|2552017002R00 - NRC Website|
|Person / Time|
|From:||Arnone C F|
Entergy Nuclear Operations
Document Control Desk, Office of Nuclear Reactor Regulation
|Download: ML17198A181 (4)|
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461 05000-255 Palisades
- 00 - 002 2017
On May 19, 2017, at0206 hours
The reactor was shutdown at the time, with all control rods inserted. The portion of the test that was in progress is designed to actuate the RPS on loss of load signal. To facilitate this part of the test with the reactor in a shutdown mode, one of two conditional steps in the procedure is to be taken. The generator motor operated disconnect 389 (MOD-389) is required to be in the open position, or protective trip circuity for the generator is required to be bypassed. Due to a conditional step of the test procedure being misinterpreted by a Nuclear Control Operator (NCO), MOD-389 was left in the closed position and the generator protective trip circuity was not bypassed. This resulted in the RPS actuation occurring prior to the preplanned sequence. The RPS responded as designed. All components operated as expected for the plant conditions. No structures, components, or systems were inoperable at the start of the event that contributed to the event. A Safety System Functional Failure, as defined in Nudear Energy Institute 99-02, "Regulatory Assessment Performance Indicator Guideline," did not occur.
CAUSE OF THE EVENT
A conditional step in the test procedure required the NCO to verify the status of MOD-389. The procedure logic directs the sequence of subsequent test steps based on the open/dose status of MOD-389. If MOD-389 is dosed, opening of a sliding link is required to bypass protective trip circuity for the generator. The NCO failed to correctly identify that MOD-389 was in the dosed position.
Believing MOD-389 was open, the next conditional step in the procedure to bypass the protective trip circuity for the generator was not performed. A subsequent step in the procedure, to manipulate a switch that activates turbine trip output functions, requires a peer check verification to ensure the correct switch is manipulated. The NCO obtained peer check support from a second NCO. As required by the test procedure, the second NCO only peer checked the step that ensures the correct switch was manipulated. The previous conditional step, to ensure MOD-389 was in the open position, did not require peer check verification.
The cause of the unexpected RPS actuation was human performance errors during procedure performance, e.g., lack of self-validation/verification, misinterpretation of information and lack of peer check verification.
ASSESSMENT OF SAFETY CONSEQUENCES
There were no adverse safety consequences as a result of this event. The reactor was shutdown in Mode 5 at the time of the event, with all control rods inserted. The unexpected RPS actuation did not cause the loss of systems or components that are needed to maintain safe shutdown conditions, remove residual heat, control the release of radioactive material, or mitigate the consequences of an accident. All plant systems responded as designed.
Corrective Actions Taken:
The NCO's licensed operator qualifications were removed until formal remediation was completed. A standing order was initiated to immediately require peer check verification of all procedure conditional steps.
Corrective Actions Planned:
Develop criteria that would require peer check verification of procedure conditional steps. Once the criteria are established, the applicable administrative procedure will be revised to add guidance for performance of peer check verifications associated with conditional steps in procedures. Additionally, a case study of the event will be developed and induded in a 2017 operations high intensity training session.
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