ML19326C048

RO 50-313/76-10:on 760526,leak Discovered in Decay Heat Flow Element Instrument Tap Socket Weld.Caused by Crack Due to Excessive Vibration or Improper Fit.Defective Weld Replaced. Cavitating Control Valves CV-1428 & 1429 Will Be Replaced

ML19326C048
Person / Time
Site:	Arkansas Nuclear
Issue date:	06/18/1976
From:	Cook R ARKANSAS POWER & LIGHT CO.
To:
Shared Package
ML19326C040	List: ML19326C039 ML19326C048
References
NUDOCS 8004180726
Download: ML19326C048 (4)

Text

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UCENSEE EVENT REPORT CONTAOL BLOCK:l l

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8 NAME LCENSE NUMBER YPE TY i

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7 89 14 15 25 28 30 31 32 CATEGORY T

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EE I i pipe lo valve weld. TL crack was circumferewl.ial around approximately V3 l

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@l leh kbe W9Id. CAu5e Ene f.o eXCetsiVe Vibration or impropey hitup. Tipe and l

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{Z.J lE la la la l (N_J 7 89 10 11 12 17 43 44 47 48 CAUSE DESCAtPTION DG lCause of Grack was due do excessive vibraUen or immoev Oduo Tioe and I

7 89 80 lvalue were rmoved and wew 3;pe and valve indalleL I

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', d I-Reportable Occurrence I:eport No.

50-313/76-10 2.

, Report Date: June l'8, 1976 3.

Unurrence Da_ty: May 26,1976 4

I:ac ility:

Arkansas Nuclear One-Unit 1 Russellville, Arkansas 5.

Identification of Occurrenec:

l Leak in socket weld in decay iteat flow element instrument tap.

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6 Conditions Prior to Occurrence:

Steady-State Power ;_

Reactor Power n

Wth llot Standby Not Output n

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'5 Cold Shutdown Porcent of Full Power n

Refueling. Shutdown X'

Load Changes During Routinc 3

Powrr Operation

}. 'j Routine Startup Operation i

Routine Shutdown Operation

.fI Other (specify)

Defueled i

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7.

Description of Occurrence:

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A leak was discovered at 1400 hrs, on 5/26/76 in a socket weld up-l stream of valve Dil-1401-A which is a root v11ve for the flow in-

,i strument for flow element FE-1401. The leak occurred at the 1/2" pipe to valve weld. The_ crack is circumferential around approxi-mately 1/3 of the weld.

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!! arch 23, 1976 N5hMO, Rev. 4 Page 2 of 1

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!!cportable Occurrence l:cport No.

50-313/76-10

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Des i gna t io n o f Appa ren t Caus.e...o.f..O..cc..u.r..rence.:

j Design Procedurc flanufacture IJnusual Service Condition I

including Environmental Installation /

1, Construction Component Failure Operator Other (specify)

X The cause is due to excessive vibration or. improper fit-up causing a_ crack.

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9.

Analysis of Occurrence:

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Since the Reactor was defueled and the decay heat system was not i

I required to be operable, there was no hasard to the health and l

safety of the public.

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Att:chment "C"

itirch 23, 1976 NSI'- 10, Itev..I l' age 3Of4 w,,

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4 Itcp0rtable Occurrence !!cport do.

50-313/76-10

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Corrective Action:

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'ihe defective weld was removed by cutting out the pipe and valve and a new valve and pipe were installed. Tle excessive vibration will be resolved by replacing the present flow control valves (CV-1428,1429),

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'I which are cavitating, with'more suitable control valves or by adding l,

orifices downstream of the present control valves with full flow Lypass lines containing ES Activated MOV's.

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Failure. Data:

None.

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,I At ta cionent "C"

March 23, 1976 NSP-10, llev. 4 Page 4 of.1 i

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