ML20084R813

AO 50-249/74-47:on 740927,waste Collector Filter Pressure Switch Taps B Failed During Backwash Cycle.Lines B Bumped & Jarred During Maint on Unit A.Failed Lines Isolated

ML20084R813
Person / Time
Site:	Dresden
Issue date:	10/04/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
723-74, AO-50-249-74-47, NUDOCS 8306150598
Download: ML20084R813 (2)

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Chicago,111inois S0690 BBS Ltr.#723-74 Dresden Nuclear Power Station R. R. #1 Morris, Illinois 60450

. October 4, 1974 E Q?

hf.00T9NE Mr. James G. Keppler, Regional Director -

4 Directorate of Regulatory Operations-Region III Z U. S. Atomic Energy Comission ElC

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799 Roosevelt Road Olen Ellyn, Illinois 60137 50-249 e 'id?8 8/

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SUBJECT:

REPORT OF AENORMAL OCCURRD;CE PER SECTION 6.6. A 0F THE TEmHCAL" '

SPMIFICATIONS.

PAILURE OF PRESSURE SWITCH INSTRU'G7P TAPS ON 2/3 RAIMASTE FILTER.

References:

1) Regulatory Guide 1.16 Rev.1 Appendix A

2) Notification of Region III of AEC Regulatory Operations Telephone Mr. F. Maura, 1320 hours0.0153 days <br />0.367 hours <br />0.00218 weeks <br />5.0226e-4 months <br /> on September 27, 1974 Telegram Mr. J. Keppler, 1320 hours0.0153 days <br />0.367 hours <br />0.00218 weeks <br />5.0226e-4 months <br /> on September 27, 1974 Report Number 40-249/1974-47 Report Date: October 4, 1974 Occurrence Date September 27, 1974 Facility: Dreedon Nuclear Fower Station, Morris, Illinois IDD7PIPICATION OF OCCURRENCE At approximately 2000 hours0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> on September 27, 1974, the pressure taps on "B" waste collector filter dome vent and dome drain lines were broken off resulting in spillage of contaminated water to the radwaste floor during the subsequent filter backwash.

CONDITIONS PRIOR TO OCCURRDICE At the time of the occurrence, Unit 2 was at 0 megawatts themal with the

. mode switch in the chutdown position. The "A" filter was out of service due to maintenance.

DESCRIPTION OP OCCURRDJCE The "B" waste collector filter precoure switch taps failed during the back-wash cycle. The failure uno discovered and reported by perconnel in the area at tha time. gfj

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s Mr. Jame3 C. Ktppler ber 4, 1974 DESIGNATION OF APPAR97P CAUSE OF OCCURRENCE (Design Deficiency)

An investigation into the problem revealed that during maintenance on the "A" unit, the "B" lines had been bumped and jarred to the point that failure occurred during initial operations of the backwash cycle.

ANALYSIS OP OCCURRDK:E The safety of the plant and public was not in jeopardy during the failure of 2/3 "B" radwaste filter pressure switch tapa. All water from the spillage was contained'in the radwaste floor drain system. All systems functioned nomally during the occurrence.

CORRECTIVE ACTION The imediate corrective action was to locate and isolate the failed lines.

The pressure switches will also be moved from the pipe to an instrument rack in order to reduce congestion in the arca and prevent possible recurrence of the event. This installation will also have an isolation valve in the line.

FAILURE DATA The failure occurred on the 3/8" diameter lines of pressure cwitches PSlB and PS2B.

There has been no previous failure record of these lines.

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