ML20082B136

Interim Deficiency Rept Re Premature Resetting of Automatic Digital Load Sequencer Sys.Initially Reported on 831004. Caused by Electric Noise Generated by Externally Located Components.Design Change Issued.Final Rept Forthcoming

ML20082B136
Person / Time
Site:	Fermi
Issue date:	11/11/1983
From:	Wells D DETROIT EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
10CFR-050.55E, 10CFR-50.55E, EF2-65293, NUDOCS 8311210019
Download: ML20082B136 (2)

Text

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Donald A. Wells

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Edison =000 Seccind Avenuene-November 11, 1983 EF2-65293 Mr. James G. Keppler, Regional Administrator Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137

Subject:

Report of 10CFR50.55(e) Item on Premature Resetting of Automatic Digital Load Sequencer System (ADLSS) (#104)

Dear Mr. Keppler:

On October 4,1983, Detroit Edison's Mr. J.E. Durkin, Quality Engineer - Construction Quality Assurance telephoned Mr. J. Konklin of NRC Region III to report on a problem with premature resetting j

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of the Automatic Digital Load Sequencer System (ADLSS) at the' Fermi 2 site.

During pre-operational testing, the ADLSS reset before completing its full cycle. This was probably caused by electric noise generated by the externally located components and induced into the low voltage sequencer logic wiring associated with the sequencer reset circuit..

The wires carrying 120 and 130V were tightly bundled with the low voltage logic wires into one harness and routed through the entire

!cngth of the panel.

The presence of electric noise of sufficient voltage level and frequency range to interfere with the intended operation of the ADLSS was confirmed by recording and analysis at various panel locations.

The vendor, Vitro Laboratories, has been contacted regarding this problem. They have not encountered, nor been notified of, any premature resetting occuring with any other unit.

Edison Engineering has issued a Design Change'to correct the pre-mature resetting of the ADLSS by retraining and regrouping the AC 4

and DC wiring within the panel unit, and shield).ig with mylar magnetic tape.

8311210019 831111 PDR ADOCK 05000341 S PDR f (

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Mr. James G. Keppler, Regional Administrator November 11, 1983 EF2-65293 Page 2 The safety implication resulting from the premature reset of the ADLSS would be inhibiting operation of some of the equipment re-quired for the safe shutdown of the reactor. The number and type of equipment inhibited depends at what stage of sequencing cycle the erroneous reset occurs. Somewhat mitigating the consequences of the above is that the start of the RilR or Core Spray Pumps do not depend on the sequencer operation. These systems have their own start logic. It is also possible to power the remaining loads by manual operation.

In the October 4, telephone call it was stated that the load shed-ding originated by the ADLSS may not function in case of a LOCA following a Loss Of Power (LOP). Upon further investigation, Edison has determined that premature reset of the ADLSS would not affect the logic provided in the ADLSS equipment for shedding loads from the engineered safety feature busses in case of a LOCA following a LOP.

Another report on this item, either interim or final, will be sent when further information is available. If you have questions con-cerning this matter, please contact Mr. G.M. Trahey, Assistant Director - Project Quality Assurance.

Very truly yourg, A

DAW /EllN/cp cc: Mr. Richard DeYoung, Director Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Washington, D.C. 20555 Mr. Paul Byron, Senior Resident Inspector U.S. Nuclear Regulatory Commission 6450 North Dixie liighway Newport, Michigan 48166 l