ML20009F473
| ML20009F473 | |
| Person / Time | |
|---|---|
| Site: | Sequoyah  |
| Issue date: | 06/15/1981 |
| From: | Mills L TENNESSEE VALLEY AUTHORITY |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| References | |
| 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8107310210 | |
| Download: ML20009F473 (4) | |
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TENNESSEE VALLEY AUTHORITY CHATTAt400GA. TCtfivE2SEE 37A01 (jppfp
' OP 3100 Chestnut Streat Tower II June 15, 1981 It)de #rl SQRD-50-326/81-36 f
ffpyl h f, Mtv. Jar:aa P. O'Reilly, Director Office of' Irmpection and Enforcemant y
U.S. Hoclear Fe6ulatory Coenission Region II - Oui.to 3100 101 Marletta Street ff CS Atlanta, Georgia 30303
Dear Mr. O'Reilly:
$EQUOYAH tiUCLCAR PLANT UNIT 2 - if0 TORS RATED WO V01.T3 GH A 480-VOLT sysTEN - SQau-50-320/81 rINAL PJWORT The subject deficiency was initially reported M HRC-0IC Inspector II. V. Crlenjak on April 27, 1961 in accordance uitt 10 CFR 50 55(e) as HCR SQ!? ESB 8111.
A.n interim report nu :n.tbisttted cat liay 28, 1981.
Enclosed is our final report aa discussed sfith Inapoctor T. Gibbona on June 12, 1981.
If you have nuy questians, please gst in tuuch with D. L. Lambert at FTC 837-2581.
Very truly yours, TCHilESSEE VALLEY AUDIORITY D
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'.h L. M. Iftlle,1 tager Huclear Regulution and Safety
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2 U.S. Nuclear flegulatory Cocclusion lOL l l) U 1*a-i Washington, DC 2055S 3;
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i encLocune SC0"OiAlf NUCLEAll PLANT UNIT 2 MOT 0l!3 11ATED 4tl0 Vot#5 OH A 480-VOLT S'tS'fttt SQhD-50-328/8 )-36 10 CFR 50.55(e)
P_IHAL REP 0fti 04scription of Derici g There are six motora in imit 2 that have a namaplate v lt volts ao and are rupplied from the 480-volt ac Clasa It auxiliary o
a6e rating of 490 system of units 1 and 2.
HEMA MG1-12.43
- 1967, power tuotors cast be capable of operating undar the steadrequires that inductLon condLttons with a voltage variation of plus or tuinus 10 percenty-state runntng frequency.
This contrasts with 506 volts thst a tootor rated 460 voltsThe mu at rated TVA desLgn allows a muitmus voltage of 506 volta at the m t can withutand.
which is 15 percent abova rated voltagd o or terzelnals This dicarepancy was dtcoovared in the prepat% tion of thi for those motors rated 40 verificati(m li.:t on the 480-volt shutdown board loud.
e field natneplato alco existo at Ifatt.s Bar Nuclear Plant and is documented aa This deficiency report Mbil8ED8104 The affected notora at Sequoyah unit 2 are rance (1) Conpanont Cootins System Pumps 24-A and 28.B to C S I l b Isolattcm Valve (2-FCV-70-78) ae (2) Component Cooling System Pumps 24-A and 28-8 to C 3 I l Inotation Valve (2-PCV-70-76) n et (3) Diestt Generator 2A-A Engine 2A1 Lubo Oil Circulation Pugn Motor (0) Diesel Generator 2A-A Engine 2A2 Lube oil Circulati on Pump Mator (5) Diesel Generator 28-B Enaino 2B1 Lube OL1 Circulati on Pump Hotor (6) Diesel Gent.'ator 28-D Engine 2B2 Lube Oil Cteculati on Pump Motor
_ Safety Impicati >ns Tha mutuart Claan IC aun).1wy power system is 460 volta plus 10 porce tvolta ac, which is in exceca of 110 percent. of 490 volts.
n, or 506 volts during plant shutdown which teuld be approxinately 20 perco Assuming uutt
- Howevor, excess of 110 peravnt of their rated values, the motors wty su n of the tLtme.
n loss of 1Lra over an extended period of time, er some attributed to the follo91ng two condi.ttons that would be presentThis loss of life c 1,
'the available, locked nator current would increase but would be charnateristic of the motor.accompanted by a corresponding decrease tn the acc qpfA)}QQA]AA0bESb
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i 2.
Thero my be a very slight rise in the total temperature of t.he motor.
Alt. hough a decrease of approxiscately 4,C could result due to a decrease l
in the f ull load amperes at 115 percent rated voltage, an increase in
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the coca losses my offnet ths doorease. Th3 core loaues would increase due to sn incresac in the total flux.
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i Loos of life dependa upon severa.1 factors such as how of ten the motors are I
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started and how long the motors remala under locked rotor conditions.
The 4
oore locaes are predominantly a function of the reluctance of both %e core
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and the air ga.6 and the total. Plux. The reluctance of the iron core is l
1 ustally di.sregarded due to its relativaly small magnitude in coicparison with the reluctence of the alc gap.
Therefore, what increase occurs in the iron core losses may offsot the temparature decranse cited in No. 2.
In any case, whether the loss of li.fo is realiced due t.o condition No. 1 cr 2, the destructive mechanism would be a loss of mechanical durability and dielectric arrength of the motor insulation system. The tctal failure of the insulation aya'em muld result in a surge of current, the magnitudo or which should t. rip the motor circuit breaker.
If the rootor breaker failed to open, the feeder breaker to the boa.rd would be requirod to trip. Thia would constitut.e a faDurs Lu that train.
Sitatitaneous (M1ure of " identical" motors subjected to identical operating conditions is very unlikely.
The dostructive m.ichantom discussed abova works on the " weak link" of the motor insulation systein.
It is not prob-able thab this vulnerability will occur in the sama locati.;m and to the same degree in each motor. As a result, t.ha destructive mechanism will act upon the vulnerable areas of different motoes at a different rate, thereby making the probability of slo:ultaneous failure of t.hene motors quite sna11.
This situation abould not affect the ability of the plant to operate sa fely. The cot:.ponent cooling system pump inlet isolatica valves are infrequently energiced for short periods of t.ima in order to isolate sections of the component cooling water system.
In all cases, thane motors are opened (or alooed) under canual control. Because of their infrequent une and t.he short periods of operation (essentially these motors on).y operate long enough to open or close associated valves), the @0V rating of these motors util not result in any detect.able leas of life.
The four lube oil circulation pump motors are not required either for alco. tup or operation of t.hs diesci Generatora, The one-horsopower motors are required solely to circulate lube oil and c:o
'n minirntm lube oil pressure when the diosels are not operating and to unist in removing heat from baarings when the en61ne is r> hut down.
Failure of those motors would result in an indication of low lube oil presnure in the 140R.
The diesel generator engine lube oil circulation pup's purpose is to ruaintain lube oil pressure whLle the diesel Genet at.or to inoperative and to remove heat, from the hearinga upon shutdown.
Although ralluro of these pumps 8 motors uould mault in a low lube oil proscure indicat.Lort in the main control inom (which would initiate operat.or acLion to investigate and resolvo any problem) it is possible that tha dicael engines could be requi. red to start during the period of tisak,that a lubs oil eleculation
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o pump motor was not operational.
ThLa teuld result in wear to Inoving engine paren that could have been prevented had the luhe oil circulatton purnpa been opeerat,lonal. This could tiot prevent diesel r;enerator startup un1*as t.he engine had repeatedly (and negligently) been started without the benefit of tubre oll circulation.
TVA had addressed this pocaibility by lesulng a report of nonconformance and has arbmitted a final report to the HRC (MBB 79-26, Octob2c 11, 1979, L.14. Ifilla to J. P. O'Reilly) which documents procedures which are now in effect at Sequoyah which admittistratively preclude t.ha posalbility of repeated startup of t.he dieselo without the benefit of Luba oLL circulatLon.
Carrcct Lve J.c tLon In itsht of the roautta of TVA's r ecent taalynia of the sub, ject deficiency, Lt is no lon6er necessary (as stated in our previous luterim report-) to contact vendora of the affected cnotors. Tht r.nalyals has clearly illustrated that no correctlve schion is required for the component cooling system isolat.Lon valve motors as these rnotora are adequately rated for their intended purpoca.
In addition, TVA will install a reduzidant direct current (notor for the lube oil circulation pumps. Tha installation of this rootor will take place during the first att 2 rerueling outage., Installation of thic rnotor will ensure lube oll circulation redundancy during all phases of diesel opera tion.
Ifo signifloant effects of loan of life (i.e., extensive losa of mechanical l
durability or dielectric strougth of motor insulat. ion) should register in I
1 t.hese stora curing the pariod from now until the first retteling otttage.
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