ML20084L799

Ao:On 740615,during Control Rod Withdrawal,Control Rod Drive L-9 Overtraveled to Uncoupled Position.Cause Unknown.Control Rod Will Be Removed During Next Extended Maint Outage

ML20084L799
Person / Time
Site:	Dresden
Issue date:	06/24/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084L796	List: ML20084L799 ML20084L803 ML20084L806
References
460-74, NUDOCS 8305230733
Download: ML20084L799 (2)

Text

_. .__ .________ _____________

• f% Commonvw- Ith Edison

". One First NI i P13:3. Chicago.1:bnois

{m . Address He to: Po2 Office Box 767

'@C) Chicago, Lino;3 C')690 BBS Ltr.#460-74 Dresden Nuclear Power Station R. R. #1 Horris, Illinois 60450 , ,a June 24, 1974 pr t ., ' /A/

(

l lf.y

-E! 11fifi[!n,

yf Hr. J. F. O' Leary, Director ,7 f.h 4;g'I/S/g g 4.

~J Directorate of Licensing U. S. Atomic Energy Comission

~~

f Q .. ,," e'r,m Washington, D. C. 20545 Y,/f y 2b x, _ g /g,

SUBJECT:

LICE"9E DPR-19, DRES]EN NUCLEAR PO'.!ER STATION, UNIT 02, REPORT MM OF ABSOR2%L OCCURRENCE PER SECTION 6.6.B. l.a OF TiiE TECliNICAL

_SPECIFICATI0::3.

UNCOUPLII:G OF CONTROL ROD DRIVE L-9.

References:

1) Notification of Region III of AEC Regulatory Operations Teleph,one: Mr. F. Maura, 1100 hours0.0127 days <br />0.306 hours <br />0.00182 weeks <br />4.1855e-4 months <br /> on June 17, 1974 Telegram: Mr. J. Keppler,1525 hours0.0177 days <br />0.424 hours <br />0.00252 weeks <br />5.802625e-4 months <br /> on June 19, 1974

2) Dwgs: P&ID H-34 D :r Mr. O' Leary:

This letter is to report a condition relating to the operation of the unit at about 0505 hours0.00584 days <br />0.14 hours <br />8.349868e-4 weeks <br />1.921525e-4 months <br /> on June 15, 1974. CRD L-9 (42-35), while being withdrawn from position "14" to 48, subsequent to placing unit on ayatem at 0433 hours0.00501 days <br />0.12 hours <br />7.159392e-4 weeks <br />1.647565e-4 months <br />, went into an overtravel condition. The overtravel l indication ic indicative of an uncoupled CRD. This calfunction is contrary to ocetion 3.3.B.1 of the Technical Specifications which requires that I

cach control rod shall be coupled to its drive or co=pletely inserted and the control rod directional or control valves disarmed electrically.

PR_0_BLEM l Unit #2 had been placed on system at 0433 hours0.00501 days <br />0.12 hours <br />7.159392e-4 weeks <br />1.647565e-4 months <br /> on June 15, 1974, I

while in the process of withdrawing the drive from position "14" to "48",

a " rod overtravel" alarm annunciated and both the four rod and full core displays for the rod went b lank.

The initial action taken was to attempt to recouple by insertin3 and withdrawing the rod three (3) ti=es. On each series of insert and withdraw, the rod went into overtravel on the coupling check.

i 0305230733 740700 PDR S ADOCK 05000237 PDR

d. . , .U ';; '/

Hr. J. F. O' Lea June 24, 1974

~

• l ItNESTICATION CRD. flange no.620C was overhauled and placed in position L-9 during the spring 1972 refueling outage. A review of previous operating data, scram times and withdraw stall flow, indicates no abnormal conditions.

CORRECTIVE ACTIONS The corrective action taken was to insert the rod to position "00",

electrically disarm it and remove it from service on June 15, 1974. In ,

addition, the three (3) rods surrounding L-9 were inserted to position "00" in order to prevent possible nuclear consequences. A shutdown margin of 2.78 Sk has been calculated for 1 rod out and all others in by BWR Syste=3 Department of General Electric Co=pany.

The control rod drive will be recoved during the next extended maintenance outage. At this time, a thorough inspection will be made to determine the node of failure and a followup letter submitted to your office.

EVALUATIONS This drive uncoupling did not endanger public health or safety because the blade was capable at all ti=es of being inserted into the

. i.ur cuca. This uuuuuviina wheuwmeuva v s o u e d i.w it.e fourute. 7eLiuutv 19,, 1973 and _ Na'rchT_14, _19 74. _ At these times, three (3) CRD's and one (1)

CRD respectively,' experienced uncoupling during reactor startup. The ancmalies were explained as having occurred because of dislocated inner filters. , At_thisAicc theu failurc mechanism is not known_, .therefore, a followup letter will te issued subsequent to L-9's overhaul.

Sincerely, 7 -/7&-.* :R Y5'

'. V-f'*-s G.

j /M:;:-; %

B. B. S tephanson Superintendent BBS: RLW: do