA Model Assessment With the Cycle 19 reload, all Mark-B12 fuel types were discharged from the core.

Currently, the limiting fuel type is Mark-B-HTP for both SBLOCA and LBLOCA. The limiting PCT for LBLOCA has been updated to 1890°F in accordance with our referenced calculation (86-9111507-000). All previous PCT assessments that are not applicable to Mark-B-HTP fuel have been removed.

The 10 CFR 50.46 report dated May 11, 2012 reported no evaluations or PCT penalties for either SBLOCA or LBLOCA.

9. Prior LOCA Model Assessment The 10 CFR 50.46 report dated May 10, 2013 reported no evaluations or PCT penalties for either SBLOCA or LBLOCA.

10. Prior LOCA Model Assessment The 10 CFR 50.46 report dated May 9, 2014 reported no evaluations or PCT penalties for either SBLOCA or LBLOCA.

11. Prior LOCA Model Assessment The 30-day 10 CFR 50.46 report dated December 22, 2014 reported a significant error due to thermal conductivity degradation (TCD) based on insufficient LOCA fuel temperature inputs in TACO-3/GDTACO computer codes. Correction of the TCD modeling in TACO-3/GDTACO results in a conservative increase of 393F in peak cladding temperature (PCT) for LBLOCA. The SBLOCA analyses are not sensitive to initial fuel temperature and therefore have an estimated PCT impact of 0°F.

Additionally, TMI has implemented a 2 kw/ft penalty to LHR limits in Cycle 20 (10/20/14).

The penalty has been applied through more restrictive operational imbalance limits and results in a reduction of PCT by 375°F for LBLOCA.

The overall cumulative impact for the error and the design input change is 0°F for SBLOCA and 18°F for LBLOCA.

12. Prior LOCA Model Assessment The 10 CFR 50.46 report dated May 8, 2015 reported no evaluations or PCT penalties for either SBLOCA or LBLOCA.

13. Prior LOCA Model Assessment The 10 CFR 50.46 report dated May 6, 2016 reported the reactor coolant system

Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of May 6, 2020 Assessment Notes Page 3 of 4 (RCS) flow rate used in the TMI Unit 1 SBLOCA analysis (106.5% of design flow) is inconsistent with the RCS flow rate used in the departure-from-nucleate (DNB) analysis (104.5% of design flow).

Additionally, a lower RCS flow rate was used in the LBLOCA analysis (102% of design flow) than that in the at-power minimum DNB analysis (104.5% of design flow). LOCA analyses are performed using the AREVA LOCA evaluation model (EM) BAW-10192P-A, which is the applicable LOCA EM for TMI Unit 1, and are required to use the RCS flow rate that is used in the at-power minimum DNB analysis. The SBLOCA and LBLOCA RCS flow rate inconsistency assessments were estimated to be a 0 °F PCT impact.

14. Prior LOCA Model Assessment The 10 CFR 50.46 report dated May 5, 2017 reported no evaluations or PCT penalties for either SBLOCA or LBLOCA.

15. Prior LOCA Model Assessment The 10 CFR 50.46 report dated May 4, 2018 reported an assessment for an update to the M5 swelling and rupture model (SRM) which had the potential to impact TMI's SBLOCA and LBLOCA analysis.

M5 SRM is used in several of AREVA LOCA methodologies and since approval of the M5 SRM in the M5 Licensing Topical Report, BAW-10227, Rev. 1 (P)(A) by the NRC in the early 2000s, additional M5 cladding rupture test data was obtained. Following the same approach as the original model, an updated M5 SRM was developed to consider the new test data. The model changes do not change the predicted occurrence or conditions at the time of rupture but would impact the post-rupture cladding characteristics for certain rupture temperatures.

The estimated SBLOCA and LBLOCA PCT impact due to the M5 SRM update was 0°F.

16. Prior LOCA Model Assessment No model changes, errors, or assessments to report for SBLOCA and LBLOCA.

17. LOCA Model Assessment at the time of final shutdown Since the last 10 CFR 50.46 report dated May 6, 2019, an assessment was completed that described two documentation errors in the licensing documentation detailing the evaluation model used to analyze Large Break Loss of Coolant (LBLOCA) and Small Break Loss of Coolant (SBLOCA) accidents for TMI Unit 1 in the early 2000s. This condition does not change the current LOCA Analysis of Record (AOR) licensing bases as the results were produced by the latest acceptable evaluation model.

Report of the Emergency Core Cooling System Evaluation Model Changes and Errors Assessments as of May 6, 2020 Assessment Notes Page 4 of 4 The first of these documentation errors is related to the cladding outside emissivity modeling approach. The M5 topical report describes a single constant emissivity value that was to be used for both inside and outside of the cladding for radiation heat transfer. The LBLOCA demonstration cases contained in the M5 topical report, however, followed the previously NRC-approved Zr-4 approach that used a constant value for the inside clad emissivity and a variable emissivity model for the outside of the cladding. The M5 demonstration cases with a variable emissivity model consistently produces more conservative PCT predictions than the constant emissivity value described in the M5 topical report. Use of the variable emissivity is consistent with what has been done in the current TMI LBLOCA M5 cladding licensing basis analysis. Therefore, the current 2019 licensing basis analysis contains this more conservative modeling and the estimated impact is 0°F PCT.

The second documentation error is related to the thermal expansion input evaluation. In 2001, the thermal expansion inputs used in all B&W LOCA analyses were revised in the alpha-beta transition region to better represent the data. The thermal expansion input differences were small, and it was expected that the changes in calculated PCT would be less than a few degrees F. The change should have been evaluated and reported in the 2001 time period. It is estimated that the PCT impact of the thermal expansion model documentation error which is part of the current licensing basis is 0°F. Therefore, there is no change to the 2019 PCTs from this documentation error.

The TMI SBLOCA licensing basis analysis was also performed with the modified thermal expansion model and the variable emissivity models used in the M5 topical report LBLOCA demonstration cases. The estimated PCT impact of the thermal expansion model documentation error is approximately 0°F and SBLOCA results are negligibly impacted by the small changes to the elastic thermal expansion models resulting in an approximately 0°F impact. Therefore, there is no PCT change to the 2019 SBLOCA licensing basis PCT related to the circa 2000 documentation errors describing the LOCA modeling in BAW-10227PA.

The estimated PCT impact of these two documentation errors on TMI LOCA analyses is 0°F.

One additional assessment describing an evaluation model correction for the SBLOCA holes and slots between the core and core baffle region was reported for the TMI-1 SBLOCA AOR. The correction was related to variations in modeling between the current 177 FA SBLOCA AOR sensitivities and results versus what was stated in the text of the SBLOCA evaluation model. The BWNT LOCA Evaluation Model states: For small break LOCA applications, all primary system junctions are modeled as non-homogenous except for the break and the RVVV junctions. The modeling in the SBLOCA for the 177 FA SBLOCA AOR modeled these junctions as homogenous. The SBLOCA PCT results are not sensitive to how these junctions are modeled because there is little phase separation that occurs in the holes between the core and core baffle. The estimated PCT impact of this modeling error correction in the TMI LOCA analyses is 0°F.