ML21236A286

License Amendment Request for Revision 1 of DPC-NE-1007-P, Conditional Exemption of the End-of-Cycle (EOC) Moderator Temperature Coefficient (Mtc) Measurement Methodology

ML21236A286
Person / Time
Site:	Catawba, McGuire, Mcguire
Issue date:	08/30/2021
From:	Bortz D Duke Energy Carolinas
To:	Office of Nuclear Reactor Regulation
Stone Z
References
Download: ML21236A286 (11)

Text

Duke Energy / NRC Pre-submittal Meeting License Amendment Request for Revision 1 of DPC-NE-1007-P, Conditional Exemption of the End-of-Cycle (EOC) Moderator Temperature Coefficient (MTC) Measurement Methodology Presenter:

David Bortz Catawba and McGuire Nuclear Stations August 30, 2021 Duke Energy - Safety Analysis Models Duke / NRC Meeting

Participants

• Dave Bortz (Safety Analysis Models)

• Mike Blom (Director Fuel Management and Design)

• Jeff Abbott (Manager Safety Analysis Models)

• Art Zaremba (Fleet Licensing Manager)

Duke Energy - Safety Analysis Models Duke / NRC Meeting 2

Outline

• Overview of DPC-NE-1007-P

• EOC MTC Measurement

• Summary of Changes

• Motivation for Changes

• Methodology Revisions

• Schedule Duke Energy - Safety Analysis Models Duke / NRC Meeting 3

Overview of DPC-NE-1007-P

• Describes the methodology to conditionally exempt the performance of the EOC MTC measurement at CNS and MNS

• Technical Specification SR 3.1.3.2 requires verification of the MTC within 7 effective full power days of reaching the equivalent of an equilibrium core boron concentration of 300 ppm at RTP conditions

• Conditional Exemption based on:

- Core performance criteria being satisfied to demonstrate the reactor core is operating as designed

- Calculation of the EOC 300 ppm RTP MTC accounting for uncertainty and differences between predicted and actual core performance

- Verification the calculated MTC is within the SR 3.1.3.2 limit

• If any single core performance criterion is not met, an EOC MTC measurement is required Duke Energy - Safety Analysis Models Duke / NRC Meeting 4

EOC MTC Measurement

• Required by SR 3.1.3.2

• Measurement is an infrequent plant evolution

• Plant systems operated in a mode or condition not typical of steady state operation

• Introduces a reactivity transient

• Difficult to accurately perform

• Loss in plant availability (decrease in thermal efficiency during the test)

• Potential for a reactivity event due to a human performance error or unanticipated equipment issue Duke Energy - Safety Analysis Models Duke / NRC Meeting 5

Summary of Changes

• Remove the incore tilt performance criterion

• Modify the power distribution performance criterion to prevent a false positive failure

• Add an alternative method for determining the most-negative MTC safety analysis limit

• No Technical Specification changes required Duke Energy - Safety Analysis Models Duke / NRC Meeting 6

Motivation for Methodology Changes

• Prevent the unnecessary performance of an infrequent plant evolution, reactivity transient and loss of plant efficiency

• Eliminate a condition where an indeterminate instrument issue causes the power distribution performance criteria to be exceeded

• Increase margin to the safety analysis most-negative MTC limit to accommodate the introduction of advanced fuel designs and fuel management strategies Duke Energy - Safety Analysis Models Duke / NRC Meeting 7

Incore Tilt Methodology Revision

• Remove the incore tilt criterion based on experience with using the method

- Frequently challenged

- Responsible for all exemption failures

- Negligibly impacts the magnitude of the MTC

- Power distribution reaction rate criterion available to demonstrate core is operating as designed

• Incore tilts are not uncommon. Can results from:

- differences in loop flows and inlet temperatures

- Asbuilt fuel and burnable absorber fabrication

- Intentional Duke Energy - Safety Analysis Models Duke / NRC Meeting 8

Power Distribution Methodology Revision

• Modify the performance criteria to remove the single failure criterion

• Current criteria is +/- 10% assembly average reaction rate error and remains unchanged

• Any single location with a reaction rate error greater than 10% absolute results in a failure of the criterion

• New criterion requires multiple failures

• Eliminates the condition where a measurement due to an indeterminate instrument issue causes a false positive (criteria exceeded)

Duke Energy - Safety Analysis Models Duke / NRC Meeting 9

SA MTC Limit Methodology Revision

• Add an alternate approach for calculating the EOC most negative MTC Safety Analysis limit

• Removes unnecessary conservatism in the method

• Current method is deterministic

• New method statistically combines parameters used to calculate the limit

• Methodology revision increases analysis margin to support higher burnup fuel designs and potential two-year fuel management strategies Duke Energy - Safety Analysis Models Duke / NRC Meeting 10

Schedule

• Expected submittal - September 2021

• One year review and approval from NRC acceptance Duke Energy - Safety Analysis Models Duke / NRC Meeting 11