L-17-040, Transmittal of 2016 Annual 10 CFR 50.46 Report of Changes to or Errors in Emergency Core Cooling System Evaluation Models

Transmittal of 2016 Annual 10 CFR 50.46 Report of Changes to or Errors in Emergency Core Cooling System Evaluation Models

ML17172A009
Person / Time
Site:	Beaver Valley
Issue date:	06/20/2017
From:	Richey M FirstEnergy Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-17-040
Download: ML17172A009 (7)

Text

FENOC Beaver Valley Power Station P.O. Box 4 FirstEnergy Nuclear Operatino Company ' Shippingport, PA 15077 Marty L. Richey 724-682-5234 Site Vice President Fax: 724-643-8069 June 20, 2017 L-17-040 10 CFR 50.46(a)(3)(ii)

ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

SUBJECT:

Beaver Valley Power Station, Unit Nos. 1 and 2 Docket No. 50-334, License No. DPR-66 Docket No. 50-412, License No. NPF-73 2016 Annual 10 CFR 50.46 Report of Changes to or Errors in Emergency Core Cooling System Evaluation Models In accordance with Title 10 of the Code of Federal Regulations, Part 50, Section 50.46(a)(3)(ii), FirstEnergy Nuclear Operating Company (FENOC) provides the attached report as the 2016 annual notification of changes or errors in emergency core cooling system evaluation models or the application of the models for the Beaver Valley Power Station, Unit Nos. 1 (BVPS-1) and 2 (BVPS-2). Current information for both large and small break loss-of-coolant accident (LOCA) transients is provided to satisfy 10 CFR 50.46 reporting requirements.

The attachments provide a summary list and description of each change or error in the acceptable evaluation models or the application of the models that affects the peak fuel cladding temperature (PCT) calculation for various LOCA transients, as well as the estimated PCT effects of the change or error.

The changes or errors communicated to FENOC since the previous annual report are listed in the attachments and the resultant PCTs associated with the large and small break LOCA transients are as follows:

BVPS-1 large break LOCA - 1840°F BVPS-1 small break LOCA- 1895°F BVPS-2 large break LOCA - 1839°F BVPS-2 small break LOCA-1917°F

Beaver Valley Power Station, Unit Nos. 1 and 2 L-17-040 Page 2 There are no new regulatory commitments contained in this submittal. If there are any questions or if additional information is required, please contact Mr. Thomas A. Lentz, Manager- Fleet Licensing, at (330) 315-6810.

Sincerely, Marty ~l~h:y Attachments:

1. Summary of 2016 Peak Fuel Cladding Temperature (PCT) Effects for Beaver Valley Power Station (BVPS) Loss-of-Coolant Accident (LOCA) Transients

2. Descriptions of 2016 Emergency Core Cooling System (ECCS) Evaluation Model Changes or Errors cc: NRC Region I Administrator NRC Resident Inspector NRC Project Manager Director BRP/DEP Site BRP/DEP Representative

Attachment 1 L-17-040 Summary of 2016 Peak Fuel Cladding Temperature (PCT) Effects for Beaver Valley Power Station (BVPS) Loss-of-Coolant Accident (LOCA) Transients Page 1 of 1 Beaver V a II ey P ower Stat"I0n U m*t No. 1 (BVPS -1) Large B rea kLOCA Description PCT Effect Attachment 2 (OF) Description General Computer Code Maintenance 0 Page 1 Error in Oxidation Calculations 0 Page 2 Error in Use of ASME Steam Tables 0 Page 3 Error in Support Column Unheated Conductor 0 Page 4 BVPS-1 Small Break LOCA Description PCT Effect Attachment 2 (OF) Description None - Not Applicable (NA) NA NA Beaver Valley Power Station Unit No. 2 (BVPS-2) Large Break LOCA Description PCT Effect Attachment 2 (OF) Description General Computer Code Maintenance 0 Page 1 Error in Oxidation Calculations 0 Page 2 Error in Support Column Unheated Conductor 0 Page4 BVPS-2 Small Break LOCA Description PCT Effect Attachment 2 (OF) Description None - Not Applicable (NA) NA NA

Attachment 2 L-17-040 Descriptions of 2016 Emergency Core Cooling System (ECCS)

Evaluation Model Changes or Errors Page 1 of 4 GENERAL COMPUTER CODE MAINTENANCE

Background

Various changes have been made to enhance the usability of computer codes and to streamline future analyses. Examples of these changes include: modifying input variable definitions, units and defaults, improving the input diagnostic checks, enhancing the computer code output, optimizing active coding, and eliminating inactive coding. These changes represent discretionary changes that will be implemented on a forward-fit basis in accordance with Section 4.1.1 of WCAP-13451, "Westinghouse Methodology for Implementation of 10 CFR 50.46 Reporting," October 1992.

Affected Evaluation Models

1. 1996 Westinghouse Best-Estimate Large Break Loss of Coolant Accident (LOCA)

Evaluation Model (Applicable to BVPS-2)

2. 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using Automated Statistical Treatment of Uncertainty Method (ASTRUM)

(Applicable to BVPS-1)

Estimated Effect The nature of these changes leads to an estimated peak cladding temperature (PCT) impact of 0°F for both BVPS-1 and BVPS-2.

Attachment 2 L-17-040 Page 2 of 4 ERROR IN OXIDATION CALCULATIONS

Background

A closely-related group of errors were discovered in the WCOBRA/TRAC software program. The errors are related to the calculation of high temperature oxidation within a realistic large break LOCA calculation. This issue has been evaluated to estimate the impact on the ASTRUM and the best-estimate (BE) large-break loss-of-coolant accident (LBLOCA) licensing-basis analysis results. The resolution of this issue represents a non-discretionary change in accordance with Section 4.1.2 of WCAP-13451.

Affected Evaluation Models

1. 1996 Westinghouse Best-Estimate Large Break LOCA Evaluation Model (Applicable to BVPS-2)

2. 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM (Applicable to BVPS-1)

Estimated Effect It was determined that correcting the high temperature oxidation calculation in WCOBRA/TRAC is estimated to have a negligible impact on the BE LBLOCA PCT analysis results, leading to an estimated PCT impact of 0°F for both BVPS-1 and BVPS-2.

Attachment 2 L-17-040 Page 3 of 4 ERROR IN USE OF ASME STEAM TABLES

Background

The American Society of Mechanical Engineers (ASME) steam tables are used to calculate the steady-state upper head liquid temperature as a function of the pressure and specific enthalpy in the ASTRUM software program. The steam table applicable to steam/gas is used to determine the upper head fluid temperature. However, the water in the upper head is in the subcooled liquid state during normal operation (and the steady-state calculation). Therefore, the steam table applicable to liquid should be used to determine the upper head fluid temperature. This issue has been evaluated to estimate the impact on ASTRUM BE LBLOCA analysis results. The resolution of this issue represents a non-discretionary change in accordance with Section 4.1.2 of WCAP-13451.

Affected Evaluation Models

1. 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM (Applicable to BVPS-1)

Estimated Effect The temperatures calculated by the ASME steam tables applicable to the steam/gas side and the liquid side are very similar within the typical upper head pressure and liquid specific enthalpy ranges. Therefore, this error was evaluated to have a negligible impact on the ASTRUM BE LBLOCA analysis results, leading to an estimated PCT impact of 0°F for BVPS-1.

Attachment 2 L-17-040 Page 4 of 4 ERROR IN SUPPORT COLUMN UNHEATED CONDUCTOR

Background

A modeling error was discovered in the support column unheated conductor in several BE LBLOCA analyses-of-record in which the metal thickness of the support columns in the upper plenum was underestimated. The heat transferred to the fluid from the support columns is small relative to the heat release from the core due to high fuel stored energy, decay heat, and since the upper plenum rapidly becomes a steam environment in a LBLOCA. Therefore, it does not significantly contribute to the transient response.

The resolution of this issue represents a non-discretionary change in the application of the evaluation model as described in Section 4.1.2 of WCAP-13451.

Affected Evaluation Models

1. 1996 Westinghouse Best-Estimate Large Break LOCA Evaluation Model (Applicable to BVPS-2)

2. 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM (Applicable to BVPS-1)

Estimated Effect The support column unheated conductor modeling error has been generically evaluated to have a negligible impact on the existing analyses, leading to an estimated PCT impact of 0°F for both BVPS-1 and BVPS-2.