Event Notification Report for December 08, 2012
U.S. Nuclear Regulatory Commission
Operations Center
EVENT REPORTS FOR
12/07/2012 - 12/08/2012
EVENT NUMBERS
48721
Power Reactor
Event Number: 48721
Facility: HATCH
Region: 2 State: GA
Unit: [1] [] []
RX Type: [1] GE-4,[2] GE-4
NRC Notified By: JOHN D SELLERS
HQ OPS Officer: MARK ABRAMOVITZ
Region: 2 State: GA
Unit: [1] [] []
RX Type: [1] GE-4,[2] GE-4
NRC Notified By: JOHN D SELLERS
HQ OPS Officer: MARK ABRAMOVITZ
Notification Date: 02/06/2013
Notification Time: 11:39 [ET]
Event Date: 12/08/2012
Event Time: 01:16 [EST]
Last Update Date: 02/06/2013
Notification Time: 11:39 [ET]
Event Date: 12/08/2012
Event Time: 01:16 [EST]
Last Update Date: 02/06/2013
Emergency Class: NON EMERGENCY
10 CFR Section:
50.73(a)(1) - INVALID SPECIF SYSTEM ACTUATION
10 CFR Section:
50.73(a)(1) - INVALID SPECIF SYSTEM ACTUATION
Person (Organization):
GEORGE HOPPER (R2DO)
GEORGE HOPPER (R2DO)
| Unit | SCRAM Code | RX Crit | Initial PWR | Initial RX Mode | Current PWR | Current RX Mode |
|---|---|---|---|---|---|---|
| 1 | N | Y | 100 | Power Operation | 100 | Power Operation |
60-DAY OPTIONAL TELEPHONE NOTIFICATION OF INVALID SYSTEM ACTUATION
"On December 8, 2012, at 0116 EST, with Unit 1 operating near 100 percent rated thermal power (RTP), annunciator 601-135 'Torus Level High' was received in the main control room and immediately cleared. Torus water level was reading between 148.1 inches and 148.8 inches on torus water level sensors but torus water level indications from the High Pressure Coolant Injection (HPCI) sensors were observed to be fluctuating between 149 inches and 150 inches immediately after the event. Technical Specification LCO 3.6.2.2 requires torus water level to remain greater than or equal to 146 inches and less than or equal to 150 inches. The Technical Specification allowable limit is 154 inches for the HPCI torus water level sensors and the actual set point for the HPCI suction swap is 152 inches. When the HPCI torus water level instruments' reference legs are not completely filled, fluctuations in indicated level occur. This was determined to be the cause for this invalid actuation. Enough fluctuation occurred such that the HPCI suction swap instruments completed the actuation logic causing the HPCI suction swap design function to occur. This resulted in HPCI automatically realigning to the torus. It had been manually aligned to the condensate storage tank (CST), which is its primary source. HPCI DID NOT realign to mitigate an event or condition nor did it realign for actuation and injection to send water to the reactor vessel. Should the automatic suction swap fail to occur, the Technical Specifications require that the suction be manually realigned to the torus in accordance with plant procedures and training. The operability of HPCI was maintained throughout the event and no HPCI system actuation signal (low reactor water level or high drywell pressure) was received during the event.
"At approximately 0337 EST, Instrumentation and Controls technicians began backfilling the reference legs for sensors 1E41N062B, 1T48N010A, and 1T48N021A. This task was completed at approximately 0503 EST at which time the normal torus water level and HPCI torus water level instrument indications were in agreement. The HPCI suction source was then realigned to the CST in accordance with plant procedures at approximately 0507 EST. This report is being made as an actuation of a system named in 50.73(a)(2)(iv)(B)(4) and is being reported in accordance with 50.73(a)(2)(iv)(A) and under the provision of 50.73(a)(1) based on an NRC interpretation that this actuation within the HPCI system was considered an ECCS actuation. Since the actual torus water level never actually reached 152 inches, the automatic realignment was determined to be an invalid actuation. SNC [Southern Nuclear Company] takes exception to the NRC interpretation on reportability of this condition, but are making this 60 day phone LER notification on a voluntary basis while this issue is being pursued with the NRC. The initiating signal was invalid and this report is being made under the auspices of 10 CFR 50.73(a)(1) for invalid specified system actuations."
The licensee notified the NRC Resident Inspector.
"On December 8, 2012, at 0116 EST, with Unit 1 operating near 100 percent rated thermal power (RTP), annunciator 601-135 'Torus Level High' was received in the main control room and immediately cleared. Torus water level was reading between 148.1 inches and 148.8 inches on torus water level sensors but torus water level indications from the High Pressure Coolant Injection (HPCI) sensors were observed to be fluctuating between 149 inches and 150 inches immediately after the event. Technical Specification LCO 3.6.2.2 requires torus water level to remain greater than or equal to 146 inches and less than or equal to 150 inches. The Technical Specification allowable limit is 154 inches for the HPCI torus water level sensors and the actual set point for the HPCI suction swap is 152 inches. When the HPCI torus water level instruments' reference legs are not completely filled, fluctuations in indicated level occur. This was determined to be the cause for this invalid actuation. Enough fluctuation occurred such that the HPCI suction swap instruments completed the actuation logic causing the HPCI suction swap design function to occur. This resulted in HPCI automatically realigning to the torus. It had been manually aligned to the condensate storage tank (CST), which is its primary source. HPCI DID NOT realign to mitigate an event or condition nor did it realign for actuation and injection to send water to the reactor vessel. Should the automatic suction swap fail to occur, the Technical Specifications require that the suction be manually realigned to the torus in accordance with plant procedures and training. The operability of HPCI was maintained throughout the event and no HPCI system actuation signal (low reactor water level or high drywell pressure) was received during the event.
"At approximately 0337 EST, Instrumentation and Controls technicians began backfilling the reference legs for sensors 1E41N062B, 1T48N010A, and 1T48N021A. This task was completed at approximately 0503 EST at which time the normal torus water level and HPCI torus water level instrument indications were in agreement. The HPCI suction source was then realigned to the CST in accordance with plant procedures at approximately 0507 EST. This report is being made as an actuation of a system named in 50.73(a)(2)(iv)(B)(4) and is being reported in accordance with 50.73(a)(2)(iv)(A) and under the provision of 50.73(a)(1) based on an NRC interpretation that this actuation within the HPCI system was considered an ECCS actuation. Since the actual torus water level never actually reached 152 inches, the automatic realignment was determined to be an invalid actuation. SNC [Southern Nuclear Company] takes exception to the NRC interpretation on reportability of this condition, but are making this 60 day phone LER notification on a voluntary basis while this issue is being pursued with the NRC. The initiating signal was invalid and this report is being made under the auspices of 10 CFR 50.73(a)(1) for invalid specified system actuations."
The licensee notified the NRC Resident Inspector.