ML19329B630

RO NP-32-77-03:on 770528,during Recalibr of RCS Pressure Bistables,Pressure Signal Rose & HV DH11 Stroked Closed, Tripping Decay Heat Pump.Caused by Inadequate Calibr Procedure.Personnel Reset Bistable & Reopened HV-D11

ML19329B630
Person / Time
Site:	Davis Besse
Issue date:	06/11/1977
From:	Batch S, Lingenfetter J TOLEDO EDISON CO.
To:
Shared Package
ML19329B551	List: ML19329B550 ML19329B630
References
NUDOCS 8002050746
Download: ML19329B630 (2)

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[jg[ Pump. HV-DHil was re-opened. Decay Heat Pump restarted and 3000 gpa fle r s ee a

[ojg i to the RCS re-established. NP-32-77-3.  !

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TOLEDO EDISON COMPA!N DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION SUPPLEMENTAL INFORMATION FOR LER NP-32-77-3 DATE OF EVENT: May 28, 1977 FACILITY: Davis-Besse Unit 1 -

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IDENTIFICATION OF OCCURRENCE: 'While recalibrating SFAS Channel 4, a simulated pressure signal rose above setpoint 433 psig; HV-DHil stroked closed and Decay Heat Punp 1-2 tripped causing a situation in violation of Technical Specifica-

tion 3.4.1.

I Conditions Prior to Occurrence: The plant was in Mode 5. Power (MRI)0 - Power

! (MWE)D. RCS Pressure less than 200 psig.

Description of Occurrence: At 0045 Hours, May 28, 1977, an I&C mechanic was i workfag on SFAS Channel 4, recalibrating the RCS pressure bistables. As the simulated pressure rose, KV-DH11 stroked closed at its setpoint of 433 psig.

Oper.stions immediately tripped decay heat pump. ,

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\s_ / Designation of Anoarent Cause of Occurrence: This event has been determined to have been caused by'a procedural inadequacy in Maintenance Instruction I 1-1701 Analysis of 'ccurrence:

O The closing of DH 11 and subsequent de-energi:ation of Decay Heat Pump 1-2 caused decay heat flow to be less than 2800 gpm for three minutes. Since flow was not needed for decay heat removal and Decay Heat Pump l-2 was re-started, no threat resulted to the health and safety of the public or station personnel.

Corrective Action: I&C mechanic i= mediately reset the bistable, operator re-opened HV-DH11, restarted Decay Heat Fump and re-established 3000 gpm flow to RCS. Maintenance Instruction I l-1701 was modified to defeat the DH 11 valve logic by utilizing a jumper across the ' interlock.

Failure Deta: DH 11 was inadvertently closed on May 27,1977 (LER NP-32-77-2) ,

but the cause was a wiring installation error, not a procedure error as caused this occurrence.

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