05000237/LER-1976-068, Regarding Discovery of Control Rod Drive F-5 to Uncouple and Overtravel When Withdrawn to Position 48

Regarding Discovery of Control Rod Drive F-5 to Uncouple and Overtravel When Withdrawn to Position 48

ML17252B410
Person / Time
Site:	Dresden
Issue date:	01/10/1977
From:	Stephenson B Commonwealth Edison Co
To:	James Keppler NRC/RGN-III
References
BBS Ltr. #27-77 LER 76-068-00
Download: ML17252B410 (3)

LER-1976-068, Regarding Discovery of Control Rod Drive F-5 to Uncouple and Overtravel When Withdrawn to Position 48

Event date:
Report date:
2371976068R00 - NRC Website

text

Commonwe9 Edison

• ~"""""""'"*,.. :Dresden Nuclear..-ower Station R.R. #1 Morris, Illinois 60450 *

, Telephone 815/942-2920 B6S Ltr. #27-77 January 1 o, 1977 Mr. James G. Keppler, Regional Director Director~te of Regulatory Operations - Region I I I U. S. Nuclear Regulatory Commission 199 Roosevelt Road G*l en E'Ll yn., 111 i no is 60*IJ ]'

Enclosed please find Reportable Occurrence report number 50-237/l976~68.

This report is being submitted to your office in accordance with the Dresden Nuclea*r Power Station Technical Specificati9ns, Section 6.6.B.

/

BBS :jo Enclosure

_.,,............ ~~?;,~~~~~~~-

~':: "A,.

B. B *' tep, en son Station Superfntendent Dresden Nuclear Power Station cc:

Director of Inspection~ Enforcement Director of Management Information & Program Control Fi le/NRC

LICENSEE EVENT REPORT CONTROL. BLOCK: l ** I~ I I I I

(.ASE PRIN:r AU REQUIRED INFORMATION].*

• ~

LICENSEE 0¥

, NAME lol 1 I I II L I o I R I, s I 2 I 7

B 9 14 CATEGORY REPORT TYPE.

1 6

LICENSE LICENSE NUMBER TYPE I 0101-101010101°1-1°1°1 14 I 1 I 11 1S 25 26..

• REPORT SOURCE OOCKl;T NUMBER EVENT DATE 30 EVENT TYPE I 0 13 I 31 32 REPORT DATE

@TI]coN'T I I I w L!J I 01 51 o 1-1 o I 21 3 I 7 I I 1 I 21 11 21 71 61 I 0 I 1 I. I *1 9 I 7 I 7 !

7 a*

57 5B 59 60 61

. 68.' 69 74 75 80*.

EVENT DESCRIPTION *.

101211 Following 50~~ core scram testing, CRD F-5 was found to uncouple and overtravel 7

8 9

~I when withdrawn to position 48.

7 *- 8 g, *.. -*.

An insertion to position 44 and subsequent with-10'41"!.drawal to position 48 showed the drive to be recoupled.

A second scram and with-7":.',:9.;9*.*.~........

'...: ~~... *r'

• • ..,.,,*x*.,,<""'*'*.""'***;x.<.*'**"!'~'*'***!*""""*,,..,...,...,...,..... ""*'""'

loJ51 I drawal to position 48 again uncoupled the.dri.ve*.

CRD F-5 was then inserted to 7

8 9 jol6I I position.oo and disarmed.

The three symmetrkc:il drives. in t~he rernain,ing quadra_n*ts 7

B 9 SYSTEM COOE

@El I RI Bl

• CAUSE*

CODE COMPONENT CODE w

I c IR I DI R I v I E I 7

8 9 10 11 12 17

CAUSE

DESCRIPTION PRIME COMPONENT SUPPUER w

43 COMPONENT

• MANUFACTURER IGIOl8lol 44

. 47 VIJLATCN (Continued)

LtU 49 101011 As stated previous 1 y, symptom and performanc~ eval~ations indic~te that a loosened I

80 I

80

. I

• • so I

~1 80

7.. 8 9 80

~I inner filter causes the blade and drive to uncouple**at the fully withdrawn position.

I*

j110jj Loosening of.the filter may have resulted from a combination of improper installation 8j'

7.

8 9 FACIUTY METHOD OF (Continued) 60 EEJ 7

8 rn 7

8 STATUS

% POWER OTHER STATUS DISCOVERY DISCOVERY DESCRIPTION W

I ol 4 I a I NA I l!J 9

10 12 13 44 45 FORM OF ACJWITY

.CONTENT.

RELEASED OF RELEASE.

AMOUNT OF. ACTIVITY

~

L~.J '-*---~NA~-------~~

. -9 10 11 44.,'.

45 PERSONNEL EXPOSURES NUMBER TYPE

DESCRIPTION

46 SCRAM TEST I NG LOCATION OF RELEASE NA 80 80

[!E] I 0 I 0 I 01 w ____

N_A ____________

7 8 9 11 12 13 80 PERS.ONNEL INJURIES NUMBER

DESCRIPTION

[IE], I 0.1.o I _0.1 NA 7

8 9 11 12 80 OFFSITE CONSEQUENCES

~

.NA 7

8 9 80 LOSS OR DAMAGE TO FACILITY

.. TYPE.

DESCRIPTION

l"il~l'l!J.

7 8 9 10 NA 80 PUBLICITY [ill) 7 8 9 NA 80 ADDITIONAL FACTORS.

~* NA***

7 8 9 80 NAME: __.

...;G::..r;,;.;e;..g~g~R.;.;e~i...;m...;e...;r...;s ______________ PHONE: __

E_x_t_. _2_6_5 __ _

GPO 181*l'lt7

EVENT DESCRIPTION (Continued) were also fully inserted.

. On 12/30/76, an on-site review determined that a loosened inner filter caused the blade and drive to uncouple at position 48.

It was also determined that the loosened filter cannot exert sufficient pressure to uncouple the blade except when the drive is fully withdrawn to position 48; upon insertion, the blade and d~ive automatically recouple, Since the possibility of uncoupling the blade exists only when the drive is withdrawn to position 48, CRD F~5 has been declared operable.

As a precautionary measure, an op~rating order has been issued to ensure that a ~oupling check is performed whenever drive F~5 is wJ.t.bd.rawn to position 48.

Should subsequent. u.ncoupl ing, o.c.cur,. immedia.te act.ion.

w,fJ.f. be taken to ensure that the drive's status:. compHe1s.. w*ith Tech Spec section 3~-3~.-B;*; 1.

• Because the potential for uncoupling the blade exists only at position 48, the safety implications of this event are minimal.

Control rod drive/blade uncoupling incidents have occurred several times in the past.

(50-237/1976-68)

CAUSE DESCRIPTION (Continued) and latching spring fatigue.

Before the end of the next Unit-2 refueling outage, CRD F-5 will be dis-assembled and inspected.

If another primary cause *of failure is determined at that time, a supplemental report, will be submitted.