ENS 46816: Difference between revisions
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| event date = 03/07/2011 11:18 EDT | | event date = 03/07/2011 11:18 EDT | ||
| last update date = 05/04/2011 | | last update date = 05/04/2011 | ||
| title = Invalid Actuation | | title = Invalid Actuation of the Auxiliary Feedwater System | ||
| event text = On March 7, 2011 at 1118 hours with Beaver Valley Power Station Unit 2 in Mode 5 during a scheduled refueling outage an invalid actuation of the Auxiliary Feedwater (AFW) System occurred. Instrumentation & Control (I&C) technicians were using a procedure to place simulated signals in two out of three channels of the narrow range level indication on all three steam generators (SG). During this activity, I&C technicians repositioned the input test relays to the test position on both channel 1 and channel 2 in two out of three SGs before inserting the simulated signals. This action resulted in a zero level input to the SG level circuits in two out of three SGs. An Engineered Safety Feature Actuation System (ESFAS) actuation signal for the Auxiliary Feedwater (AFW) System was generated based on having a two out of three low-low level signal in at least one SG (starts turbine driven AFW pump) and subsequently having a two out of three steam generators low-low level signal in at least two SGs (starts motor driven AFW pumps). The AFW initiation signal resulted in a successful automatic start of both the Train A and Train B motor driven AFW pumps. The AFW pump discharge flow control valves were closed per procedure prior to this event, so the motor driven AFW pumps operated on 100% recirculation flow following their automatic start. The turbine driven AFW pump did not start since steam pressure was not present in the main steam lines due to the plant being in Mode 5. A Reactor Protection Signal (RPS) signal was also generated due to having a two out of three low-low level signal in at least one SG. The RPS actuation signal did not result in opening of the reactor trip breakers since the breakers were previously opened as part of the plant shutdown procedures. The reactor control rods had been fully inserted into the reactor core prior to this event. Plant operators took appropriate actions to secure AFW flow after determining that the actuation was invalid and the issue was entered into the corrective action program for evaluation. | | event text = On March 7, 2011 at 1118 hours with Beaver Valley Power Station Unit 2 in Mode 5 during a scheduled refueling outage an invalid actuation of the Auxiliary Feedwater (AFW) System occurred. Instrumentation & Control (I&C) technicians were using a procedure to place simulated signals in two out of three channels of the narrow range level indication on all three steam generators (SG). During this activity, I&C technicians repositioned the input test relays to the test position on both channel 1 and channel 2 in two out of three SGs before inserting the simulated signals. This action resulted in a zero level input to the SG level circuits in two out of three SGs. An Engineered Safety Feature Actuation System (ESFAS) actuation signal for the Auxiliary Feedwater (AFW) System was generated based on having a two out of three low-low level signal in at least one SG (starts turbine driven AFW pump) and subsequently having a two out of three steam generators low-low level signal in at least two SGs (starts motor driven AFW pumps). The AFW initiation signal resulted in a successful automatic start of both the Train A and Train B motor driven AFW pumps. The AFW pump discharge flow control valves were closed per procedure prior to this event, so the motor driven AFW pumps operated on 100% recirculation flow following their automatic start. The turbine driven AFW pump did not start since steam pressure was not present in the main steam lines due to the plant being in Mode 5. A Reactor Protection Signal (RPS) signal was also generated due to having a two out of three low-low level signal in at least one SG. The RPS actuation signal did not result in opening of the reactor trip breakers since the breakers were previously opened as part of the plant shutdown procedures. The reactor control rods had been fully inserted into the reactor core prior to this event. Plant operators took appropriate actions to secure AFW flow after determining that the actuation was invalid and the issue was entered into the corrective action program for evaluation. | ||
The initiation of an ESFAS and RPS actuation signal, due to a SG low-low level signal, was not in response to any valid system or plant condition. There was no event, transient or condition that required any type of mitigation in Mode 5. Plant equipment responded as expected based on the conditions prior to the event. | The initiation of an ESFAS and RPS actuation signal, due to a SG low-low level signal, was not in response to any valid system or plant condition. There was no event, transient or condition that required any type of mitigation in Mode 5. Plant equipment responded as expected based on the conditions prior to the event. | ||
Latest revision as of 21:07, 1 March 2018
| Where | |
|---|---|
| Beaver Valley Pennsylvania (NRC Region 1) | |
| Reporting | |
| 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
| Time - Person (Reporting Time:+1388.12 h57.838 days <br />8.263 weeks <br />1.901 months <br />) | |
| Opened: | David Haser 10:25 May 4, 2011 |
| NRC Officer: | Howie Crouch |
| Last Updated: | May 4, 2011 |
| 46816 - NRC Website
| |