ML20212H497
| ML20212H497 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 01/15/1987 |
| From: | Youngblood B Office of Nuclear Reactor Regulation |
| To: | White S TENNESSEE VALLEY AUTHORITY |
| References | |
| NUDOCS 8701210458 | |
| Download: ML20212H497 (13) | |
Text
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Docket Nos.: 50-327 and 50-328 15 JAN 1987 Mr. S. A. White l
Manager of Nuclear Power Tennessee Valley Authority 6N 38A Lookout Place 1101 Market Street Chattanooga, Tennessee 37402-2801
Subject:
Recommended Actions for Resolution of Specific Cable Pulling i
Concerns, Sequoyah linits 1 and 2 The Technical Evaluation Report (TER) related to cable pulling and bend radii concerns for Sequoyah is being prepared by our consultants. To allow timely resolution of the identified concerns for Sequoyah, enclosed is information on recommended actions for resolution of specific cable pulling concerns that are necessary for Sequoyah restart. There are other cable pulling concerns addressed in the TER which will need resolution but are rot necessary for Sequoyah restart.
If you have any questions, contact Tom Alexion at (301) 492-7286.
Sincerely, B.J. Youngblood, Director PWR Proiect Directorate #4 Division of PWR Licensing-A
Enclosure:
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n ENCLOSURE RECOMMENDED ACTIONS FOR RESOLUTION OF SPECIFIC CABLE PULLT'lG CONCERNS AT SEnUOYAH NUCLEAR POWER PLANT, UNITS 1 A 2 The preparation of the Technical Evaluation Report (TER) relating to cable pulling and bend radii concerns for the Sequoyah plant is in progress. During the preparation of the TER, the need for additional actions by TVA to allow resolution of the concerns has been recognized. To allow timely resolution, the following information is provided which the staff believe describes an acceptable means of choosing the cable and conduit configurations to be evaluated.
In ad-dition, a list of tests is provided to be used to determine if significant damage has occurred due to pullbys,,iamming and from lack of support of vertical cable runs with 90 condulets at the top of the run. While other types of installation damage may be observed during the cable evaluations, the predominant concerns are for saw-through and mashing of the jacket and insulation during pullbys, tearing 0
and mashing from jamming, and insulation cutting by the corner of 90 condulets at or near the top of long vertical runs.
To determine whether cable. pulling abuses did or did not lead to significant cable damage, cable in a worst case conduit for pullbys, a worst case conduit for jamming and a worst case conduit for a vertical run supported by a 40" condulet should be evaluated.
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CONSIDERATIONS FOR DETERMINING THE WORST CASE CONDUIT ANDCABLECOMRINATIONSFORPULLBfS,.1AMMING AND VERTICAL RUNS SUPPORTED RY 90 CONDULETS The following criteria are provided for consideration in determining the most appropriate cable and conduit combinations for evaluation of the extent of damage resulting from cable installation problems. The criteria are listed in descending order of importance.
It is recognized that no one conduit / cable combination will necessarily fulfill all of the considerations.
Criteria For Pu11bys (1) The pull required consultation with ejigineers due to trouble encountered.
(2) The pull required mechanical pulling assistance.
(3) The length of the run between iubrication points was long.
(4) Several PVC jacketed cables were present in the conduit before the pullby.
(5) There were multiple pullbys in the conduit.
(6) The conduit bends were near the pull point.
(7) The pulls were made before Polywater J was used as a lubricant.
5 (8) The first portion of the conduit was an upward or horizontal section such that lubricant could not be poured into the conduit.
(9) There were seve al pulling points prior to the segment being evaluated, especially those that were condulets.
(10) The pullby consisted of a large rubber,iacketed cable or multiple smaller rubber jacketed cables.
Criteria For.lammina The actual conduit and cable sizes should be used to determine if the.iam ratio was of concern where 3 or 4 cables were pulled. This review should extend beyond the 16 worst case conduits presently evaluated by TVA.
If the iam ratio indicates the potential for oroblems, the following should be considered in choosing a conduit for physical insoection.
(1) Any record of a sudden increase in tension during a pull especially if it required engineering assistance for resolution.
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(2) The pull had multiple bends with a ;arge combined total of degrees of bend.
(3) The conduit contained field fabricated bends.
(4) The pull required mechanical pulling assistance.
(5) There were multiple pulling points prior to the segment of conduit of highest interest.
(6) The cables in the pull had large conductors by comparison to the cable diameter (i.e., the cable should.not be prone to reshaping when compressed.),
Criteria For Vertical Cable Suoported by 90 Condulets 0
(Note: Each of the following are of roughly equal importance.)
(1) The cables have silicon rubber insulation.
(2) The conduit should contain multiple cables resting upon the U
cable supported by the corner of the 90 condulet.
(3) The length of the vertical run is long.
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RECOMMEMDED TESTS AND INSPECTIONS The following are recommended tests and inspections that the staff believes will provide the needed information to allow resolution of concerns related 0
to pullbys, janning and support of cable by 90 condulets.
Tests and Inspections for Pullbys Upon selection of the worst case conduit for pullbys, the following should be performed.
(1) With the cable in conduit, perform a de high voltage test.
For shielded cable, perform the test between the shielo
..u the conduit (at 50% of -
insulation test voltage value), and between each individual conductor and the remaining conductors and shield tied together.
For nonshielded cables perform the test between each conductor and the remaining conductors and the conduit tied together. (Note: Failure of this test will indicate that signif,icant damage occurred during installation. However, passing this test will not rule out damage, because much of the cable will be insulated from the conduit by air. The test is an attempt to determine, to the extent practical, the condition of the cable prior to its removal from the conduit.1
i (2) The cables should be removed from the conduit in a engineered, fully supervised manner and carefully transported to a controlled, laboratory type environment where the remainder of the evaluation is performed.
Dch cable should be identified by its cable number. A means should be provided to identify the location of conduit bends, pull points, etc.,
with respect to the length of the cables for use in further evaluations.
(3) A detailed physical inspection of the entire length of each cable should be performed and signs of such conditions as saw-through, mashing, abrasion, twisting and kinks should be documented.
If obvious signs of significant damage are observed, the following tests are not necessary.
(4) A de high voltage test should be perfomed on each cable with the cable imnersed in water with a duration of at least 5 minutes.
For shielded cables, a test between the shield and the water (at 50% of the insulation test voltage value), and a test between each conductnr, and the shield, the tank and remaining conductors should be performed.
For nonshielded cable, the tests should be perfomed between each conductor and the remainder of the conductors tied to the tank.
If an abnormality is observed in leakage I
current the test should be continued until the current stabilizes or the cable fails.
(5) An ac stepped voltage breakdown test should be perfomed while the cables l
are immersed:
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On the cables removed from the conduit, b.
On a similar new cable specinen.
For shielded cable each conductor should be tested to the remaining conductors tied to the shield and the tank. For nonshielded each conductor should be tested with respect to the remaining conductors tied to the tank.
The starting voltage for the test should be reasonably low to allow evaluation of the extent of dama'ge to the cable. A step duration of 10 minutes is suggested.
If a failure occurs at the terminals, the cable should be reterminated and re-tested until either the cable fails or the terminals fail at a voltage that is a multiple of 3 tines the factory withstand test.
(6) The position of the failures from step 5 should be determined for each cable that failed at a significantly lower breakdown voltage value than a similar new cable. The mode and cause of failure should be evaluated through in-spection and disection to determine if the cause of the failure was due to cable pulling damage or other causes such as manufacturing defects. The j
locations of significant damage observed in step 3 should also be evaluated l
and inspected to deternicie the extent of damage both at the surface and throughout the cable.
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. (7) For multi-conductor cables, remove the jacket for the entire length and inspect the insulation of the individual conductors for damage.
If damage is observed, disect and evaluate the extent and type of damage.
Tests and Inspections for Jamming If.iamming has been detemined to be a valid concern, upon selection of the worst case conduit and cable combination, perform the efforts listed in steps 1 and 7 for pullbys. Then examine the length of the cable for indications of mashing and tearing.
If obvious signs of significant damage are observed, no further tests
- need be perfomed.
If the worst case cable for jamning is an 8 KV cable and TVA has the facilities for corona discharge testing or can arrange for timely use of such facilities, the cables should be corons tested for inception and extinction voltages. A new piece of cable should be similarly tested for comparison purposes.
The tests described in steps 4, 5, and 6 for pullbys should then be performed.
Finally, the jacket should be removed from the entire length of cable and the in-sulation should be inspected for damage.
U Tests for Cable Supported by 90 Condulets For the worst case conduit, perforn a de high voltage test between the conductors of the cable and the conduit. The voltage level should be that specified by ICEA
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for the factory de test level. The purpose of this test is not to determine if additional support of the cable is needed but rather to detemine if the cable has been damaged by the corner of the 90 condulet and should be replaced in addition to being properly supported.
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& ACCEPTANCE CRITERIA For the cables removed for evaluation of pullbys and jamming damage, the following are suggested acceptance criteria:
1.
The cables must pass both the in-conduit and immersed de high voltage tests.
2.
The jackets, insulations and shields must be free of significant-damage that,. had it been observable in the plant, would have dictated removal and replacement.
3.
The insulation material must have ac breakdown voltages that are not significantly different from that of a new cable.
4 If corona tests are performed on 8 Kv cable, the inception and extinction voltages should not be significantly different from that of new cable.
If cables do not meet the acceptance criteria for pullbys and/or jamming, then these problems are significant and further action will be necessary to evaluate the extent of the problem and the need for further corrective action.
For cable supported by a 90 condulet, the cable must not fail the de high voltage test.
If it does, it must be replaced and properly supported.
If it passes, the
11-4 concern for imediate.significant damage is reduced; however, the cable must be resupported.
If the cable fails the de high voltage test, a further sample of similar installations will have to be tested to detennine the extent of the problen.
All vertical cables supported by 90 condulets should be resupported based on the criteria of NEC Article 300-19 even if they pass dc high voltage tests.
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T-Mr. S.A. White Tennessee Valley Authority Sequovah Nuclear Plant cc:
Tennessee Department of Public Regional Administrator, Region II Health II.S. Nuclear Regulatory Comission, ATTN: Direct.or, tL eau of 101 Marietta Street, N.W., Suite 2900 Environmental Health Services Atlanta, Georgia 30323 Cordell Hull Building Nashville, Tennessee 37219 J.A. Kirkebo ATTN:
D.L. Williams Mr. Michael H. Mobley, Director Tennessee Valley Authority Division of Radiological Health 400 West Sumit Hill Drive, W12 A12 T.E.R.R.A. Building Knoxville, Tennessee 37902 150 9th Avenue North Nashville, Tennessee 37203 Mr. Bob Faas Westinghouse Electric Corp.
County Judge P.O. Box 355 Hamilton County Courthouse Pittsburgh, Pennsylvania 15230 Chattanooga, Tennessee 37402 R. L. Gridley Tennessee Valley Authority 5N 157B Lookout Place Chattanooga, Tennessee 37402-2801 M. R. Harding Tennessee Valley Authority Sequoyah Nuclear Plant P.O. Box 2000 Soddy Daisy, Tennessee 37379 Resident Inspector /Sequoyah NPS c/o U.S. Nuclear Regulatory Commission 2600 Igou Ferry Road Soddy Daisy, Tennessee 37379 H.L. Abercrombie Tennessee Valley Authority Sequoyah Nuclear Plant P.O. Box 2000 Soddy Daisy, Tennessee 37379