ML20150C947

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Safety Evaluation Re Employee Concern Element Rept EN 24000, Cable Derating
ML20150C947
Person / Time
Site: Sequoyah  Tennessee Valley Authority icon.png
Issue date: 03/11/1988
From:
NRC OFFICE OF SPECIAL PROJECTS
To:
Shared Package
ML20127A683 List: ... further results
References
NUDOCS 8803220457
Download: ML20150C947 (3)
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UNITED STATES

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,7, NUCLEAR REGULATORY COMMISSION 5

5 WASHINGTON, D. C. 20555 jf

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SAFETY EVALUATION REPORT BY THE OFFICE OF SPECIAL PROJECTS EMPLOYEE CONCERN ELEMENT REPORT EN 24000 "CABLE DERATING" TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR POWER PLANT, UNITS 1AND 2 00CKET NOS. F0-327 AND 50-328 1.

SUBJECT Category:

Engineering (20000)

Subcategory:

Cable Ampacity (24000)

Element:

Cable Derating (24000)

The basis for Element Report EN 24000, Revision 2, dated May 27, 1987 was the generic applicability determination resulting from employee concerns at all other nuclear plants. One specific concern was identified for Sequoyah Nuclear Plant (SQN).

Employee concerns:

The cable ampacity and cable derating concerns are identified as follows:

WI-85-100-009 XX-85-122-027 XX-85-122-028 XX-85-027-029 IN-85-272-004 IN-85-289-006 IN-86-254-005 IN-86-262-002 IN-85-036 II.

SUMMARY

OF ISSUE Employee concerns have been expressed aoout cable.derating in the follcwing areas:

Cables in seneral.

Cables with fireproof coatings.

Cable trays or conduit wrapped in a fire blanket.

Cables in firestop or pressure seal barriers.

Overfilled cables in conduit, trays, firestop or pressure seal barriers.

~3 III. EVALUATION Inadequacies had been found by Insitute of Nuclear Power Operations (INPO) in TVA's electrical design standards' These design standards had been used to size all the insulated power cable ampacities (auxiliary and control) 9803220457 880311 ADOCK 050 g 8 DR

throughout all TVA nuclear plants prior to September, 1986.

A new standard DS-E12.6.3, "Ampacity Tables for Auxiliary and Control Pcwer Cables (0-15,000V)" has been developed.

The standard also addresses ampacities for cable in conduit, cable tray and duct bank as well as derating factors for cable coatings, Appendix R fire wraps, tray covers and bottoms.

The acceptability of this standard by the NRC staff is discussed in a separate safety evaluation.

A program to determine the adequacy of electric cables, with respect to ampacity ratings, using the new design standard has been developed.

As a result of this prograra auxiliary AC and DC power cables (V3), operating at a voltage up to 277V and a current of less than 30 amperes, were acceptable as installed, This acceptability was based upon a sampling procedure.

Other power cables (V4) rated 600V with current greater than 30 ampere and (VS) rated voltage 5, S, or 15KV were reverified 100%. A total of 1446 cables were reverified cf which 457 were found to not reet the ampacity of the new standard.

However, after further evaluation only 125 cable had to be replaced.

The acceptability of this program including the res( 's and corrective action is discussed in a separate safety evaluation report.

This safety evaluation discusses the effect of overfilled cable on conduits, cable trays, and wall & floor penetration firestops/ pressure seals.

Also discussed are the V4 (480V) pcuer cable bundled in trays and coated with Flamenastic.

Further, the application of multicoats of Flamemastic and the accuracy of the cable schedule data base is discussed.

The fire stop test configuration will be reviewed by TVA to determine the effect of the everfilled conditions on the allowable ampacity.

An appropriate derating factor will be determined to ensure that cables in an everfilled firestop do not exceed their qualified insulation temperature rating.

The.;esign Standard DS-E12.6.3 will be revised to include the derating effects of overfilled trays in firestops.

An analysis will be perfomed by TVA to detennine the ef fect of ampacity of a catie due to bundling the cables in a portion of the tray, as opposed to spreading them cut over the full width, as well as the applicaticn cf multiple coats of Flacemastic.

The analysis will be based on data on overfilled trays.

Installation specification G-38 will be revised to mandate installation ever the full tray width.

The ampacities of cable in V4 tray are based on a maximum fill of 30%.

All safety-related and associated nonsafety-rclated cables routed in V4 trays, which exceed the fill criteria, will be individually reviewed by TVA to ensure acceptability.

Problems associated *ith the cable and raceway prrgrams had caused overfilled raceways.

Also, the validity of the cable and raceway progran database will have to be established to assure accurate cable fill infomation.

Accurate cable fill information is required to establish the validity of the cable ampacity reevaluation.

These problems and corrective

3-action are addressed in Employee Concerns Efi 23900 report and safety evaluation.

IV.

CONCLUSION The fiRC staff concludes that the licensee's investigation of the concerns was adequate and the resolution of the concerns described in Element Report EN 24000-SQN, Revision 2, is acceptable.

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