ML19242A841

LER 79-072/03L-0 on 790708:position Indication on Rod Two of Group Eight Was Inoperable.Caused by Component Failure of Reed Switch within Position Indicator Tube.Part Was Replaced & Returned to Svc

ML19242A841
Person / Time
Site:	Davis Besse
Issue date:	08/02/1979
From:	Naylor R TOLEDO EDISON CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML19242A839	List: ML19242A838 ML19242A841
References
LER-79-072-03L, LER-79-72-3L, NUDOCS 7908060450
Download: ML19242A841 (2)

Text

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rn F C,H T D A T E EVENT DESCmrTION AND FHOB ABLE CONSEQUENCES h o 2 l On July 8, 1979 at 1315 hours, it was observed that the position indication on Rod 2 l o 3 lof Group 8 was inoperable. The action statement of Technical Specification 3.1.3.3 l This o a j was not applicable as the unit was in Mode 3 at the time of this occurrence. J There was no danger to thel o s [ repor t is beinr, submitted to document a componcnt failure. The unit uas shutdoen, and o c l health and saf ety of the public or station personnel. l 0 7 bhe relative position and zone ref erence indications were onerable. (?!P- 33-7 9-90) l 1 0 8 l g3

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CAUPE DLtCHIPTION AND CCHHECTI' E ACTIONS i o lThe exact cause is not known; the apparent cause ic- connonent failure of a reed switchI i i luithin the position indicator tube. Th e tube i s b e i-'c returred to the vender for I i ,

                           ] final determinat ion of the cause of f ailure. The rosition ladicator tube was renlaced!

i a and tested per Surveillance Test ST 3C13.03. ihe red and nosition indicator were j [ijal l returned to operability on July 10, 1979. tli 7 8

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TOLEDO ED130N COMPA N D^.VIS-BESSE NUCLEAR POWER STATIO:. UNIT ONE SUPPLEMESTAL INFORMATION FOR LER i:P-33-79-99 DATE OF EVENT: July 8, 1979 FACILITY: Davis-Besse Unit 1 IDENTIFICATION OF OCCURRENCE: Position Indication fcr Red 2 of Group 8 Inoperable Conditions Prior to occurrence: The unit was in Mode 3, with Pcwcr (L'T) = 0, and Load (Gross FME) = 0. Description of Occurrence: On July 8, 1979 at 1315 hours, it was discovered that the position indication on Rod 2 of Group 8 was inoperable. The actica stat (rent of Tech-nical Specification 3.1.3.3 (which requires that all safety regulating and axial power shaping control rods absolute position indication channels shall be operable and capa-ble of determining the control rod positions within i i  ;"T was not applicable, as the unit was in Mode 3 at the time of this occurrence. This report is being submitted as docuneatation of a componant 1silure. D e m gi.a :_i t . J ',,

• C=rc_cf Occurrence- Tha epparent cause of the ccrurronco has not been specifically found. The nost likely cause is that of a faulty reed switch within the position indicator tabe (component failure). Thic caused fluctua-tions of the absolute position indication signal for the rod.

The position indicator will be returned to the vendor for final determination of cause of failure. Analysis of Occurrence: There was no danger to the 1 ealth and saf ety of the public or to station personnel. The unit was shutdown in h>t standby, and the relative position and zone reference indications for the rod,were operable. Correc tive Action: On July 8, 1979, the positior. indicator tube f or Rod 2 of Group 8 was replaced with a rebuilt spare per Maintenance v:ork Order 79-2459 and tested per systan Surveillance Test ST 5013.03, " Control Rod Prcgran Jerification Test". The rod and position indicator were returned to operaticn on July 10, 1979. Failure Data: There have been several previously reported position indicator failures due to component failure of the position indicator tube in Licensee Event Reports NP-33-78-02, NP-33-78-135, and NP-33-78-144. LER #79-072 516 OC5}}