Reactor Oversight Process Reactor Oversight Process

Unplanned Scrams with Complications Unplanned Scrams with Complications (USwC) Performance Indicator (USwC) Performance Indicator

Unplanned Scrams with Complications Performance IndicatorPurpose of the Evaluation

Determine if the Unplanned Scrams with Complications ROP performance indicator is effective Does the indicator capture risk significant

events? Understand recent clustering of USwC Identify potential changes to improve the indicator

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Unplanned Scrams with Complications Performance Indicator USwC indicator has been used since 2006 Replaced Unplanned Scrams with Loss of Normal Heat Removal Threshold: Greater than one USwC within 4 quarters Indicator does not have yellow or red thresholds

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Analysis

Phase 1 ROP Historical Performance Indicator Summaries LER search Characterize Complication(s) that caused USwCPhase 2 Reactive Inspections (MD 8.3) Accident Sequence Precursor (ASP) ProgramPhase 3 Data Analysis

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Events per year (2007-2014)

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Year % Complicated 2007 18%2008 12%2009 11%2010 8%2011 17%2012 21%2013 17%2014 22%AVG 16%

BWR 19%PWR 13%

Events Per Unit (2007-2013)

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Complication Frequency by Reactor Type (PWR/BWR)

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PWR

BWR

Results Industry Performance

44% of reactors have had no USwC, 38% had one, 9% two, 7% three, 1% four, and 1% five

16% of Unplanned Scrams are complicated (BWR 19%, PWR 13%) 6 Reactors have tripped the White Threshold, 4 BWRs, 2 PWRs The White Threshold has been crossed 8 times (3 by the same unit) 19 of 20 scram events that resulted in ASP Analysis were captured by

the USwC PI PWR Loss of Feedwater Events

Most PWR USwC events involving an inability to recover main feedwater were also loss of offsite power events (21 of 35).

No USwC events involving loss of FW that did not involve LOOPs were evaluated under ASP.

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Recommendations Consider revising PWR question from “Was Main Feedwater

Unavailable or Not Recoverable Using Approved Plant Procedures During the Scram Response” To “Was Power Lost to All Non 1E Busses?” Would reduce confusion for licensees. Would better capture risk significant events (fewer false

positives).

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Conclusion

Indicator is successful in capturing risk significant events Drivers for clustering of USwC are indeterminate Changing focus from loss of feedwater to LOOP events for PWRs

would better capture events of interest.

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QUESTIONS?

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