ML20207D207

Forwards Info Re Cable Ampacity Sampling Program,Including History of Origin of Problem,Areas of Concern,Implementing Procedures & Verification of as-built Raceway Configuration

ML20207D207
Person / Time
Site:	Sequoyah
Issue date:	12/23/1986
From:	Gridley R TENNESSEE VALLEY AUTHORITY
To:	Youngblood B Office of Nuclear Reactor Regulation
Shared Package
ML20207D213	List: ML20207D207 ML20207D233 ML20207D294
References
NUDOCS 8612300350
Download: ML20207D207 (11)

Text

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TENNESSEE VALLEY AUTHORITY CH ATTANOOGA TENNESSEE 374ol SN 157B Lookout Place DEC 23 E86 Director of Nuclear Reactor Regulation Attention:

Mr. B. Youngblood, Project Director PWR Project Directorate No. 4 Division of Pressurized Water Reactors (PWR)

Licensing A U.S. Nuclear Regulatory Commission Washington, D.C.

20555

Dear Mr. Youngblood:

In the Matter of

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Docket Nos. 50-327 Tennessee Valley Authority

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50-328 SEQUOYAH NUCLEAR PLANT (SQN) UNITS 1 AND 2 - CABLE AMPACITY INFORMATION On October 1, 1986, in a telephone conversation between NRC staff reviewers and the TVA staff, the subject of ampacity was identified as a topic that needed task definition. On October 16, 1986 an informal information package on ampacity was provided to NRC which contained current instructions for an ampacity sampling program and the TVA electrical design standard with ampacity tables. The purpose of this letter is to document the program for sampling cable ampacity at Sequoyah units 1 and 2.

The generic problem identification report for all TVA nuclear plants, included as enclosure 1, provides the history on the origin of the problem and identifies the areas of concern. outlines the TVA ampacity program. Enclosures 3 and 4 provide the specific Sequoyah implementing procedures for the sampling program and verification of the as-built raceway configuration, respectively. All identified inadequacies in the design standard were corrected with the issuance of the design standard that is included as enclosure 5.

In order to determine the adequacy of previously designated and installed electrical cables with respect to ampacity, a sample program was established. A list of commitments related to this submittal is included as enclosure 6.

To determine the acceptability of each cable in the sample, the actual load current with margin as required to account for reduced voltage, service factor, etc., is ccmpared to the allowabic cable ampacity provided in enclosure 5.

The allowable ampacity takes into consideration the derating effects of tray covers and/or bottoms, flame retardant coatings and Appendix R fire ways. It also takes into consideration raceway fill and ambient temperatures.

Cables which are identified as failures are specifically reviewed to reduce conservatism in the required ampacity (i.e., such as the use of a transformer's rated current versus its connected load), as well as reduced conservatism in the installed configuration (i.e., determining the actual raceway fill percentage or removing tray covers if not required for physical protection). Those cables in which continued operation is not technically justified will be replaced or supplemented before unit restart.

8612300350 B61223 PDR ADOCK 05000327 0[

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pop An Equal Opportunity Employer gh

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.. Director of Nuclear Reactor Regulation A summary of the results and dispositions of the sampling program will be provided along with supporting documentation January 30, 1987.

If you have any questions regarding this subject, please get in t' ouch with M. R. Burzynski at 615/870-6172.

Very truly yours, TENNESSEE VALLEY AUTHORITY ghdR. Gridley, Director Nuclear Safety and Licensing Enclosures cc (Enclosures):

U.S. Nuclear Regulatory Commission Region II Attn:

Dr. J. Nelson Grace, Regional Administrator 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30323 Mr. Carl Stahle Sequoyah Project Manager U.S. Nuclear Regulatory Commission 7920 Norfolk Avenue Bethesda, Maryland 20814 Mr. G. G. Zech, Director TVA Projects i

U.S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgic 30323 i

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7 ENCLOSURE 1 PROBLEM IDENTIFICATION REPORT b

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PIRGENEEB8605

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4 Description of Condition A. INPO finding on BLN revealed the lack of design calculations to show the adequacy of the cable ampacities provided in electrical design standseds DS-E12.1.1 through DS-E12.1.4.

This finding was later confirmed by the Bellefonte Electrical Evaluation team.

As'a result of these findings calculations were performed which supposedly verified the adequacy of the existing TVA standards.

A recent review of both the standards and the supporting calculations indicates that the standards are incomplete and lact the definition and information required for proper application. The supporting calculations failed to recognize this and are therefore incorrect.

Some of the factors which were not properly considered are as follows:

1. Cables in conduit were sized assuming only single conductor cable was utilized.

TVA has purchased large quantities of 3 conductor cable (#14-#2 AWG) for use in cable trays however it is not restricted to this application. Use of 3 conductor cable in conduits would lead to nonconservative results.

2. Cables in conduits were sized assuming that the con'duits were installed with a spacing of at least one conduit diameter.

There is however, no corresponding installation or inspection requirement to ensure this spacing in the field.

3. Ampacities for 0-600 volt cables in tray were provided for a single assumed minimal depth of cable installation. TVA's standard cable tray fill allowances however result in a depth of cable greater tnan that assumed which produces nonconservative results.

4. Ampacities for 0-600 volt cables in tray failed to provide a correction factor to account for variations in cable dia=eters feco that assumed in the standards to that purchased by TVA.

The diameters of TVA's cables are smaller than assumed in the standards leading to nonconservative results.

5. Ampacities for 8 and 15 LV 2/0 cables were based on inste.11ation with maintained spacing.

The installation specification bowever, allows these cables to be random laid with no spacing. This impairs the allowable ampacity of the 2/0 cables as well as other cables installed adjacent to these.

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6. The cable sizing standards failed to consider the effects of fire n

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retardant cable coatings, tray covers, fire ba?rier stops, and fire i g..

blantet wraps.

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3g i-PIRGENEEB8605 Proposed Corrective Action Revised standard criteria are being developed to reflect the minimum requirements necessary for proper sizing of electrical cables considering all applicable factors. Upon completion of the revised criteria a comparison will be made with the old standards to identify the areas and magnitudes of potential disparities.

This review will begin on a generic level and will take into consideration all cable sizing and installation procedures in an attempt to identify those practices which are conservative.

The objective is to fully substantiate current operation of these cables by equating any lack of previous conservatism with a justified loss of operating life. This would provide an interval in which individual verification of cable size would be performed.

For those cables for which generic substantiation is not achievable project specific guidelines will be issued idencifying the steps required for resolution.

These guideline's are expected to consist of a sampling program to parallel that.which is in progress at BFN.

Again the objective will be to provide firm justification for interim operation pending individual cable confirmation.

Finally those cables for which interim operation is not justified will be replaced or supplemented.

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ENCLOSURE 2 CORRECTIVE ACTION AND SAMPLING PROGRAM

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October 7, 1986 ALL NUCLEAR PLANTS - CORREC IVE ACTION AND

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For V4-and VS-level the p'ercent fill for the trays conductors in the conduits in which the cables identi

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routed must be known.

The effect of cables which are abandoned in t are raceway but are not indicated in present cable schedules mus for.

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bottoms and Appendiz R fire wraps must be known.Th overs and In order to demonstrate the adequacy of the auxiliary and c with respect to ampacity each project shall establish a samplin ontrol power cables' guidelines will be developed and the sampling performed in acc Military Standard 105D dated April ram. The 29, 1963.

ordance with lots or batches.The sampling program will be developed by each project b to Design Standard E12.6.3 for the definition of the varioThe on 9 inspection 1.

us volta 6e levels):

V3 level cables routed in tray.

2.

V3 level cables routed in conduit without Appendix R fire wra p.

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V3 level cables routed in conduit with Appendix R fire wrap 4

V4 level cables routed in tray without tray covers fire wrap.

, bottoms or Appendix R 5.

Appendiz R fire wrap.74 level cablos routed in tray with tray covers an ems and/or 6.

V5 level cablos routed in tray without tray covers fire wrap.

, bottoms or Appendix R 7.

V5 level cables routed Appendiz R fire wraps. in tray with tray covers, and/or bottems and/or 8.

V4 and V5 level cables routed in conduit without Appendix R fir e wrap.

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V4 and V5 level cables routed in conduit with Appendiz R fi

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For each ot.the innpection lots shown the project shall det

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T-number of units (Class 1E cablos or non-Class 1E cables i

cables) in thht lot.

ermine the total

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in the. inspection lot reflecting the most limitingEach such cad 10 with Class 1E

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October 7, 1986 ALL NUCLEAR PLANTS - CORRECTIVE ACTION A CABLE AMPACITY ECTRICAL least limiting are as follows:The order of raceway configurations by s ost limiting to

1. V3-level A.

Inspection lot 1 B.

Inspection lot 3 C.

Inspection lot 2 2.

V4-level A.

Inspection lot 5 B.

Inspection lot 9 C.

Inspection lot 4 D.

Inspection lot 8 3.

VS-level A.

Inspection lot 7 B.

Inspection lot 9 C.

Inspection lot 8 D.

Inspection lot 6 Therefore, as an example, cables routed in Va in other inspection lots even if they are additionally again After the total number of units in each inspection lot is det Table I for General Inspection Level II. sample si:e code letter ermined the cation 105D level is 4.0. letter the sample size is specified in Table IV-A.Following selection The acceptable quality

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Having established the first sample size the project shall randoml cables from the inspection lot.

y select Design Standard E12.6.3. determined, considering its actual installe load ampacity including appropriate multiplying factors to de acceptability of the installed cable with respect to ampacity ermine the respective inspection lot, no further sampling is esq y

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defective units in the initial sampling is above the specifi dIf the numbe n the

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additional-sample lots shall be selected and the allowable limit

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level is achieved in accordance with the Military Specificat "7 * '-"~..' T

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-,;;r2 adequacy with respect to ampacity determined individua n or until the

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ALL NUCLEAR PLANTS - CORRECTIVE ACTION AND SAM s.

CABLE AMPACITY

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An SCR must be written to cover all defective units and the mod for those units shall be explained and documented.

made as to the possible generic implications of any failure.A determination must be r

can be shown to be due to an isolated cause, no further review in thip. rega If the failure is necessary.

If the cause of failure could apply to a particular subset of cables, further review, which may include additional sampling, of the cables

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For the purposes of this sampling program, control power cables are those

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cables routed in a V3-level raceway whose load current for the particular t conductor size could produce sufficient heat to warrant consideration.

V3-level cables are, by definition, limited to less than 30 amperes this As consideration is restricted to conductor size No. 8 AWG and cmaller.

Therefore, a control power cable is defined as a No. 8,10,12, or 14 AWG below except No. 10, 12, or 14 AVG conductors whose exceed 15 amps and whose load operation does not exceed a totc1 of 20 minutes

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in any 5-hour interval.

Cables which meet the exception or whose load currents are below those T

indicated do not warrant further consideration of ampacity and are not considered control power cables.

Those cables which exceed these limitations must have the specific allowabla empacity of the cable selected verified for adequacy for the load current and installation configuration.

Conductor Size (AWG) is a control power cable, if the load current exceeds (amporosit 14 Y

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10 12 8

22 This information will be substantiated by a DNE calculation to be issue l

EEB Central Staff.

below are applicable for the configurations listed:For the purpo l

Confir.uration

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ALL NUCLEAR PLANTS - CORRECTIVE ACTION AND SAMPLING PROG' RAM FOR ELECTRICAL CABLE AMPACITY

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TSI Fire Wrap Material Plant Description / Attachment Multiplier

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BFN 1-He Condult <2" 0.91 BFN 1-He Conduit 12" WBN 3-He Conduit <2" 0.925 0.88 VBN 3-He Conduit 12" 0.90 SQN Panels to Construct 0.87 1-Hr trays.(V4 only)

SQN Panels to Construct 0.79 3-He trays (V4 only)

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3M Fire Wrap Material Plant Ty.p. e.

Description / Attachment Multiplier WBN M-20A Oonduit - 5 Layers of 0.625 Wra; ping WBN M-20A Cable Tray - 4 Layers of 0.40 1

Vrapping l (x VBN CS-195/M-20A Cable Tray Rigid Panels 0.41 t

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This information will also be substantiated by a DNE calculation to be issued s

st by EEB Central Staff and will be incorporated into the next revision of Electrical Design Standard DS-E12.6.3.

Resolution of the concerns on cable ampacity has been tied to plant restart / fuel load. Implementation of the actions specified in this memorandum should be scheduled by each project accordingly.

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W. S. Raugh3by j J. D. Collins, P-205 SB-K y

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..... R, R. H o e s ly, 9 -113 S B -X D. W. Wilson, DNE, DSC-E, Sequoyah R. W. Cantrell, V12 A8 C-K Xanti Gandhi, 108-C102 WBN

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T. M. Shea, Extension 2672

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ENCLOSURE 3 IMPLEMENTING PROCEDURES FOR PROGRAM e-1

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