ML20056B682

Ro:On 711124,trip Setting of ECCS Valve Opening Permissive Switch Ps 2-3-52B Found Below Required Setting Limits.Caused by Lack of Setpoint Locking Device.Locking Device Installed

ML20056B682
Person / Time
Site:	Monticello
Issue date:	12/21/1971
From:	Mayer L NORTHERN STATES POWER CO.
To:	Morris P US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 9102080344
Download: ML20056B682 (2)

Text

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'1 STATES POWER COMPANY 1.'

NORTHERN  :

M I N N E A PO W S. MlN N E S OTA 9 5 4 01 $

December 21, 1971 &  %

{p k Dr. Peter A Morris, Director w '#

Division of Reactor Licensing United States Atomic Energy Commission Q T(pg. g h %-q D [7 Washington, D C 20545 v), . -e 7

Dear Dr. Morris:

N MONTICELLO NUCLEAR GENFRATING PLANT Docket No. 50263 License No. DPR-22 Failure of ECCS Valve Opening Pemissive Switch Plant A condition has occurred recently at the Monticello Nuclear 6 C 1Generating of the which we interpret to be reportable in accordance with Section 6. . .

Technical Specifications.

of this event.

i Summary of Occurrence _ l t

On November 24, 1971, while perfoming a regularly scheduled surveillance itchtes

1. 1,,

the trip setting of ECCS Valve Opening permissive switch PS 2-3-52B, sw f 2 450 psig.

was found to be at 407.5 psig, 42.5 psi below the required setting o i

An investigat!on revealed that the instrument lacked a setpoint The locking de/ ice" locking" d  ;

l a modification recommended by the instrument manufacturer. 60 peig.

was immediately installed, ano the instrument calibrate

" locking" device. h Surveillance testing will be performed for all modified switches at twice t e forming normal properly.

frequency until we gain confidence thatl cement, the instrumen erating policy used to evaluate instrument performance following rep aThis policy d

setpoint change, or other problems detected during testing d

A Significant Operating Event report has been writtnn for this for review occurrence during j will bt made available to the Region III Compliance ,

Inspector m .

his next visit.

Yours very truly, 4

A ,

[f L 0 Mayer / DEC 2% b g

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Director of Nuclear Support Services

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13 M-G It has been an established Practice to Operate the No. ,

set weekly to demonstrate its availability to the essential {

rrene of this type of inci j systems. To prevent r strainer in question wi - -

' dent at which time an appropriate l p eti ter a f r the traine will be determined based on the results of that inspection. g

~f view l' This incident is not significant from a safety pois guration }

s ince Unit No. 1 had been in the cold, refueling ec.-

at the time and the station batteries were capable or supplying all essential loads for eight hours, which would have provided more than ample time to effect the corrective measures outlined previously in the event off-site power had not been available.

Our Nuclear Facilities Safety Committee has reviewed the circumstances related to this incident and concurs in the remedial measures described herein.

Very truly yours, n '

4 W a- 7

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