Event Notification Report for August 27, 2013
U.S. Nuclear Regulatory Commission
Operations Center
EVENT REPORTS FOR
08/26/2013 - 08/27/2013
EVENT NUMBERS
49312
!!!!! THIS EVENT HAS BEEN RETRACTED !!!!!
!!!!! THIS EVENT HAS BEEN RETRACTED !!!!!
Power Reactor
Event Number: 49312
Facility: MONTICELLO
Region: 3 State: MN
Unit: [1] [] []
RX Type: [1] GE-3
NRC Notified By: ANGEL BRAY
HQ OPS Officer: JOHN SHOEMAKER
Region: 3 State: MN
Unit: [1] [] []
RX Type: [1] GE-3
NRC Notified By: ANGEL BRAY
HQ OPS Officer: JOHN SHOEMAKER
Notification Date: 08/28/2013
Notification Time: 05:16 [ET]
Event Date: 08/27/2013
Event Time: 21:52 [CDT]
Last Update Date: 10/13/2013
Notification Time: 05:16 [ET]
Event Date: 08/27/2013
Event Time: 21:52 [CDT]
Last Update Date: 10/13/2013
Emergency Class: NON EMERGENCY
10 CFR Section:
50.72(b)(3)(ii)(B) - UNANALYZED CONDITION
10 CFR Section:
50.72(b)(3)(ii)(B) - UNANALYZED CONDITION
Person (Organization):
RICHARD SKOKOWSKI (R3DO)
RICHARD SKOKOWSKI (R3DO)
| Unit | SCRAM Code | RX Crit | Initial PWR | Initial RX Mode | Current PWR | Current RX Mode |
|---|---|---|---|---|---|---|
| 1 | N | Y | 100 | Power Operation | 94 | Power Operation |
RECIRC PUMP RUNBACK AND POWER REDUCTION
"On August 27, 2013 at 2152 CDT, Monticello Nuclear Generating Plant (MNGP) experienced a runback of [the] 'B' Recirc pump from 87% speed to 71% speed. Operators took action to lock [the] 'B Recirc pump scoop tube. This runback resulted in a power reduction from 100% to 94% RTP [Rated Thermal Power]. With the resultant mismatch between total jet pump flows of the two loops greater than required limits, should a LOCA [Loss of Coolant Accident] occur, the core flow coastdown and resultant core response may not be bounded by the LOCA analyses. It has been determined that this is an unanalyzed condition as defined by 10CFR50.72(b)(3)(ii)(8).
"At 0121 CST on August 28, 2013, MNGP completed reducing power to 88% using 'A' Recirc pump to match total jet pump flows and [the plant] is no longer in an unanalyzed condition. The 'B' Recirc scoop tube remains locked pending investigation."
The licensee has notified the NRC Resident Inspector.
* * * RETRACTION ON 10/11/13 AT 1253 EDT FROM MARK HOESCHEN TO DONG PARK * * *
"This is a retraction for ENS 49312: The licensee reviewed the MNGP design basis analysis to determine if the event was bounded. The licensee determined that the Loss of Coolant Accident (LOCA) provides a bounding analysis for this event.
"The limiting LOCA event for the MNGP as analyzed in accordance with 10CFR50 Appendix K conditions is based upon single failure of the Low Pressure Coolant Injection (LPCI) injection valve, effectively making LPCI inoperable for the event. The large break Design Basis Accident (DBA) with LPCI injection valve failure (which is analytically equivalent to the condition of both LPCI subsystems being inoperable) is the event analyzed for the current Licensing Basis Peak Cladding Temperature (PCT). This analysis bounds the event as a recirculation pump flow mismatch event is less limiting than the LOCA with LPCI injection valve failure analysis.
"Therefore, this recirculating loop flow mismatched event is less limiting than a previously analyzed event and ENS 49312 may be retracted as an unanalyzed event."
The licensee has notified the NRC Resident Inspector. Notified R3DO (Skokowski).
"On August 27, 2013 at 2152 CDT, Monticello Nuclear Generating Plant (MNGP) experienced a runback of [the] 'B' Recirc pump from 87% speed to 71% speed. Operators took action to lock [the] 'B Recirc pump scoop tube. This runback resulted in a power reduction from 100% to 94% RTP [Rated Thermal Power]. With the resultant mismatch between total jet pump flows of the two loops greater than required limits, should a LOCA [Loss of Coolant Accident] occur, the core flow coastdown and resultant core response may not be bounded by the LOCA analyses. It has been determined that this is an unanalyzed condition as defined by 10CFR50.72(b)(3)(ii)(8).
"At 0121 CST on August 28, 2013, MNGP completed reducing power to 88% using 'A' Recirc pump to match total jet pump flows and [the plant] is no longer in an unanalyzed condition. The 'B' Recirc scoop tube remains locked pending investigation."
The licensee has notified the NRC Resident Inspector.
* * * RETRACTION ON 10/11/13 AT 1253 EDT FROM MARK HOESCHEN TO DONG PARK * * *
"This is a retraction for ENS 49312: The licensee reviewed the MNGP design basis analysis to determine if the event was bounded. The licensee determined that the Loss of Coolant Accident (LOCA) provides a bounding analysis for this event.
"The limiting LOCA event for the MNGP as analyzed in accordance with 10CFR50 Appendix K conditions is based upon single failure of the Low Pressure Coolant Injection (LPCI) injection valve, effectively making LPCI inoperable for the event. The large break Design Basis Accident (DBA) with LPCI injection valve failure (which is analytically equivalent to the condition of both LPCI subsystems being inoperable) is the event analyzed for the current Licensing Basis Peak Cladding Temperature (PCT). This analysis bounds the event as a recirculation pump flow mismatch event is less limiting than the LOCA with LPCI injection valve failure analysis.
"Therefore, this recirculating loop flow mismatched event is less limiting than a previously analyzed event and ENS 49312 may be retracted as an unanalyzed event."
The licensee has notified the NRC Resident Inspector. Notified R3DO (Skokowski).