05000458/LER-2012-003, Reactor Scram Following a Loss of Main Reactor Feedwater Pump Due to Electrical Fault

Reactor Scram Following a Loss of Main Reactor Feedwater Pump Due to Electrical Fault

ML12209A097
Person / Time
Site:	River Bend
Issue date:	07/23/2012
From:	Olson E Entergy Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
RBG-47266 LER 12-003-00
Download: ML12209A097 (5)

LER-2012-003, Reactor Scram Following a Loss of Main Reactor Feedwater Pump Due to Electrical Fault

Event date:
Report date:
Reporting criterion:	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)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 10 CFR 50.73(a)(2)(iv)(A), System Actuation 10 CFR 50.73(a)(2)(x) 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
4582012003R00 - NRC Website

text

vEntergy Entergy Operations, Inc.

River Bend Station 5485 U. S. Highway 61 N St. Francisville, LA 70775 Tel 225 381 4374 Fax 225 381 4872 eolson@entergy.com Eric W. Olson Site Vice President RBG-47266 July 23, 2012 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555

Subject:

Licensee Event Report 50-458 / 2012-003-00 River Bend Station - Unit 1 Docket No. 50-458 License No. NPF-47 RBF1-12-0099

Dear Sir or Madam:

In accordance with 10 CFR 50.73, enclosed is the subject Licensee Event Report.

This document contains no commitments. If you have any questions, please contact Mr. Joseph Clark at 225-381-4177.

Sincerely, EWO/dhw Enclosure Zý19-

Licensee Event Report 50-458 / 2012-003-00 July 23, 2012 RBG-47266 RBF1 0099 Page 2 of 2 cc:

U. S. Nuclear Regulatory Commission Region IV 1600 East Lamar Blvd.

Arlington, TX 76011-4511 NRC Sr. Resident Inspector P. O. Box 1050 St. Francisville, LA 70775 INPO Records Center E-Mail (MS Word format)

Ms. Tracie Lowery Public Utility Commission of Texas 1701 N. Congress Ave.

Austin, TX 78711-3326 Department of Environmental Quality Office of Environmental Compliance Radiological Emergency Planning and Response Section JiYoung Wiley P.O. Box 4312 Baton Rouge, LA 70821-4312

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013 (10-2010) digits/characters for each block) the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

3. PAGE River Bend Station - Unit 1 05000-458 1 OF3

4. TITLE Reactor Scram Following a Loss of Main Reactor Feedwater Pump Due to Electrical Fault

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED I

FACILITY NAME DOCKET NUMBER 1SEOUENTIAL 1 REV MONTH IDAY YEAR n/a05 0

MONTH DAY YYEAR NUMBER NO.

05000 FACILITY NAME DOCKET NUMBER 05 24 2012 2012-003-00 07 23 2012 n/a 05000

9. OPERATING MODE

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)

Ul 20.2201(b)

[I 20.2203(a)(3)(i)

[] 50.73(a)(2)(i)(C)

EU 50.73(a)(2)(vii) 1 20.2201(d)

EU 20.2203(a)(3)(ii)

Ul 50.73(a)(2)(ii)(A)

EU 50.73(a)(2)(viii)(A)

EU 20.2203(a)(1)

EU 20.2203(a)(4)

EU 50.73(a)(2)(ii)(B)

EU 50.73(a)(2)(viii)(B)

Ul 20.2203(a)(2)(i)

U 50.36(c)(1)(i)(A)

U 50.73(a)(2)(iii)

EU 50.73(a)(2)(ix)(A)

10. POWER LEVEL EU 20.2203(a)(2)(ii)

U 50.36(c)(1)(ii)(A)

[

50.73(a)(2)(iv)(A)

U 50.73(a)(2)(x)

EU 20.2203(a)(2)(iii)

EU 50.36(c)(2)

U 50.73(a)(2)(v)(A)

U 73.71 (a)(4) 32 U 20.2203(a)(2)(iv)

EU 50.46(a)(3)(ii)

EU 50.73(a)(2)(v)(B)

U 73.71(a)(5)

U 20.2203(a)(2)(v)

U 50.73(a)(2)(i)(A)

U 50.73(a)(2)(v)(C)

Ul OTHER U 20.2203(a)(2)(vi)

Ul 50.73(a)(2)(i)(B)

U 50.73(a)(2)(v)(D)

Specify in Abstract below or in NRC Form 366A

12. LICENSEE CONTACT FOR THIS LER FACILITY NAME TELEPHONE NUMBER (Include Area Code)

Joseph A. Clark, Manager - Licensing 225-381-4177I AU RPRAL MANU-REPORTABLE

CAUSE

SYSTEM COMPONENT MANU-REPORTABLE

CAUSE

SYSTEM COMPONENT FACTURER TO EPIX FACTURER TO EPIX

______T___

E EA 86 GE yes

14. SUPPLEMENTAL REPORT EXPECTED

15. EXPECTED MONTH DAY YEAR SUBMISSION [U YES (If yes, complete 15. EXPECTED SUBMISSION DATE)

O NO DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)

On May 24, 2012, at 3:40 p.m. CDT, a manual reactor scram was initiated in response to the loss of the running reactor feedwater pump. The plant was operating at approximately 32% power. The reactor core isolation cooling system was manually started to provide high pressure makeup to the reactor. The high pressure core spray system was manually started during the recovery from the event, but was not aligned to the reactor vessel. An electrical transient caused by the failure of a lockout relay resulted in the main supply breaker to the "B" 13.8kv switchgear to trip. Reactor recirculation pump "B" tripped due to the loss of its power source; the "A" reactor recirculation pump continued to operate in slow speed. The electrical transient also caused a loss of power to all main condenser circulating water pumps and normal service water pumps, necessitating the manual closure of the main steam isolation valves. The standby service water system actuated as designed in response to low normal service water pressure. The operators manually operated selected SRVs for reactor pressure control and for reactor cooldown.

Personnel in the turbine building reported the presence of smoke in the area of the feedwater pumps, but no actual fire was observed. There were no safety-related systems out of service at the time. This event is being reported in accordance with 1 OCFR50.73(a)(2)(iv)(A) as an actuation of the reactor protection system and the standby service water system. This event was of low safety significance to the health and safety of the public.

NRC FORM 366 (10-2010)

ILICENSEE EVENT REPORT (LER)

U.S. NUCLEAR REGULATORY COMMISSION (10-2010)

CONTINUATION SHEET

1. FACILITY NAME

2. DOCKET

6. LER NUMBER

3. PAGE YEAR I SEQUENTIALI REV.

River Bend Station - Unit 1 05000 -458 2 OF 3 2012 -- 003 -- 00 REPORTED CONDITION On May 24, 2012, at 3:40 p.m. CDT, a manual reactor scram was initiated in response to the loss of the running reactor feedwater pump (**P**). The plant was operating at approximately 32%

power at the time.

The reactor core isolation cooling system (BN) (RCIC) was manually started to provide high pressure makeup to the reactor. The high pressure core spray (BG) (HPCS) system was manually started during the recovery from the event, but was not aligned to the reactor vessel.

An electrical transient caused by the failure of a lockout relay (**86**) resulted in the main supply breaker (**BKR**) to the "B" 13.8kv switchgear (EA) to trip. Reactor recirculation (AD) pump "B" tripped due to the loss of its power source; the "A" reactor recirculation pump continued to operate in slow speed. The electrical transient also caused a loss of power to all main condenser circulating water pumps (NN) and normal service water pumps (KG), necessitating the manual closure of the main steam isolation valves. The standby service water system (BS) actuated as designed in response to low normal service water pressure.

No reactor safety-relief valves (SRVs) operated automatically as a result of the scram. The operators manually operated selected SRVs for reactor pressure control and for reactor cooldown.

The residual heat removal system (BO) was manually started in the suppression pool cooling mode to support RCIC operation, as well as for control of suppression pool level.

Personnel in the turbine building reported the presence of smoke in the area of the feedwater pumps, but no actual fire was observed.

This event is being reported in accordance with 10CFR50.73(a)(2)(iv)(A) as an actuation of the reactor protection system (JC) and the standby service water system. There were no safety-related systems out of service at the time of the event.

INVESTIGATION and CAUSAL ANALYSIS At the time of the event, the "C" reactor feedwater pump was in service. When the operator started the "B" feedwater pump, an electrical fault occurred at the pump motor. The lockout relay on the pump's feeder breaker failed to trip the breaker, and the main supply breaker to the "B" 13.8kV switchgear tripped to clear the fault. This caused the loss of power to the "C" pump, as well as switchgears supplying the circulating water system and the normal service water system.

The inspection of the terminal box on the "B" feedwater pump determined that fault occurred due to an inadequately crimped terminal lug on one of the three current transformers. The motor

(**MO**) had been rewound by a vendor in 2008. When the motor was returned, new lugs wereLICENSEE EVENT REPORT (LER)

U.S. NUCLEAR REGULATORY COMMISSION (10-2010)

CONTINUATION SHEET

1. FACILITY NAME

2. DOCKET

6. LER NUMBER

3. PAGE YEAR SEQUENTIAL REV.

NUMBER NO.

River Bend Station - Unit 1 05000 -458 3 OF 3 2012 -- 003 -- 00 supplied by the vendor to be installed onsite. The lugs were installed by a local vendor. The investigation found that the lugs were too large for the application. Additionally, the crimping tool used for the installation did not fully compress the lugs, leaving an inadequately bonded connection.

The lockout relay installed on the breaker for the "B" feedwater pump is a General Electric HEA

61. The analysis of this event found that the lockout relay failed to operate as designed due to age-related mechanical binding and a possible coil failure. This condition resulted from an inadequate preventative maintenance program for the relays and a design issue with the trip plate.

Prior to plant restart, similar lockout relays were functionally tested. Additional failed relays were discovered (none in safety-related service), and these were replaced.

CORRECTIVE ACTION TO PREVENT RECURRENCE The preventative maintenance program for lockout relays is being evaluated to develop appropriate changes. A training needs analysis is being conducted for those departments responsible for development and implementation of the preventative maintenance program.

Thermographic imaging will be performed on other large motors potentially susceptible to this same type of lug failure.

These actions are being tracked in the station's corrective action program.

PREVIOUS OCCURRENCE EVALUATION No previous scrams have occurred with the same root cause as this event. There was a failure of the same type of lockout relay in February 2011.

SAFETY SIGNIFICANCE

No plant parameters requiring the automatic actuation of the emergency diesel generators or the emergency core cooling systems were exceeded. The RCIC system operated properly in response to the operators' manual control and provided high pressure makeup to the reactor.

Control of reactor pressure was accomplished by manual actuation of selected SRVs. The plant was placed in cold shutdown. The standby service water system operated as designed. This event was of minimal safety significance to the health and safety of the public.

(NOTE: Energy Industry Component Identification codes are annotated as (**XX**).)