ML20238E772

Part 21 Rept Re Special high-potential Withstand Tests on Number of Installed 14 Silicone rubber-insulated Single Conductor Cables.Initially Reported on 870904.Evaluation of Silicone Rubber Cable Continuing

ML20238E772
Person / Time
Site:	Sequoyah
Issue date:	09/10/1987
From:	White S TENNESSEE VALLEY AUTHORITY
To:	James Keppler NRC OFFICE OF SPECIAL PROJECTS
References
REF-PT21-87, REF-PT21-87-159-000 PT21-87-159, PT21-87-159-00, NUDOCS 8709150193
Download: ML20238E772 (5)

Text

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v-TENNESSEE VALLEY AUTHORITY CHATTANOOGA. TENNESSEC 37401 6N 3BA Lookout Place l~

l September 10, 1987 y,

b, Mr. James G. Keppler, Director Office of Special Projects U.S. Nuclear Regulatory Commission 4350 East-West Highway EWW 322 Bethesda, Maryland 20814

Dear Mr. Keppler:

SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 - DOCKET NOS. 50-327 and 50-328 -

FACILITY OPERATING LICENSES DPR 72 AND 77 - PRELIMINARY 10 CFR 21 REPORT'ON SILICONE RUBBER-INSULATED CABLES TVA has conducted special high-potential withstand tests on a number of installed No. 14 silicone rubber-insulated single conductor cables. As of this date, 9 of 66 tests of cables have not met the environmental qualification acceptance criteria of 240 volts per mil of insulation.

Cables from two of the three vendors that supplied this type of cable to TVA are involved.

TVA has conducted laboratory tests on cables from each vendor and has been unsble to determine the nature or cause of this condition.

However, these laboratory tests did indicate that significant decreases in insulation wall thickness result from lower than expected impact forces. The level of impact force which results in such decreases may be caused by damage occurring during manufacturing. shipping, or handling.

Cables from all three vendors were tested in the laboratory and evidenced similar reductions in wall thickness.

As a result, a determination has been made that this problem is reportable pursuant to the requirements of 10 CFR 21.

As you know, I received a September 4, 1987 briefing on the potential problem.

Subsequently, I gave you a verbal report by telephone that day.

In addition, on September 5, 1987, R. L. Gridley of my staff gaue a verbal report by telephone to Dr. J. Nelson Grace, Regional Administrator of NRC Region II.

8709150193 870910 PDR ADOCK 05000327 f1 S

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'\\g An Equal Opportunity Employer

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_Nr.~ James G. Keppler September 10, 1987 u

The enclosed preliminary report contains' additional information about this' matter. An extension to September 10, 1987 for submittal of this report was discussed with and approved by you on September 9, 1987. TVA is providing this report before completion of further tests and evaluation in order to keep the NRC fully apprised of the situation.

TVA will submit a further report upon completion of the additional tests'and evaluation.

Very truly yours, TENNESSEE VALLEY AUTHORITY 5.CL d u S. A. White Manager of Nuclear Power Enclosure cc (Enclosure).:

U.S; Nuclear Regulatory Commission Region.II-Attn:

Dr. J. Nelson Grace, Regional Administrator 101 Marietta St., NW, Suite 2900

-Atlanta, Georgia 3032,3 U.S. Nuclear Regulatory Commission

.Sesion'II

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Attn:

Mr. G. G. Zech, Director of TVA Projects 101 Marietta St., NW, Suite 2900 Atlanta, Georgia 30323 (t

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f ENCLOSURE j

SEQUOYAH NUCLEAR PLANT l

PRELIMINARY REPORT j

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SILICONE RUBBER-INSULATED CABLES 1

1 Nature of Defect and Cause t

As a result of the nonconformances of three silicone rubber-insulated single conductor No. 14 cables identified during special high potential tests, subsequent testing was initiated by TVA on silicone rubber-insulated cables installed at the Seguoyah Nuclear Plant (SQN). The subsequent testing i

identified three additional nonconformances each of AIW Corporation and I

Rockbestos conductors. The sample population of Anaconda conductors did not j

experience any failures. TVA has now identified a tota) of 9 nonconformances j

out of 66 tested conductors. To date, TVA has been unable to idertify a definitive cause for these nonconformances. TVA has concluded that the

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3 performance of silicone rubber-insulated cables is significantly different than expected. In addition, the performance of silicono rubber-insulated cables is significantly different from other cables at TVA of which 923 tests were just completed with no failures.

TVA authorized laboratory testing of silicone rubber-insulated cables, and this testing indicated that significant decreases in insulation wall thickness result from lower than expected impact forces. The level of impact force which results in such decreases may be within that which could possibly occur during (1) manufacturing operations following the factory high potential withstand test. (2) handling at the manufacturer, (3) shipping, (4) receipt / storage by TVA, or (5) the installation process. TVA has, however, been unable to consistently correlate this data to the nonconformances identified.

These cables are manufactured by American Insulated Wire (AIW) Corporation, 36 Freeman Street, Pawtucket, RI 02862; Anaconda-Ericsson (Continental),

P.O. Box 1863, York, PA 17405; and the Rockbestos Company, P.O. Drawer 1102, New Haven, CT 06504.

The determination that a reportable condition may exist was reached on September 4, 1987.

Ertort of Safety Hazard A nonconformance of the cable at voltages below that accepted by the industry to demonstrate insulation integrity during equipment qualification testing may indicate the inability of the cable to perform its intended function under design basis accident conditions. The inability of these cables to perform as designed could create a substantial safety hazard.

Silicone rubber-insulated cables are used in low voltage power and control circuits (both safety and nonsafety related) inside the reactor containment buildings of SQN units I and 2.

These cables have also been utilized in limited applications in other areas of these two units.

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i l Number of Identical Components in Use There are approximately 252 silicone rubber-insulated cables which requ(re qualification under the requirements of 10CFR50.49, installed inside thd..

containment of SQN unit 2.

It is expected that a similar number exists'faside the containment of SQN unit 1.

I-I Location of Components J

The silicone rubber-insulated cables at SQN are located primarily insid'e'!the reactor containment buildings in units 1 and 2.

These cables have als4;been utilized in limited applications in other areas of these two units.

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Corrective Action and Recurrence Control Taken or To Be Taken TVA will continue to evaluate silicone rubber cable. TVA will continue performing high voltage withstand tests on an expanded sample of the installed cables.

This testing is intended to provide a level of confidence in the Integrity of the cable commensurate with that provided during the equipment qualification (i.e. 10CFR50.49) testing previously performed.

The results of the additional testing planned by TVA as well as those previously performed on installed cables will be analyzed to determine the extent of the problem.

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