05000261/LER-2013-002
| H. B. Robinson Steam Electric Plant, Unit No. 2 | |
| Event date: | 0-5-2013 |
|---|---|
| Report date: | 06-19-2014 |
| 2612013002R01 - NRC Website | |
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 interne( 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.
H. B. Robinson Steam Electric Plant, Unit No. 2 SEQUENTIAL REV
PLANT IDENTIFICATION
Westinghouse - Pressurized Water Reactor
IDENTIFICATION OF EVENT
At 0041 hours4.74537e-4 days <br />0.0114 hours <br />6.779101e-5 weeks <br />1.56005e-5 months <br /> EST on 11/05/2013, with the Unit in Mode 2 and startup low-power physics testing in progress, there was an inadvertent automatic actuation of the Auxiliary Feedwater System due to an 'A' Main Feed Pump (MIT) trip. While placing the Condensate Polishers in service, a secondary-side perturbation occurred resulting in the loss of the running 'A' Main Feedwater Pump on low suction pressure coincident with low flow. There was no plant damage or personnel injury as a result of this event.
EVENT DATE
November 05, 2013
REPORT DATE
June 19, 2014
CONDITIONS PRIOR TO EVENT
MODE 2, 0% Power
DESCRIPTION OF EVENT
At 0041 hours4.74537e-4 days <br />0.0114 hours <br />6.779101e-5 weeks <br />1.56005e-5 months <br /> EST on 11/05/2013, with the Unit in Mode 2 and startup low-power physics testing in progress, there was an inadvertent automatic actuation of the Auxiliary Feedwater System due to an 'A' Main Feedwater Pump [P] (MFP) trip. While placing the Condensate Polishers [DM] in service, the non-licensed Auxiliary Operator (AO) closed the primary Condensate Polisher bypass valve [V] manually, which secured flow to the running 'A' MFP. The 'A' MFP then tripped on low suction pressure coincident with low flow. Both motor driven Auxiliary Feedwater Pumps started due to both MFP breakers being open simultaneously. The Control Room entered Abnormal Operating Procedure (AOP)-010, Main Feedwater/Condensate Malfunction, for loss of the MFP. Steam generator [SG] water levels were maintained by the auxiliary feedwater flow, and the Auxiliary Feedwater System remained in service pending investigation of the cause of the 'A' MFP trip. The 'B' motor-driven AFW pump [P] was secured following its automatic start to stabilize steam generator water levels and Reactor Coolant System (RCS) temperature. The NRC Resident Inspector was notified, and the Control Room exited AOP-010. After successful restart of the 'A' MFP, the 'A' AFW pump [P] was secured.
CAUSAL FACTORS
An investigation into the cause of the 'A' Main Feedwater Pump (MFP) trip identified that low suction pressure coincident with low flow resulting from manual manipulations of the Condensate Polishing System initiated the trip. This manipulation resulted in isolating main condensate flow to the only running feedwater pump.
The root cause investigation into the cause of this event determined that this was an individual operator error resulting from inadequate utilization of the procedure use and adherence process. The Makeup Water Treatment/Condensate Polisher non-licensed Auxiliary Operator (MWT/CP AO) placed the Condensate Polishers in service at approximately midnight without receiving a pre-job brief from the Work Control Center senior reactor operator (SRO). Although the AO did conduct a simple task briefing himself, this briefing did not meet the standards established in HUM-NGGC-0003, Conduct of Pre-Job Briefings/Post-Job Critiques, and did not meet the Robinson Operations Management expectations for pre-job briefings.
CORRECTIVE ACTIONS
Corrective action consisted of completion of confidential personnel actions for the Makeup Water Treatment/Condensate Polisher Auxiliary Operator responsible for the event, and enhancement of expectations for supervisory oversight of risk significant evolutions will be employed.
SAFETY ANALYSIS
The risk consequences of this event were minimal based on the successful auto-actuation of the Auxiliary Feedwater System (AFW) due to a Main Feed Pump (MFP) trip, and steam generator water levels were maintained by AFW. Although there was a very slight, measurable reactivity impact from the AFW actuation, no trip setpoints or pre-established manual trip setpoints were approached. The change in core reactivity was controlled using normal operating procedures. Therefore, there was no reactor trip. Additionally, there was no important accident mitigation equipment unavailable due to maintenance.