ML20090E168

AO 50-220/74-12:on 740824,during Surveillance Testing,One Barton Instrument Used in Drywell High Pressure Reactor Protection Sys Drifted High.Caused by Setpoint Drift. Switch Recalibr

ML20090E168
Person / Time
Site:	Nine Mile Point
Issue date:	08/28/1974
From:	Schneider R NIAGARA MOHAWK POWER CORP.
To:	Skovholt D US ATOMIC ENERGY COMMISSION (AEC)
References
9074, AO-50-220-74-12, NUDOCS 8303110628
Download: ML20090E168 (4)

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NIAGARA MOHAWK POWER CORPORATION NfAGAftA MOHAWK 50-2202-300 ERIE DOut.E'f ARD. WEST SYRACUSE. N, Y.13 202

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-i SEP- n 19k \G Mr. Donald J. Skovhott N$ 4?: ca$. .f#I'W.-

Assictant Dircator for Reactor Operations ' G' > LONl.'ii!, /.%

Division of Reactor Licensing

• United States Atomic Energy Conenission Washington, D.C. 20545 ,

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Dear Mr. Skovholt.- .

In accordance with Technical Specifications 1.13d for Nine y Mile Point Unit 1, the enclosed Abnormal l Occurrence Report is submitted. This . report is in accordance uith the format set forth in Regulatory Guidelinc.1.16. This ocburrence was reported to EO:I on August 26, 1974.

Very truly yours, Original Signed by R.~R. Schneider.

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R.R. Schneider ^

s Vice Presidant - Electric Operations TJD: con .

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. ABNORMAL OCCURRENCE REPORT I

'1. Report No. 50-220/74-12 2a. Date August 26, 1974 2b. Occurrence Date August 24, 1974

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3. Facility Nine Mile Point Unit 1 t

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4. Identification of Occurrence Set point drift on Drywell High Pressure

5. Conditions Prior to Occurrence 2

Unit I was at steady state 98% power -

6. Description of Occurrence -

1 During routine surveillance testing on August-24, 1974'at approximately

. 1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br />, one Barton Instrument used in the Drywell High Pressure-l (3.5 psig) RPS was found to have drifted .015 psi higaer than required.

- The surveillance test consists of operating the switch thru regulated (mercury manometer) air signal to the' sensor. The three other Barton instruments in the two trip systems actuated within the prescribed j' s,et point.

7. Designation of Apparent Cause of the Occurrence Set point drift

8. Analysis of Occurrence The high drywell pressure trip requires a one out of two twice ~1ogic.

to actuate the protective function. One channel in.each' trip. system would have actuated at the required setpoint and thus produced the

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protective function. Therefore, no' hazard would have been presented to the general public or statien had' the protective function-baen'

required.

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9. ' Corrective' Action l

The immediate corrective action involved recalibration ofLthe Barton ,

switch. The normal valveof setpoint'is 3.5_+;.053 psig. :A modifica--

! tion'had been made-to<the Barton switch. A new1uwitch plate locking

device to prevent setpoint drift had been. installed. L (AOR 74-8) .

This' modification was installed to"minimizef set point drift in -this '

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model of Barton-instruments.and isl currently being' evaluated to'its. '

usefulness.

10. - IFailure Data-1 Previous setipoint7drift occurred on May;31, 1974 - AOR'74-8~

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1. Report No._

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• QD-220/74-12 f

I 2a. Date August 26, 1974 w

C 2b. Occurrence Date August 24,194 '

Ii 3. Facility Nine Mile Point Unit 1 .K.; $

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4. Identification of Occurrence b

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g Set point drift on Drywell liigh Pressure Qgf E 5. Conditions Prior to Occurrence gg-

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mr Unit I was at steady state 98% power N TI1 w

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E During routine surveillance testing on August 24, 1974 at approximately E

1000 hours0.0116 days <br />0.278 hours <br />0.00165 weeks <br />3.805e-4 months <br />, one Barton Instrument used in the Drywell Iligh Pressure R{Jf.

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E (3.5 psig) RPS was found to have drifted .45 psi higher than required. '% (.'

th The surveillance test consists of operating the switch thru regulated d.%

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(mercury manoccter) air signal to the sensor. The three other Barton instrur,cnts in the two trip syster:s actuated within the prescribed

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set point.

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- 7. Desir. nation of Apparent Cause of the Occurrence a-T d N:

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Set point drift w ..

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L The high drywell pressure trip requires a one out of two twice logic  :

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g te actuate the protec'ive function. One channel in each trip system 3 7' g woula have actuated at the required setpoint and thus produced the a, 7

E prot ective funct ion. 'iherefore, na hazard would have been presented e E.

gr to 'he general public or station had the protective function been

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required.

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9. Corrective Action 4 j.7.$

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F_ The immediat .orrective action involved recalibration of thc Barton f[. -b

switch, lhe normal valve of setpoint is 3.5 + .053 psig. A modifica-

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L tion had been made to the Barton switch. A new switch plate locking  ? R,i . -

7 device to prevent setpaint drift had been installed. (AOR 74-8) .

F This nodification was installed to minimize set point drift in this f[.!(

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A F model of P,arton instruments and is currently being evaluated to its j.

a usefulness.

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10. Failure Data ~~

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Previous set point drift occurred on May 31, 1974 - AOR 74-8 7

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1. Report No. - -

2a. Date_ 0 '

O ^us se 2s im 2b. Occurrence Date August 24, 1974

3. Facility Nine Mile Point Unit 1 ..

4. Identification of Occurrence .$

g.c Set point drift in RE-18C Rx Lo-Lo-Lo Level f .

& 3 Conditions Prior to Occurrence

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IJnit at steady state 98% full load jy. [

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6. Description of Occurrence F.;

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During routine surveillance testing Barton instrument 288-3471 @i provided the desired trip action sooner than required. M 73

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7. Designation _of Apparent Cause of the Occurrence W M--

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Set point drif t. W.Q

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8. Analysis of Occurrence i f,-[

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Each of two instruments provide inputs to one instriment channel in kg:]

each trip systes. RE-18C provided a trip in system 12 at 124.5" p"Of' instead of 128 + 2.6". (Technical Specifications 3.6.2) The signals for initiating automatic blowdown differ from other initiating signals in that only one of the two trip systccs is required to _

start blowdown. This is due to the requirement that auto:ratic [j' depressurization be prevented unicss A.C. power is available to ,,l.d the ECCS. In order to cause a trip both instrument channels in oither trip system must be energized. With RE-18C tripping sooner pk ,

than required, the desired action af required would still have - -

occurred at the e..tablished set point. The*efore, no hazard was

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g presented to the health and general welfare ot the public.

9. Corrective Action .

The imruediate correction action was to recalibrate the instrument to the required ser point.

10. Failure Data Previous set point drift on this instrument occurred on Oct. 21, 1972.

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