ML20084E048

AO 50-237/75-21:on 750416,freon Leak Rate Test on Standby Gas Treatment Sys Showed Leakage Rate Past Charcoal Cells Exceeded Tech Spec Limits.Caused by Ripped Sealing Gasket on Charcoal Cell.Torn Gasket Replaced & Cell Reinstalled

ML20084E048
Person / Time
Site:	Dresden
Issue date:	04/24/1975
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
267-75, 4746, AO-50-237-75-21, NUDOCS 8304130557
Download: ML20084E048 (2)

Text

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Oni Fers Nst onal Plaza. Chicago. Illinois Address R: ply to: Post Office Box 767 Chicago. lilinois 60690 BBS Ltr. #267-75 Dresden Nuclear Power Station R. R. #1 Morris, Illinois 60450 .

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Mr. James G. Keppler, Director Directorate of Regulatory Operation-Region III

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Glen Ellyn, Illinois 60137

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SUBJECT:

REPORTOFAEMORMALOCCURRENCEPERSECTION6.6.A0FTHETEENICALY SPECIFICATIONS FREON LEAKAGE 15

References:

1) Regulatory Guide 1.16 Rev. 1 Appendix A

2) Notification of Region III of U. S. Nuclear Regulatory Connission Telephone: P. Johnson, 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br /> on April 16, 1975 Telegram: J. Keppler, 1540 hours0.0178 days <br />0.428 hours <br />0.00255 weeks <br />5.8597e-4 months <br /> on April 16, 1975 Lpvc1, Lisera 50-237/1975-2i Report Date: April 23, 197$

Occurrence Date: April 16, 1975 Facility: Dresden Nuclear Power Station, Morris, Illinois' 60450 IDENPIFICATION OF OCCURRDJCE The Freon leak rate test performed on the "A" train of the Dresden Standby Gas Treatment System (SBGTS) on April 16, 1975 indicated that the leakage rate past the charcoal cells was 1.8%. This was in excess of the allowable limit of 1% leakage, as specified in Technical Specification number 4.7.B.1.b.(2).

CONDITIONS PRIOR TO OCCURRDICE 3

Both units 2 and 3 were in cold shutdown and no fuel moves were in progress.

Thus, the SBGTS was not required to be operable.

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88 DESCRIPPION OF OCCURRD;CE by l N

$$ The results of the routine semi-annual Freon leak test en the "A" train of the gO SBGTS indicated a leakage rate slightly greater than the 1% limit. The "A"

< train was innediately taken out of service and, even though reactor conditions did not require operability of the SBGTS, the "B" train was tested and proved Ou 'to be operable. .(The "B" train had passed its Freon leak test on 4/15/75).

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i c Mr. Jam:s G. Kspp O Avr11 24. 4975 Work request #4638 was initiated to inspect the "A" train charcoal cells to determine the cause of the leakage.

DESIGNATION OF AFPARENT CAUSE OF OCCURRENCE (Personnel Error)

Upon inspection of the charcoal cells, it was found that one of the twelve cells had approximately a two inch section of its sealing gasket ripped off and a few tears elsewhere along the gasket. Apparently, the gasket caught on the metal housing during installation in May 1974.and eventually ripped due to the pressure. This gasket failure was determined to be the cause of the excess leakage.

ANALYSIS OF OCCURRMCE The purpose of the Standby Gas Treatment System is to limit the release of radioactive material to the environment in the case of high airborne radioactivity levels in the reactor building. During recent operation. of the SBGTS, the iodine release rates have not exceeded the limits specified in the Technical Specifications, limits which are for continuous release and which do not endanger the health an! safety of the public. The release rates are based on measure =ents at the reint of release and are not based on any cla-culations which assume a certain SBGTS charcoal efficiency.

In the case of a design basis loss of coolant accident, the SBGTS is designed to reduce the airborne activity released to the environment from the primary cent

• Ont. B:::d en cl ule.tions in the I'CA'.l which awa a 99% CLGTS charcoal efficiency, the calculated thyroid dose to an individual at the site boundary will be at the : raw , 1/100,000 of the units specified in 10 CFR 100. With an actual charcoal efficiency of 98.2% of thyroid dose would still be well below 10 CIR 100 limits. Therefore, it is concluded that at no time was the safety of the public or plant personnel jeopardizegl.

CORRECTIVE ACTION The torn gasket was replaced and the charcoal cell reinstalled. The freon leak test was repeated on "A" train and gave satisfactory results. Care in the installation of the charcoal cells has been brought to the attention of the maintenance department and should eliminate this problem in the future.

The corrective action is considered complete and adequate and the "A" train has been returned to service.

FAILURE DATA ,

This was the first failure of this type on th'e Dresden Standby Gas Treatment System.

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'B. Stgphenson Superintendent BBS:RC:smp i l

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