05000250/LER-2013-006

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LER-2013-006, Reactor Protection and Auxiliary Feed Water System Actuations Due to Trip of Operating Feedwater Pump
Turkey Point Unit 3
Event date: 3-13-2013
Report date: 5-13-2013
Reporting criterion: 10 CFR 50.73(a)(2)(iv)(A), System Actuation
Initial Reporting
ENS 48821 10 CFR 50.72(b)(3)(iv)(A), System Actuation
2502013006R00 - NRC Website

On March 13, 2013 at approximately 1120 with Unit 3 in Mode 3, the Auxiliary Feed Water (AFW) System [BA] automatically actuated. In order to faciliate planned work on Steam Generator Feed Pump (SGFP) [SJ, P] power supplies, feed water supply to the steam generators (SG) [SB, SG] was to be swapped from the operating 3B SGFP to the 3A SGFP. With the 3A Condensate Pump (CP) [SD, P] and the 3B SGFP running, the 3A SGFP was started for a one minute run to fully vent the suction header and pump casing through the pump minimum flow recirculation line causing the operating 3B SGFP to trip and AFW to actuate. Operators then manually shut down the 3A SGFP.

SGFP protection logic ensures that at least two CPs are operating when two SGFPs are operating. In this event with only one CP in operation, upon start of the 3A SGFP, the 3B SGFP tripped automatically after a short time delay. AFW actuated because of the trip of the 3B SGFP which was aligned to the SGs.

AFW actuation added cooler water into the SGs reducing reactor coolant system (RCS) [AB] temperature.

Operators opened the reactor trip breakers [JC, BKR] via the manual reactor trip switch [JC, HS] at approximately 1131 to obtain additional shut down margin, as a conservative measure.

At approximately 1205, the 3A Standby Steam Generator Feed Pump (SBSGFP) [SJ, P] was started to maintain level in the SGs. By approximately 1240, both trains of AFW were secured to operable standby status.

Because reactor protection system (RPS) and AFW actuations occurred, this event is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A). Event Notification 48821 was made on 3/13/13.

CAUSE OF THE EVENT

The root cause is that licensed unit operators did not maintain adequate command and control of activities outside the control room. A contributing cause is that the decision to start the second SGFP with only one CP operating was made at the wrong organizational level.

ANALYSIS OF THE EVENT

A non-licensed operator (NLO) was given the task to start the 3A SGFP. The NLO reviewed the procedure, received a brief from the nuclear watch engineer, verified plant conditions and had a peer check for assurance of correct actions. The procedure review included the precautions and limitations regarding required CP/SGFP operating combinations — at least one CP for one SGFP, at least two CPs for two SGFPs, however the NLO misunderstood a note in the procedure. The note stated that the SGFP breaker was simulated open, but this was only correct in regard to AFW auto-start logic and not the operating CP interlock. The mistake was not recognized. The 3A SGFP was started by the NLO locally without coordination with the control room operator who did not maintain command and control of the evolution.

ANALYSIS OF SAFETY SIGNIFICANCE

Upon the trip of the SGFP supplying the SGs, AFW automatically actuated. Subsequently, the 3A SBSGFP was started to maintain SG levels and AFW was restored to operable standby status. The manual RPS actuation was conservatively employed to prcvide additional shut down margin when AFW actuation lowered RCS temperature. The unit was not critical in Mode 3 when this event occurred. The systems discussed in this report operated as designed. Therefore, the safety significance of this event is very low.

CORRECTIVE ACTIONS

Corrective actions are documented in AR 1856476 and include the following:

Implement and assess the effectiveness of the improvement plan to reinforce operational standards.

FAILED COMPONENTS IDENTIFIED: None PREVIOUS SIMILAR EVENTS: None