05000285/LER-2011-008-01, Regarding Fire in Safety Related 480 Volt Electrical Bus

Regarding Fire in Safety Related 480 Volt Electrical Bus

ML113010208
Person / Time
Site:	Fort Calhoun
Issue date:	10/27/2011
From:	Bannister D Omaha Public Power District
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
LIC-11-0106 LER 11-008-01
Download: ML113010208 (6)

LER-2011-008, Regarding Fire in Safety Related 480 Volt Electrical Bus

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(x) 10 CFR 50.73(a)(2)(ii)(8) 10 CFR 50.73(a)(2)(v), Loss of Safety Function 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)(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)(i)(B), Prohibited by Technical Specifications
2852011008R01 - NRC Website

text

LlC-11-0106 October 27, 2011 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 Reference: Docket No. 50-285

Subject:

Licensee Event Report 2011-008, Revision 1, for the Fort Calhoun Station Please find attached Licensee 'Event Report 2011-008, Revision 1, dated October 25,2011. This report is being submitted pursuant to 10 CFR 50.73(a)(2)(x), 10 CFR 50.73(a)(2)(ii)(8) and 10 CFR 50.73(a)(2)(v). Changes are noted by revision bars.

If you should have any questions, please contact me.

Sincerely, D.. Bannister Vice President - Nuclear DJB/rmc Attachment c:

E. E. Collins, Jr., NRC Regional Administrator, Region IV L. E. Wilkins, NRC Project Manager J. C. Kirkland, NRC Senior Resident Inspector INPO Records Center Employment with Equal Opportunity

NRC FORM 366 (10-2010)

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

LICENSEE EVENT REPORT (LER)

(See reverse for required number of digits/characters for each block)

APPROVED BY OMB: NO. 3150-0104 EXPIRES: 10/31/2013

, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

1. FACILITY NAME Fort Calhoun Station

2. DOCKET NUMBER 05000285

3. PAGE 1 OF 5

4. TITLE Fire in Safety Related 480 Volt Electrical Bus

5. EVENT DATE

6. LER NUMBER

7. REPORT DATE

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

MONTH DAY YEAR FACILITY NAME DOCKET NUMBER 05000 6

7 2011 2011 - 008 -

1 10 27 2011 FACILITY NAME DOCKET NUMBER 05000

9. OPERATING MODE 5

11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 20.2201(b) 20.2203(a)(3)(i) 50.73(a)(2)(i)(C) 50.73(a)(2)(vii) 20.2201(d) 20.2203(a)(3)(ii) 50.73(a)(2)(ii)(A) 50.73(a)(2)(viii)(A) 20.2203(a)(1) 20.2203(a)(4) 50.73(a)(2)(ii)(B) 50.73(a)(2)(viii)(B) 20.2203(a)(2)(i) 50.36(c)(1)(i)(A) 50.73(a)(2)(iii) 50.73(a)(2)(ix)(A) 20.2203(a)(2)(ii) 50.36(c)(1)(ii)(A) 50.73(a)(2)(iv)(A) 50.73(a)(2)(x) 20.2203(a)(2)(iii) 50.36(c)(2) 50.73(a)(2)(v)(A) 73.71(a)(4) 20.2203(a)(2)(iv) 50.46(a)(3)(ii) 50.73(a)(2)(v)(B) 73.71(a)(5) 20.2203(a)(2)(v) 50.73(a)(2)(i)(A) 50.73(a)(2)(v)(C)

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

10. POWER LEVEL 0

12. LICENSEE CONTACT FOR THIS LER FACILITY NAME Erick Matzke TELEPHONE NUMBER (Include Area Code) 402-533-6855 CAUSE SYSTEM COMPONENT MANU-FACTURER REPORTABLE TO EPIX

CAUSE

SYSTEM COMPONENT MANU-FACTURER REPORTABLE TO EPIX B

EC 52 NLI Y

14. SUPPLEMENTAL REPORT EXPECTED YES (If yes, complete 15. EXPECTED SUBMISSION DATE)

NO

15. EXPECTED SUBMISSION DATE MONTH DAY YEAR ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)

On June 7, 2011, at approximately 0930 CDT, a failure of a safety related 480 volt AC (V) load center supply breaker in the switchgear room occurred (Bus 1B4A). Fire alarms were received in the control room and the Halon system that protects the switchgear rooms discharged. The fire brigade responded and found the room filled with smoke, but no active fire. At 0940 CDT an Alert was declared for a fire affecting the operability of plant safety systems required to establish or maintain safe shutdown. At 1313 CDT on June 7, 2011, Fort Calhoun Station (FCS) exited the Alert after confirming that the fire was extinguished and the area was ventilated to restore access.

Shutdown cooling remained in-service during the event.

FCS was also in an emergency classification of a Notification of Unusual Event (NOUE) due to high Missouri river level.

The root cause of the event was the FCS design process failed to identify the silver plating of bus bar material as a critical interface when specifying replacements for the original circuit breakers. The design process failure extended to other safety-related 480 V load center circuit breakers as well.

Corrective actions included replacing 480 V bus 1B4A and performing bus maintenance. Affected circuit breaker cradles will be realigned to ensure proper fit in the bus cubicles. Maintenance procedures are being revised to enhance maintenance practices. LICENSEE EVENT REPORT (LER)

CONTINUATION SHEET

SAFETY SIGNIFICANCE

As a direct result of the fire in bus 1B4A and the tripping of bus 1B3A, spent fuel pool cooling was lost for approximately 90 minutes. Shutdown cooling was powered from the unaffected 4160 V bus. The loss of both safety-related 480 V bus trains is a potentially unanalyzed condition in circuit breaker coordination and impacted nuclear safety.

The twelve 480 V Square D circuit breakers were installed during the 2009 RFO and were in-service for an 18 month operating cycle. As noted in the conclusion section above, an extent of condition existed in the remaining ten safety-related 480 V buses which could have impacted nuclear safety if a fire occurred while the plant was above 300 degrees F.

SAFETY SIGNIFICANT FUNCTIONAL FAILURE This event does result in a safety system functional failure in accordance with NEI-99-02.

PREVIOUS EVENTS None