ML20236T963

PN-75-044:during Extended Refueling Outage,Licensee Discovered Circumferential Cracks in Thin Section of CRD Collet Housing.Cracks Have Been Found on 12 of 21 Drives Checked & Stated to Result from Thermal Stress

ML20236T963
Person / Time
Site:	Dresden
Issue date:	07/02/1975
From:	Jennifer Davis, Thornburg H, Warnick R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE)
To:
References
PN-75-044, PN-75-44, NUDOCS 9807290203
Download: ML20236T963 (1)

Text

_ _-_-_______ ____________ ____ . _ _

PRELIMINARY NOTIFICATION - NOT FOR PUBLIC DISCLOSURE July 2, 1975 -

PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE --PN-75-44

'This preliminary notification constitutes EARLY notice of' events of

.+ POSSIBLE safety or public interest significance. The information presented is as initially received without verification or evaluation l and is basically all that is known by OIE staff as of 11:30 a.m. on date of this notification. IT SHOULD BE SPECIFICALLY NOTED THAT THIS l

l NOTIFICATION MAY CONTAIN INFORMATION THAT LATER MAY BE DETERMINED TO BE INACCURATE OR INCONSISTENT. AN OFFICE OF INSPECTION AND ENFORCEMENT

! NOTIFICATION OF AN INCIDENT OR OCCURRENCE (BLUE SHEET) SUBSEQUENTLY WILL BE ISSUED IF WARRANTED.

i'"~

Tacility: Commonwealth Edison Co. (Dresden 3)

Subject:

CRACKS IN CRD COLLET HOUSING During the extended refueling outage, the licensee discovered circum-ferential cracks in the thin section of the CRD collet housing. To date cracks have been found (using PT) on 12 of 21 drives checked.  ;

The cracks are stated by GE to result from therral stress. The  !

cracks apparently are not through-wall, and do not go around the entire circumference. The licensee reported complete shear of the [2 collet housing at this location would interfere with control rod N

~withdrawal. Evaluation is still in progress to determine whether  !

ya a complete failure could interfere w'ith the scram function. The licensee is determining what corrective action will be required. [

IE:III inspectors are at the site following the matter.

Decision on a press release will be made after evaluation of the cracks by GL and Commonwealth Edison. c;

/'

OIE (Region III) received notification of this occurrence by telephone from the IE inspector at the site at 11: a.m. on 6/27/75. The potential consequences of the cracks were determined on 7/2/75.

f)

Contact:

RFWarnick, IE x7261 HDThornburg, IE x7353 JGDavis, IE x7541 A

g Distribution: 2 Chairman Anders Commissioner Mason S. J. Chilk, SECY Commissioner Gilinsky Commissioner Rowden G. F. Murphy, JCAE .

Commissioner Kennedy C. C. Kammerer, CA L. V. Goyd.ck, EDO .- D. F. Knuth, IE J. A. Harris, P4 .

B. C. Rus'che, NRR H. H. Brown, ISP T. J. McTiernan, AIA

! K. R. Chapman, NMSS H. K. Shapar, ELD Transmitted: PBldg[.  ; H St  ; MNBB7  ; Luge t

a PRELIMINARY NOTIFICATION - NOT FOR PUBLIC DISCLOSURE

\ ..

9807290203 750702 ""

PDR 18 E PN-75-044 PDR (J ,.

_ _ _ _ _ _ _ _ . _ _ _ _ _ . _ _ _