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| {{#Wiki_filter: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: | | {{#Wiki_filter:}} |
| David Bortz Catawba and McGuire Nuclear Stations August 30, 2021 Duke Energy - Safety Analysis Models Duke / NRC Meeting
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| Participants
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| * Dave Bortz (Safety Analysis Models)
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| * Mike Blom (Director Fuel Management and Design)
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| * Jeff Abbott (Manager Safety Analysis Models)
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| * Art Zaremba (Fleet Licensing Manager)
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| Duke Energy - Safety Analysis Models Duke / NRC Meeting 2
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| Outline
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| * Overview of DPC-NE-1007-P
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| * EOC MTC Measurement
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| * Summary of Changes
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| * Motivation for Changes
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| * Methodology Revisions
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| * Schedule Duke Energy - Safety Analysis Models Duke / NRC Meeting 3
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| Overview of DPC-NE-1007-P
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| * Describes the methodology to conditionally exempt the performance of the EOC MTC measurement at CNS and MNS
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| * 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
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| * Conditional Exemption based on:
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| - Core performance criteria being satisfied to demonstrate the reactor core is operating as designed
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| - Calculation of the EOC 300 ppm RTP MTC accounting for uncertainty and differences between predicted and actual core performance
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| - Verification the calculated MTC is within the SR 3.1.3.2 limit
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| * If any single core performance criterion is not met, an EOC MTC measurement is required Duke Energy - Safety Analysis Models Duke / NRC Meeting 4
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| EOC MTC Measurement
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| * Required by SR 3.1.3.2
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| * Measurement is an infrequent plant evolution
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| * Plant systems operated in a mode or condition not typical of steady state operation
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| * Introduces a reactivity transient
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| * Difficult to accurately perform
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| * Loss in plant availability (decrease in thermal efficiency during the test)
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| * Potential for a reactivity event due to a human performance error or unanticipated equipment issue Duke Energy - Safety Analysis Models Duke / NRC Meeting 5
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| Summary of Changes
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| * Remove the incore tilt performance criterion
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| * Modify the power distribution performance criterion to prevent a false positive failure
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| * Add an alternative method for determining the most-negative MTC safety analysis limit
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| * No Technical Specification changes required Duke Energy - Safety Analysis Models Duke / NRC Meeting 6
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| Motivation for Methodology Changes
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| * Prevent the unnecessary performance of an infrequent plant evolution, reactivity transient and loss of plant efficiency
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| * Eliminate a condition where an indeterminate instrument issue causes the power distribution performance criteria to be exceeded
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| * 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
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| Incore Tilt Methodology Revision
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| * Remove the incore tilt criterion based on experience with using the method
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| - Frequently challenged
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| - Responsible for all exemption failures
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| - Negligibly impacts the magnitude of the MTC
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| - Power distribution reaction rate criterion available to demonstrate core is operating as designed
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| * Incore tilts are not uncommon. Can results from:
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| - differences in loop flows and inlet temperatures
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| - Asbuilt fuel and burnable absorber fabrication
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| - Intentional Duke Energy - Safety Analysis Models Duke / NRC Meeting 8
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| Power Distribution Methodology Revision
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| * Modify the performance criteria to remove the single failure criterion
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| * Current criteria is +/- 10% assembly average reaction rate error and remains unchanged
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| * Any single location with a reaction rate error greater than 10% absolute results in a failure of the criterion
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| * New criterion requires multiple failures
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| * Eliminates the condition where a measurement due to an indeterminate instrument issue causes a false positive (criteria exceeded)
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| Duke Energy - Safety Analysis Models Duke / NRC Meeting 9
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| SA MTC Limit Methodology Revision
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| * Add an alternate approach for calculating the EOC most negative MTC Safety Analysis limit
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| * Removes unnecessary conservatism in the method
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| * Current method is deterministic
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| * New method statistically combines parameters used to calculate the limit
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| * 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
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| Schedule
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| * Expected submittal - September 2021
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| * One year review and approval from NRC acceptance Duke Energy - Safety Analysis Models Duke / NRC Meeting 11}}
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