05000255/LER-2011-002, Regarding Automatic Reactor Trip and Auxiliary Feedwater System Actuation

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Regarding Automatic Reactor Trip and Auxiliary Feedwater System Actuation
ML110830007
Person / Time
Site: Palisades Entergy icon.png
Issue date: 03/23/2011
From: Kirwin T
Entergy Nuclear Operations
To:
Office of Nuclear Reactor Regulation, Document Control Desk
References
PNP 2011-026 LER 11-002-00
Download: ML110830007 (5)
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LER-2011-002, Regarding Automatic Reactor Trip and Auxiliary Feedwater System Actuation
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)(iv)(A), System Actuation
10 CFR 50.73(a)(2)(i)
10 CFR 50.73(a)(2)(vii), Common Cause Inoperability
10 CFR 50.73(a)(2)(ii)(A), Seriously Degraded
10 CFR 50.73(a)(2)(viii)(A)
10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition
10 CFR 50.73(a)(2)
10 CFR 50.73(a)(2)(v)(A), Loss of Safety Function - Shutdown the Reactor
10 CFR 50.73(a)(2)(v)(B), Loss of Safety Function - Remove Residual Heat
10 CFR 50.73(a)(2)(i)(A), Completion of TS Shutdown
10 CFR 50.73(a)(2)(v), Loss of Safety Function
10 CFR 50.73(a)(2)(i)(B), Prohibited by Technical Specifications
2552011002R00 - NRC Website
v • d • e

text

,.

  • ~ Entergy PNP 2011-026 March 23, 2011 U. S. Nuclear Regulatory Commission A TIN: Document Control Desk Washington, DC 20555-0001 Entergy Nuclear Operations, Inc.

Palisades Nuclear Plant 27780 Blue Star Memorial Highway Covert, MI 49043 Tel 269 764 2000 Thomas P Kirwin Site Vice President

SUBJECT:

Licensee Event Report 2011-002, Automatic Reactor Trip and Auxiliary Feedwater System Actuation Palisades Nuclear Plant Docket 50-255 License No. DPR-20

REFERENCES:

10 CFR 50.73

Dear Sir or Madam:

Licensee Event Report (LER) 2011-002 is enclosed. The LER describes an automatic actuation of the reactor protection system and the auxiliary feedwater system. The occurrence is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A).

This letter contains no new commitments and no revisions to existing commitments.

TPKlTAD Enclosure (1)

CC Administrator, Region III, USNRC Project Manager, Palisades, USNRC Resident Inspector, Palisades, USNRC

ENCLOSURE LER 2011-002 AUTOMATIC REACTOR TRIP AND AUXILIARY FEEDWATER SYSTEM ACTUATION 3 Pages Follow

NRC FORM 366 APPROVED BY OMB NO. 3150-0104 EXPIRES 10/31/2013 U.S. NUCLEAR REGULATORY COMMISSION (10-2010)

Estimated burden per response to comply with this mandato~ information collection request 80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />. Reported lessons leamed are Incorporated into the icenSing~rocess and fed back to industry. Send comments regarding burden estimate to the Records anagement Branch (T -6 LICENSEE EVENT REPORT (LER)

E6), u.s. Nuclear Regulatory Commission, Washington, DC 20555-0001, or ~ntemet e-mail to b~~rcoi0v, and to the Desk Officer, Office of Information and RegUlatS1. A irs, NEOB-10202 (1

1), Office of Management and Budget Washington, DC 2050. If a means used to impose information collection does not display a currently valid OMS control number, the NRC (See reverse for re~uired nUmbe{lof may not conduct or sponsor, and a person is not required to respond to, the information collection.

diaits/characters or each block 13* PAG 1

E PALISADES NUCLEAR PLANT 05000255 OF 3

4. TITLE Automatic Reactor Trip and Auxiliary Feedwater S~stem Actuation
5. EVENT DATE
6. LER NUMBER
7. REPORT DATE
8. OTHER FACILITIES INVOLVED YEAR I SEQUENTIAL I REV FACILITY NAME DOCKET NUMBER MONTH DAY YEAR NUMBER NO MONTH DAY YEAR FACILITY NAME DOCKET NUMBER 01 22 2011 2011 -

002 - 00 03 23 2011

9. Ur-C", "III'1U NIODE
11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 0 20.2201(b) o 20.2203(a)(3)(i) o 50.73(a)(2)(i)(C) o 50.73(a)(2)(vii) 1 0

20.2201(d) o 20.2203(a)(3)(ii) o 50.73(a)(2)(ii)(A) o 50.73(a)(2)(viii)(A) 0 20.2203(a)(1 )

o 20.2203(a)(4) o 50.73(a)(2)(ii)(B) o 50.73(aX2)(viii)(B) 0 20.2203(a)(2)(i) o 50.36(c)(1Xi)(A) o 50.73(aX2)(iii) o 50.73(aX2)(ix)(A) 10 ** _ ** _ *. LEVEL 0

20.2203(a)(2Xii) o 50.36(c)(1 )(ii)(A)

~ 50.73(a)(2)(ivXA) o 50.73(a)(2Xx) 0 20.2203(a)(2Xiii) o 50.36(cX2) o 50.73(a)(2)(v)(A) o 73.71(a)(4) 100 0

20.2203(a)(2)(iv) o 50.46(a)(3)(ii) o 50.73(a)(2)(v)(B) o 73.71(a)(5) 0 20.2203(a)(2)(v) o 50.73(a)(2)(i)(A) o 50.73(a)(2)(v)(C) o OTHER 0

20.2203(a)(2)(vi) o 50.73(a)(2)(i)(B) o 50.73(a)(2)(v)(D)

Specify in Abstract below or in 12. LICENSEE CONTACT FOR THIS LER FACILITY NAME I

TELEPHONE NUMBER (1(;u~e~e~C;~_2117 Terry Davis CAUSE SYSTEM COMPONENT MANU-REPORTABLE

CAUSE

SYSTEM COMPONENT MANU-REPORTABLE FACTURER TO EPIX FACTURER TO EPIX 8

EA G8L5 CABLEC Y

14. SUPPLEMENTAL REPORT EXPECTED
15. EXPECTED I MONTH I DAY YEAR o YES (If yes, complete 15. EXPECTED SUBMISSION DATE)

SUBMISSION I

I

~ NO DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines On January 22, 2011, at 1735 hours0.0201 days <br />0.482 hours <br />0.00287 weeks <br />6.601675e-4 months <br />, with the plant in Mode 1 at 100% power, the operation of relay 251-2/SPG3, station power transformer 1-3 neutral to ground, actuated relay 3868, generator direct trip lockout relay (backup), opening the main generator output breakers to the transmission system causing a turbine trip. The turbine trip actuated the reactor protective system to trip the reactor due to a loss of load. As expected, the auxiliary feedwater system started automatically to recover steam generator level.

The cause for operation of the neutral to ground relay, and subsequent automatic plant trip, was a ground fault on a medium voltage cable that provides electrical power to bus 1 G, via breaker 252-401, from station power transformer 1-3. The probable cause of the ground fault on the cable was determined to be flaws in the insulation, with the effects of moisture acting on these flaws over time, causing the insulation to degrade.

The event is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) as an event that resulted in an actuation of both the reactor protection system and the auxiliary feedwater system.

NRC FORM 366 (10-2010) U.S. NUCLEAR REGULATORY COMMISSION (10-2010)

1. FACILITY NAME PALISADES NUCLEAR PLANT

EVENT DESCRIPTION

LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET

2. DOCKET YEAR 05000255 2011
6. LER NUMBER I

SEQUENTIAL I REVISION NUMBER NUMBER 002 00

3. PAGE 2

OF 3

On January 22,2011, at 1735 hours0.0201 days <br />0.482 hours <br />0.00287 weeks <br />6.601675e-4 months <br />, with the plant in Mode 1 at 100% power, the operation of relay 251-2/SPG3 [51 ;EA], station power transformer 1-3 neutral to ground, actuated relay 386B [86;EA], generator direct trip lockout relay (backup), opening the main generator output breakers [BKR;FK] to the transmission system causing a turbine [TRB;El] trip. The turbine trip actuated the reactor protective system [JD] to trip the reactor [RCT;AB] due to a loss of load. As expected, the auxiliary feedwater system [BA] started automatically to recover steam generator [SG;AB] level.

There were no inoperable structures, systems, or components at the start of this event that contributed to the event.

The event is reportable in accordance with 10 CFR 50.73(a)(2)(iv)(A) as an event that resulted in an actuation of both the reactor protection system and the auxiliary feedwater system.

CAUSE OF THE EVENT

An event evaluation determined the cause for operation of the neutral to ground relay, and subsequent automatic plant trip, was a ground fault on a medium voltage cable [CBl5] providing electrical power to bus 1 G, via breaker 252-401, from station power transformer 1-3. The probable cause of the ground fault on the cable was determined to be flaws in the insulation, with the effects of moisture acting on these flaws over time, causing the insulation to degrade. The shielded cable, manufactured by Cablec with ethylene propylene rubber (EPR) insulation, was installed in 1989 with the expected lifetime to be much longer than exhibited.

The evaluation identified additional causes that include ineffective use of operating experience related to medium voltage cable insulation problems, and testing methods that were incapable of trending insulation condition to support repair and/or replacement.

The cable has not been removed and physically examined. Therefore, the cause of the suspected fJaw(s) in the insulation is unknown at this time. Cable removal and analysis is planned.

CORRECTIVE ACTIONS TAKEN A temporary modification was approved and implemented that allows bus 1 G to be isolated from station power transformer 1-3 and re-energized from start-up transformer 1-3.

CORRECTIVE ACTIONS TO BE TAKEN A plan is being developed to remove samples of the failed cable for laboratory testing and analysis. u.s. NUCLEAR REGULATORY COMMISSION (10*2010)

1. FACILITY NAME PALISADES NUCLEAR PLANT LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET

2. DOCKET
6. LER NUMBER I

SEQUENTIAL I REVISION YEAR NUMBER NUMBER 05000255 2011 002

- 00
3. PAGE 3 OF 3 The original design will be restored to allow supply of power to bus 1 G from station power transformer 1-3.

A condition monitoring method will be established which will identify progressive deteriorization of medium voltage shielded cable insulation.

Monitoring plans will be created for buried medium voltage shielded, and unshielded, cables that will provide timely identification of adverse insulation changes.

ASSESSMENT OF SAFETY CONSEQUENCES

The event is considered to be of very low safety significance. All safety systems functioned as expected.

PREVIOUS SIMILAR EVENTS

None

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