ML19317F383

Unusual Event 270/75-19:on 751031,valve 2LP-21 Failed to Close During RCS Fill.Caused by Loose Mounting Bolts on Valve Motor Operator.Motor on Valve 2LP-21 Replaced & Bolts Tightened & Lock Wired.Valves Checked for Loose Bolts

ML19317F383
Person / Time
Site:	Oconee
Issue date:	12/05/1975
From:	DUKE POWER CO.
To:
Shared Package
ML19317F377	List: ML19317F376 ML19317F383
References
RO-270-75-19, NUDOCS 8001140636
Download: ML19317F383 (2)

Text

_ _

+ ,

bN -

IDUKE POWER' COMPANY -.

OC014EE NUCLEAR STATION' ((gg kpg f$ ,

(Report No.: UE-270/75-19 Report Dates: December 5, 1975 g.g.g g g {$"[l

. Event Date: October 31, 1975 Facility: Oconee Unit 2,, Seneca, South Carolina ES valve failure during Reactor Coolant System fill

~Identif cation of Event:

Conditions Prior to' Event _: Unit.in Cold Shutdown Description of Event:

' On october 31, zl975, _0conee Unit 2 Reactor Coolant System was being An attempt was filled following a' shutdown.for reactor coolant pump seal repair. '

made to cycle valve 2LP-21'to complete a station modification involving The replacement of thermal overloads'in the valve's electrical cables.

valve, which is located in the line between the unit's borated water storage d but-failed to-tank-(BWST) and low. pressure injection (LPI) pumps, opene ,

close and resulted in water from the BWST draining to the Reactor Coolant System.

Valves 2LP-1, 2LP-2,yand 2LP-3 were immediately closed, isolating the LFI reactor coolant return line from the BWST and securing the. Reactor Coolant System fill through valve 2LP-21. Valve 2LP-21 was then closed manually.

-Apparent Cause of Event:

This-event was apparently caused by failure of the motor which operates the valve. This resulted from binding which. occurred between the valve stem Investigation and revealed the-motor operator while the valve was being cycled.

that the four bolts securing the motor operator to the valve body were loose, causing the valve to bind when the motor was operated.

Analysis of Event:

Valve 2LP-21 'is an Engineered- Safeguards valveLPI which is normally pumps following closed, an ES but

. opens to supply water'from the Unit 2 BWST to'theopen as would have been

~

actuation. In this incident, the valve failed In addition, the redundant valve 2LP-22 was required byJan ES' actuation.- .

It is concluded that the operable'and is-sized to supply,both LPI pumps.

~

health and safety of.the public was not affected.

Corrective Action:

' The damaged motor. on valve 2LP-21 was replaced, and the motor-operatc -

mounting bolts were. tightened. A further check revealed that theILP-22, bolts and

! securing the motor-operator to the. valve body on valves ILP-21, As a corrective: measure, these bolts on valves 2LP-22 were also? loose.

LP- 21: and LP for all three Oconee units:have been lock wired to prevent 11oos'ening. ,

i M. ,

'2 '

gd911401,36  ;

b ) \%'

- _ _m.m. . t

xn e ,y '?(

~ p - - .

(

n s

-Q' , ^;,' , , _ ~ ' ,' k : n '

• c .

s

, , a c; y ..

-r, -.c -

. f ,

' ,- . . n 3, y - . 4 r t f

.n+y - - , -

~

.' f- -.~

g/[A:a

-. ii M- ,

s

L ,

- <e ic'of other ES-motor-operate d~ valves will.

m..

_. . f w. s

. , . . . i.. .~

/AdditionallyF a!representat ve samp

, - be necked for loose' bolts by1 January 15,- 197 6. :- - If.-this is determined to be .

eneriegproblem,'all ES motor-operated valves will'have lock wires placed

(

fe die motor-operator modnting' bolts.'

'J .

fj-o

& J k M l

( _

4.

t

- a r

's f :

,e b

%d

..t.

k gk

,'s 4  ?

.- *-L  !

. , - l-I l

/

w =

' 6*

f H.

i f r .

p .-

f. ,

-~

g 6 s16 S

f I

',J " , [- i n ' 1:  ?'

) ,

m .,. , g" ,g-I

. ., (  ;,

6 1

. s.

y

- 4 -a - r h.k j ,

4

1. # 4 s

a- <

,\

y 3

, Jl y[?:.

' ~

l y- . - - f?: ;

.  :\

s ,'

O

• p.

t -

y "

g ' , , ' " , ', v ,

1 '."-

,ey.

6 #

[  % '

,, t

'. y;.,h(-. _. [

.a

?

,-)

p-e.,

ll

.-_r- ..

,, 3 _ ;y

,s

+

N ',, -

g _

., . , ; . q- ; -. .- -+, , ,, . . _ . . . ., , _;

• " *