ML20223A373
| ML20223A373 | |
| Person / Time | |
|---|---|
| Issue date: | 08/11/2020 |
| From: | Joylynn Quinones-Navarro NRC/NRR/DRO/IRAB |
| To: | Linthicum R Exelon Corp |
| joylynn Quinones-Navarro NRR/DRO | |
| References | |
| Download: ML20223A373 (2) | |
Text
Proposed FAQ 20-03 Generic - Restoration of Train Monitoring After PRA Model Changes Plant: Generic Date of Event: N/A Submittal Date:
Licensee
Contact:
Roy Linthicum Tel/email: 630-926-3034 Roy.linthicum@exeloncorp.com NRC
Contact:
TBD Tel/email: TBD Performance Indicator:
MS06 Mitigating System Performance Index, Emergency AC Power Systems MS07 Mitigating System Performance Index, High Pressure Injection Systems MS08 Mitigating System Performance Index, Heat Removal Systems MS09 Mitigating System Performance Index, Residual Heat Removal Systems MS10 Mitigating System Performance Index, Cooling Water Systems Site-Specific FAQ (see Appendix D)? (__)Yes or (XX) No FAQ to become effective (XX) when approved or (other date)
Question Section NEI 99-02 Guidance needing interpretation (include page and line citation):
New Guidance Required FAQ 15-03, Unavailability Monitoring of Low-Risk Trains, allows the removal of trains/segments from unavailability monitoring if the Birnbaum value for the Train/Segment is <1E-7. However, no guidance is provided on what is required when, due to PRA model updates, the Birnbaum value of an unmonitored train/segment increases above 1E-7.
Specifically, is it required to perform a 3-year historical review and capture unavailability data for the train/segment when it is restored to MSPI monitoring?
This has happened in a few instances in the industry.
Event or circumstances requiring guidance interpretation:
FAQ 15-03, Unavailability Monitoring of Low-Risk Trains, allows the removal of trains/segments from unavailability monitoring if the Birnbaum value for the Train/Segment is <1E-7. However, no guidance is provided on what is required when, due to PRA model updates, the Birnbaum value of an unmonitored train/segment increases above 1E-7.
Specifically, is it required to perform a 3-year historical review and capture unavailability data for the train/segment when it is restored to MSPI monitoring?
This has happened in a few instances in the industry.
If licensee and NRC resident/region do not agree on the facts and circumstances, explain:
N/A - this is new proposed guidance Page 1 of 2 Revised 20200619
Proposed FAQ 20-03 Generic - Restoration of Train Monitoring After PRA Model Changes Potentially relevant FAQs:
FAQ 15-03 (available in ADAMS package ML15343A137)
Response Section Proposed Resolution of FAQ:
It is proposed that when restoring trains/segments to MSPI monitoring, unavailability data be required only moving forward (including the quarter in which monitoring is restored).
This is justified as the exclusion threshold (Birnbaum <1E-7) is sufficiently low that capturing past data is not expected to significantly impact the indicator or change MSPI colors. Trains/segments with Birnbaum values near 1E-7 typically have margin to White on the order of thousands of hours.
If appropriate, provide proposed rewording of guidance for inclusion in next revision:
If a previously excluded train/segment is restored to monitoring as a result of a PRA model revision, unavailability data only for the quarter in which the train/segment is restored (and future quarters) needs be included for reporting purposes. A value of 0 (zero) should be entered for the previous 11 quarters with a note that unavailability reporting was not required for those quarters as the train/segment was previously excluded.
PRA update required to implement this FAQ?
No MSPI Basis Document update required to implement this FAQ?
No Proposed NRC Response:
TBD Page 2 of 2 Revised 20200619