ML20086B154

AO 50-267/74-7A:on 740424,fuel Handling Machine Failed to Engage & Lift Reflector Element 09-06-R-01.Caused by Mfg Error.Reflectors de-burred & Ga Co Will Supply Two Column 1 Metal Clad Reflector Elements

ML20086B154
Person / Time
Site:	Fort Saint Vrain
Issue date:	12/18/1975
From:	Hillyard H, Mathie F, Swart F DUKE POWER CO., PUBLIC SERVICE CO. OF COLORADO
To:	Howard E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
Shared Package
ML20086B156	List: ML20086B154 ML20086B164
References
50-267-74-7A, AO-50-267-74-7A, P-75033, NUDOCS 8311170080
Download: ML20086B154 (6)

Text

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~~~ Mrr E. Morris'Howard, Director og Nuclear Regulatory .Co-mf asion.c u.i f u_s ,, -

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wSuitet1000J to ' ':e anu m C "' '" 2" f Arlington, Texas 76012 This event was con::1dered to be an abnor=al eccurrence a; defined .in the Tech-i nical Specificacions, paragraph 2.11-Raf: Facility Operating License CONDITIONS PRIC?-

No. DPR-34 T9 OCCUFF. NCF.: "" "

Steady Stat"DoSGrNo. 50-267 .

Dear Mr. Howard:

Hot Shutdm.*n Routine Lend C':iann' v

Enclosed please find _a_ copy _os'Ebnoiinal"decurrence ReporUNdr50-267/ Crher (s pecify)

, 74/IA, Final, submitted per E2""3'"

cations.

• the requirements " " of the Technical Specifi- M tal tiv

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nv-Please note that the. change _to 'this 'ab'nornal' occurrence 're.w.

port ~is'that

}' the manufacturer, General Atomic, is to. supply Public Service Company i nwithitwo-(2) ccolumreno.~31 setal clad ieflector' elements rather than ,

six (6) as originally stated in Abnormal Occurrence Report No. 50-267/ \

i 74/7.mThis action section. change may be noted in--paragraph-three~under the~c6dective

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Secondary Coolant 1yery te 34;' truly yours, pfA

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cca Mr. Roger S. Boyd N/A 'F Core Outlet Flev N/A f/hr.

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REPORT DATE': December 18. 1975 ABNORMAL OCCURRENCE 74/7A l Page 1 of 5 OCCURRENCE DATE: April 24, 1974 FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO P. O. BOX 361 PLATTEVILLE, COLORADO 80651 REPORT No. 50-267/74/7A Final IDENTIFICATION OF OCCURRENCE:

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 permanent Californium 252 neutron sources, the fuel handling machine failed to engage and lift reflector element 09-06-R-01.

This event was considered to be an abnormal occurrence as defined in the Tech-nical Specifications, paragraph 2.1F.

CONDITIONS PRIOR TO OCCURRENCE: Steady State Power Routine Shutdown.

Hot Shutdown Routine Load Change Cold Shutdown X Other (specify)

Refueling Shutdown Startup Test A-0, installing permanent neutron sources in Routine Startup reactor.

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

Power RTR N/A - MWth ELECT N/A MWe Secondary Coolant Pressure N/A psig i l

Temperature N/A 'F.

Flow N/A f/hr.

l Primary Coolant Pressure N/A psig Temperature N/A 'F Core Inlet N/A 'F Core Outlet Flow N/A #/hr.

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ABNORMAL OCCURL ENCE 74/7A Page 2 of 5 i

DESCRIPTION OF OCCURRENCE:

When the fuel handling machine tried to engage and pick up reflector element

! 09-06R-01 in the automatic mode, che grapple would not engage the reflector element. It was noted by the operator that no dowel pin engagement lights came i on as they should to indicate proper insertion of the grapple into the block and proper orientation for the reflector element.

Thinking the element was possibly rotated slightly, the operator rotated the I grapple head mechanism from +15* to -15* in 1* increments and manually t'ried '

] to engage the element with no success. Digital indication of the grapple position indicated it was within 1/4" - 3/8" of being "down" on the reflector

! element. With management permission, the grapple interlock from dowel pin engage-ment was bypassed and an attempt made to grapple the element. The attempt was I

unsuccessful.

The fuel handling machine was then moved from the refueling penecration, and radiation monitoring devices were lowered through the refueling penetration j to the top of the core to determine if radiation levels produced by the 252 Cf.

j source already installed would prevent entry into the reactor vessel. Radiation i levels were found to be relatively low (approximately 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 ridg'e'at the grapple engagement surface protruding into the grapple hole reducing the dia-meter, 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 same a ridge.

EJesent 09-06-R-0?. was manually lif ted. from the reactor vessel for closer in-spection and the reactor vessel access cover replaced until further analysis and resolution of the problem could be made.

APPARENT CAUSE OF OCCURRENCE: Design _U'nusual Service Cond.

, Including Environment X Manufacture Component Failure Installation /Const. Other (specify) -

Operator Procedure __

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o o ABNORMAL OCCURRENCE 74/7A i

Page 3 of 5 l

ANALYSIS OF

OCCURRENCE

Closer inspection of reflector element 09-06-R-01 revealed that the ridge pre-  !

1 sent 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.

i

' The presence of this machining " burr" in no way presents a hazard to the public but does indicate a deficiency in the manufacturer's quality assurance program.-  %

! CORRECTIVE ACTION:

l Corrective action was to remove the " burr" by " hand" machining.

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A special tool was 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 inmediately under the control rod asseminly orifice valves, j with the exception of regions 2, 9,10, and 16, were "de-butred".

Those elements immediately under the orifice valves were not "de-burred" since this would require removal of all the control rod drive and orifice assemblies

! to gain access to them.

It was determined that the manufacturer, General Atomic, is to supply Public Service Company with two (2) column no. 1 metal clad reflector elements to be utilized in the event problems are experienced in the future with removal of these elements at the time of fuel reloading. Analysis of the problem indi-

' cates that these elements can be removed with the " remote maintenance" tools t already supplied for core maintenance. Problems at time of refueling with these elements 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:

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No further impact.

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. CODE IMPACT:

None i

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o o ABNORMAL OCCURRENCE 74/7A Page 4 of 5 Submitted by: ,

H. W. Hi}yyard /

Technical Services Supervisor Reviewed by: _

Francis M. Mathie Superintendent, Maintenance '

Approved by: b .M F/edericE. Swart - ~

superintendent, Nuclear Production t

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ABNORMAL OCCURRENCE 74/7A'

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