05000219/LER-2017-003

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LER-2017-003, Automatic Scram while Suberitical due to Low Reactor Level
Oyster Creek Nuclear Generating Station
Event date: 07-03-2017
Report date: 08-31-2017
2192017003R00 - NRC Website
LER 17-003-00 for Oyster Creek Regarding Automatic Scram while Subcritical due to Low Reactor Level
ML17249A123
Person / Time
Site: Oyster Creek Exelon icon.png
Issue date: 08/31/2017
From: Gillin M F
Exelon Generation Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
RA-17-053
Download: ML17249A123 (4)


comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

Oyster Creek Nuclear Generating Station

3. LER NUMBER

2017 - 00 003

Plant Conditions Prior To Event

Event Date:

Unit 1 Mode:

July 3, 2017 Hot Shutdown Event Time: 10:30 hours ET Power Level: 0%

Description of Event

On July 3, 2017 at approximately 10:30 hours a subcritical automatic reactor scram was received while stabilizing plant parameters after a manual scram. The automatic scram was due to low RPV water level. Prior to this, MCR operators established reactor water letdown, reset the manual scram and were placing RPV water level control in automatic using a LFRV. Reactor pressure control was automatically being maintained with turbine bypass valves.

A low reactor water level occurred when a bypass valve opened as expected to lower reactor pressure. Operators reset the scram signal without fully evaluating other plant conditions. By resetting the scram signal with water level not yet stabilized, an automatic scram was received on low reactor water level.

Operator fundamentals and human performance tools were not properly utilized prior to resetting the scram.

Operations personnel did not ensure plant parameters of pressure and level were stable prior to resetting the scram. An expected pressure transient resulted in an automatic scram due to RPV level dropping below the scram setpoint.

Cause of Event

MCR Operators did not confer with the Unit Supervisor their intended actions nor did they provide an update to other control room personnel prior to resetting the scram. Operations personnel did not perform a thorough review of all system conditions prior to peer checking the scram reset. Additionally, the procedure did not provide details of conditions to verify prior to resetting the scram.

Analysis of the Event

The personnel involved did not display distinct thought to understand the impact that the action would have with reactor water level control in its current state. The operators should have taken the time to understand that resetting the scram at that time was not the correct action. The operators were not fully engaged and did not think about the consequences of resetting the scram prior to reactor water level stabilization. Their behavior represents a gap as described in SOER 10-2, Engaged, Thinking Organizations.

Assessment of Safety Consequences

Following the automatic scram actuation all systems responded as expected; therefore, this event is of low safety significance.

comments regarding burden estimate to the FOIA, Privacy and Information Collections Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

Oyster Creek Nuclear Generating Station

3. LER NUMBER

2017 - 00 003

Corrective Actions

1) The station revised the Abnormal Operating Procedures for MCR operators to verify plant conditions are stable prior to resetting the scram signal.

2) Reinforcement of the requirements and proper use of operator human performance fundamental tools through training and evaluations.

3) Reinforcement of teamwork in MCR operations during training scenarios.

Previous Occurrences

automatic reactor scram when operators placed the Mode Switch from Refuel to Shutdown. The actuation was a result of jumpers not installed as required by procedure to prevent a full scram for this Mode Switch change.

Component Data Component IEEE 805 System ID IEEE 803A Component N/A N/A N/A