05000482/LER-2002-005, From Wolf Creek Generating Station Regarding Engineered Safety Features Actuation Including Emergency Diesel Generator Start

From Wolf Creek Generating Station Regarding Engineered Safety Features Actuation Including Emergency Diesel Generator Start

ML023050079
Person / Time
Site:	Wolf Creek
Issue date:	10/24/2002
From:	Fader G Wolf Creek
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
ET 02-0047 LER 02-005-00
Download: ML023050079 (4)

LER-2002-005, From Wolf Creek Generating Station Regarding Engineered Safety Features Actuation Including Emergency Diesel Generator Start

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation
4822002005R00 - NRC Website

text

a W>LF CREEK-

'NUCLEAR OPERATING CORPORATION Gary B. Fader Vice President Technical Services OCT 2-4 2002 ET 02-0047 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555

Subject:

Docket No. 50-482: Licensee Event Report 2002-005-00, Engineered

- Safety Features Actuation including Emergency Diesel Generator Start.

Gentlemen:

The enclosed Licensee Event Report (LER) 2002-005-00 is being submitted pursuant to 10 CFR 50.73(a)(2)(iv)(A) regarding an Engineered Safety Feature Actuation at-Wolf Creek -

Generating Station.-

Wolf Creek Nuclear Operating Corporation has made no commitments in the enclosed LER.

If you should have any questions-regarding this submittal, please contact me at (620) 364-4034 or Mr. Tony Harris at (620) 364-4038.

Very truly yours,

- Gary B. Fader GBF/rIg Enclosure cc:

J. N. Donohew (NRC), w/e D. N. Graves (NRC), w/e E. W. Merschoff (NRC), wle Senior Resident Inspector (NRC), w/e -

~ PO Box 411 /Burlington, KS 66839/ Phone (620) 364-8831 An Equal Opportunity Employer M/F/HCNVET

Abstract

On September 9, 2002, at 3:58 p.m. Central Daylight Time (CDT), Wolf Creek Generating Station (WCGS) experienced a Degraded Voltage signal on Emergency Power Bus NB01 causing an automatic actuation of the

'A" Emergency Diesel Generator ('A" EDG) and the associated Load Shedder and Emergency Load Sequencer (LSELS). The cause of the degraded voltage signal was determined to be due to a hardware failure in an electronic relay driver card in the LSELS degraded voltage circuitry. An actual degraded emergency bus voltage situation did not exist.

The safety significance of this event is low. All safety related equipment responded to the actuation signal as expected. There were no adverse effects on the health and safety of the public.

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

Root Cause:

The failure that initiated the degraded voltage alarm and subsequent opening of the normal feeder breaker to bus NB01 has been identified as occurring in an integrated circuit (IC) on a relay driver board in the NF039A cabinet. Specifically, a logic gate between pins 4, 6 and 7 in the "U1" IC on relay driver board #17 in the NF039A cabinet experienced a hardware failure to a logic Hi condition. This caused LSELS output relays 1148 and 1149 to energize and trip the NB01 feeder breakers.

Corrective Actions

Troubleshooting activities performed following this event concluded that the failure of the "Ul" chip on the relay driver board described in the root cause was the initiator of this event, and was classified as a random failure of an electronic semi-conductor integrated circuit. Following successful testing of a replacement board, it was installed and the system restored to service. LSELS was declared operable at 11:53 p.m. on September 9, 2002.

Safety Significance

The safety significance of this event is low. This event is bounded by the current licensing basis analysis as reported in Wolf Creek Generating Station (WCGS) Updated Safety Analysis Report (USAR), section 8.3.1,

'AC Power Systems", as indicated in Table 8.3.4. All safety related equipment performed as designed and there were no adverse effects on the health and safety of the public.

Previous Events:

Research into the corrective action program database was conducted for keywords "LSELS" and "sequencer", as well as systems NF and SA. No similar failures were found, nor were any other ESF actuations found attributed to these electronic cards. There are sixty (60) cards of this type used at WCGS.

They are all used in the NF and SA systems. Twenty-eight (28) are used in the NF cabinets, and thirty-two (32) are used in the SA cabinets. There have been six (6) failures in seventeen (17) years. The reliability of these boards, over a one-year period, is 99.4%. Three of these failures have occurred in NF039A, two in SA075B and one in the SA075A cabinet. One failure occurred in 1988, one in 1992, one in 1993, one in 2001 and two in 2002. To date, this event has been the only significant incident resulting from a failure of these electronic cards. The other failures have been minor equipment failures and were corrected under the work controls process.