ML20084J435

Ro:On 730120,during Partial Closure Testing of Msiv,Valve 2-203-1A Found to Have Faulty Position Indication.Caused by Bank of Limit Switches W/Loose Actuating Arm.Switches Repaired

ML20084J435
Person / Time
Site:	Quad Cities
Issue date:	02/09/1973
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084J415	List: ML20084J421 ML20084J427 ML20084J435
References
BBS-73-15, NUDOCS 8305120625
Download: ML20084J435 (3)

Text

_, _.. _. - ._

r .

^

-C.S

c. -

• MM 'f .-ComrOwealth Quad-Ljs Nuclear Pcwcr Edison Station 'l I i *

• 4i .j

( E d. ~ PostCordova, Offico Illinois Dox 216 G1242 n

c '/ /g' f,

g N (f ':!Telephonc300/654-2241 f 7 .

J_%

. I T.

Ma o ,. '.3 J: 3 D

'b (f & } lI0 fi >CX BBS-73-15' A .,

\'hG / Q '/

'M','m % L..

o February 9,1973 t

Mr. A. Giambusso

Deputy Director for Reactor Projects  ; '"

Directorate of Licensing U..S. Atomic Energy Commission Washington, D.C. 205 45

Reference:

Quad-Citics Nuclear Power Station, Unit 2 -

, . Docket.- No . 50-265, License DPR-30, Appendix-A t

Section 6.6.C.

Dear Mr. Giambusso:

1The purpose _of this letter is to inform you of the details Econcerning the failure of an electromatic relief valve P .following an isolation and scram on Unit 2. This . o ccurren ce

~was . reported to Mr. John Fishbaugher of Region III Compliance

..on January 20, 1973.

~

DESCRIPTION - 0F INCIDENT

j. At'2: 53 AM-on; January 20,-1973, routine partial closure -

r. ;I - testing of the Main Steam Isolation Valves was -being per-crormed in -accordance with Technical 'Spe cification 1. 7.1.d. 4 Ih- During testing, MSIV 2-203-1A ("A" steam line inboard valve) gg a

was-found,t'o-have. faulty position ind' cation;rall other MSIV's ~ prov_ed toJoperate - satis factor 11y . Upon' subsequent-jh .

retesting --of MSIV 1A, the -test switch was -held -to ~ the " TEST"

,SR positions for a _ long enough . time _ to1cause : the valve _ tc con-

hf tinue to close - beyond the 110 per lcentJ closed position. -

4 g: ' This : action fled :-to. high steam flow -(7120%) -in :the' other

- three Esteam linesLfollowed by e- Group. I- isolation and reactor

- ' (1 . scram from MSIV: closure. The1resulting' pressure: transient cp3 Y caused 'neveralz eleotromatic relief valves -to operate' auto-

' matically ~ and, at-: least .two safety valves to -leak or:partiallyj open. : One; additi.onal; relief valve was : also manually operated. -

-The reactor fwas subsequently brought : to the fcold' shutd '

condition.

, .. 9 E '

COPY SENT REGION ~

h

~

F 3 -8305 E M a go625 =a % 'h 6 A y $_- ;1179 I' I

{--

7 m

(~N 5

+- O  : o

, , Mr. A. Giambusco ~2- February 9,1973 IMMEDI ATE ACTIONS Upon receipt of the isolation and scram, the reactor was verified to be properly shutdown. Electromatic relief valve 2-203-3E was operated manually to control the pressure.

Prior to this operation relief valve 2-203-3A was observed to be oscillating open and closed during the pressure tran-hient. Later an " Auto Blowdown System Power Failure" alarm was received and the 3A relief valve was found to have blown its control circuit' fuses..

Station management personnel were notified of the incident and an Operating Engineer was called out to evaluate the plant condition. Electrical maintenance personnel uere subsequently called in to investigate and repair the faulty position indication 'of the 1A MSIV, and the control circuit j problem of the 3A relier valve.

INVESTIGATICH i

i Inspection of the position indicating limit switches on the 1A MSIV revealed that one of the two banks of limit switches.

on that valve had its actuating arm loosened so that the "normally Closed" contacts were in the open position. Addi-tionally, the contacts on both banks of limit switches were found to be corroded. This condition caused one relay (2-590-102A) in Reactor Protection System Channel "A" Trip Auxilliary ,

circuit to be de-energized when it should normally be energised.

. Although this failure was in the safe direction, the operator was unable to detect valve travel by actuation of this relay and he did not realize the valve was closing. The switches were cleaned, repaired, and tested during the shutdown period.

Inspections of the "A" Electromatic relief valve solenoid and control circuit revealed that the operating coil was.

burned and that one set of control relay contacts had welded shut. She rapid oscillations of this valve may have ' caused the operating coil to overheat since during. initial opening

- the circuit draws a much higher current than uhen it is holding the .valveL open . _ Also, this valve had been operated numerous times -in the past during the special -testing to inves tigate premature opening of safety valves. and torus pressure tran-sients. . These operations _. may have ' deteriorated the coil windings to the extent 'that a complete ' failure - occurred when the coil'was operated several times rapidly. This' possibility is currently being investigated .uith 'the vendor.. ' Die need for. special testing and a thorough study cf the. coil per-formance in being evaulated.

.~-Q'

, ,., p ', i w/

g Mr. A. Giambusso February 9,19 73 The coil failure caused the circuit to continuously draw high current and ultimately welded shut the control relay contacts. The circuit was then interrupted by the control fuses blowing. This failure did not affe ct the operability of the other four relief valves and as stated above the reactor was brought to cold shutdown thereby complying with Limiting Condition for Operation 3.5. D. 4.

During the shutdown, the rupture discs on the main steam line safety valves were inspected. It uns found that one of these was blown out and that six others were broken.

Upon inspection of the multi-point control room temperature recorder it was concluded that tuo of these discs were probably ruptured during this incident. The other five may have been broken by a safety valve ler1 king during this incident or they may have broken during the previously men-tioned special relie f and safety valve tes ting.

No signs of damage or significant steam release from the safety valves were detected in the drywell. The conclusion that a minimum amount of steam was released to the drywell is also supported by several other facts. Activity levels never exceeded 10,000 cpm on the Continuous Air fionitor sampling drywell air throughout the incident. Tnis is typical of previous c::perience following any scram from high power.

Drywell pressure increased from cero to 3 psig during the first 10 minutes of the transient and then spiked to .4 psig for about 1 minute. This increase was primarily due to relief valve operation. Experience obtained during the torus pressure transient tes ts on Octcber 20, 1972 substan-

) t$ntes this. When the 3A relief valve was opened for 25 minutes during this test, the drywell pressure increased by .4 psig due to noncondensible gases discharged to the torus and ternerature increase. The torus to drywell vacuun breakers relleved the prensure to the drywell during the transient. The valves were then tested satisfactorily prior to s tartup in accordance uith surveillance requirement 4.7.A.4.a.

This incident has been reviewed with our Mechanical and Struc-tural Engineering Department. Investigations into the reasons and causes of the premature opening and leakaFe of safety valves is centinuing by that department. A report, "Dresden Safety Valve Analysis", will be submitted by Commonwealth Edison in the near future.

Qy c,.>,a y rmd em u$.

Very truly.yours,

,4 8[

COMMONWE ALTH EDISON COMP ANY QUAD-ClyIES .NUCLBAR-P,0WER STATION y,[ [ p/,,nf) > ,gM t hI R. B./Stephenson "

St h Station Superintendent BBS/lk

.- .n