ML20150C937

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Safety Evaluation Re Employee Concern Element Rept EN 23801, Conduit Overfills & Cable Damage
ML20150C937
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 8803220431
Download: ML20150C937 (3)
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SAFETY EVALUATION BY THE OFFICE OF SPECIAL PROJECTS EMPLOYEE CONCERN ELEMENT REPORT EN 23801 CONDUIT OVERFILLS AND CABLE DAMAGE TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 DOCKET NOS. 50-327 AND 50-328 I.

SUBJECT Category:

Engineering (20000)

Subcategory:

Raceway Overfills and Cable Pulling (23000)

Element:

Conduit Overfills and Cable Damage (23G01)

The basis for Element Report EN 23801,'Rev. 3, dated May 12, 1987 was the generic applicability determination resulting from Watts Bar Nuclear Plant (WBN) Employee Concerns Employee Concern:

The following conduit overfills and cable damage concerns are identified as follows:

IN-85-432-001 IN-85-036-001 IN-86-310-001 IN-85-313-001 IN-85-506-001 IN-85-622-001 IN-85-685-001 IN-85-743-008 IN-86-034-001 IN-86-226-003 IN-85-642-001 IN-85-856-003 IN-86-028-002 IN-86-262-001 IN-85-832-001 IN-86-312-001 IN-85-734-001 IN-85-367-001 IN-86-262-004 IN-86-254-009 IN-86-206-001 OW-85-007-003 II.

SUMMARY

OF ISSUE The overfilling of conduits may cause cable damage during installation, over-heating of cables, and is not in accordance with the National Electric Code (NEC).

III. EVALUATION TVA reviewed documents of employee concerns, NRC investigative interviews, FSAR commitments, engineering and construction procedures for conduit overfill problems and interviewed personnel associated with scheduling and installation of the conduit raceway system.

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2-The TVA review indicated that the FSAR and the Design Criteria are.in agree-ment. Conduits shall not have a cable fill where the cross section area of the cable exceeds 40% of the cross section area of the inside of the conduit.

However, the TVA Electrical Design Standard anc' the NEC allow 53% for conduits having one cable and 31% for conduits having two cables.

Cables were manually routed in conduits by designers and documented in the computer cable schedule.

The designer performing the cable reuting was responsible for determining the total cross section area (CSA) of the cables in the conduit.

The evaluation revealed that accurate conduit fill information is not readily available and, therefore, compliance with FSAR comitment for conduit fill is not verifiable through QA documentation.

After September 1986 a procedure was issued to require a checker to verify the manual cable routing and check CSA prior to releasing the cable pull slips for cable installation.

Further,

.I additional concerns of CSA were raised because the cable diameters used by the designers were not frnm an approved QA list, therefore, causing overfill and overheating. The employee concerns for WBN cited some specific locations, but the implied generic concerns for.SQN are general in nature.

The SQN concern addresses overall problems related to conduit overfill and cable damage with a specific concern related to conduit fill which exceeded that established in the Electrical Design Standard, SCR'SQNEEB 8529 R0.

The concerns associated with conduit overfill discussed in the TVA report are as follows:

i Cable ampacity may not be valid because the cable diameters.used by the~

designers were not from an approved QA list.

These cable diameters used, if less than actual, cculd cause conduit overfill and thus overheating.

Cable supports nay not be adequate, because cable weight were not used from a QA list.

The cable fill criteria in the FSAR and Design Criteria are not in agreement with neither the Electrical Design Standard nor the National Electrical Code for one and two cables in a conduit.

Cable damage cculd haue occurred because the ranufacturers recomrend side wall pressure may have been exceeded from excessive bends, pullbys, and jaming.

TVA determined that the cable OD differences would have no effect on the cable ampacities and darating.

Cable ampacities in conduit are a function of the-number of cables in a conduit and not the physical conduit fill.

TVA cetermined that there was no program to verify adequacy of corduit supports for overfill conduits.

TVA has retained the services of United Engineers and Construction (UE&C) to conduct a full systematic analysis of the SON cable and conduit scheduling program.

UE&C will identify any necessary corrective-

-actions required to establish the accuracy of the conduit and cable _ schedules.

The UE&C effort will include a review of the practices and procedures utilized for routing, installing, and abandening cables in conduit during SQN's design, construction, and modification phases up to present.

All corrective actions

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s required to resolve problems identified by the UE&C review will be evaluated per restart criteria.

The review will also determine conduit support adequacy.

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Those items meeting the criteria will be corrected before Unit 2 restart.

1 The remaining items will be completed as part of a long-term program after restart. The details of staff evaluation with regard to the structural / support adequacy is addressed elsewhere (CEB-16 Calculation Review Inspection Open item).

The staff concurs with this effort to determine potential root causes for discrepancies and to correct any identified problem areas resulting from these root causes.

Electric utilities are exempt from the requirements of the National Electrical Code (NEC) for those facilities which are used for electrical power generation.

However, the licensee, TVA, will revise both the FSAR and the Design Criteria to agree with the Electrical Design Standard and, NEC concerning cenduit fill requirements.

The staff concurs that TVA sFeuld follow the industry standards concerning allowable conduit fill.

Cable damage associated with pullbys and janning is addressed in Employee Concern Element Report C010900-SON and TVA's cable test program submitted for staff review on July 31, 1987.

Other Employee Concerns for conduit design and installation are addressed it: Element Report C0 19201-SQN.

IV.

CONCLUSION The NRC staff concludes that the licensee's investigatien of the concerns were adequate and their resolution of the concerns described in Elenent Report EN 23801-SQN, Revision 3, is acceptable except for identification of cable damage.

However, the staff concludes that the cable test program has adequately addressed the cable damage ccncern for purposes of restart.

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