LD-84-063, Part 21 Rept Re Evaluation & Corrective Action for Excessive Setpoint Drift in Some Potentiometers in Auxiliary Feedwater Actuation Sys Cabinet at St Lucie Unit 2 & Plant Protection Sys Cabinets at Palo Verde

Part 21 Rept Re Evaluation & Corrective Action for Excessive Setpoint Drift in Some Potentiometers in Auxiliary Feedwater Actuation Sys Cabinet at St Lucie Unit 2 & Plant Protection Sys Cabinets at Palo Verde

ML20107N147
Person / Time
Site:	Palo Verde, Saint Lucie, 05000000
Issue date:	10/26/1984
From:	Scherer A ABB COMBUSTION ENGINEERING NUCLEAR FUEL (FORMERLY
To:	Baer R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE)
References
REF-PT21-84-533-000 LD-84-063, PT21-84-533-000, NUDOCS 8411140419
Download: ML20107N147 (2)

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C-E Power Systems Tel. 203/688-1911 Combustion Engineering. Inc. Telex: 99297 l 1000 Prospect Hill Road l

Windsor, Connecticu' 06095 POWER M SYSTEMS October 26, 1984 LD-84-063 Mr. Robert L. Baer, Chief Division of Emergency Preparedness and Engineering Response Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, D.C. 20555

Subject:

Excessive Drift of Setpoint Potentiometers

Reference:

C-E Letter LD-84-050, A. E. Scherer to R. L. Baer, dated September 10, 1984

Dear Mr. Baer:

In the reference letter, Combustion Engineering sumarized the evaluation and corrective action taken regarding the excessive setpoint drift in some potentiometers in the Auxiliary Feedwater Actuation System (AFAS) cabinet at St. Lucie 2 and the Plant Protection System (PPS) cabinets at Palo Verde. This letter provides additional information on our evaluation with respect to other plants and clarifies the implication, in the reference letter, that only one production batch was involved.

In the evaluation of the St. Lucie 2 excessive setpoint drif t (several hundred millivolts), it was determined that the problem with the subject ootentiometers would become apparent shortly af ter initial use of the potentiometers and would be detected during startup testing or routine surveillance checks. It was concluded, therefore, that potentiometers from earlier production batches, which previously had been installed at other plants (ANO-2, SONGS-2/3, Waterford-3), did not have a similar defect.

For potentiometers from production batches subsequent to that for St. Lucie 2, testing has been performed. Setpoint drift in potentiometers for the WPPSS-3 PPS were within design specifications. For the WPPSS-5 PPS, four potentiometers showed drift slightly greater (a few millivolts) than design specifications and were replaced. Testing is also being done for potentiometers installed in the three Palo Verde PPS cabinets. Twelve potentiometers on Unit 1 exhibited drift slightly greater than the design specification and were replaced. Test results for Unit 2 will be evaluated, fM '

8411140419 841026 PDR ADOCK 05000 s  ;

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Mr. Robert L. Baer LD-84-063 0ctober 26, 1984 Page-2 with any needed potentiometer replacements expected to be completed in 1984.

For Unit 3, setpoint drifts were within specification.

If you would like to discuss .the above information, please contact me or Mr. S. E. Ritterbusch of my staff at (203) 285-5206.

Very truly yours, N db A. E. Sch rer Director Nuclear Licensing AES:js -

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