05000416/LER-1990-021-01, :on 901024,uncontrolled Lowering of Fuel Bundle Occurred

:on 901024,uncontrolled Lowering of Fuel Bundle Occurred

ML20062F604
Person / Time
Site:	Grand Gulf
Issue date:	11/23/1990
From:	Cottle W, Ruffin R ENTERGY OPERATIONS, INC.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
AECM-90-0200, AECM-90-200, LER-90-021-01, LER-90-21-1, NUDOCS 9011280071
Download: ML20062F604 (5)

LER-1990-021, on 901024,uncontrolled Lowering of Fuel Bundle Occurred

Event date:
Report date:
4161990021R01 - NRC Website

text

.

e e.

J i

Enterav

== -ma>. ian.

'aa.

P O (ku 766

. -~ Operations

onwn us

1 le!601437 6409 November 23, 1990 w. T. cotue

+, nne tram,

~

ps i

U.S. Nuclear Regulatory Commission L

Mail Station P1-137 i

Washington, D.C.

20555 i

Attention: Document Control Desk Gentlemen:

SUBJECT:

Grand Gulf Nuclear Station Unit 1 Doclet.No. 50-416 License No. NPF-29

. Uncontrolled Lowering of

- i Fuel' Bundle-LER 90-021 AECM-90/0200 Attached is Licensee Event' Report (LER)90-021 which is a final report.

Yours.truly, l

MY W WTC/RR:cg Attachment cc:

Mr. D. C. Hintz (w/a)-

Mr.R.B.McGehee(w/a)

Mr. N. S. Reynolds (w/a)

Mr. H. L. Thomas (w/o)

Mr.H.O.Christensen(w/a)

Mr. Stewart D. Ebneter (w/a)

Regional Administrator U.S. Nuclear Regulatory Commission Region-11~

- 101 Marietta St., N.W., Suite 2900 Atlanta, Georgia 30323

.i Mr. L. L. Kintner, Project Manager (w/a)

Office of Nuclear Reactor Regulation U.S. ' Nuclear Regulatory Commission Mail Stop 11D21 Washington, D.C.

20555 (g128co71awcx wowm:3 l#yf 90112

?

s ene i

y

\\

LER90021/SCMPFLR - 1

~u

Attichment to AECM-90/0200 gR,C f.ee J88 U 5 NUCLE Am RtGULATOR Y COesettstON APPROvt0 0488 NO ##4188 LICENSEE EVENT REPORT (LER)

'""'s a ave PLCitif V NAMG til OOCKET NutIS4R QI rates W.

Grand Gulf Nuclear Station - Unit 1 01610 l 010141116 1 loFh 14 Ilf LE s.1 Uncontrolled Lowering of Fuel B,dndle G WENT DATE Ill LER NVh8SE R foi RED 4f Datt i?l OTHER P ACILITits INv0Lvt0 ISI MONYM oaf VGAR VIAR I(O MM WON'i H 1s A Y Ytan FAm6tyhawas DOCKEY NUMDERt31

6

]

NA 016[0l0l0 1 l l l

1l 0 d/ 9 0 9l0

~

0l2I

- 0l0 1 l1 2l 319 l 0 1

0 1 5 to lo i 0 1 1 1

,,, y y,,,

TMis REPont is susMiftso PumsveNT 10 TMt Atouintutwts os to CeR i rea.ee eae e,,=.. es ea. ro".-aed n u s

a m.i i

n.ai.,

nn.m-n n. -

n.ai. o n,i n.m.i gm n.,

0,o in

= =. n iw

==wm

. n imm 1

gg;gg,,,,,_

=m

. n an.

n o..in nei

=

.in n.

n,.i a.,

. n.. n A, mu yoluntary n,.,a n.,

un,..an n.,

n.c.

,n n.,

n.an.,

uni.ian.i Report LICENSEE CONTACT PCR TM,8 LER n3l NAME

• t LEPHONE NUM98R ARS A CQQt Riley Ruffin / Licensing Specialist 61011 413l 7l -12 11 l617 COMPLETE ONE LINE FOR E ACH COMPONENT P AILumt 048CRl980 IN TMiG REPORf 435 van AC-

• {0

• R OS' Cault 8VSTs u Cou'ONENT

• "hc 5"

CAvit Sv57tv COM*ONt%f R

g y

O h*R l

! ! I I I I I

I i f I I I t

I

'l l l l l

I l i l I i SUP9LIMENT AL REPORT E MPGCitD ne, MONTH DAY VGAR SV0ui$$ ION Yt14I9 v.e e ego.,. ixotCTlO Sugut$$10N Oe rli NO l

l l

AufAAC1-,,,,a,....,,,,..,o,,.....,,,....,,,,,.,n.,

On October 24, 1990 during fuel moves, a fully grappled fuel bundle was lowered into the vessel in an uncontrolled manner due to independent failures of redundant refueling equipment brake systems.

The bundle entered it's targeted core location striking no adjacent structures.

The failure of the normal safety brake is attributed to the safety brake manual disengage lever binding in the disengaged position due to close proximity with the brake housing cover. The emergency brake also failed due to the emergency brake manual disengage lever binding in the disengaged position due to a deformed spring.

1 Chemistry analyses and radiation surveys indicated no detectable fission product or gas release occurred.

The motor / brake assembly was replaced and tested satisfactorily.

The emergency brake disengage rod.was removed from both the refueling and fuel handling bridges.

Even though inspection revealed no apparent physical damage, the subject fuel-bundle was replaced in the core configuration with a slightly less reactive bundle.

l l

I LER90021/SCMPFLR - 3 l

F,"S,"" "

Attachment to AECM-90/0200 aac,w ama-

,,,,,,,,,,,,va,,,,--

-- 3 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION smovio oue ao sino+os exmes: sime f ACsuiv haast til DOCEtt Nunesh (33 Len hunega es PA44 is -

< Pe e,y,pp t=,;;

i 0 l0 0 l2 or 0 l4 Grand Gulf Nuclear Station o l5 jo lo lo l4 l1 l6 9]O 0l 2l 1 l

- -a

.I,<

L A.

Reportable Occurrence i

On October 24, 1990 during fuel moves, a failure of the refueling equipment brake systems caused an uncontroiled lowering of a fuel bundle into it's respective core location. This event is not reportable per 50.73 but is reported as a valuntary report'.

B.

Initial Cause The plant was in Operational Condition 5, Refueling, at the time of the occurrence.

C.

Description of Occurrence On October 24, 1990 at approximately 2135, fuel bundle XNB-487 was being moved to a new location in the core.

The Refueling Platform Laser Track System was being used to position the bundle over it's targeted core location and to lower it to a preset mast height where it could be manually lowered into the core. The system started its automatic descent. Upon reaching the preset mast height,-which would automatically stop the bundle's descent, the bundle failed to stop and appeared to accelerate during its descent.

During the accelerated descent, the emergency stop button was depressed, which should have engaged the emergency brake, with no apparent affect. The bundle continued to descend until it was seated l

in its support piece without striking any adjacent structures.

It is estimated that the bundle descended.at an approximate average speed of-3 feet per second.

There was no evidence of gases being released from l

the bundle after it was seated.

An investigation was performed prior to restoring the refueling bridge to service.

D.

Apparent-Cause During the investigation, two abnormalities were observed.

The emergency brake manual disengage rod was found in the disengaged position and the manual safety brake.. lever was also found in the disengaged position.

l LER90021/SCMPFLR - 4 romaa seea -

u

. ~..

Attachm:nt to AECM-90/0200 e

esetC Pwsa ageA U.S. feUCLlaA A80VLATORY ConsasfS4080 UCENSEE EVENT REPORT (LER) TEXT CONTINUATION

• • aovio oue no mo-oio4 expines swa

'aciurv aame m ooc..,,,u ma

" M.*

• • 7 ::

Grand Gulf Nuclear Station 010 Ol1 0' olA -

012l1 o 5lolo1014l116 91 0 TEKT W aume desse e M est cEudement MC Fwne JWd W IfM,

Further investigations were performed in a lab environment. Following l

the testing of the motor and brake, it was determined that the normal safety brake manual disengage lever was susceptible to binding on the brake housing cover and remain disengaged when the brake solenoid was deenergized (normally deenergizing the brake solenoid would cause the

.I brake to engage).

Additionally, one of the brake adjustment screws was loose and the solenoid air gap was found out of tolerance.

Investigation of the emergency brake revealed that the manual disengage rod was susceptible to binding due to a deformed spring which was normally in contact with the manual disengage rod Demonstrations indicated that the rod bound at a high enough posiiton to disengage the brake.

Based on the results of the investigation, the probable causes of the normal and emergency brake failures, as determined by olant personnel, were the binding of normal brake lever on the motor housing due to close tolerances and the binding of the emergency brake lever in the up position due to a deformed spring.

E.

Supplementai Corrective Actions o

The motor / brake assembly was replaced.and was tested to verify proper logic functions. The brake adjustment was verified per the vendor requirements.

Additionally, the housing cover was milled out so that sufficient clearance existed between the safety brake's manual disengage lever and the housing cover.

The manual disengage rod for the emergency brake was also removed from the refueling and fuel handling bridges as a part of the corrective actions leaving energization of the emergency brake soelnoid as a means for releasing this brake.

During the remaining fuel moves, frequent inspections were performed on both the refueling and-fuel handling bridges to ensure proper operation, o

An inspection and evaluation was performed on the fuel bundle components, no apparent structural damage was identified.

Even though the bundle appeared fully intact, it was removed from the core and discharged to the spent fuel pool.

The bundle was replaced in the core configuration by a suitable bundle l

scheduled for discharge.

i o

Chemistry sample. analyses and radiation surveys were performed l

l and indicated no detectable fission gas or fission product l

release occurred. Therefore, there was no indication of a loss l

of cladding integrity.

l l

t PD o n n 91 I gr'Mp pt D ' -- 8; scans smaa

Attachm:nt to AECM-90/0200

~

......o<.ro..

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION areaovio one ao sino-o*

EXMAES.S/31/W f actury maass Hi 0.CKET nuesta saa tem myntaen tes PAS 4131 cen' w. m g:

a

,e -

e Grand Gulf Nuclear Station 0l2l1

) p 0l 4 oF 0 {.

o l5 l o j o j o p l1 l6 9 10 I

rirr n -. -.

anc e

.w nn,

i l

F. Safety Assessment

The fuel bundle was initially inserted into the core during Cycle 3 and reinserted during Cycle 4.

Based on the results of the surveys and analyses performed by plant personnel, the event did not adversely impact plant or public safety, i

The control rod which is associated with the subject bundle was stroked and no abnormal operation was observed.

The revised core configuration replaced bundle (XNB-487)'with a' slightly less reactive bundle which will result.in a slight decrease in reactivity.

Therefore, the shutdown margin analysis bounds the revised core configuration.

l l

l LFR00021/SCMPFLR - 6 romu sans