ML17252A956

Letter Reporting a 07/29/1973 Occurrence at Dresden Unit 3 Relating to the Fast Closure of MSIV 3-203-1B

ML17252A956
Person / Time
Site:	Dresden
Issue date:	08/07/1973
From:	Worden W Commonwealth Edison Co
To:	Giambusso A US Atomic Energy Commission (AEC)
References
WPW Ltr. #559-73
Download: ML17252A956 (2)

Text

.!'* .*.

Commonw.&. Edison

~-~ Nati~;aza,

. One First Chicago, Illinois

~-_; '1"'!1 Address Reply to: Post Office Box 767 Chicago, Illinois 60690

• Regulatory Docket File WPW *u.r. #559-73 Mr. A. Giambusso Deputy Director for Reactor Projects Directorate of Licensing U. S. Atomic Energy Canmission Washington, D.C. 20545 S~T: IJ:CENSE DPR-25. DRESDEN NUCIEAR POWm STATION, UNIT {f3, SECTION 6,6,0.l OF THE WHNICAL SPECIFICA'l'IONS, FAST CLOSURE OF MSIV 3-203-;m,

References:

l) Letter tran W. P~ Worden to Mr. Giambusso dated December S, 1972, concerning Fast Closure Time on 11 lB11 MSIV.

2) .Notification of Region m of AEC Regulatory Operations.

Telephone: F ~ Maura; 1030 on Juq .30; 1973 Telegram: B. Grier, 1250 on Ju4r 30, 1973

3) Dwgs: P+ m M-345

Dear Mr. Giambusso:

.This is* to report a con:iition relating to the operation of the unit, when during surveillance testing, main steam isolation valve (MSIV) 3-203-lB was found to h.8.ve a closure time of 2.6 *secs, which is outSide the limi.ts specified in the Technical Specifications *(Table *3. 7 .1). *These limits are *$ 5 secs and .?: .3 secs.

FROBUM AND INVESTIGAT:l(!{

At 0050, July 29, 197.3, with the reactor at a power ~l of ;o MWe, quarterq MSIV tim:!llg surveillance was being conducted.

During these tests, it was discovered that M3IV .3-203-lB had a closure time of 2.6 seconds, taster than the .3 second to 5 second limits

• specified. in the Technical ,.speCit:l.cations .(Table 3. 7. l). Both valves in

. the "B" steam line were prompt;q closed in accordance with section .3. 7. 2 ot the Technical Specifications, .am was maintained in that condition until a subsequent shutdown. The* MSIV's on the other three steam lines had closure times within the 3 second to. 5 second limits.

~~ Mr. A. Giambusso .~ ,.

The lim1ts specified on fast cl.osure or the MSIV*s are iDten:ied

. to preVent a rapi.Cil. ~ctor .isolation, and .subsequent rapid reactor pressuri-zation* am resu1ting relier valve operation. Closure ot one 1'5IV in 2.6 secom:ls instead ot 3 seconds does not significantq increase the* pressure spike or the potential tor relief valve operation. Add.itionalq, ~

pressure transient tram the fast closure of. one MSIV would be ti softened II b:r the slower :MSIV closure on the other three lines. Consequentq, it is concluded that the fast closure of the .3-203-lB MSIV was* ot no saf'et:r significance to the public or plant personnel.

CORREx:tlVE ACTION At present, Unit .3 is in the shutdown condition. Inspection of.

11 1B11 MSIV speed control will not be performed prior to letter issuance but will be made before.*unit startup.

A f'ollowup report will. be issued to specify the results of the investigation, the corrective action taken,. the resul.ting MSIV travel time, and the date on which "B" steam, line is returned to service.

Sincereq, w.t~

W. P. Worden SuperintelXlent Dresden station WPW:U>:jw cc: File/Are Corr. Gat. I