05000286/LER-2008-003
| Docket Number | |
| Event date: | |
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| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv)(B), System Actuation 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(v), Loss of Safety Function |
| 2862008003R00 - NRC Website | |
Note:
� The Energy Industry Identification System Codes are identified within the brackets fl.
DESCRIPTION OF EVENT
On March 25, 2008, while at 100% steady state reactor power, during the performance of monthly surveillance test 3-PT-M62B, "480 Volt AC Degraded Grid/Undervoltage Functional Testing Bus 5A," an inadvertent actuation of the undervoltage sensing circuit occurred that resulted in the opening of the normal supply breaker {BRIO and an automatic actuation of emergency diesel generator (EDG) 33 {ER} which started and re-energized the bus {BU}. In accordance with design, as a result of the undervoltage actuation, the loads on bus 5A were stripped and then sequentially re-loaded back onto the bus. All systems performed as designed. The condition was recorded in the Indian Point Corrective Action Program (CAP) as CR-IP3-2008-00818.
The onsite AC power distribution system is composed of 480 Volt AC buses 5A, 6A, 2A and 3A {ED} which is divided into three safeguards power trains. The three trains are designed such that any two trains are capable of meeting minimum requirements for accident mitigation and/or safe shutdown. The three safeguards power trains are train 5A (Bus 5A and EDG-33), Train 6A (Bus 6A and EDG-32), and Train 2A/3A (Bus 2A and 3A and EDG-31). The 480 Volt AC Electrical Distribution System {ED} is designed with protection against undervoltage conditions using relays that sense loss of voltage .(LOV) and degraded grid voltage (DGV). The bus undervoltage relays will initiate the opening of the power feeds from the Station Service Transformer {FK} and 480 Volt AC tie breaker at a degraded voltage level after being timed out on a particular bus. Each of two voltage sensing relays has its own associated timing relay to provide a time delay to insure proper coordination with plant electrical transients. Actuation of the DGV relays will trip the bus supply breaker removing power to the buses which will actuate the LOV relays. When the feeder breaker trips, the two bus undervoltage relays will initiate bus stripping, actuate EDG start, and provide signals that will begin load sequencing to reload the bus.
On March 25, 2008, at approximately 10:51 hours, three qualified Instrumentation and Control (I&C) Technicians initiated actions in accordance with surveillance test procedure 3-PT-M62B to perform the scheduled monthly functional test of the 480 Volt AC undervoltage/degraded grid protection system for Bus 5A. The test is performed to demonstrate that the 480 volt AC undervoltage/degraded grid protection system functions properly. The 480 Volt AC bus 5A undervoltage/degraded grid protection fuctions are tested locally at a switchgear {SWGR} in the Switchgear Room on the 15 foot elevation of the Control Building {NA}. Performance of the test requires manipulation of various components including the following: 1) a three position key operated test switch with a normal (middle position) and two test positions, 2) a bus voltage sensing signal is manually disconnected by operation of knife (i.e. stabs) switches, 3) adjustment as needed of Agastat timing relays through use of their adjustment knobs.
Cause of Event
The root cause of actuation of the undervoltage sensing circuit that resulted in actuation and start of EDG-33 was a failure to adhere to the test procedure.
There was a lack of adherence and reinforcement to the Conduct of Maintenance procedure standards and expectations for procedure adherence and usage.
Contributing causes (CC) were as follows: CC1: Human performance. The Technicians failed to apply learned HU tools together to achieve maximum effectiveness such as 3-point communication, peer checking, S.T.A.R. and "Point and Shoot" to ensure that the correct Agastat was adjusted. CC2: Verbal Communication. Notifying the I&C Supervisor at either point when the wrong Agastat was adjusted or just prior to working the procedure steps out of sequence may have prevented the event. CC3: Place Keeping. Utilizing good place keeping techniques such as re-initialing or circle/slashing the steps when the Technicians went back into the procedure to re-check the misadjusted Agastat may have prevented the event.
Corrective Actions
The following corrective actions have been or will be performed under Entergy's Corrective Action Program to address the cause and prevent recurrence:
- I&C personnel were briefed on the event and lessons learned, counseled on expectations and standards for procedure adherence and usage, and briefed on the human performance tools that were ineffectively used for this event.
- Conduct procedure adherence reinforcement training and reinforce expectations and standards for use of the Conduct of Maintenance Procedure, the Procedure Use and Adherence procedure, and Procedure Adherence and Level of Use procedure for I&C personnel. Scheduled completion of training is September 15, 2008.
- Conduct oral boards for I&C Supervisors on the Conduct of Maintenance Procedure, the Procedure Use and Adherence procedure, and Procedure Adherence and Level of Use procedure. Scheduled completion of oral boards is September 15, 2008.
- Prepare a TEAR to incorporate this event into the I&C re-qualification training program. Scheduled completion for preparation of the TEAR is June 15, 2008.
Event Analysis
The event is reportable under 10CFR50.73(a)(2)(iv)(A). The licensee shall report any event or condition that resulted in the manual or automatic actuation of any system listed in 10CFR50.73(a)(2)(iv)(B). The systems to which the requirements of 10CFR50.73(a)(2)(iv)(A) apply include (#8) Emergency AC electrical power systems including emergency diesel generators (EDG). This event meets the reporting criteria because the 33 EDG actuated to start when I&C Technicians inadvertently actuated the undervoltage sensing circuit on 480 Volt AC Bus 5A.
The 33 EDG started at approximately 11:18 hours on March 25, 2008. At 12:25 hours, 480 Volt AC Bus 5A was returned to its normal power supply. At 12:32 hours, the 33 EDG was returned to its normal standby condition. All required safety systems performed as designed. As a result of the event, there were no safety systems that were not capable of performing their safety function. In accordance with reporting guidance in NUREG-1022, an additional random single failure need not be assumed in that system during the condition. Therefore, there was no safety system functional failure reportable under 10 CFR 50.73(a)(2)(v).
Past Similar Events
A review was performed of Licensee Event Reports (LERs) for the past three years for any events reporting Engineered Safety Feature actuation due to inadvertent actuation during testing. LER-2005-002 reported a reactor trip on May 6, 2005, during I&C troubleshooting of the condensate system. The direct cause of the event was poor work practices. The root causes were 1) I&C and Operations failure to verify and recognize the required switch position for the condensate polisher post filter bypass valve, 2) Operations misunderstanding whether the activity constituted operational maintenance or troubleshooting thereby allowing I&C to work outside the normal work process. The actions in the condensate polisher procedure were inadequate for the condition. This event was considered not to be similar as the root cause was not procedure adherence. LER-2005:003 reported an inadvertent actuation of the Auxiliary Feedwater (AFW) Pumps on May 16, 2005, during Reactor Protection Logic Channel Functional Testing. The cause of the event reported in LER-2005-003 was human error due to inadequate work practices were the I&C technician performing the test failed to follow up on a known worst that can happen by allowing himself to be distraCted and failed to disarm the actuation circuit within the known time frame noted by the procedure.
The event reported in LER-2005-003 has a similar cause to this event as both were caused by human performance issues. The corrective actions for LER-2005 003 included counseling I&C personnel on use of human performance tools, high intensity training on use of human performance tools, and procedure enhancement..
Safety Signifitance This event had no effect on the health and safety of the public.
There were no actual safety consequences for the event because there were no accidents or transients requiring the EDGs. Required power from both offsite sources and onsite emergency power were available and the actuation circuitry and EDG performed in accordance with design.