05000370/LER-2010-001, Regarding Loose Connection in a Panel Board Serving a Solid State Protection System Train Maintenance Could Have Prevented Fulfillment of a Safety Function

Regarding Loose Connection in a Panel Board Serving a Solid State Protection System Train Maintenance Could Have Prevented Fulfillment of a Safety Function

ML100970041
Person / Time
Site:	Mcguire
Issue date:	03/26/2010
From:	Repko R Duke Energy Corp
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LER 10-001-00
Download: ML100970041 (9)

LER-2010-001, Regarding Loose Connection in a Panel Board Serving a Solid State Protection System Train Maintenance Could Have Prevented Fulfillment of a Safety Function

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v), Loss of Safety Function
3702010001R00 - NRC Website

text

SDuke REGIS T. REPKO Vice President YEnergyo McGuire Nuclear Station Duke Energy MG01VP / 12700 Hagers Ferry Rd.

Huntersville, NC 28078 980-875-4111 980-875-4809 fax regis. repko@duke-energy. com March 26, 2010 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555

Subject:

McGuire Nuclear Station, Unit 2 Docket No. 50-370 Licensee Event Report 370/2010-001, Revision 0 Problem Investigation Process No. M-10-00260 Pursuant to 10 CFR 50.73 Sections (a)(1) and (d), attached is Licensee Event Report (LER) 370/2010-001, Revision 0, regarding the inability to initiate the Unit 2 Safety Injection Diesel Generator actuation safety function and the Unit 2 Containment Spray safety function due to a loose bus bar connection in an electrical panel board serving one train of vital equipment concurrent with maintenance on the redundant train.

This report is being submitted in accordance with 10 CFR 50.73 (a)(2)(v)(D), "Event or Condition That Could Have Prevented Fulfillment of a Safety Function Neededto Mitigate an Accident". This event is considered to be of no significance with respect to the health and safety of the public. There are no regulatory commitments contained in this LER.

Please contact Julius Bryant at 980-875-4162 with any questions related to this report.

Very truly yours, Regis T. Repko Attachment www. duke-energy. com

U.S. Nuclear Regulatory Commission March 26, 2010 Page 2 of 2 cc:

L. A. Reyes Administrator, Region II U.S. Nuclear Regulatory Commission Sam Nunn Atlanta Federal Center 61 Forsyth Street, SW, Suite 23T85 Atlanta, GA 30303 J. H. Thompson Project Manager (McGuire)

U.S. Nuclear Regulatory Commission 11555 Rockville Pike Rockville, MD 20852-2738 Mail Stop 0-8 G9A J. B. Brady NRC Senior Resident Inspector McGuire Nuclear Station B. 0. Hall, Section Chief North Carolina Department of Environment and Natural Resources Division of Environmental Health Radiation Protection Section 1645 Mail Service Center Raleigh, NC 27699-1645

Abstract

approximately 15 single-spaced typewritten lines)

Unit Status: At the time of the event, Units 1 and 2 were in Mode 1 at 100% power.

Event Description

From approximately 1907 hours0.0221 days <br />0.53 hours <br />0.00315 weeks <br />7.256135e-4 months <br /> to 1938 hours0.0224 days <br />0.538 hours <br />0.0032 weeks <br />7.37409e-4 months <br /> on January 19,

2010, the Control Room received intermittent annunciators and bi-stable indications.

Investigation determined this was due to power cycling off and on to some loads served by 120VAC Vital I&C panel board 2EKVA.

One load affected was Channel 1 of Train A of the Unit 2 Solid State Protection System (SSPS).

While power was removed from this Channel, Train A would have been incapable of generating an Engineered Safety Features Actuation System signal. Concurrent with the cycling of power to Channel 1 of Train A of Unit 2 SSPS, the 2B Train of Containment Spray (NS) and the 2B Diesel Generator (DG) were inoperable for scheduled maintenance.

The above conditions could have delayed initiation of the Unit 2 safety injection DG actuation and the Unit 2 NS safety functions. McGuire is reporting this as a condition that could have prevented fulfillment of a safety function needed to mitigate the consequences of an accident.

Event Cause

Fabrication deficiency caused a loose bus bar connection in panel board 2EKVA which rendered Train A of Unit 2 SSPS inoperable concurrent with maintenance on the redundant train.

Corrective Actions

Moved Unit 2 SSPS Train A Channel 1 power to another 2EKVA breaker. Maintenance procedure for Unit 1 & 2 120VAC/125VDC Vital I&C panel boards was revised to ensure these panels are adequately inspected for loose bus bar connections.

Inspections of panel connections are planned and, based upon results, replacement of these panel boards will be considered.

NRC FORM 366(7-2001)

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SAFETY ANALYSIS

On January 19,

2010, from approximately 1907 hours0.0221 days <br />0.53 hours <br />0.00315 weeks <br />7.256135e-4 months <br /> to 1938 hours0.0224 days <br />0.538 hours <br />0.0032 weeks <br />7.37409e-4 months <br />, if Unit 2 SSPS had attempted to initiate the Unit 2 NS safety function and the Unit 2 safety injection DG actuation safety function while Channel 1 of Train A of unit 2 SSPS power was cycled off, fulfillment of these safety functions would have been delayed for a period of time which would not support the assumptions and conclusions of the applicable safety analyses.

Note, when power to Channel 1 cycled back on, SSPS contacts associated with the Unit 2 NS Train A safety function and the Unit 2 Train A safety injection DG actuation safety function would have latched in and these functions would have initiated.

Upon latch in, these Train A safety functions would have continued as needed even if power to Channel 1 of Train A of Unit 2 SSPS cycled back off.

The longest period of time that power to Channel 1 of Train A of Unit 2 SSPS was cycled off between 1907 hours0.0221 days <br />0.53 hours <br />0.00315 weeks <br />7.256135e-4 months <br /> and 1938 hours0.0224 days <br />0.538 hours <br />0.0032 weeks <br />7.37409e-4 months <br /> on January 19, 2010 was approximately 2.25 minutes. This represents the longest duration of time on that date where fulfillment of the Unit 2 NS safety function and the'Unit 2 safety injection DG actuation safety function would not have occurred if needed.

A risk-informed approach was used to determine the significance associated with unavailability of Train A of Unit 2 SSPS and coincident unavailability of the Unit 2 NS Train B and the Unit 2 B Train DG.

Conservatively, the unavailability duration used in this analysis was assumed to be 31 minutes (from approximately 1907 hours0.0221 days <br />0.53 hours <br />0.00315 weeks <br />7.256135e-4 months <br /> to 1938 hours0.0224 days <br />0.538 hours <br />0.0032 weeks <br />7.37409e-4 months <br /> on January 19, 2010).

Due to the short duration of unavailability of Train A of Unit 2 SSPS, the Conditional Core Damage Probability (CCDP) and Conditional Large Early Release Probability (CLERP) associated with this event are negligible, based on being less than 1E-8 and 1E-9, respectively.

Given the above, this event is considered to be of no significance with respect to the health and safety of the public.

ADDITIONAL INFORMATION

To determine if a recurring or similar event exists, a search of the McGuire Problem Identification Process (PIP) database was conducted for a time period covering 5 years prior to the date of this event.

Based on Duke's definition of a recurring event, similar significant event with the same cause code, no recurring events were identified.

NRC FORM 366 (7-2001)