ML20010B503

LER 80-004/03X-1:on 800107,control Rod 5-11 Absolute Position Indication Declared Inoperable Due to Fluctuating Signals,Causing Numerous Asymmetric Rod Alarms.Apparently Caused by Defective Reed Switch Assemblies

ML20010B503
Person / Time
Site:	Davis Besse
Issue date:	08/04/1981
From:	Werner J TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML17275B377	List: ML17275B376 ML20010B493 ML20010B495 ML20010B497 ML20010B499 ML20010B500 ML20010B501 ML20010B503 ML20010B504
References
LER-80-004-03X, LER-80-4-3X, NUDOCS 8108170115
Download: ML20010B503 (2)

Text

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y' T lL Q ]O l5 [0 l- l0 l3 l4Gl6 gl0 l1 l0 [7 l8 l0 @l0l8l0l4l8l1lg b3 EVENT CATE 74 M 9EPORT DATE sJ 7 60 61 000<E T '.W/3 Ea fvENT DESCRIPTION AND PROBABLE CONSEQUENCES h (T,2i l On January 7,1980 at 2115 hours0.0245 days <br />0.588 hours <br />0.0035 weeks <br />8.047575e-4 months <br /> Control Rod 5-11 absolute position indication (API) l g j was declared inoperable due to fluctuating siFnals which caused numerous " asymmetric l

[aj:il rod" alarms. This placed the unit in the action statement of T.S. 3.1.3.3 which re- l jo;3; [ quired the position of the control rod to be verified by actuating one of its zone lc p ;1 referenca indicators. The rod was verified at its 100% withdrawn position, and the  ;

g o ); l l position indication placed in asymmetric bypass. There was no danger to the public or; ia la I Lstati n Personnel. The ' control rod never deviated from its intended position. (hr-JJ-OU-U/) sc 7 6 g SYSTENt CAUSE CAUSE CO* 9P. VA LV E CODE CCCE SUBOODE COWonENT CODE SUSCCOE SUSCODE Lt.L9J lI I E lh [D_j@ [z_J @ lI l Ni SITlRlUl@ [E_jh (2.jh 1J is is 20 3 C 9 IG II 12 OCCURRENCE REPORT REVISION SEQUENTI A L

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The apparent cause has been determined to be defective API reed switch assemblies.

, U]0] I I ml major contributing cause to ihis failure is the excessive temperatures to which the

,,33; l assemblies and their cables were subjocted due to a procedure deficiency

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PDR ADOCK 05000346 419-259-5000, Ext. 231 ,

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TOLEDO EDISON COMPANY DAVIS-BESSE NUCLEAR POWER STATION UNIT ONE SUPPLEME'NTAL INFORMATION FOR LER NP-33-80-07 DATE OF EVENT: January 7, 1980 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Control Rod 5-11 Absolute Position Indication (API) fluctuations Conditions Prior to Occurrence: The unit was in Mode 1, with Power (MWT) = 637, and Load (Gross MRE) = 212.

Description of Occurrence: On January 7,1980, at 2115 hours0.0245 days <br />0.588 hours <br />0.0035 weeks <br />8.047575e-4 months <br /> Control Rod 5-11 API was declared inoperable due to fluctuating signals which caused numerous " asymmetric rod" alarms. All API channels are required to be operable and capable of determining control rod position within + 6.5% in Modes 1 and 2. This placed the unit in the action statement of Technical Specification 3.1.3.3 which required the position of the control rod to be verified by actuating one of its zone reference indicators. The rod position was verified at its 100% withdrawn position, and the rod position indication '

was placed in asymmetric bypass.

Designation of Apparent Cause of Occurrence: After several months of collecting data on Contro. Rod 5-11, the apparent cause has been determined to be defective API reed switch assemblies. A major contributing cause to this failure is the excessive tempera-tures to which the assemblies and their cables were subjected. This occured during 1 several months of operation in which the head assembly cooling fans were not in operation due to a deficient procedure which allowed restsrt following the 1978 outage without reconnecting the cooling fan power cables. The Reactor Vessel Closure Head Removal and Replacement Procedure, SP 1504.01, was corrected.

Analysis of Occurrence: There was no danger to the health and safety of the public or to station personnel. The control rod never deviated from its intended position, only the API was faulty.

Corrective Action: During the last shutdown in December, 1979, and with vendor assistance, a test connection under Facility Change Request 79-424 was placed be-I l tween the position indication (PI) assembly and its associated cabling to monitor the various voltages at that point. This was done as a corrective action to the same type of occurrence reported under Licensee Event Report NP-33-79-141.

Under Facility Change Request 79-413 a new "R4C" API system was installed. This 1 system features built-in channel redundancy and high temperature API cables.

Failure Data: There have been previous failures of control rod API's. Control Rod 5-ll's current symptoms were previously reported in Licensee Event Eeport NP-33-79-141.

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l LER 180-004

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