ML20085L802

Ro:On 710803,following High Temp Isolation Signal in Offgas Sys,Mechanical Vacuum Pump Automatic Isolation Valve AO-5402-A Observed Not Fully Closed.Caused by Binding within Valve.Mechanical Stop Installed in Valve Operator

ML20085L802
Person / Time
Site:	Dresden
Issue date:	08/12/1971
From:	Hoyt H COMMONWEALTH EDISON CO.
To:	Morris P US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085L803	List: ML20085L802 ML20085L813 ML20085L826
References
NUDOCS 8311020495
Download: ML20085L802 (2)

Text

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( [. / Com monwealth Edison Company ONE FIRST N A T IO N A L PLA2A 4 C H I C A G O. BLLING85 w.. e.s, . Poli O F F IC E 80s 767 A C H I C A G O, 6 L L I N O 15 60690 Dresden Nuclear Power Station R. R. #1 Morris, Illinois 6C+50 August 12, 1971

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Dr. Peter A. Morris, Director .. I 6 Jg Division of Reactor Licensing U. S. Atomic Energy Connaission d " J,yp c.x.7; ' i.f/ y! Washington, D. C. 20545 Q g// TQS

SUBJECT:

LICENSE DPR 25, DRESDDI NUCLEAR POWER STATION UNIT #3, SECTION 6.6.B.2 0F THE TECHNICAL SPECIFICATIONS

Dear Dr. Forris:

This is to report a condition relating to the operation of the Station when, following a high temperature isolation signal i;. the off gas systen, it was observed that valve A0-5402-A (mechanical 1acuum pump automatic isolation valve) was not fully closed. Failure of this

         } valve to fully close rendered the mechanical vacuum pump incapable of jbeingisolatedonasignalofhighradioactivityasrequiredbyS;ction 3.8.B.1 of the DPR-25 Technical Specifications.

Problem - Investigation At 0815 hours on August 3,1971, the unit was at 550 ps:g and heating. Main condenser vacuum was being established. A high temperature signal in the off gas system initiated an automatic closure of the mechanical vacuum pump suction valves. Following the isolction signal, it was observed that rechanical vacuum pump suction valve A0-5402 A started but did not complete closure. The valve was then closed manually. The main steam isciation valves (MSIV's) were then closed and the 5402-A valve was inspeettd. Investigation revaaled that there was binding within jiha-yalve in the last two inches of the opening stroke. Apparently, the binding m.s sufficient to prevent closure of the valve using the air operator. Operation of the valve over the remainder of its stroke was normC.. YN

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8311020495 710812 DR ADOCK 0500024 . bQ2 jg [ < COPY SENT REGION e

Dr. Pster A. No a, Directer 2- Augu 12, 1971 As a temporary measure, a mechanical stop was installed in the valve operator to prevent the valve from opening the last tw, inches and consequently binding. Operability was then demonstratad - by repeated valve operation. Corrective Action , The operability of the valve, following the temporary installation of the mechanical stop, was desenstrated as mentioned above. The valve was then declared operable and plant heatup was resumed at 1:45 a.m. on August 4, 1971. At the first opportunity the valve will be disassembled and inspected to determine the cause of the binding. Sincerely,

                                                           .-{-! !, /. ,,,'_,p -

H. K. Hoyt ,e Superintendent HKH:LDB:ls 5 Y}}