05000397/LER-2016-004

LER-2016-004, 1 OF 3

Columbia Generating Station
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation
3972016004R00 - NRC Website

LER 16-004-01 for Columbia Generating Station Regarding Automatic Scram Due to Off-site Load Reject

ML17164A443
Person / Time
Site:	Columbia
Issue date:	06/08/2017
From:	Hettel W G Energy Northwest
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
GO2-17-121 LER 16-004-01
Download: ML17164A443 (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 Infocollects,Resource©nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (31500104), Office of Management and Budget, Washington, DC 20503. If a means 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.

2016 Columbia Generating Station 397

3. LER NUMBER

004 00 05000-

Plant Conditions

The plant was operating at 100% power prior to the event. There were no safety related systems out of service prior to the event.

Event Description

On December 18, 2016 at 11:24 hours, an automatic scram occurred due to a fault on an off-site transmission network. A reactor scram was automatically initiated by the plant response to the transient.

All rods fully inserted and Main Steam Isolation Valves [SB,V] automaticaly dosed due to loss of power to both Reactor Protection System (RPS) [JC] busses that occurred during the transient following the scram. All safety systems operated as designed. A full safety system isolation occurred due to the loss of RPS, which isolated Reactor Closed Cooling [CC] flow from containment. This caused Primary Containment (PC) temperature and pressure to increase causing high PC pressure actuations to occur. Two Safety Relief Valves [SB,V] were initially cycled automatically, then several manually to maintain Reactor Pressure Vessel (RPV) [AC] pressure. Reactor water level was restored with Reactor Core Isolation Cooling (RCIC) [BN], Control Rod Drive [AA] flow, and High Pressure Core Spray (HPCS) [BG].

After the initial successful start and injection of RCIC, a plant operator failed to establish the proper line up for re-initiation.

This resulted in a trip of RCIC and using HPCS to maintain RPV level.

Per plant procedures after the scram an operator tripped the main turbine (MT) [TA], but failed to trip the main generator (MG) [TB]. This allowed voltage to degrade until power was automatically transferred to the backup power sources. The PC was vented through a Standby Gas Treatment Filter [BH] per plant procedures to lower PC pressure.

Cause

Bonneville Power Administration (BPA) (operator of the off-site transmission network) is performing an evaluation of the off-site transmission network failure. This is estimated to be completed in April 2017.

Plant personnel are performing a Root Cause Evaluation on the station's response to the reactor scram, including failure to trip both the MT and MG, and human performance issues operating RCIC. This evaluation is estimated to be completed by late February.

A supplemental LER will be issued when updates are available.

Corrective Actions

BPA took immediate actions to perform maintenance on the off-site electrical equipment.

Plant operators took immediate actions addressing operator human performance issues regarding RCIC, and MT and MG operations.

Operating Experience and Previous Occurrences There were no occurrences of a scram due to a loss of off-site power in the last 10 years 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.

3. LER NUMBER

05000- Columbia Generating Station 397 2016 00

Assessment of Safety Consequences

This event did not challenge the ability of Columbia Generating Station to safely shutdown, and all plant systems responded as designed. Human performance issues resulted in a trip of RCIC, and an automatic transfer of power supplies to backup power supplies per design. The reactor scram and resulting transient caused a loss of RPS which resulted in a full safety system actuation and a reduction of cooling to the PC. The trip of RCIC was not consequential since HPCS was available, and was used, to maintain RPV level. The power supplies transferred to backup power supplies as designed. The reduction of cooling to the PC did not challenge PC integrity, and was restored by operator action. There were no adverse impacts to those systems due this event. There were no undesired radiological or industrial safety aspects resulting from this event.

Energy Industry Identification System Information Energy Industry Identfication System information codes from IEEE Standards 805-1984 and 803-1983 are represented in brackets as [X] and [XX] throughout the body of the narrative.