ML20058K549

Ro:On 710922,RHR Svc Water Pump 12 Motor Failed During Operation.Caused by Pump Discharge Pressure Below Required Pressures.On 710908,RWCU Demineralizer Isolation Valve Mo 2398 Failed to Close.Interlock Removed

ML20058K549
Person / Time
Site:	Monticello
Issue date:	10/21/1971
From:	Duncanson R NORTHERN STATES POWER CO.
To:	Morris P US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 9102120476
Download: ML20058K549 (3)

Text

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[w[e fly, DOCKETED UULC z (',- r lh L $> q Dr. Peter A. Morris DCT 2 71971

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p' Division of Reactor Licensing United States Atomic tnergy Commission g EtcutATCRY ^S C 00T2 7107 - Y s# , at stenen 6-66 0;cm ctEn u mnc ruar Washington, D.C. 20545 & man ro

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Dear Dr. Morris:

(b t LDiJTICELLO IUCLEAR GETERATI TG PLAIR 'u m Docket No. 50-263 Li cense fjo. DPP-22 ,

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.( Repo r t i ng o f Occu r ren ces  ;

, Two conditions have occurred recently at the Monticello iluclear Generating Plant which we interpret to be reportable in accordance wi th Section 6.6.C.1 '

of the Technical Specifi cations. The Region l l i Compliance i nsoector has been noti fied of these occurrences.

1. RHR Servi -e seier P- r e: 1 orn On September 22,1971 the #12 RHR Servi ce hater Pump motor f ailed during operation. At the ti me o f the failure, the pump was supplying water to the E12 RHR heat exchanger whi ch was being used to cool the torus water following HPCI tes t i ng. ' The motor failure resulted from a thrust

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bearine failure whi ch allcaed the rotor to rot aie eccent ri cally.

severely damaging the stator windings and laminations. T he pump mo t o r was repaired and reinstalled on October 16th. Fo!! cuing successfu.

testing of the system, the #12 RHR Service saier Pump was declared operational.

Following the failure of the #12 RHR Service Water Pump, testing of the remaini ns operable RHR servi ce water cumos disclosed that the pumo discharge pressures were below the recuired pressures when operating at indi cated rated ficw. Although the available data indicated that the flow measurements were erronesus, the plart was shutdown on September 24 while an investication of the si tuation continued. On September 25th, it was discovere'd that the basi c calibration data for the flow ori fi ce was in error. As a result of this error. the flow meters were not correct 1v calibrated and the indicated ficws were several hundred gpm below t he actual flow values. Ni t h t he co rrect ori fi ce cali bration data, it was veri fied that the RHR service water system performance was as requi red.

The plant was restarted on Septe :ber 25th.

2. Fi'..ra o r e Gr~ m ' le-iei-- Ve!va 4 0 len! ate On September E,1971, a reactor water cleanup demineralizer outboard isolation valve LD 2393 failed to close when an isolation signal existed following a reacto r scram. !he inboard isolation v'alve LO 2397 and the outboard isolation valve LO 2399 isolated the reactor water cleanup system as requi red.

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. w y The investigation of the problem revealed that a mechanical i n te r l o ck between the opening relay coil anc the closing relay coil was installed improperl y and was preventino the :!csing relay frem cperating. The improper installation of the mechanical interlock, whi ch woul d be expected to cause intermittent 'ype failures, was apparently made du ri ng t he manu f a ctu r i ne o f t he va l ve b re ake r. One previous coeratine failure of valve !.D 2392, which was reported in the Septembei 9 1971, letter to Dr. Peter k rris, may have Eeen caused by 3

the mechanical i nterlock problem.

The mechani cal interlock was removed and reinstalled properly. Val ve f 0 2398 was demonstrated to operate properly and isolate automati cally.

Unusual Occu rrence repo rts have been wri t ten for these two occu r rences and will be available to the Region 11! Concl i ance I nspector for re vi ew during his next visi t.

Yours very l y, P.O. Duncanson. Jr.. P.E.

Gen. Sp ui. of Power Plants e hani cal Chai rman I1ont i cel10 Eafety Audi + Comm ree RJD/caf '

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.CTION ECES$.RY h CONCURRENCE D ATE ANSWERED: [

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C ENT o .T cwsgy :

U Roc NO. Jo-M3 pE4CRIPTION: (Must US Uncl&&Salsed) REFERRED TO DATE RECEfvED ST DATE l I,tr reporting smusal occurrences at the km WM Monticello Delane Generating Plant... g , g , a yans (1) @ 9-22-71 the #12 alot service ,

, Water Ptamp motor failed during operation i  ;

pm; o.CwSU REs: 1,.;v  ; seg ylle (2) On 996-71 a Group 3 Isolation AE": Poa Yalva (HO 2398) failed to close* *

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