05000499/LER-2010-005, Regarding Startup Feed Pump 24 Breaker Failure and Unit 2 Reactor Trip

Regarding Startup Feed Pump 24 Breaker Failure and Unit 2 Reactor Trip

ML110070064
Person / Time
Site:	South Texas
Issue date:	01/03/2011
From:	Peter L South Texas
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
NOC-AE-10002630 LER 10-005-00
Download: ML110070064 (6)

LER-2010-005, Regarding Startup Feed Pump 24 Breaker Failure and Unit 2 Reactor Trip

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)(viii)(B) 10 CFR 50.73(a)(2)(iii) 10 CFR 50.73(a)(2)(ix)(A) 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
4992010005R00 - NRC Website

text

Nuclear Operating Company South Texas Project Electric Generating Station PO. Box 289 Wadsworth Tcs 77483 January 3, 2011 NOC-AE-1 0002630 File No.: G25 10 CFR 50.73 STI: 32805150 U. S. Nuclear Regulatory Commission Attention: Document Control Desk One White Flint North 11555 Rockville Pike Rockville, MD 20852-2738 South Texas Project Unit 2 Docket No. STN 50-499 Licensee Event Report 2010-005 Startup Feed Pump 24 Breaker Failure and Unit 2 Reactor Trip Pursuant to 10 CFR 50.73, STP Nuclear Operating Company (STPNOC) submits the attached Unit 2 Licensee Event Report (LER) 2010-005 to address the Unit 2 Reactor trip that occurred on November 3, 2010.

This condition is considered reportable under 10 CFR 50.73(a)(2)(iv)(A), any event or condition that resulted in manual or automatic actuation of any of the systems listed in paragraph (a)(2)(iv)(B) of this section, This event did not have an adverse effect on the health and safety of the public.

This is this initial LER submittal. A planned supplement will be submitted no later than April 4, 2011.

There are no commitments contained in this LER.

If there are any questions on this submittal, please contact either J. A. Loya at (361) 972-8005 or me at (361) 972-7158.

L. W. Peter Plant General Manager JAL

Attachment:

LER 2010-005: Startup Feed Pump 24 Breaker Failure and Unit 2 Reactor Trip

NOC-AE-10002630 Page 2 of 2 cc:

(paper copy)

(electronic copy)

Regional Administrator, Region IV U. S. Nuclear Regulatory Commission 612 East Lamar Blvd, Suite 400 Arlington, Texas 76011-4125 Mohan C. Thadani Senior Project Manager U.S. Nuclear Regulatory Commission One White Flint North (MS 8 G14) 11555 Rockville Pike Rockville, MD 20852 Senior Resident Inspector U. S. Nuclear Regulatory Commission P. 0. Box 289, Mail Code: MN1 16 Wadsworth, TX 77483 C. M. Canady City of Austin Electric Utility Department 721 Barton Springs Road Austin, TX 78704 A. H. Gutterman, Esquire Morgan, Lewis & Bockius LLP Mohan C. Thadani U. S. Nuclear Regulatory Commission John Ragan Catherine Callaway Jim von Suskil NRG South Texas LP Ed Alarcon Kevin Polio Richard Pena City Public Service Peter Nemeth Crain Caton & James, P.C.

C. Mele City of Austin Richard A. Ratliff Texas Department of State Health Services Alice Rogers Texas Department of State Health Services

NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES: 08/31/2010 (9-2007)

, the NRC may digits/characters for each block) not conduct or sponsor, and a person is not required to respond to, the information collection.

3. PAGE South Texas Unit 2 05000499 1 OF 4

4. TITLE

__StartuD Feed Pump 24 Breaker Failure and Unit 2 Reactor Trip

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

8. OTHER FACILITIES INVOLVED MONTH DAY YEAR YEAR SEQUENTIAL REV FACILITY NAME DOCKET NUMBER NUMBER NO.

MONTH DAY YEAR N/A N/A FACILITY NAME DOCKET NUMBER 11 03 2010 2010 - 005 -

0 01 03 2011 N/A N/A

9. OPERATING MODE

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

El 20.2201(b)

El 20.2203(a)(3)(i)

E-50.73(a)(2)(i)(C)

El 50.73(a)(2)(vii) 1E 20.2201(d)

El 20.2203(a)(3)(ii)

El 50.73(a)(2)(ii)(A)

El 50.73(a)(2)(viii)(A)

[I 20.2203(a)(1)

El 20.2203(a)(4)

El 50.73(a)(2)(ii)(B)

El 50.73(a)(2)(viii)(B)

E] 20.2203(a)(2)(i)

El 50.36(c)(1)(i)(A)

El 50.73(a)(2)(iii)

El 50.73(a)(2)(ix)(A)

10. POWER LEVEL [E 20.2203(a)(2)(ii)

El 50.36(c)(1)(ii)(A) 0 50.73(a)(2)(iv)(A)

El 50.73(a)(2)(x)

El 20.2203(a)(2)(iii)

El 50.36(c)(2)

C3 50.73(a)(2)(v)(A)

[I 73.71(a)(4)

El 20.2203(a)(2)(iv)

El 50.46(a)(3)(ii)

[I 50.73(a)(2)(v)(B)

El 73.71(a)(5) 100%

El 20.2203(a)(2)(v)

El 50.73(a)(2)(i)(A)

El 50.73(a)(2)(v)(C)

[: OTHER E3 20.2203(a)(2)(vi)

El 50.73(a)(2)(i)(B)

El 50.73(a)(2)(v)(D)

Specify in Abstract below or in SUMMARY OF THE EVENT On November 3, 2010, the Startup Feed Pump (SUFP) 24 was being started to support a scheduled Partial Discharge Analysis as a preventive maintenance activity. Following the pre-job brief, a Licensed Operator Training (LOT) Trainee made a plant announcement and then placed the hand switch to Start at 1021 hours0.0118 days <br />0.284 hours <br />0.00169 weeks <br />3.884905e-4 months <br />. The SUFP started but then after approximately 4 seconds the pump breaker tripped open. Computer data shows that approximately 8 seconds after the pump breaker tripped the voltage on Standby Bus 2H (which supplies power to the SUFP) spiked low to near zero volts and the Unit 2 reactor tripped on Reactor Coolant Pump (RCP) Undervoltage (the 2C RCP is also powered by Standby Bus 2H).

Standby Diesel Generator (SDG) 23 started and began supplying Engineered Safety Features (ESF) Bus E2C due to Loss of Offsite Power (LOOP) to the ESF bus. Standby Bus 2F experienced a momentary voltage drop of approximately 1 second duration (Standby Buses 2F and 2H are both fed by the X winding of the Unit 2 Auxiliary Transformer) resulting in some A train loads being secured, however the low voltage condition cleared on Bus 2F prior to the point at which associated time delay relays would have started Standby Diesel Generator 21 (ESF Train A). Following the reactor trip, the plant was stabilized in MODE 3 at Normal Operating Pressure and Temperature.

At 1038 hours0.012 days <br />0.288 hours <br />0.00172 weeks <br />3.94959e-4 months <br /> an Unusual Event was declared for Unit 2 due to the breaker cubicle explosion associated with the SUFP breaker failure (ENS Event Number 46387). The breaker malfunction did not result in a fire. The Unusual Event was terminated at 1240 hours0.0144 days <br />0.344 hours <br />0.00205 weeks <br />4.7182e-4 months <br /> when the plant was stabilized in MODE 3.

An Operator in the Turbine Generator Building (TGB) reported substantial damage had occurred to the SUFP Breaker. The front door and access panels for Cubicle 1A in 13.8 KV Standby Bus 2H had been blown open or deformed.

(If more space is required, use additional copies of (If more space is required, use additional copies of NRC Form 366A) (17)

C.

SAFETY CONSEQUENCES AND IMPLICATIONS OF THE EVENT There was no impact to radiological safety, safety of the public, or safety of station personnel during this event.

The Incremental Conditional Core Damage Probability (ICCDP) for the Reactor Trip in Unit 2 on November 3, 2010 is 2.82E-07. The resulting Incremental Conditional Large Early Release Probability (LERP) given a turbine trip is 7.21 E-09.

III. CAUSE OF THE EVENT

The Root Cause of the breaker failure is under investigation and will be submitted in the planned LER supplement.

IV. CORRECTIVE ACTIONS

The Root Cause of the event, including the resulting corrective actions, is under investigation and will be submitted in the planned LER supplement.

V. PREVIOUS SIMILAR EVENTS

There have been no similar events within the last three years.

VI. ADDITIONAL INFORMATION

A supplement to this Licensee Event Report will be submitted by April 4, 2011.