05000348/LER-2016-002

LER-2016-002, Automatic Reactor Trip and Safety Injection Due to Closure of Main Steam Isolation Valve

Joseph M. Farley Nuclear Plant
Event date:	10-1-2016
Report date:	11-30-2016
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation
LER closed by
IR 05000348/2017001 (1 May 2017)
3482016002R00 - NRC Website

LER 16-002-00 for Joseph M. Farley Nuclear Plant, Unit 1 Regarding Automatic Reactor Trip and Safety Injection Due to Closure of Main Steam Isolation Valve

ML16335A450
Person / Time
Site:	Farley
Issue date:	11/30/2016
From:	Gayheart C A Southern Nuclear Operating Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NL-16-2438 LER 16-002-00
Download: ML16335A450 (6)

Reported lessons learned are incorporated into the licensing process and fed back to industry.

Send 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 Infocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), 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.

Joseph M. Farley Nuclear Plant, Unit 1 05000- 348

A. PLANT AND SYSTEM IDENTIFICATION

Westinghouse - Pressurized Water Reactor

B. DESCRIPTION OF EVENT

On 10/1/2016 at 0512 CDT with Unit 1 at 99 percent power and coasting down in power for a planned refueling outage, the Control Room received dual indication for the 1 A Steam Generator (SG) Main Steam Isolation Valve (MSIV), a closed indication for the 1A MSIV test switch, and a Main Control Board (MCB) annunciator for main steam line isolation valve air pressure being low. Operations personnel implemented the Annunciator Response Procedure (ARP) for this annunciator and followed the first step, which was to attempt to recharge the accumulator by placing the switch for the 1 A MSIV to the 'open' position. Although the second step directed tripping the reactor if the alarm was in and dual indication was indicated, Operations instead dispatched licensed and non-licensed personnel into the plant to investigate the cause for the alarm. The normally closed test solenoid vent port was found to be releasing air. Operations initiated steps to isolate the leaking test solenoid valve; however, the leaking solenoid and check valves caused air pressure in the 1 A MSIV actuator to fall low enough to cause inadvertent 1 A MSIV closure. Actuation of the 1A MSIV turbine trip limit switch initiated a turbine trip and subsequent reactor trip.

The closure of the 1A MSIV caused a rapid pressure reduction in the remaining two Steam Generators' steam lines and resulted in actuation of a Safety Injection (SI). The Emergency Core Cooling System (ECCS) actuated and injected into the Reactor Coolant System (RCS). Auxiliary Feedwater (AFW) auto-started. All Control rods fully inserted and all equipment actuated as designed. The unit was stabilized in Mode 3 with decay heat removed through the condenser.

The test solenoid had last been replaced in 2003. The Preventive Maintenance (PM) task for this component was improperly deactivated in 2004 due to inadequate technical justification.

Decision making by control room personnel not to strictly adhere to the ARP was a contributing cause to the reactor trip being automatic versus manual, and led to the SI. Manual actuation of a reactor trip prior to the closure of the 1 A MSIV would have prevented the SI from occurring.

C. UNIT STATUS AT TIME OF EVENT

Unit 1, Mode 1, 99 percent power Unit 2, Mode 1, 100 percent power

D. CAUSE OF EVENT

The 1 A MSIV closure was caused by failure of its test solenoid in conjunction with other air system leakage, which vented the air pressure from the 1A MSIV actuator. An inadequate technical justification allowed the improper deactivation of the PM task of the test solenoid valve in 2004 and led to the component failure. Decision making by control room personnel not to strictly adhere to the ARP was a contributing cause to the reactor trip being automatic versus manual, and led to the SI.

Reported lessons learned are incorporated into the licensing process and ted back to industry.

Send 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 Infocollects.Resource@nrc.gov, and to the Desk Officer. Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office .of Manatiement 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.

Joseph M. Farley Nuclear Plant, Unit 1 05000- 348 2016 - 002 - 00

E. REPORTABILITY ANALYSIS AND SAFETY ASSESSMENT

This event is reportable per 10 CFR 50.73(a)(2)(iv)(A) due to actuation of the reactor protection system, actuation and injection of ECCS into the RCS, and automatic actuation of the AFW system.

The 1A MSIV closing caused steam flow in steam line A to decrease, and steam flow increased and steam pressure decreased in steam lines B and C. The rate of steam pressure decrease in steam lines B and C resulted in the initiation of the safety injection signal. All systems responded as required, including all control rods fully inserting into the core, AFW system auto-starting to supply the Steam Generators, and decay heat removal occurring through the condenser. This system response to the event was as designed for turbine trip, reactor trip, and SI actuation.

Because all systems responded as required and there were no actual adverse effects on the health and safety of the public, the safety significance of this event is considered very low.

F. CORRECTIVE ACTION

The 1A MSIV test solenoid was replaced. In addition, all of the test solenoids for all Unit 1 MSIVs were solenoid will be reinstated. The technical justifications of a sample of previously extended or deleted PM strategies will be reviewed and corrected. Prior to Unit 1 entering Mode 3 all Unit 1 MSIV test solenoid isolation valves were closed to prevent a loss of air through the test portion of the lines.

The Unit 2 main steam system was walked down for similar issues, and needed test solenoid replacements will be completed by the end of the next refueling outage. In addition, the Unit 2 MSIV test solenoid isolation valves were closed to prevent a loss of air through the test portion of the lines.

Procedure use and adherence standards have been reinforced with Operations personnel, simulator just- in-time training was conducted for all crews, and further causal analysis is planned to investigate operations fundamental performance gaps.

G. ADDITIONAL INFORMATION

1) Failed Components: Loop A test solenoid valve for the 1A MSIV 2) Previous Similar Events: None 3) Other system affected: None 4) Commitment Information: None 5) Energy Industry Identification System Code:

[JC]- Reactor Protection System [BA] -Auxiliary Feedwater [SB] - Main Steam System