ML20215N407
| ML20215N407 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 04/22/1986 |
| From: | Brock M, Hooper B TENNESSEE VALLEY AUTHORITY |
| To: | |
| Shared Package | |
| ML20215N324 | List: |
| References | |
| MI-10.20, NUDOCS 8611050365 | |
| Download: ML20215N407 (28) | |
Text
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-TENNESSEE VALLEY AUTHORITY SEQUOYAH NUCLEAR PLANT-MAINTENANCE INSTRUCTION MI-10.20 6900 AND 480 VOLT MOTOR INSULATION RESISTANCE TEST Revision 9 l PREPARED BY: Mark E. Brock RESPONSIBLE SECTION: Electrical Maintenance _
REVISED BY: Billy W. Hooper ; SUBMITTED BY: ' /% /I.4mm Responsible Section Supervisor PORC REVIEW DATE: APR 22 886 APPROVED BY: T im d cL N ibc- - PlSnt' Manager-DATE-APPROVED: APR 2 2 WSS __ Reason for revision (include all Instruction Change Form Nos.): Revised in accordance with ICF No. 86-0602, PORC approved 04/02/86. The last page of this' instruction is number: 10 geht iB8eR8%!8)gg7 . P-
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! SEQUOYAH NUCLEAR PLAllT PLANT INSTRUCTION-REVISION LOG MAINTENANCE INSTRUCTION MI-10.20 REVISION Date Pages REASON FOR REVISION (INCLUDE COMMIT-LEVEL Approved Affected MENTS AND ALL ICF FORM NUMBERS) 0 02/19/82 All 1 07/12/82 4 2 09/29/82 1,2,10 3 10/6/82 10 4 10/26/82 7,10 5 05/26/83 9 6 11/28/83 2,9 7 07/09/84 4 Revised in accordance with ICF 85-0720, 8 07/31/85 1,2,4-7 PORC approved 07/26/85.
Revised in accordance with ICF 86-0602, 9 .A )R 22 G86 2,7,9 PORC approved 04/02/86. 0195L/mbs I 6 e
SQNP MI-10.20 Page 1 of 2 Rev. 8 1.0 PURPOSE ', The purpose of this instruction is to perform routine maintenance tests on all 6.9kV and 480V motors over 100 HP. These tests consist of a 1,000 ' volt megger test and bridge test on the stator windings of 480V motors, and a bridge test and d-c step voltage test on the stator winding of all 6.9kV motors. This instruction may also be utilized for testing motors after trip-ou't by protective relays (reference SQM 30) or after routine maintenance. 2.0 PREREQUISITES 2.1 Before removing a motor from service verify that there will be no violation of the technical specifications or plant operating instructions by the removal from service of the motor. Operations will have racked out the breaker prior to work performance (on drawout breakers). 2.2 Whenever possible coordinate the performance of this instruction with MI-10.4, MI-10.5 and MI-10.10. (Breaker inspection and maintenance instructions).
~ 3.0 PRECAUTIONS -
3.1 Ensure that the circuit breaker for the motor to be tested is racked out or in the off position. 3.2 The board may be energized. Use appropriate caution. 3.3 The motor leads should be grounded before and immediately after the megger test to ensure that the motor and cabling are completly discharged. 4.0 PREPARATION FOR WORK (Tools Needed) 4.1 480V Motors 4.1.1 1000 Volt CSSC Megger 4.1.2 CSSC Bridge Test Set 4.2 6.9kV Motors 4.2.1 CSSC Bridge Test Set , m 4.2.2 CSSC DC High Potential Test Set 4.2.3 Thermometer
- - 4.2.4 Humidity Meter ~
m
SQNP r MI-10.20 Page 2 of 2 Rev. 9 5.0 WORK PERFORMANCE Perform the work steps given below for each motor. Notify the Unit ASE prior to beginning work and have him sign after completion of work on each motor. N/A non applicable steps on the data sheets. 5.1 480 Volt Motors 5.1.1 Perform 1000 volt megger test. Record readings on data sheet. 5.1.2 Perform bridge test. Record readings on data sheet. 5.2 6.9 kV Motors 5.2.1 Perform bridge test. Record readings on data sheet. 5.2.2 Perform DC High Potential Test Per attachment 1. Record readings on data sheet. 96 5.3 Record temperatures and humidity at the. motor. 5.4 On synchronous motors: bridge and megger (500 V) the field windings. Record in remarks section.
- 4
& 5.5 Should a comparison of bridge readings be required, all ohm values must be
(- converted 75 C resistance value (R@75 C). Perform conversion using to aformula: p the following R@750 C
= R 309.5 toc + 234.5 1
R = ohms reading i j toc
= Temperature at windings in C.
R@75 C
= Ohms corrected to 75*C.
5.6 Bridge reading percent unbalance acceptance criteria: The three bridge readings A-B, B-C, and C-A should have less than one percent unbalance to be acceptable. Percent unbalance is calculated using the following equation: Percent Maximum deviation of any one bridge reading from the average unbalance = 100 X Average of bridge readings- , l
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A e SQNP MI-10.20
, Attachment 1 Page 1 of 4
_ . . Rev. 0 Unit 1
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MOTOR BOARD COMPT CCW Cooling Twr Lift Pump 1A 6.9 CCW Cooling Twr Bd A 7 CCW Cooling Twr Lift Pump 1B 6.9 CCW Cooling Twr Bd A 6
, CCW Cooling Twr Lift Pump IC 6.9 CCW Cooling Twr Bd A' 5 i CCW Cooling Twr Lift Pump 1D 6.9 CCW Cooling Twr Bd A 4 Aux Bldg Chiller A' 6.9 TB Common Bd A 3
- Aux Bldg Chiller B 6.9.TB Common Bd B 3 No. 3 Htr Drain Pump 1A 6.9 Unit Bd 1A 6 Hotwell Pump 1A 6.9 Unit Bd 1A 7
. CCW Pump 1A 6.9 Unit Bd 1A 8 RCP 1 6.9 Unit Bd 1A 9 .
No. 7 Htr Drain Pump 1A 6.9 Unit Bd IB 3
- No. 3 Htr Drain Pump IB 6.9 Unit Bd IB 4 CCW IB 6.9 Unit Bd IB. ,
5 Condensate Booster Pump 1A 6.9 Unit Bd IB 6 RCP 2 6.9 Unit Bd 1B 7 j No. 7 Htr Drain Pump IB 6.9 Unit Bd'1C 5 No. 3 Htr Drain Pump IC 6.9 Unit Bd IC 6
; Hotwell Pump 1B 6.9 Unit Bd IC 7 ;
Condensate Booster Pump IB 6.9 Unit Bd IC 8 p RCP 3 6.9 Unit-Bd IC 9 Hotwell Pump IC 6.9kV Unit Bd ID 4 l CCW IC 6.9kV Unit Bd ID 5 1 - Condensate Booster Pump IC 6.9kV Unit Bd ID 6 RCP 4 Aux Feedwater Pump 1A-A 6.9kV Unit Bd ID . 7 6.9kV.Shtdn Bd 1A-A 10 ERCW JA 6.9kV Shtdn Bd 1A-A 8 ERCW QA- 6.9 Shtdn Bd 1A-A 9 Centrifugal Charging Pump 1AA 6.9kV Shtdn Bd IA-A 18 Safety Injection Pump 1A-A 6.9kV Shtdn Bd 1A-A 15 J Residual Heat Removal Pmp 1A-A 6.9kV Shtdn Bd 1A-A 14 Containment Spray 1A-A 6.9kV Shtdn Bd 1A-A 13 Containment Spray IB-B 6.9kV Shtdn Bd IB-B 13 u- Aux Feedwater Pmp 1B-B 6.9kV Shtdn Bd IB-B 10 ERCW LB 6.9kV Shtdn Bd IB-B 8 ERCW NB , 6.9kV Shtdn Bd IB-B 9 -
,__ Centrifugal Charging Pump 1B-B '6.9kV Shtdn Bd IB-B '
Safety Injection Pump IB-B 18 -l 6.9kV Shton Bd 1B-B 15 l Residual Heat Removal Pump IB-B 6.9kV Shtdn Bd IB-B 14 l w
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I SQNP HI-10.20 Attachment 1 Page 2 of 4 Rev. 8 Information on this page has been deleted. P s 9 I 1 i i I t l [ 1 l. l- . , . -- j o
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SQNP MI-10.20 ~ Attachment 1 s Page 3.of 4 Rev. 8 ' .s , Information on this page has been deleted.
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A - \ n, SQNP , MI-10.20 Attachment 2 Page 1 of 1 Rev. 9 D-C. STEP-VOLTAGE TEST FOR MOTORS Test Procedure is as'follows for\6,600-volt motors:
- 1. Energize motor under test and increase voltage-from zero to 1-kV d-c. Take ,
current reading in microamperes after waiting 3 minutes. Plot this point on a kV versus microamperes sheet. Label microamperes scale to accomodate the range of the test readings.
- 2. Increase test voltage in 1-kV d-c increments up to.and including 13-kV d-c for 6,600-volt motors, taking current reading after waiting 3 minutes at each step. Plot points on kV versus microamperes sheet so curve trend can be noted.
-3. At any voltage step,,should the microampere reading increase to twice the previous microampere reading, reduce the voltage by 500 volts and take -
microampere reading after waiting 1-1/2 minutes. f NOTE: Intermediate reading must be plotted on the kV versus microampere curve p (Data Sheet 2).
- 4. Should this reading indicate that the " knee" of the curve has been reached, stop the test-immediately. Disconnect motor from cable and test motor and cable separately. Investigate trouble and correct as required.
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SQNP 7 MI-10.20
- s Data Package Cover Sheet Page 1 of 1
- Rev. 0 I. To be completed by the originator of the work data package. List the docu-ments that are required to perform the work and return the equipment to service.
^ 1. MR number (s):
- 2. MI data sheet number (s):
~
- 3. SI data sheet number (s):
- 4. Material certification requirements:
i
- 5. Other documents:
All required documentation is in the data work package.
/
Originator of Work Data Package Date II. Results review and approval of the above data package (attached).
/
Responsible Maintenance Representative Date s
/
Maintenance Supervisor Date -
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M
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~ SQNP MI-10.20 Data Sheet I Page 1 of 1 Rev. 9 Motor Date i
ASE Notified By / / Signature Time Date - Megger leads connected / Signature Date 5.1.1 Megger CSSC # Cal Due Date Acceptance >l megohm A to GD B to GD C to GD Megger leads disconnected Signature Signature Date Bridge test set leads connected / Signature Date 5.l.2 & Bridge Test set CSSC # CalDueDage f5.2.1 Terminal Reading Multiplier Ohms Temp C p A-B 4 B-C f- C-A 5.6 Percent unbalance Bridge test set leads removed: . Signature Signature Date 5.2.2 D.C. High Potential D.C. High Potential test set leads connected:
/
Signature Date Time-Min kV Microamperes T~
. 2 3
4 5 6 7 8 9 10 11 12 13 D.C. High Potential test . set leads disconnected Signature Signature Date Winding Temp: Dry Balb Wet Bulb Re1 Humidity % Data Taken By: / / ' Signature Time Date Motor returned for service: / / ASE Time Date Remarks:
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1 t SQNP MI-10.20 Data Sheet 2 Page 1 of 1 Rev. 4 Motor Plant Date k
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ITEM 13 Describe any testing or monitoring programs that TVA will implement relating to the cables suspected of having been abused?
RESPONSE
Testing is planned as described in item 12. In addition, TVA will implement an extensive trend analysis program to track, consolidate, and categorize identified conditions adverse to quality. This program will be implemented in November 1986. The trend analysis program will readily identify any adverse trends associated with cabling at any TVA nuclear plant. It should be noted that neither TVA or the industry has identified any adverse trend with cable failures. If negative trends develop either from within TVA or the industry, TVA would implement actions necessary to ensure safety is maintained. f e # 4
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TTEM 14
- . Prior to pulls,.were the conduits known to be clean and obstruction free?
RESPONSE . Since 1968, TVA General Construction Specifications for installing electrical conduit systems and conduit boxes require that after a conduit ls installed, it shall be inspected and cleaned out, and compressed air.shall be used in blowing out any accumulation of trapped liquids. SQN's post-construction' procedure M&AI-06, " Installation of Conduit'and Junction Boxes," includes the requirements referenced above. t f l 4 l t I
ITEM 15 Describe the types of repairs that were performed on cables or their jackets.
RESPONSE
In the early stages of construction at SQN there were no site construction procedures which delineated the cable repairing process. The initial site construction cable pulling procedure did stipulate that craft forces take measures to prevent physical damage to cables and that engineering personnel monitor the measures taken by craft personnel for protection of the cable. Engineers from the onsite Electrical Engineering Unit were present in the field to provide engineering judgment on the appropriato corrective measures in the event of cable damage. Documented guidance was p ovided to SQN construction personnel by memorandums dated October 12, 1978 and March 12, 1979 (attached) from the SQN Design Project Manager. These memorandums state that outside primary containment in areas of possible steam-water spray, the repair of damaged cable jackets shall utilize Raychem's S-1024 red tape (half-lapped) over the damaged area a minimum of two inches on either side. A properly sized Raychem type WRS repair sleeve shall be installed over the jacket area covered by the S-1024 tape. In several documented instances where insuiation was damaged, the damaged area was covered with 3-1/2 wraps of Scotch 33 tape, with the jacket repaired as described above. Where any damage to insulation or jacket of cables occur inside primary containment, the cable shall be replaced, except-for any minor fraying of braided jacketed cables which can be repaired using the same impregnating material as the cable manufacturer. Presently, when an insulated cable becomes damaged.(1.e., conductor strands are nicked or insulation cut) It shall be spliced, replaced, or repaired depending on the extent of damage. TVA General Construction Specification No. G-33, " Installing Insulated Cables Rated Up To 15,000 Volts," has the following criteria for Class 1E cable repair. A. For low-voltage (600V or less) cables, repair to the jacket, shield (where applicable), and insulation may be made with the following restrictions:
- a. If the conductor or insulation has been damaged, the cable shall be spliced or replaced.
- b. Where damage involves other cable components (i.e., jacket and/or shield) each component shall be repaired individually.
- c. Damaged Class 1E coaxial and triaxial cables shall be replaced.
Raychem Type N materials are required to be used for splicing Class IE-cables that are required to function in harsh environments. B. For medium-voltage (5KV-15KV) power cables, repair may be made to the jacket only. (If damage extends beyond the jacket, the cable shall be spliced or replaced.) Repairs to both Class IE low-voltage (except as noted in A.c above) and medium-voltage cable jacket damage requires use of Raychem Type N heat-shrinkable sleeving or Raychem NJRS wraparound cable jacket repair sleeve. SQN's post-construction procedure M&AI-07, " Cable Terminations, Splicing, and Repairing of Damaged Cables," includes the G-38 requirements referenced above.
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4 To TENNESSEE 781018G005i VALLEY AUTHOR i
. . s, C. C. Stack. Project Manager. Sequoyah Nuclear Plant CONST (4) ^ .-
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SUBJECT:
SEQUOYAH NUCLEAR P! ANT INSUIATED CONDUCTOR *.
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- I# . REPAIR OF DAMAGED OUTER JACKET r < p;. .
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" f, W This is to confirm telecon between your Don Simpson and our Howard Romanowski
' '., ..^ , 9 , on September 26. 1978.
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sle:$;Y# 3. .f,?. .I.:' f '2.:'. ! 'T' 1. The following procedures will be applicable to minor damages (i.e.
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damage only to jacket with no insulation damage as determined by
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e Q e (-* CONST personnel) to cables outside the primary containment area. e,
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'- Class 1E cables or non-Class IE cables in area where there is a e
(( $?f*$h!.:p possibility of a steam-water spray. ' o r:s
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.[2 I* $((. . :' Thoroughly clean the area to be repaired by removing all foreign
,. material.
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, 2. Apply a layer of Raychem S-1024 red adhesive tape (half lapped) , ,
. over the damaged area with a minimum of two inches on either q..,;. ,j' f2// ?/, ,
side. P.?.:*2{.f .
- 3. A properly sized Raychem cable repair sleeve, type b'RS. shall be
'..h!I; 2.I$-: '7# applied over the area covered by the Raychem S-1024 red tape.
6 . : ,. 4. Follow manufacturer's instructions in completing repair--except 9,g./.j
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..;.'.. use an electric beat gun (no open flame) to shrink repair sleeve.
,c 5.
* ' e'- " g The repaired circuit shall have a permanent identification cable -
'f'?; : #4 *O'; *. ',' ,,7< tag with its unique designation per cable schedule or pull card
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.;} installed adjacent to the repair per electrical standard drawing
* ?.h'!,*d. *. * 'l' SD-E15.3.4. Documentation shall be made on cable schedule and/or f /*K.+.* .
A, cable pull cards where repairs have been made. g- g g ..., ..,
--a The manufacture shall be required to furnish a certificate stating the
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repair sleeves have been manufactued to an established quality cont rol
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*./' / ;. , - Non-Class 1E cables in area where there la no possibility of ste.im-1
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".y;.h?fC- . e.:. 2. A properly sized Raychem cable repair sleeve. type JRS. sh al l 0.
$ , _ ygi applied over damaged area with a minimum of two inches on cf t h.-r side . e e c
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. .:.4 ;:;2,.;i. :. October 12,1978 s '
1.t :.:p . . w w 4 SEQUOYAH NtlCIEJJL PIAVf * *
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INSULATED CDNDt!CTOR
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, . REPAIR OF DAMAGED OUTER JACKff * .*.;. f.(^.*
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e e eg 3. Follow manufacturer's instructions in completing repair--except ,' W W if.**j.y.* N.. *'. ., N use an electric heat gun (no open flame) to shrink repair ' I* *
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- sleeve. -
.,. ". 4. The repaired circuit shall have a permanent identification cable
'. . , tag with its unique designation per cable schedule or pull card
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c.s Installed adjacent to the repair per electrical standard drawing a w e SD-El$.3.4. Documentation shall be made on cable schedule and/or * *
<l .: s'.- cable pull card where repairs have been made.
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[.R '#' - 2.; .;. 2:* II. Where any damage to insulation or jacket of cables is found inside 1
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- .' primary containment, the cable (s) shall be replaced.
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sw 79031200.8 .- l Memorandum rnwnsessa vmmr wrnoarrr ! TO G. O. Black, Project manger, sogrooyah yealear Plaat, C32T (4) 790314F0551 ! I y . * *
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FROM : 1. M. Pieroe, segnoyah end Matta Bar Design Projoeta manger, 204 GB-K l DATE : March 12,15r19 EUBJECT: SE370TAE RK'I2AR PIAE - IMUIATED CSIUCTCR REFAIR W DMEG E @TER JACIEf
Reference:
My memoran&an to you dated October 12, ISrl8 (IIB 781013 936) 4 l This memoran&na supersedes the instructions given in the referenced w w w. .; ,
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s amoranA= and the following instructions shall apply: " . 1 l s I. The following procedures will be applicable to minor daneses (i.e. damage only to jacket with no insulatica damage as determined by
.. . .] CCEST personnel) to cables outside the primary contab=mnt area. re ~ _ _
-. h, Class lE cables or non-Class lE cables in area where there is a
],. Possibility of a steam-water spray.
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- , 1. Thoroughly clean the area to be repaired by remaring all foreign O material. Ew~ N y e
- 2. Apply a layer of Raychem 8-1024 red adhesive tape (half lapped) .
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- - over the damaged area with a mininum of 2 inches on either side.
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- a 3 A properly sized Raychen cable reImir sleeve, type WR3, shall be
- t applied over the area covered by the Raychem S-1024 red tape. c m ---e-g k k. Follow manufacturer's instructions in ecupleting repair--except use on electric heat gun (no open flame) to shrink repair sleeve. s Q 3 4 f.
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- 5. Class lE cables that have damage as defined above shall be non. '
N conformed. The NCR shall give the actual location of the damaged i ~ _. 9 area (i.e. tray identification, elevation, coluan line, building), e ' w/ Q The repaired area shall be identified by a permanent identification s ' y tag giving the nonconformance number to provide documentation of 5, or
. the repair.
. j kf The manufacturer chail be required to furnish a certificate stating
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'. . e' the repair sleeves have been manufactured to an established quality ;....... -
control pro 6 ram. .'. ~.$ I,
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.'. f.s Non-Class lE cables in area where there is no possibility of steam- cp.-
water spray.
.k 1. b,'fb' Thoroughly clean the area to be repaired by removing all foreign
.g material, .
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' SEDOIRE WCERR FIAEf = INTIATED COEIUCTOR l MM*TM W DMSGED CUTER JACIEE
- 2. A 3moperly sised Barches cable repair sleeve, type JES, shall be applied over danged area with a minh of 2 inches on either side.
Y 3. Foller manufacturer's instructions in caeleting reair--except use en electric heat gun (no open fisme) to shrink repair sleeve.
.'s II. Where any damage to insulation or Jacket of cables is found inside primary contaiment, the cable (s) ohall be replaced. fg
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.4 j1 n1 B. M. Pierce BNP HBR IB cc J. M. B.tllentine, Sequoyah P PROD '#
F. W. Chandler, W8Cl26 C-K (Coordinated with C. H. Sudduth)
- Roy H. Dmh , W149 c.x MEDs. E4BYT c-r N E. H. Hull, E7B24 C-K
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ITEM 16 Describe the extent to which repaired or spliced cable were allowed to be pulled into a conduit.
RESPONSE
TVA General Construction Specification No. G-38 and drawings require Class IE cables to be spliced in boxes or enclosures in seismic Category I structures, in electrical. manholes, handholes, and cable trenches. Splices for Class 1E cables are typically made where the circuit length exceeds the full standard cable reel length, the cable insulation or conductor has been damaged, or the point of termination must be extended because of a design change. General Construction Specification No. G-38 does not prohibit repaired Class IE cable from being pulled in conduit. However, repairs to the cable jacket
, generally are made after the cable has been pulled. Cable jacket damage to Class lE cables reautres use of either Raychem Type N (Nuclear grade) sleeving or NJRS repair sleeve, except Class 1E coaxial and triaxial cables which are not allowed to be repaired but must be replaced.
SQN's M&AI-07 includes the requirements referenced above. MKB:KEH - 1036h 10/23/86 O 4
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e be o f ENCLOSURE 2 9
7 SQN EMPLOYEE CONCERNS RELATED TO NRC QUESTIONS ON CABLE PULLING Concern Number Category Subcategory
~EX-85-076-003 CO 10900 -
IN-85-018-004 CO 10900 IN-85-097-018 NU 00000 IN-85-112-001 OP 30401 IN-85-138-001 Co 19200 IN-85-201-003 CO 19200 IN-85-207-001 EN 23800 IN-85-207-002 OP 30402 IN-85-213-001 CO 10900 IN-85-255-001 CO 10900 IN-85-295-003 CO 10900 IN-85-300-002 CO 10900 IN-85-325-005 CO 10900 IN-85-367-001 EN 23800 IN-85-433-002 CO 10900 IN-85-506-001 EN 23800 IN-85-581-001 CO 10900 IN-85-743-006 EN 23900 IN-85-743-008 EN 23800 IN-85-856-004 CO 19200 IN-85-856-005 CO 10900 IN-85-919-001 EN 23800 IN-85-935-001 CO 10900 CO 15100 IN-85-978-001 CO 10900 IN-86-028-001 CO 10900 IN-86-034-001 EN 23800 IN-86-036-001 EN 23800 IN-86-199-001 CO 10900 IN-86-201-001 CO 10900 IN-86-206-001 EN 23800 IN-86-262-003 CO 10900 IN-86-266-006 CO 10900 IN-86-310-001 EN 23800 XX-85-008-001 CO 10900 XX-85-094-004 CO 10900 XX-85-094-005 CO 10900 1936T Page 1 of 1 g .. .
s - m,a - e 9 l t O ENCLOSURE 3 t i 4 O l l { 1 I I I i ,1 1 1 i i
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., t!NITED STATES GOVERNMENT Memorandum ' TENNESSEE VALLEY AUTHORITY B43 '861014 901 70 : John A. Raulston, Chief Nuclear Engineer, W10 C126 C-X -
FROM : W. S. Raughley, Chief Electrical Engineer, W8 C126 C-K DATE : October 14, 1986
SUBJECT:
SEQUOYAH NUCLEAR PLANT CABLE ISSUES - NRC RESPONSE 1 l The purpose of this memorandum is to respond to NRC safety issues relative to ) SQNP cable issues. The NRC requested TVA to address this issue upon exit from SQN on September 22, 1986. ' s - [ _ Cable Damage Caused By Pull-Bys j The purpose of this section is to address the potential for cable damage which 4 might be caused by puli lines saving through adjacent cables during pull-bys. Due to the size of the cables relative to the size of the conduit, pull-bys occur generally in instrumentation and low voltage power and control level j conduits only. Typical conductor sizes routed in such conduits are #8 - #16 AWG. The inherent conductor strength limitations of these conductor sizes restricts the total tension applied to the pull cope and thereby the potential for damage to adjacent cables. { j In addition, TVA has restricted the type of pull ropes utilized to manila, synthetic fiber or hemp and does not allow the use of steel cable for cable pulling.
' The basis of this requirement is to prevent the abrasion of the conduit situation. inturior as well as the jackets s
of the cri= ting cchics in a pull.by i Recent interviews of Electricians who had actually performed the cable i ' installation, conducted by the NRC/ Consultants, indicated a thorough 4 ' understanding of the cable installation process and the relevant concerns. - These interviews substantiated conformance to proper construction practices j used throughout the industry and utilization of the engineering approved installation procedures and' specification and confirmed the presence of a I Quality Control Inspector on all Class IE cable pulls. In addition, the close j working relationship between construction and engineering was outilned j including the evaluation made prior to each class 1E pull to determine the
- best method of installation including determining the direction of the pull and the need for manual assistance at pu11' points to reduce tensions. If any
~
problems arose during a pull construction personnel stated that the activity was stopped until the cause could be determined. Engineering was often j consulted again at this time. - l To confirm the adequacy of its cable installation practices TVA recently { i reviewed nucioar the identified cable failures on several of its plants including five units. . This review did not identify any failures attributable ~ to improper cable installation. The results of all cable failures were well i j ROM i
, 10/14/85 13:03 P .12 ~
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l
. 2 J. A. Raulston '
October 14, 1986 SEQUOYAH NUCLEAR PLANT CABLE ISSUES - NRC RESPONSE within that predicted by IEEE-500-1984 " Guide to the Collection and
' Presentation of Electrical, Electronic, Sensing Component, and Mechanical Equipment Reliability Data for Nuclear-Power Generating Stations."
In addition. TVA has established a trending program to evaluate all failures, including those related to electrical cable, to determine the cause, potential generic applicability, and corrective action. This program will annure
, immediate action is taken should a future failure occur.
i s Cable pull-bys are not unique to TVA. The design, modification and addition process of any utility or industrial project mandates the routine need for cable pull-bys. A review of TVA's practices and procedures, including discussions with the personnel performing the work, indicates that proper methods were employed during such installations. This is confirmed by TVA's cable performance record to date and will be continually monitored for similar success in the future. This program of specification reouirements. translated into oroner installation practices through the use of trained personnel, and monitored for adherence to the initial goals has and will continue to ensure the adequacy and integrity of the electrical cables. The practice of cable pull-bys has not led to any degradation of the cables' ability to perform its function. Adequacy of Cables Installed In Vertical Runs - - The purpose of this section is to address TVA's approach to ensuring the adequacy of electrical cables installed in vertical runs which contain ' condulets at or near the top. The concern here is twofold. First, if the cable is stretched by its own weight over the small inside radius of the condulet the conductor may gradually creep through the cable insulation, shorting the cable. Second, the cables that are bent around this small radius may develop insulation cracks under mechanical stresses caused by thermal cycling or by their own weight. - TVA currently addresses these concerne by invoking the National Electrical Code (NEC) Article 300-19 " Supporting Conductors in Vertical Raceways." These requirements have been further refined to recognize the inherent support provided by frictional forces in horizontal conduits. In the refined evaluation the effective vertical cable weight is calculated and verified not to exceed the maximum working load of the conductor (s), not to result in excessive cable bearing pressure being exerted on the cable as it pass.es around the raceway bend and not to contribute any tension, beyond that
-inherent in the NEC (Article 300-19) limitations, to the termination point (s) of the cable (s). ,
l _ _FROM 1 0 / 1 4 / 8 5 .t.3 : 0 3 P. 3 .. _;i_-- . _-:-- M g,,
3 J. A. Raulston . October 14, 1986 , SEQUOYAH NUCLEAR PLANT CABLE ISSUES - NRC RESPONSE . As the above requirements were implemented only within the last two years, the Sequoyah project is currently inspecting all vertical conduit runs which contain 10CFR50.49 cables. These cables in a harsh environment have been selected since the mode of failure has only been linked to high temperature and/or high humidity environments as discussed below. All conduit runs which do not meet the requirements of the NEC are documented for the installed configuration and evaluated by engineering against the refined criteria discussed above. In particular, if a condulet which contains a cable bend (ELL or TEE type) exists at the top of a vertical run which exceeds the NEC limitations the cover of the condulet is removed and the cables inspected for adherence to the . minimum bend radius requirements. Assuring the adequacy of the cable bend radius also verifies that the cables are not stretched around the small inside radius of the condulet, and therefore not subject to conductor creep or insulation cracking identified as the failure mode of concern. It is noted that there may exist condulets in a vertical run which contain
- cable bends but which are not located at the top of the run and thorefore not
- i. Individually inspected. The basis for this is derived from a review of such a l conduit configuration. The worst case configuration would assume a vertical conduit turning horizontal through a standard field bend and then, after some horizontal distance..again turning vertical in a condulet. This conduit run would be evaluated under one of the following scenarios. If the lower vertical conduit section exceeded the NEC limitations the entire vertical run would be evaluated by engineering to ensure, among the other attributes described earlier, that excessive cable bearing pressure was not exerted on the cables. This would be determined for each conduit based on the smallest bend in the vertical run, in this case obviously the condulet. If the lower vertical dult section did not exceed the NEC limitations it can be seen from Art ca 300-19 and exception No. 1 that the length of cable could not exceed 25'Y'est. The acceptability of this cable length and the associated weight of cable is established below. In either scenario it must be noted that the frictional forces in the standard field bend and horizontal conduit section would serve to reduce tia resulting tension and therefore the bearing pressure on the cable in the condulat.
To substantiate TVA's position the results of 3-year detailed experimental and analytical study on cablo failure in a reactor containment have been reviewed and correlated to the specific configurations of concern noted above. This study prepared by Sandia Laboratories for the US NRC is entitled " Correlation of Electrical Reactor cable Failure With Materials Degradation";and was printed in March 1986. .
- FROM . 10/14/.85 13:04 P. 4 . u-Aa , _m.~,,.M .
, 4 I
J. A..Raulston October 14, 1986 ' SEQUOYAH NUCLEAR PLANT CABLE ISSUES - NRC RESPONSE These experiments were performed by hanging cable samples over curved supports, the curvature radit varying from .008 inches to .126 inches. The cables utilized were rated 600V with EpR insulation and a hypalon jacket. The purpose of these tests was to specifically determine the potential for the two modes of failure identified at the beginning of this section. The following conclusions are drawn from this report :
- 1. While the testing was performed on EPR/Hypalon the report recognizes the ability "to generalize the results to other cable types by correlating the observed cable damage with the rather well-known materials deterioration." The insulation types utilized in Class lE applications inside the containment at Sequoysh, a harsh environmental area, are silicon rubber and cross-linked polyethylene (XLPE). Of these two cablo materials, silicon rubber is composed of cross-linked bonds only while XLPE is composed of both cross-linked and crystalline bonds. The properties of cross-linked bonds, within the temperatures range encountered in the containment, demonstrate that they will not break and therefore as supported by this test data, ensure the adequacy of the silicon rubber cables installed. The crystalline bondo in the ILPE cables are subject to breakage at higher temperatures however the material is more dense and therefore results in lower deformation for a given load.
It should be noted that silicon rubber insulation with its superior material is utilized on all 10CFR50.49 power and control cables inside containment. It is these cables which are the heaviest and therefore subject to the greater bearing pressure loads.
- 2. " Creep shortout is observed only at very high temperatures (>1750 C) in ecmbination with very high stress (>500 lb/sg in)..."- "To generate an equivalent stress for a standard cable, a free overhang of about 120 foot would be needed." The highest temperatures experienced at Sequoyah would be 1640 C for less than 3 hours. This is less than that to which.the experimental cables were subjected. The experimental cable failed after 52 hours at 1900C with a stress of 880 lb/sq in. More importantly the report stresses the need for a combination of very h'igh temperature and very high stress (>500 lb/sq in or 120 feet of a #12 cable). As discussed above the stross on any 10CFR50.49 cable at SQN is limited by either the NEC limitations (25 feet for a #12 cable) or the allowable bearing pressure which is based on a limitation of 50 lb/sq in. Both are significantly lower than the values determined by test to cause failures.
- 3. "It has been found that with increasing time two phenomena occur which decrease the likelihood of creep shortout. First, the strands will position themselves such that the effective support areas increase.
Second, plastle bending of the wire leads to further increase of the effective support area. With this, the effective stress decreases and creep slows down." - FROM 10/14/85 13 05 P. 5 ;
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. s J. A. Raulston '
October 14, 1986 SEQUOYAH NUCLEAR PLANT CABLE ISSUES - NRC RESPONSE
- 4. " Temperature and radiation hardening slow down treeping with increasing exposure time and the mitigating phenomena described above (item 3) come
, into play." J
- 5. " Crack failure is, in principle, a phenomenon of lesser concern, as in addition to cracks extending through to the wire, considerable and long-term moisture is needed to permit or cause breakdown." "Once a crack starts enlarging, it relieves tensional stresses in its neighborhcod and prevents further cracking there." " Experiments have been performed during this investigation that show that the existence of a crack through jacket and insulator does not always lead to an immediate shortout, even if the cable in immersed in a conducting 11guld."
- 6. "...mechanica1 compression near the support improves the insulating material (e.g.. by removing bubbles, closing microcracks, and densifying the polymers)." " Cable breakdown in the support region therefore becomes less likely with increasing exposure..."
The above summarizes the most extensive and comprehensive industry testing performed and was for precisely the potential failures of concern. This testing however did not identify a credible mode of cable failure, given the temperature and analytical restraints of the Sequoyah design. This testing i confirms the adequacy of cables installed in vertical conduits, including the 4 use of condulets, and ensures that the integrity of the cable is maintained. 1 i w i g.p ~ . .
. S. Raughley l
l TMS:RB !' cc: RIMS, SL 26 C-K G. T. Hall, DNE, DSC-A, SQN G. Harding, ONP, O&PS-4, SQN ' N. J. Scruggs, DNE DSC-A, SQN R. C. Williams, W8 D225 C-K Principally Prepared By: T. Shea. Extension 2672 l DNEl-1075V l FROM 10/14/85 13:08 P. 6 TOTAL P...S
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