ML20209D442

Forwards Written Rept for Occurrence 35 Re Main Steam Line Snubber Monitoring Sys,In Response to Confirmatory Action Ltr 85-04

ML20209D442
Person / Time
Site:	Dresden
Issue date:	05/29/1986
From:	Scott D COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
86-368, CAL-85-04, CAL-85-4, NUDOCS 8609090302
Download: ML20209D442 (2)

Text

~

v J

Commonwealth Edison Dresden Nucle;r Pow:r St1 tion 0-#7

@ Telephone 815/942-2920 R.R #1 Morris, Illinois 60450 May 29, 1986 DJS LTR: 86-368 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.86-281 to J. G. Keppler from D. J. Scott, dated April 21, 1986.

Dear Sir:

This letter is in reference to the Confirmatory 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.

One occurrence has been identified during this reporting period:

Occurrence #35 Notification made to D. Danielson by J. Williams on May 1, 1986 The written report and safety evaluation for this occurrence is attached.

Sincerely, DLt D. . Scott l Station Manager Dresden Nuclear Power Station DJS:JW:hj b l Enclosure cc: J. Almer 1 l

J. Welch l l J. Achterberg J. Williams File / Misc.

File / Numerical

?

8609090302 860529 l gDR ADOCK 0500 7 MAY 3 0 IW6 h

. . . __ .. . . . . . ... . . - . ~ . . - . . . .-

}

P 8 l0ccurrence #35 On April 30, 1986, at 1153 hours0.0133 days <br />0.32 hours <br />0.00191 weeks <br />4.387165e-4 months <br />, Unit 2 was operating at a steady power l 1evel of 95.6% (2413 MWT) and a load of 800 MWe when the Strain Gauge (SG) associated with snubber #52 exhibited two negative and one positive spikes of -20 kips, +17 kips and -30 kips within three milliseconds. Occurrences nearly identical to this one occurred on May 1, 1986, at 0540 hours0.00625 days <br />0.15 hours <br />8.928571e-4 weeks <br />2.0547e-4 months <br /> and 0632 hours0.00731 days <br />0.176 hours <br />0.00104 weeks <br />2.40476e-4 months <br />. Similarly the unit was at a steady power level of 97.5% (2462 MWT) and a load of 800 MWe during both of these trips.- It was discovered through subsequent investigation that as installed, the weight of the cables had caused the connection between the field cable and the megadac to loosen.

As corrective action all the field cables have been secured and trained in such a manner as to preclude any recurrence of this type. Since no abnormali-ties or unusual steam line transients were identified and the source of the traces have been identified and corrected, the safety significance of this event is minimal.

In addition, two triggers on May 1, 1986, at 0525 and at 0825 were identified as radio noise. These traces were compared and similarities noted to traces generated during preliminary testing of the megadac. As corrective action the 1- Operating Department was informed of the magadac's sensitivity to radio trans-mission inside the equipment building. Since no abnormalities or unusual i steam line transients were identified and the source of the traces were identified, the safety significance of this event is minimal.

1 1

4 i

I i

I i

i l

1 l

1 J