ML20086B483

AO 50-267/74-7: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

ML20086B483
Person / Time
Site:	Fort Saint Vrain
Issue date:	05/08/1974
From:	Swart F PUBLIC SERVICE CO. OF COLORADO
To:
Shared Package
ML20086B482	List: ML20086B483 ML20086B488
References
AO-50-267-74-7, NUDOCS 8311170446
Download: ML20086B483 (7)

Text

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r q public Sen' lee Company *f Odendo P. O. Box 361, Platteville, Colorado 80651 g

May 8, 1974

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Mr. Angelo Giambusso *b /f Deputy Director for Reactor Projects Directorage of Licensing U. S. Atomic Energy Commission Washington, D. C. 20545 REF: Facility Operating License No. DPR-34 Docket No. 50-267

Dear Mr. Giambusso:

Enclosed please find 3 copies of Abnormal Occurrence Report No. 50-267/74/7, submitted per the requirements of the Technical Specifications. This report was originally submitted as No. 6.

Please replace your present No. 6 with this copy.

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Very truly yours Afo Frederic E. Swart Superintendent Fort St. Vrain Nuclear Generating Station FES:ll r,

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Originh11y issued as #6 DATE: April 24, 1974 ABNORMAL OCCURRENCE FORT ST. VRAIN NUCLEAR GENERATING STATION PUBLIC SERVICE COMPANY OF COLORADO P. O. BOX 361 PLATTINILLE, COLORADO 80651 REPORT No. 50-267/74/7*

Preliminary  ;

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

. This even t is considered to be an abnormal occurrence as defined in the 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. installine ver _

Routine Startup manent neutron sources in reactor

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. . O' page 2 The major plant parameters at the time of the event were as follows:

Power RTR, 'NA MWth ELECT, NA Mye Secondary Coolant Pressure NA psig Temperature NA *p Flow NA #/hr.

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

DESCRIPTION OF OCCURRENCE:

When the fuel handling machine tried to engage and pick up reflector element 09-06-R-01 in the automatic mode, the grapple would not engage the reficctor 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 into 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 l' increments and manually tried.to .cngage the ele' m ent 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 inter-lock from dowel pin engagement was bypassed and an attempt made to grapple the element. The attempt was unsuccessful.

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O Page 3 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 by the 252 Cf. source aircady installed would prevent entry into the reactor vessel. Radiation levels were found to be relatively low (s 5-7 mr/hr neutron, 1-2 mr/hr gamna) 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 same ridge.

Element 09-06-R-01 was manually lif ted from the reactor vessel for

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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 /Const. Other (specify)

Operator Procedure O

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O Page 4 ANALYSIS OF OCCURRENCE:

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

1 CORRECTIVE ACTION:

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

A special tool has .bcen designed and built to f acilitate removal of the burr with the reflectcss in place in the reactor vessel. All metal clad top reflectors except those elements immediatelv 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 assemblics to gain access to them.

It was determined that the manufactur er, 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 elements at the time of fuel reloading. Analysis of the

Page 5 problem indicates that these elements can be removed with the " remote maintenance" tools already supplied for core maintenance. Probicos at time of refueling with these elements would be a nuisance but not a hazard to either the general public or plant personnel.

Fall,URE DATA /SIM11.AR REPORTED OCCURRENCES:

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

PROGRMDIATIC l'! PACT:

l It appears at this time that approximately one week of delay will )

result from this problem.

CODE IMPACT:

j No codes involved.

1 Prepared By: Approved:

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' rederic E. Swart Fgederic E. Swart Superintendent Superintendent Fort St. Vrain Nuclear Fort St. Vrain Nuclear Generating Station Generating Station

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