ML20154L509

Forwards Repts & Safety Evaluations Re 860204 & 06 Instrumentation Monitor Actuations During Plant Shutdown for Repair of Packing Leak on Main Steam Line Drain Valve & Startup

ML20154L509
Person / Time
Site:	Dresden
Issue date:	03/03/1986
From:	Scott D COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20154L512	List: ML20154L509 ML20154L570
References
86-154, CAL-85-04, CAL-85-4, NUDOCS 8603110502
Download: ML20154L509 (6)

Text

. Commonwealth Edison

• Dresden Nuclear Power Station R.R. #1 Morris, filinois 60450 Telephone 815/942-2920 March 3, 1986 DJS LTR: 86-154 James G. Keppler Regional Administrator Director of Inspection and Enforcement Region III U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137 ,,

Reference:

DJS Ltr. 86-80 to J. G. Keppler from D. G. Scott, dated February 4, 1986.

Dear Sir:

This letter is in reference to the Conformatory Action Letter 85-04 regarding the Main Steam Line Snubber Monitoring System for Dresden Unit 2. Item 2 of this Confirmatory Action Letter requires a verbal notification to Region III within 2 working days followed by a written report and safety evaluation within 30 calendar days.

Two occurrences have been identified during this reporting period:

Occurrence #31 Notification made to J. Harrison by G. Smith on February 5, 1986.

Occurrence #32 Notification made to D. Danielson by J. Achterberg on February 10, 1986.

The written reports and safety evaluations when required for these occurrences are attached.

Sincerely, TV D.p. Scott Station Manager Dresden Nuclear Power Station DJS:JW:hjb Enclosure cc: J. Almer Q-2, J. Welch J. Achterberg J. Williams File / Misc.

File / Numerical 31gggg2ggg%y7 og IdAR 5 586 S

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Occurrence #31

, On February 4, 1986 at 0353, Unit 2 was at 26.5% (670 MWt) power and a load of 180 MWe decreasing 200 MWe/hr to hot standby for repair of a packing leak in a steam line drain valve. During the unit shutdown, several instrumenta-tion monitor actuations were noted. After reviewing the sequence of events during shutdown, it was determined that the snubber instrumentation triggers occurred during the insertion of the source range monitors (SRM's) and intermediate range monitors (IRM's) . These traces were compared and similari-ties noted to those obtained during testing on June 3, 1985, which is described in Occurrence #5. That occurrence was attributed to electrical interference generated from the movement of SRM's and IRM's. Since the unit shutdown progressed normally, no steam line transients were identified and the source of these traces have been attributed to specific plant evolution (SRM/IRM movement), the safety significance of this event is minimal. -

Occurrence #32 On February 6, 1986, following the repair of the packing leak on the main steam line drain valve, an orderly startup was commenced. Unit 2 was placed in the run mode at 2131 on February 7, 1986 and synchronized to the system grid at 0244 hours0.00282 days <br />0.0678 hours <br />4.034392e-4 weeks <br />9.2842e-5 months <br /> on February 9, 1986.

During the unit startup several snubber instrumentation monitor actuations were noted. After reviewing the sequence of events during the startup, it was determined that the snubber instrumentation triggers occurred during the with-drawal of the source range monitors (SRM's) and the intermediate range monitors (IRM's). These traces were compared and similarities noted to those obtained during testing on June 3, 1985 which is described in Occurrence #5. That occurrence was attributed to electrical interference generated from the move-ment of the SRM's and IRM's. Since the unit startup progressed normally, no steamline transients were identified and the source of the traces have been attributed to a specific plant evolution (Smi/IRM movement), the safety significance of this event is minimal.

On February 24, 1986, notification was made by telephone, as required by the Confirmatory Action Letter, that on February 21, 1986 the strain gage (SG) associated with snubber #51 2nd the linear variable displacement transformer (LVDT) associated with snubber #50 were taken out of service for preliminary testing and calibration of the OPTIM Megedec Data Aquisition system. The C main steam line (MSL) has three monitored snubbers (44, 50, 51). The LVDT associated with snubber #50 and the SG associated with snubber #51 were chosen for testing of the new monitoring system because they are located on the C MSL. The C MSL still has sufficient snubber monitoring since the LVDT on snubber #51 and the SG on snubber #50 located at the same node on the MSL are operable. The third monitored snubber #44 allows verification of any transien.s a noted on C MSL during the out of service period. Taking these particular instruments out of service for testing and calibration reduces the safety significance because the possibilities of transients going undetected are minimized.