ML19329B638

RO NP-33-77-02:on 770507,borated Water Added to Reactor Vessel to Raise Water Level to Install Incore Detectors. Caused by Leakage Through Demineralized Water Valve.All Core Operations Suspended

ML19329B638
Person / Time
Site:	Davis Besse
Issue date:	06/07/1977
From:	Lingenfelter J, Williams J TOLEDO EDISON CO.
To:
Shared Package
ML19329B556	List: ML19329B555 ML19329B638
References
NUDOCS 8002050753
Download: ML19329B638 (2)

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TOLEDO EDISON COMPA@t DAVIS-BESSE ITIIT ONE NUCLEAR POWER STATICN i -. SUPPLEMENTAL INFORMATION FOR LER NP-33-77-2 .

s DATE OF EVE';T: May 7, 1977 FACILITY: Davis-Besse Un't i 1 IDENTIFICATION OF OCCURRENCE: After an addition of boric acid and demineralized water to the vessel; analysis of vessel water showed a concentration of 1763 ppo B.

Conditions Prior to Occurrence: Plant in Mode 6 operation with reactor vessel s head off. Insertion of incore detectors was in progress. .

Description of Occurrence: In order to insert the incore detectors, demineralized water and concentrated boric acid were added to the RCS to raise vessel water level to the desired height. During addition of boric acid, a leaking deminera-lized water shutoff valJe (MU-39) caused dilution of the boric acid. The operators thought they were measuring and adding conc.entrated boric acid when, in fact, they were measuring a diluted mixture.

De'signation of Annarent Cause of Occurrence: This event has been determined to be caused by the demineralized water valve MU-39 leaking through. An inspection of the valve revealed that the valve operator was i= properly adjusted and would not allow the valve to completely shut.

v Analysis of Occurrence: Although boron concentration dropped to li63 ppm 3, K ettective cia not exceed .92 and the health and safety of the public or station

. .' personnel was not threatened. ._.

Corrective Action: Boric acid addition was begun immediately and continued until analysis of the RCS water showed a concentration in excess of 1850 ppm B. All core operations were suspended. Further action consisted of correcting MU-39 valve leak and post adjustment testing to ensure that valve no longer leaked.

Failure Data: No preiious similar events have occurred.

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