ML20052G665

LER 82-020/03L-0:on 820409,while in Mode 6,station Experienced Loss of 120-volt Ac Distribution Panel Y2.Caused by Blown YV2 Inverter Fuse When Short to Ground Occurred During Maint on Control Room Emergency Ventilation Sys

ML20052G665
Person / Time
Site:	Davis Besse
Issue date:	05/07/1982
From:	Matheny D TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20052G650	List: ML20052G649 ML20052G665
References
LER-82-020-03L, LER-82-20-3L, NUDOCS 8205180555
Download: ML20052G665 (2)

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LICENSEE EVENT REPORT

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60 61 DOCK ET NUMBER 68 63 EVENT DATE 74 75 REPORT DATE 80 EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h l o 121 l (NP-33-82-24) On April 9, 1982 at 1015 hours0.0117 days <br />0.282 hours <br />0.00168 weeks <br />3.862075e-4 months <br /> the station experienced a loss of 120VAC l

[ o l a l I distribution panel Y2 while in Mode 6. Since Y4 had already been deenergized for rou- l Io la l l tine maintenance, SFAS actuation channel 2 actuated when power was lost to SFAS chan- l loisi inel 2, and RPS channel 2 deenergized causing a loss of one channel of Source Range ]

Io is l l Nuclear Instrumentation. The station entered the action statement of Tech Specs I, <

l o l 7 I I 3.8.2.2, 3.3.2.1, and 3.9.2. There was no danger to the health and safety of the pub- l

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42 43 44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h to 11 lolIThe loss of Y2 was due to a blown YV2 inverter fuse. The fuse blew when a short l 11 lil Iground occurred during maintenance on the Control Room Emergency Ventilation System. I i, 171 lThe control power supplied from Y2 to control power panel C6709 was overlooked when l

[il3l l the system was tagged out by a contractor personnel. Under MW0s 82-1547 and 82-1595, l li [4 l l the fuses were replaced. The responsible person was counseled by the Maintenance EngrJ 7 8 9 80 ST S  % POWER OTHER STATUS ISCO RY DISCOVERY DESCRIPTION Fits 1 Laj@ l 0101 Ol@l NA l l Al@l Operator Observation. l ACTIVITY CO TENT RELEASED OF RELEASE AVOUNT OF ACTIVITY LOCATION 0F RELEASE l1 l 6 l l a l @ W@l NA l l NA l PERSONNEL EXPOS ES

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TOLEDO EDISON COMPANY

, DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEMENTAL INFORMATION FOR LER NP-33-82-24 DATE OF EVENT: April 9, 1982 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Inadvertant blowing of Inverter YV2 Input Fuse.

Conditions Prior to Occurrence: The unit was in Mode 6, with Power (MWT) = 0 ~

and Load (Gross MWE) = 0.

i Description of Occurrence: On April 9, 1982, at 1015 hours0.0117 days <br />0.282 hours <br />0.00168 weeks <br />3.862075e-4 months <br />, the input fuse to inverter YV2 blew, deenergizing essential 120VAC distribution panel Y2. Due to the fact that essential 120VAC distribution panel Y4 had already been deenergized for routine maintenance per Maintenance Work Order 82-1149, the station entered the action statements of Technical Specifications 3.8.2.2, 3.9.2, and 3.3.2.1.

All core alterations and positive reactivity changes were immediately suspended in accordance with the appropriate action statements. Further investigations revealed that the fuse to circuit Y204, Control Room Emergency Ventilation Standby .

Condensing Unit Panel C6709, was also blown. Circuit Y204 was tagged in the off condition and Y2 was reenergized from alternate supply bus YBR. At that time, 1410 hours0.0163 days <br />0.392 hours <br />0.00233 weeks <br />5.36505e-4 months <br />, the station was removed from the action statement of T.S. 3.8.2.2.

At time.1750, applicable portions of ST 5031.01, Safety Features Actuation Sys-tem Monthly Test, were successfully completed, and SFAS Channel 2 and RPS Channel 2 were declared operable. At that time, the station was removed from the action statements of T.S. 3.9.2 and 3.3.2.1.

Designation of Apparent Cause of Occurrence: The apparent cause of this occur-rence was a personnel error. A contractor performing routine maintenance on the Control Room Emergency Ventilation System 1-2 overlooked the control power sup-plies from Y2 to the control panel C6709 when tagging out the system for' main-tenance. Consequently, a short to ground occurred during the removal of a flow switch on the water cooler condenser. This short caused the Y204 and YV2 fuses l to blow.

Analysis of Occurrence: There was no danger to the health and safety of the public or to station personnel. The affected safety systems went to their fail safe status, and.the redundant source range NI Channel was operable.

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Corrective Action: Inverter YV2 input fuse was replaced per Maintenance Work Order-82-1547. Circuit Y204 was investigated and the fuse replaced per Maintenance Work Order 82-1595. The contractor responsible for this occurrence was ' counseled by the Maintenance Engineer.

Failure. Data: Previous occurrences where a short to ground on a load downstream of the inverter also failed the input inverter fuse were reported NP-33-80-105 (LER 80-081) and NP-33-80-070 (LER 80-056) .

LER.#82-020

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