05000346/LER-1978-109-03, /03L-0:on 781031,reactor Coolant Pumps 1-2 & 2-1 Tripped,Placing Unit in Action Statement of Tech Spec 3.4.1. Caused by Blown Main Fuse for nonsafety-related Reactor Coolant Pump Cabinet.Fuse Replaced & Pumps Restarted

/03L-0:on 781031,reactor Coolant Pumps 1-2 & 2-1 Tripped,Placing Unit in Action Statement of Tech Spec 3.4.1. Caused by Blown Main Fuse for nonsafety-related Reactor Coolant Pump Cabinet.Fuse Replaced & Pumps Restarted

ML20027A465
Person / Time
Site:	Davis Besse
Issue date:	11/28/1978
From:	Batch S, Kovach S TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20027A464	List: 05000346/LER-1978-109, Forwards LER 78-109/03L-0 05000346/LER-1978-109-03, /03L-0:on 781031,reactor Coolant Pumps 1-2 & 2-1 Tripped,Placing Unit in Action Statement of Tech Spec 3.4.1. Caused by Blown Main Fuse for nonsafety-related Reactor Coolant Pump Cabinet.Fuse Replaced & Pumps Restarted
References
LER-78-109-03L, LER-78-109-3L, NUDOCS 7812050206
Download: ML20027A465 (3)

LER-1978-109, /03L-0:on 781031,reactor Coolant Pumps 1-2 & 2-1 Tripped,Placing Unit in Action Statement of Tech Spec 3.4.1. Caused by Blown Main Fuse for nonsafety-related Reactor Coolant Pump Cabinet.Fuse Replaced & Pumps Restarted

Event date:
Report date:
3461978109R03 - NRC Website

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U.S. NUCLEAR REGULAftRY COMMISSloN I

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8 EVENT DESCRIPTION AND PROBA8LE CONSEQUENCES h This I

10121 l On 10/31/78 at 0700 hours0.0081 days <br />0.194 hours <br />0.00116 weeks <br />2.6635e-4 months <br />, Reactor Coolant Pumps (RCP) 1-2 and 2-1 tripped.

(b) of Technical Specification 3.4.1.

On 11/13/74 g l placed the unit in Action Statement l

ITT71 ; at 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br /> with the unit at 99% of full power, RCPs 1-2 and' 2-1 tripped and a [77!q l reactor trip occurred. Since the reactor trip occurred just prior to the loss of the lo is i I second RCP, the unit was not placed in the Action Statement on 11/13/78 and was in One other RCP in each loop was operable dur- ]

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TOLEDO EDISON COMPANY DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION SUPPLDIE',TAL INF010!ATION FOR LER NP-33-78-129 DATE OF EVENT: Sctober 31, 1978 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Reactor Coolant Pumps 1-2 and 2-1 Inoperable.

Conditions Prior to Occurrence: On October 31, 1978, the unit was in Mode 2, with Power (mI) = approximately 110, and Load (MWE) = 0.

Descriotion of Occurrence: On October 31, 1978, at 0700 hours0.0081 days <br />0.194 hours <br />0.00116 weeks <br />2.6635e-4 months <br />, Reactor Coolant Pump

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(RCP) 1-2 and RCP 2-1 (in Reactor Coolant System (RCS) Loops 1 and 2, respectively) tripped. This placed the unit in Action Statement (b) of Technical Specification 3.4.1 for Modes 1 and 2.

The Technical Specification requires the operability of both reactor coolant loops and both Reactor Coolant Pumps on each loop. Action Statement (b) states that startup and power operation may be initiated and may pro-ceed provided thermal power is restricted to less than 50.6% of rated thermal power.

The setpoints for high flux and flux-41 flux-flow trips must be reduced within four-hours to the values specified in Technical Specification 2.2.1.

In addition, this occurrence was not in accordance with the Operating License Condition 2c(3)(a) which requires at least three Reactor Coolant Pu=ps in operation while in Modes 1 or 2.

On November.13,1978, at 1300 hours0.015 days <br />0.361 hours <br />0.00215 weeks <br />4.9465e-4 months <br />, with the unit at 99% of full power, Reactor Coolant Pu=ps 1-2 and 2-1 tripped, and a reactor trip occurred. Since the reactor trip occurred just prior to the loss of the second Reactor Coolant Pump (which placed the unit in Mode 3), the unit was not placed in the Action Statement of Tech-nical Specification 3.4.1, and was in ec=pliance with the Operating License Condition 2c(3) (a). The November 13, 1978 event is included in this report since the cause of the RCP trip s was determined during the investigation of the November 13,1978 event.

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Designation of Apoarent Cause of Occurrence: On October 31, 1978, Instrument and Control technicians f ound that the main fuse for the non-safety related RCP Cabinet 3718 was blown, which caused the RCP l-2 and 2-1 trips. It was planned to further investigate the cause of the blown fuse during the next plant outage.

After the reactor trip on November 13, 1978, it was discovered that two non-safety related relays were defective in Relay Cabinet RC 3718. Further investigation under Maintenance Work Order 78-2647 revealed improper initial wiring of the fuse circuit which caused both the pumps to trip from the main power supply fuse in the relay cabinet.

Analysis of Occurrence: There was no danger to the health and safety of the public or to unit personnel. One other Reactor Coolant Pump in each loop was operable during the period that RCP l-2 and 2-1 were inoperable.

LER #78-109

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TOLEDO EDISON COMPAhT i

DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION SUPPLEMENTAL ISTORMATION FOR LER NP-33-78-129 PAGE 2

Corrective Action

Maintenance electricians replaced the fuse for RCP Relay Cabinet 3718 on October 31, 1978. RCP 2-1 was started at 0940 hours0.0109 days <br />0.261 hours <br />0.00155 weeks <br />3.5767e-4 months <br />, and RCP 1-2 started at 0945 hours0.0109 days <br />0.263 hours <br />0.00156 weeks <br />3.595725e-4 months <br /> on October 31. The unit was thus removed frem Action Statement (b) of Technical Speciff. cation 3.4.1.

Thermal power was maintained at less than 50.6% of rated thermal power. Since the unit was in the Action Statement for less than four hours, it was unnecessary to reduce the setpoints for high flux and flux-d flux-flow trips as given in the Cl Action Statement.

On November 13, 1978, under Maintenance Work Orders 78-2647, 78-2651 and 78-2652, the defective relays were replaced and.all Reactor Coolant Pump relay cabinets fuse circuits were rewired in accordance with the wiring diagram.

I Pailure Data: There have been no previously reported f ailures of RCPs due to i

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blown fuses.

LER #78-109 i

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