So here is the 2014 Christmas scram that got the first inspection. An event like this happens with the mixture of poor plant maintenance and general incompetence of the employees...poor training across the board.
Doesn't it raise the hairs in the back of your neck with all degradation of components showing up in one event?
This is a dangerous plant in many ways...
I believe the first half scram with the turbine control scam over instrumentation problem was basically a turbine grounding problem throwing electrical spikes at the instrumentation...creating a set of scrams.
I see the problem as in many cases as intermittent equipment and electrical problems...they really don't have a means to record the event. They are uncertain what caused it...they guess what did it or on a quick and expensive fix...then quickly startup into the next scram.
Licensee Event Report 50-458 /2014-006-00:Automatic Reactor Scram and Primary Containment Isolation Due to Loss of Power on the Division 2 Reactor Protection System With a Concurrent Division 1 Half-scram On December 25, 2014. at 0836 CST, a reactor scram occurred while the plant was operating at approximately 85 percent power. This event resulted from the loss of power on the Division 2 reactor protection system (RPS) (**JD**) bus, in conjunction with a preexisting half-scram on Division I. The loss of Division 2 RPS power also resulted in a Division 2 containment isolation signal. Approximately four minutes after the scram, reactor water level increased to the Level 8 setpoint, causing the running main feedwater pump (**SJ**) to trip. As reactor water level decreased back through the normal operating range, operators attempted to re-start main feedwater pump "C," but its supply breaker failed to close. Main feedwater pump "A" was subsequently returned to service. As reactor water level decreased to the point at which the startup feedwater regulating valve (FRV) should have opened to establish automatic control, the valve failed to open. Attempts to open it with a manual input signal were unsuccessful, and the "C" main FRVwas put back into service. By that time, reactor water level had decreased slightly below the Level 3 RPS actuation setpoint, resulting in a second scram signal. INVESTIGATION and IMMEDIATE ACTIONS
The Division I half-scram had been inserted two days prior to the event, in compliance with Technical Specifications, following the failure of an instrumentation channel on the no. 2 main turbine control valve. Teams were formed to investigate the separate significant aspects of the event, as follows: Loss of Division 2 RPS Bus
Power was lost when the output breaker on the RPS motor-generator (MG) in the Division 2 subsystem tripped. The mostly likely cause of the output breaker trip was an intermittent failure of the MG field flash card due to a degraded capacitor. The capacitor was replaced, and the MG was tested and returned to a standby condition as a backup power supply. The alternate power supply will remain in service carrying the bus until completion of a modification to eliminate the field flash card as a potential source of recurrence of this problem. Misoperation of the Startup FRV The operation of the startup FRV was investigated to determine why it was unresponsive to either the automatic controller or the operator's manual input. Maintenance technicians discovered a failed circuit card in the "manual" side of the valve controller. The ".automatic" function of the controller had operated correctly in the post-scram environment once reactor water level had returned to normal, and this was confirmed again during the troubleshooting. Additionally, Engineering personnel determined that the performance of the valve was consistent with its design criteria. The valve and its control logic are designed for flow control, and not simply for isolation. When the valve receives a gradual "open" signal from the closed position, there is no specific time response requirement. This design feature can allow a delayed response that, in the scram recovery scenario, may be too slow to arrest a significant downward trend in reactor water level. Malfunction of Main Feedwater Pump "C" The failure of main feedwater pump "C" was found to have been was caused by an "over-racked" condition of its supply breaker (that is, the breaker racking mechanism had slightly over-travelled the last time the breaker was returned to service). This caused the limit switches that detect the position of the breaker mechanism within the cabinet to give the control logic circuit a false indication that the breaker was not connected to the bus. Interim instructions have been implemented to have electricians verify the condition of all similar breakers each time they are racked in.
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