05000388/LER-2016-005

LER-2016-005, Unit 2 HPCI Manually Overridden Prior to a Manual Scram During a Plant Transient

Susquehanna Steam Electric Station Unit 2
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v), Loss of Safety Function
3882016005R00 - NRC Website

LER 16-005-00 for Susquehanna, Unit 2, Regarding HPCI Manually Overridden Prior to a Manual Scram During a Plant Transient

ML16194A251
Person / Time
Site:	Susquehanna
Issue date:	07/12/2016
From:	Franke J A Susquehanna, Talen Energy
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
PLA-7504 LER 16-005-00
Download: ML16194A251 (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 internet 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.

CONDITIONS PRIOR TO EVENT

Unit 1 — Mode 1, 100 percent Rated Thermal Power Unit 2 — Mode 1, 069 percent Rated Thermal Power At 23:55 on 5/12/16, Unit 2 experienced an electrical transient resulting in a loss of 213246 Reactor Building Engineered Safeguard System (ESS) Division 480 volt Motor Control Center (MCC) (EIIS: B) and 2Y246 208/120 Volt Alternate Current (AC) Instrument Panel (EllS:JL). With the loss of the Reactor Building ESS Division 480 volt MCC, several drywell cooling fans were lost leading to an increase in drywell pressure.

EVENT DESCRIPTION

On 5/12/16 at 2355, Unit 2 experienced an electrical transient caused by a loss of 480VAC MCC 2B246 breaker. Operations reduced reactor power by reducing reactor recirculation flow. Drywell pressure and temperature began to rise and it was reported by Maintenance that the 2B246 bus faulted and was not able to be re-energized. Operations determined that a manual scram was required based upon a loss of drywell cooling. On 5/23/2016 at 0055 HPCI (EIIS code: BJ) was overridden prior to the manual scram to prevent the trip of all feedwater pumps on reactor pressure vessel high water level alarm (EIIS: JB). Technical specification 3.5.1 was entered for HPCI inoperable due to manual override. At 0110, Unit 2 was manually scrammed and HPCI was restored to AUTO at 0122.

The Unit Supervisor directed the override of HPCI without following station procedures which require adequate core cooling to be assured by at least two independent indicators. The Reactor Operator at the HPCI controls did not question the Unit Supervisor's decision.

The Unit 2 scram event will be addressed under LER 388/ 2016-004-00.

CAUSE OF EVENT

There were two causes of this event. First, the Unit Supervisor made a decision to prematurely override HPCI to minimize distractions later in the shutdown without procedural guidance to do so. OP-AD-300, Administration of Operations, provides direction for overriding ECCS systems and clearly defines when such a system may be placed in manual. This procedure was not followed. Second, weaknesses in teamwork and oversight prevented the mistake from being corrected by the crew. A crew update was not conducted to announce the placing of HPCI in manual override, preventing the crew from providing a peer check of the Unit Supervisor's decision.

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 intemet 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.

Susquehanna Steam Electric Station, Unit 2 05000388

ANALYSIS/SAFETY SIGNIFICANCE

The actual consequences of this event were the inability of an ECCS system to perform its automatic function.

The potential consequence of overriding HPCI is, in the event of a small break loss of coolant accident, that operations would not be able to maintain adequate core cooling.

There were no actual or potential consequences to the health and safety of the public as a result of this event.

CORRECTIVE ACTIONS

Immediate corrective actions include removing qualifications from the individuals involved and communicating expectations with the remaining crews. Additional corrective actions being taken include incorporating this event into initial licensed operator training and a Human Performance Improvement Plan will be created to address gap noted in the crew's performance.

PREVIOUS SIMILAR EVENTS

There were no previous similar events in which an ECCS system was incorrectly overridden.