ML17252A171

Report of A.O. Per Section 6.6.A of the Technical Specifications Isolation Condenser High Flow Sensor Setpoint Drift

ML17252A171
Person / Time
Site:	Dresden
Issue date:	08/15/1975
From:	Stephenson B B Commonwealth Edison Co
To:	Keppler J G NRC/RGN-III
References
Download: ML17252A171 (2)

Text

r, One F1rst--nal Plaza, Chicago, lll1no1s \* ::

e Commoa&alth Edison . _ .-*. Address Reply to: Post Office Box 767 Chicago, Illinois 60690 --

Nuclear Power Station 111-ft J; li(. R. #1 --____... __ BBS Ltr.#506-75 Morris, Illinois l.J August 15, 1975 1)fa). .

Mr.

G. Keppler, Reg+/-"onal Director Directorate of Regulatory Operation-Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137

SUBJECT:

REPORT OF A.O. PER SECTION 6.6.A OF THE TECHNICAL SPECIFICATIONS ISOLATION CONDENSER HIGH FLOW SENSOR SEIT'POINT DRIFTo

References:

1) Regulatory Guide Rev *. 1 Appendix A 2) Notification of Region III of U. s. Nuciear Regulatory Commission Telephone:

Mr._ P. Johnson,_

133(5"-1 hrs. on August 8, 1975. Telegram: J. Keppler, on August 8, 1975 * . : ,-3) Drawing Number M..,.359 12E2506 . Report Number:;P 50-249/75--34 Report D:=i-te:

August 13, 1975 Occurrence Date: August 7, 1975 Facility:

Dresden Nucle.9,r Power Station, Morris/-Illinois 60450 IDENTIFICATION OF OCCURRENCE An instrument setpoint drift of isolation condenser high flow switches 1349A & B . occurred on Unit-3. CONDITIONS PRIOR TO OCCURRENCE Unit-3 was in the cold shutdown mode for a refueling outage. DESCRIPTION OF OCCURRENCE At approximately 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br /> on August 7, 1975, during routine sur.yeillance of ferential

• switches 1349A & B, both switches were found with setpoints above the limit of 32" H20. * -Switch 349A was -fountl a:t* 3611 H20, and -switch 1349B at 38.5" H20. . DESIGNATION OF APPARENT CAUSE OF OCCURRENCE No definitive cause can be established at this time. Surveillances have not been performed on the switches during the outage. Review of prior surveillances has indicated that the setpoints of these switches are subject to a slow drift. AUG 1 8 1975 8'107 .. .ANALYSIS OF OCCURRENCE Switches*1349A

& B setpoj.nts during the routine surveillance conducted

• on __ March 11,. 1975, days before Unit-3 was for refueling.

It is considered unlikely that the switches' points exceeded Tech. Spec. limits whi;I.e the unit was operating, given the 150-day span between surveillances.

Analysis of the past performance of the switches indicates that setpoint drift occurs very gradually.

The phenomenon of decreasing instrument setpoint values extended outages was noted on Barksdale pressure switches (report no. 50-237/75-17 dated March 27, 1975). Based on the demonstrated reliability of switches 1349A & B when checked routinely during operation, it is concluded that this occurrenc*i?

in, no way endangered plant personnel or the _general public. CORRECTIVE ACTION The switches were Action to prevent recurren9e wi:J.l be __ .taken :should specific problei;ns identified.

FAILURE DATA .< .... Dresden has had a history of instrument drift on all types *of insi;rumentation.

A program including training of personnel and reconditioning and replacement of switches has been underway for some time. Switches 1349A & B were inspected rebuilt irl October, 1974. Pressure sensors 1349A & B are Barton model 288 dif-. -ferential pressure switches with a range of l0011H2o. BBS : WEH ea ,_B. B. Stephenson Superintendent