ML20084L776

AO 50-237/1974-29:during Routine Monthly Surveillance, Pressure Switch PS-504C Setpoint Found High.Caused by Instrument Calibr Drift.Switch Reset & Will Be Precycled Later in Yr

ML20084L776
Person / Time
Site:	Dresden
Issue date:	07/25/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
References
531-74, NUDOCS 8305230713
Download: ML20084L776 (2)

Text

~

Comm  ::lth Edison Ona First . i.onal Flata. Chicsgo. liliners Address hipTy~iOost 0:fice Box 767 O'

Chicago, ilhnois S0630 BBS Ltr.#531-74 Oresden Nuclear Power Station r is Illinois 60450 A

1. ' % '\

July 25, 1974 E.5 0- 2 3 4 # k,

~

h.

W SD ,+

p- ggg3g ?M 9 7u--

Mr. J. F. O' Leary, Director ,' D

• g' e 7, . 2;[ / 'N Directorate of Licensing .

S U. S. Atomiic Energy Com: mission '

,i L" 6

Washington, P C. 20545

' g/ p3 {s,F

SUBJECT:

REPORT OF ABNOPFAL OCCURRENCE PER SECTION 6.6.B.1.a CF THE 12CHNICAL SPEC 171 CATI 0lM.

TURBI!E IST STAGE PHESSURE SCRAM INSTRtHEh"P DRIFT.

References:

1) Regulatory Guide 1.16 Rev.1 Appendix A 1 2) Notification of Region III of AEC Regulatory Operations Telephono: Mr. F. Maura, 1145 hours0.0133 days <br />0.318 hours <br />0.00189 weeks <br />4.356725e-4 months <br /> on 7/22/74 Telegram: Mr. J. Keppler, 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br /> on 7/22/74

3) Drawing Number H-12 Rcoort Number: 50-237/74-29 Report Date: July 25,,1974 Occurrence Date: July 20, 1974 Facility: Dresden Nuclear Power Station, Morris Illinois IDENTIFICATION OF OCCURREN_CE Pressure switch PS-504C was found to have a setpoing of 397 psi.

The purpose of the switch is to prevent a scram due. to a turbine trip when the reactor power Icvel is below 45%. This das been found to be equivalent to 395 psi first stago pressure.

CONDITIO:1 PRIOR TO OCCURPINCE Dresden Unit 2 was operating in the run mode at 721 HW. Routine monthly instrurnent surveillance was in progress.

DESCRIPTION OF OCCURRENCE During routine autvnillance of pressure switch PS-504C its set-point was found to be 397 psi.

\ l' B305230713 740725 PDR ADDCK 05000237

)' [' t ief")

S PDR '-

t'? 80,9- ,

PJPY SENr REGION ' ' .  !

l. _ l

7 f

W. J. F. C' Leary ly 25, 1974 ,

DESIGNATION OF APPARENT CAUSE OF OCCURRENCE nose instrument calibrations drift due to causes which are unknown at this time. . However, Barksdale factory believes the problem is caused by a lack of precycling before use.

ANALYSIS OF OCCURRENCE Switch PS-504C is one of four switches that provide 45% scram bypass., he remaining three switches operated below the 395 psi limit.

and therefore the system was operable at all tiuss.

CORRECTIVE ACTIONS We inumediate corrective action was to reset the switch to 382' psi. In addition, the setpoint target band which was previously 38515 psi was lowered to 38315 psi. His switch is included in a program now underway to precycle all Barksdale and Haletron switches of this type.

H is switch is due to be precycled later this year.

FATLURE DATA Switch PS-504C has had similar failures during June of 1973 (403 psi) December of 1973 (379 psi) and May of 1974 (401 psi). He switch is a Barksdale model 32T-A122SS with a range of 50-1200 psi.

Sincerely, N

. B. Stephenson Superintendent i j

BBS:WEH:do -

6 4

f A

t

..