ML20086B488

AO 50-267/74-6:on 740418,fuel Handling Machine Failed to Engage & Lift Reflector Element 09-06-R-01.Caused by Mfg Error.Burr Will Be Removed by Hand Machining

ML20086B488
Person / Time
Site:	Fort Saint Vrain
Issue date:	04/25/1974
From:	PUBLIC SERVICE CO. OF COLORADO
To:
Shared Package
ML20086B482	List: ML20086B483 ML20086B488
References
AO-50-267-74-6, NUDOCS 8311170447
Download: ML20086B488 (7)

Text

A v Oa Public service company @ edemeo

.P. O. Box 361, Platteville, Colorado 80651 April 25, 1974 Mr. William Gilbert 7920 Norfolk Avenue Bethesda, Maryland 20024 REF: Facility Operating License No. DPR-34 Docket No. 50-267

Dear Mr. Gilbert:

Enclosed please find one copy of Abnormal Occurrence Report No.

50-267/74/6, submitted to the Directorate of Licensing, for your infe =:tien.

Very truly yours, f i

Mt *O '

M '

Frederic E. Swart Superintendent Fort St. Vrain Nuclear Generating Station FES/kal Yg \

8311170447 741209 PDR ADOCK 05000267 h'3, t{#93.h*

Ed "j h.I S PDR y,, f(Tgj3g /*

hh' g' t(

COPY SENT REGION- 37d2 <k _

~

g o

. - . o L) i

1 DATE

April 24, 1974 ABNORMAL OCCURRENCE FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO l i

P. O. Box 361 -

PLATTEVILLE, COLORADO 80651 g

\  %

REPORT No. 50-267/74/6 b

Preliminary f L Final x APR271974"5

• g3, mmeEMEG1 7, tantt3A gy,ta.:ff unt SSb8 O.

IDENTIFICATION OF ' '

OCCURRENCE: Q4 g .,

On Thursday, April 18, 1974, while using the fuel handling machine to remove top reflector elements from core region No. 9 to facilitate installation of the second of two per=aaent 252 Cf. neutron sources, the fuel handling machine failed to engage and lift reflector elenent 09-06-R-01.

This event is ceasidered to be an abnormal occurrence as defined in the

- 1. . :.

Technical Specifications, paragraph 2.lF.

CONDITIONS PRIOR TO OCCURRENCE: Steady State Power Routine Shutdown Hot Shutdown Routine Load Change Cold Shutdown X Other (specify)

Refueling Shutdown Startun Test A-0. Insta11tne eer _

Routine Startup manent neutron sources in reactor 1

l l

I I

3744

_ a

hv

,r g V

l

~Page 2 The major plant parameters at the time of the event were as follows:

Power RTR, "NA MWth ELECT, NA MWe NA psig

. Secondary Coolant Pressure Temperature NA *y Flow NA #/hr. .

NA psig Primary Coolant Pressure Temperature NA *F Core Inlet NA *F Core Outlet Flow NA #/hr.

DESCRIPTION OF OCCURRENCE:

" hen the fuel h:ndling machine tried te engage end pick up reflecter element 09-06-R-01 in the au'tomatic mode, the grapple would not engage the reflector element. It was noted by the operator that no dowel pin engage-ment lights came on as they should to indicate proper insertion of the grapple inti the block and proper orientation for the reflector element.

Thinking the element was possibly rotated slightly, the operator rotated the grapple head mechanism from +15* to -15* in 1* increments and manually tried to engage the element with no success. Digital indication of the grapple position indicated it was sithin 1/4" - 3/8" of being "down" on the reflector element. With management permission, the grapple inter-lock from dowel pin engagement was bypassed and an attempt made to grapple the element. The attempt was unsuccessful.

m -

jy Q,I G l Page 3 l l

The fuel handling machine was then moved from the refueling penetration, and radiation monitoring devices were lowered through the refueling pene-tration to the top of the core to determine if radiation icvels produced f i

reactor  ;

by the 252 Cf. source already installed would prevent entry into the vessel. Radiation levels were found to be relatively low (s 5-7 mr/hr neutron, 1-2 mr/hr gamma) and preparations for vessel entry were made. {

inspections of reflector element 09-06-R-01 revealed a small ridge at the grapple engagement surface protruding into the grapple hole reducing the diameter, thereby preventing the grapple from fully entering the element.

Dowel pin alignment was found to be correct. (See Attachment 1)

A brief inspection of other metal clad top reflector elements was made.

This inspection revealed a number of other elements that possibly had the

.. \

meme stu3e.

Element 09-06-R-01 was manually lifted from the reactor vessel for closer inspection and the reactor vessel access cover replaced until further analysis and resolution of the problem could be made.

APPARENT CAUSE OF OCCURRENCE: Design Unusual Service Cond.

Including Environ.

X Manufacture Component Failure Installation /Censt. Other (specify)

Operator Procedure

l l b% i Pegs 4 ANALYSIS OF l OCCURRENCE:

I Closer inspection of reflector element 09-06-R-01 revealed that the ridge present at the transition in the grapple hole was apparently formed in the machining of the element and had not been removed. This machining

" burr" reduced the grapple hole diameter by approximately 0.025", preventing ,

the grapple from passing.

The pres nce of this machining " burr" in no way presents a hazard to the public but does indicate a deficiency in the manufacturers QA Program.

CORRECTIVE ACTION:

Corrective action, presently under way, in to remove the " burr" by " hand" machining.

A special tool has been designed and built to facilitate removal of the burr with the reflectors in place in the reactor vessel. All metal clad top reflectors except those elements immediately under the control rod assembly orifice valves, with the exception of regions 2, 9, 10 and 16, are to be "de-burred".

Those elements immediately under the orifice valves will not be "de-burred" in so far as this would require removal of all the control rod drive and orifice assemblies to gain access to them.

i I

It was determined that the manufacturer, General Atomic, is to supply Public Service Company with six (6) column no.1 metal clad reflector elements to be utilized in the event problems are experienced in the future with removal of these elcaents at the time of fuel reloading. ' Analysis of the l

l k_2a - *

• g a f

' ~

O O

,, Page 5 problem indicates tha't these elements can be removed with the " remote a

maintenance" tools already supplied for core maintenance. Problems at time of refueling with these clunents would be a nuisance but not a

, hazard to either the general public or plant personnel.

FAILURE DATA /SIMILAR REPORTED OCCURRENCES:

Abnormal Occurrence Report No. 50-267/74-3 and 3A discuss deficiencies similar in nature to this report.

PROGRAMMATIC IMPACT:

It appears at this time that approximately one week of delay will result from this problem.

c~nne wowr.

No codes involved.

Prepared By: Approved:

7 L w t )

J r '< r _ o , -.s tM . L t_cr o L. . t rsw .

. Swart Fgederic E. Swart

/FredericE Superintendent Superintendent Fort St. Vrain Nuclear Fort St. Vrain Nuclear Generating Station Getierating Station 4

0 4 0

e 40 -

[]' ATTACIDiEhT 1

%_/

. b COOLANT HOLES

/

l'

- J.b

f t l

D '  !

@ g l l l I  :

@bh. , al \

!y: i  : r c,

3OO O 09 O 'l . , .;' I 4

'N ' i 3 O o OYO i I N l --

OO OOOO dI l

.'I 4

(O OO :

f F L LM' SP4AYE0 CONTACT PADS

\ N FUEL HANDLING PICKUP HOLE g -t '

l INLET FLOW DOWEL PLENUM

, n e

//q sp /n , ' ,y _.- .-

, g __

f TYPICAL KEYWAY KEY HEllUM INLET e /

FLOW + . . I

\

e t . . . I y p  %'

w - ,

. , a Il  ! -

9 .h v

.I il Rl

' lE E

[y l0 l '-

E {'

BORONATED li iL_jl $lb N l j l __! l i .

3 fi h

GRAPHITE , , . ,,, ,

_JI N l GRANULES i- w ra r l a r c - 1 1

.s =

l COOLANT HOLES DOWEL SOCKET Machining burr Top reflector orifice plenum

~ f