05000286/LER-2009-001

LER-2009-001, 450 Broadway, GSB
P.O. Box 249
Buchanan, N.Y. 10511-0249Entergy Tel (914) 734-6700
J. E. Pollock
Site Vice President
NL-09-114
October 30, 2009
U.S. Nuclear Regulatory Commission
ATTN: Document Control Desk
Mail Stop O-P1-17
Washington, D.C. 20555-0001
Subject:M Licensee Event Report # 2009-001-01, "Automatic Actuation of an
Emergency Diesel Generator and Two Auxiliary Feedwater Pumps
During Surveillance Testing due to Inadvertent De-Energization of the
Normal Supply Breaker to 480 Volt Safeguards Bus 6A"
Indian Point Unit No. 3
Docket No. 50-286
DPR-64
Dear Sir or Madam:
Pursuant to 10 CFR 50.73(a)(1), Entergy Nuclear Operations Inc. (ENO) hereby provides
revised Licensee Event Report (LER) 2009-001-01. The attached revised LER identifies
an event where there was an automatic actuation of an emergency diesel generator and
two auxiliary feedwater pumps, systems listed in 10 CFR 50.73(a)(2)(iv)(B), which is
reportable under 10 CFR 50.73(a)(2)(iv)(A) . The revised LER incorporates changes as a
result of an evaluation of troubleshooting and testing performed during the Unit 3 refueling
outage. This event was recorded in the Entergy Corrective Action Program as Condition
Report CR-I P3-2009-00011.
There are no new commitments identified in this letter. Should you have any questions
regarding this submittal, please contact Mr. Robert Walpole, Manager, Licensing at
(914) 734-6710.
Sincerely,
JEP/cbr
cc:M Mr. Samuel J Collins, Regional Administrator, NRC Region I
NRC Resident Inspector's Office, Indian Point 3
Mr. Paul Eddy, New York State Public Service Commission
LEREvents@inpo.org
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not conduct or sponsor, and a person is not required to respond to, the
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1. FACILITY NAME: INDIAN POINT 3 2. DOCKET NUMBER 13. PAGE
05000-286 1 OF 5
4. TITLE: Automatic Actuation of an Emergency Diesel Generator and Two Auxiliary Feedwater
Pumps During Surveillance Testing due to Inadvertent De-Energization of the Normal Supply
Breaker to 480 Volt Safeguards Bus 6A

Indian Point 3
Event date:	1-02-2009
Report date:	30-01-2009
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
2862009001R01 - NRC Website

Note:� The Energy Industry Identification System Codes are identified within the brackets {).

DESCRIPTION OF EVENT

On January 27'2009:while at-100% steady-state reactor power, Instrumentation and Control (I&C) Technicians were performing monthly surveillance test 3-PT-M62C, "480 Volt AC Degraded Grid/Undervoltage Functional Testing Bus 6A," when at approximately 10:08 hours, the normal power supply breaker {BRK) for 480 Volt AC safeguards bus 6A {ED) inadvertently opened causing the bus to de-energize. The bus undervoltage control circuitry {JE) caused an automatic actuation of emergency diesel generator (EDG)-32 {EK) which started and re-energized the bus {BU); actuation of motor driven auxiliary feedwater (AFW) pump (AFWP) 33 and steam driven AFWP 32 {BA). In accordance with design the loads on bus 6A were stripped and then the assigned loads were sequentially re-loaded back onto the bus. All systems performed as designed. AFW was injected into the steam generators (SG) {AB) that resulted in an approximate 1-2% change in SG.level, and an approximate 0.1% increase in reactor power. There was no control rod movement while in automatic. The event was recorded in the Indian Point Corrective Action Program (CAP) as CR-IP3-2009-00011.

The onsite AC power distribution system is composed of 480 Volt AC buses 5A, 6A, 2A and 3A which is divided into three safeguards power trains. 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 safeguardS - buses receive power from 6.9 kV bus sections through their respective Station Service Transformer {FK) (SST) or from three onsite EDGs. The 480 Volt safeguard buses are designed with protection against undervoltage (UV) and degraded grid voltage (DGV) using relays that sense'UV or DGV conditions:- Non-- Safety Injection (SI) Blackout relays will send start signals to timers for essential loads that include the motor driven AFWPs and the turbine driven AFWP. The bus undervoltage relays will initiate the opening of the power feed-s from'the SST and 480 Volt AC tie breaker for a DGV condition after DGV relays are timed out on a particular bus. Each of two DGV 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 UV relays._ .When the-feeder breaker trips, the bus UV relays will initiate bus stripping, actuate EDG start, and provide signals that will begin load sequencing to reload the bus.

On January 2, 2009, at approximately 8:30 hours, three qualified I&C Technicians initiated TS required monthly functional testing of the three 480 Volt safeguards buses in accordance with surveillance test procedure 3-PT-M62A,B,C using a Fluke digital volt meter. The test is performed as required by Technical Specifications (TS) to demonstrate that the 480 Volt AC UV/DGV protection system functions properly. The 480 Volt AC bus UV/DGV protection functions are tested locally at switchgear {SWGR) in the 480 Volt Switchgear Room on the 15 foot elevation of the Control Building {NA). The technicians started with bus 2A/3A which was satisfactorily completed at 9:30 hours, then started testing bus 5A at 9:35 hours which was satisfactorily completed at 9:52 hours. At approximately 9:53 hours, the TS was entered for testing bus 6A in accordance with surveillance procedure 3-PT-M62C which tests the 480 Volt AC UV/DGV protection system for Bus 6A. The test was progressing with no issues until the steps used to confirm that DGV protection had been restored to 480 Volt bus 6A (Steps 4.2.55 and 4.2.56) were performed.

Cause of Event

A root cause analysis (RCA) of the event was performed but no cause could be identified. A monitoring plan was developed to collect circuit parameters in the 52/6A trip circuitry during testing. Monitoring was performed in regularly scheduled tests with additional monitoring and testing performed in the spring 2009 refueling outage. Despite rigorous investigation, the root cause is indeterminate. The probable cause was determined to be a meter lead short from terminal 4 to terminal 2 of DGV time delay relay 62-1/6A. A meter lead short from relay 62-1/6A terminal 4 to terminal 2 would not have resulted in an arc as determined by a failure analysis of the relay and leads. An evaluation of organizational and programmatic weaknesses identified inadequate work practices during performance of test 3-PT-M62C where the test leads used had the potential for shorting the terminals of Agastat time delay relays. The potential for causing a short with a meter lead exists anytime an exposed meter lead is long enough to short between terminals.

An analysis determined the trip was caused by energizing the shunt trip coil of the normal supply breaker for 480 volt safeguards bus 6A. Breaker trip shaft actuation can be accomplished in three ways; 1) Amptector (over current trip) which was excluded, 2) manual push button, which was excluded, and 3) energizing the shunt trip coil. The RCA performed determined the possible causes for the shunt trip energizing then each possible cause was evaluated and those causes that had overwhelming refuting objective evidence were excluded. Possible causes that were excluded include the following: 1) defective DGV relay 62-1/6A, 2) defective degraded grid test switch (TS/DGV/6A), 3) defective relay 62-2/6A, 4) defective UV relay 27-6A/X2, 5) operation of control switches 1-1 and 1-2, 6) breaker red lights low resistance through light to shunt coil trip coil, 7) intermittent short in circuit breaker 52/6A trip circuit wiring (DC), 8) intermittent break in relay sensing circuit (AC) causes UV relay to actuate, 9) intermittent break in relay sensing circuit causes DGV relays to actuate, 10) breaker trips on its own, 11) UV relay faulty, 12) DGV relay defective (27-3 and/or 27-4) providing a false trip, 13) faulty meter, 14) grounds in circuit cause 52/6A shunt trip relay to actuate, 15) circuit has a combined low resistance between positive and negative causing current flow through the shunt trip coil that is near the current required to actuate the coil.

Corrective Actions

The following corrective actions have been or will be performed under Entergy's Corrective Action Program to address the possible cause and prevent recurrence:

• Degraded Grid time delay relay 62-1/6A was replaced and testing in accordance with 3-PT-M62C was re-performed and satisfactorily completed.

• The replaced Degraded Grid time delay relay 62-1/6A and the DVM leads used during the test were sent to an independent vendor for performance of a failure analysis. The results of the independent vendor analysis concluded neither the meter leads or relay 62-1/6A were faulty.

• A monitoring plan was developed to collect circuit parameters in the 52/6A trip circuitry during testing. Monitoring was performed in regularly scheduled tests prior to the March 2009 refueling outage.

• A test plan was developed for testing the 52/6A trip circuitry and performing measurements and collection of data on the circuit to identify the cause of the event. The test plan was implemented and monitoring was performed in the March 2009 refueling outage.

• Degraded Grid Voltage Protection Tests (3-PT-M62A, 3-PT-M62B, and 3-PT-M62C) were revised to specify the use of test leads that do not have the potential to create a short circuit between terminals of the Agastat time delay relays.

• Maintenance and Operations personnel were briefed on, the possibility of meter lead probes causing a short circuit during meter reading activities and that pre-job briefs should include this precaution. The brief included the expectation that during an activity that identifies that terminals could be shorted by standard meter lead probs, different leads should be used.

• Insulated test leads by Pomona were purchased to help reduce the possibility of a short circuit.

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; (#6) PWR auxiliary or emergency feedwater system, and (#8) Emergency AC electrical power systems including emergency diesel generators (EDG).

This event meets the reporting criteria because the 32 EDG actuated to start and the 32 and 33 AFWP actuated to start when the UV control circuit on 480 Volt AC Bus 6A actuated. On January 2, 2009, the normal power supply to safeguards bus 6A was inadvertently de-energized at approximately 10:08 hours, resulting in undervoltage on bus 6A.

In accordance with design the 32 EDG, AFWP-32 and 33 were actuated to automatically start. At 10:37 hours, the 33 AFWP was secured and at 10:38 hours the 32 AFWP was secured. At approximately 20:33 hours, 480 Volt AC Bus 6A was returned to its normal power supply and the condition for TS 3.8.1 was exited.

At approximately 20:45 hours,- the 32 EDG was secured and returned to its normal standby condition. At 21:04 hours, entered TS 3.3.2, TS 3.3.5, and TS 3.81 to re-perform the test. The test was satisfactorily re-performed and TS 3.3.2, TS 3.3.5, and TS 3.81 were exited at 21:19 hours. 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 inadvertent Engineered Safety Feature actuation during testing. The review identified three LERs: LER-2008-003, LER-2008-004 and LER­ 2008-006. LER-2008-003 reported the actuation of an EDG due to the inadvertent action of the UV sensing circuit on bus 5A. The cause of the inadvertent actuation was procedure use and adherence. LER-2008-004 reported inadvertent actuation of AFWPs 31 and 33 during Reactor Protection Logic Channel Functional testing caused by incorrect jumper connection due to personnel error.

LER-2008-006 reported an inadvertent start of the 32 EDG and the 32 and 33 AFWPs. The events reported in LER-2008-003, LER-2008-004 may be a similar cause to this event because those events were caused by human performance errors although there was no evidence that was the cause of this event. LER-2008-006 was the same as this event and the cause for that event was also indeterminate but it reported a likely cause was a faulty DMV which has since been determined to be incorrect.

Safety Significance

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 and minimum safeguards power was available to power safety loads. There was no significant core reactivity change as there was no automatic movement of the control rods, reactor power increased approximately 0.1%, and there was an approximate 1-2% change in SG level. The changes were well within the actuation limits of the reactor protection system.