ML20235H004
| ML20235H004 | |
| 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-PT21-87-171-000 PT21-87-171, PT21-87-171-000, NUDOCS 8709300329 | |
| Download: ML20235H004 (4) | |
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E' TENNESSEE VALLEY AUTHORITY
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September 10, 1987 l
Mr. James G. Keppler, Director Office of Special Projects U.S. Nuclear Regulatory Consnission 4350 East-West Highway EW 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 4
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 unable to determine the nature or cause of this condition.
However, these laboratory t%sts 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 t
manufacturing, shipping, or handling.
Cables from all three vendors were tested in the laboratory and evidenced similar reductions 'a wall thickness.
As a result, a determination has been made that this problem is reportable pursuant to t,he requirements of 10 CFR 21.
As you know, I received a September 4, 1987 briefing on the potential problem. Subsequently, I ga've you a verbal report by telephone that day.
In addition, on September 5, 1987 R. L. Gridley of my staff gave a verbal report by telephone to Dr. J. Nelson Grace, Regional Administrator of NRC Region II.
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5 An' Equal Opportunity Employer
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3 Mr. James G. Keppler September 10, 1987
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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
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S. A. White Manager of Nuclear power Enclosure cc (Enclosure):
U.S. Nuclear Regulatory Commission Region II Atta:
Dr. J. Nelson Grace, Regional Administrator 101 Marietta St., NW, Suite 2900 Atlanta, Georgia 30323 U.S. Nuclear Regulatory Commission Region II Attn:
Mr. G. G. Zech, Director of TVA projects 101 Marietta St'., NW, Suite 2900 Atlanta, Georgia 30323 s
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ENCLOSURE SEQUOYAH NUCLEAR PLANT PRELIMINARY REPORT
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SILICONE RUBBER-IN'UL&TED CABLES j
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Nature of Defect and Cause 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 Sequoyah Nuclear Plant (SQN). The subsequent testing identified three additional nonconformances each of AIW Corp 1 ration and i
Rockbestos conductors. The sample population of Anaconda conductors did not experience any failures. TVA has now identified a total of 9 nonconformances out of 66 tested conductors. To date. TVA has been unable to identify a definitive cause for these nonconformances.
TVA has concluded that the i
performance of silicone rubber-insulated cables is significant13 different than expected.
In addition, the performance of silicone rubber insulated -
cables is significantly different from other cables at IVA of waich 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 i
which results in such decreases may be within that which could possibly occur during (1) manufacturing operations following the factory high potential
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withstand test, (2) handling at the manufacturer (3) shipping, 1
(4) receipt / storage by TVA, or (S) the installation process.
TVA has, j
however, been unable to consistently correlate this data to the nonconformances identified.
i 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, C7 06504.
The determination that a reportable condition may exist was reached on September 4, 1987.
Extent of Safety Hazard A nonconformance of the cable at voltages below that accepted by the industry to demonetrati 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 1 and 2<
These cables have also been utilized in limited applications in other areas of these two units.
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-2 Number of Identical Components in Use There are approximately 252 silicone rubber-insulated cables which require qualification under the requirement's of 10CFR50.49, installed inside the containment of SQN unit 2.
It is expected that a similar number exists inside the containment of SQN unit.1.
l Location of Components i
The silicone rubber-insulated cables at SQN'are located primarily inside the reactor containment buildings in units 1 and 2.
These cables have also been utilized in limited applications in other areas of these two units.
Corrective Action and Recurrence Control Taken or To Be Taken
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i TVA will continue to evaluate silicone tubber cable.
TVA will continue performing high voltage withstand tests on an expanded sample of the installed I
cables. This testing is intended to provide a level of confidence in the l
integrity of the cable conenensurate 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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