ML20092A429

Special Rept:On 840419,during Fuel Reshuffling for Cycle 8, Fuel Assembly FA 0297 Became Stuck in Fuel Location E-10 During Insertion & Fuel Assembly FA 029Q Damaged.Caused by Inadequate Procedure Change

ML20092A429
Person / Time
Site:	Oconee
Issue date:	06/06/1984
From:	Tucker H DUKE POWER CO.
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
NUDOCS 8406190205
Download: ML20092A429 (5)

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DuxE POWER GOMPANY P.O. Box 33180 CHAMLOTTE, N.C. 98242 HAL B. TUCKER TE LEPHONE VM2 PSRSIsrNT (704) 07J-4531 June 6, 1984 lI4 pq. 52 Mr. James P.'O'Reilly, Regional Administrator U. S. Nuclear Regulatory Commission Region II 101 Marietta Street, NW, Suite 2900 Atlanta, Georgia 30303

Subject:

Oconee Nuclear Station, Unit 3 Docket No.3ESO M )

Dear Mr. O'Reilly:

Please find attached a Special Report concerning the Unit 3 fuel handling incident that occurred during the recently completed refueling outage. Initial notification of this incident was made with the NRC Operations Center via the ENS on April 24, 1984. The incident was considered' to be of no signif 4.cance with respect to the health and safety of the public.

Very truly yours, Hal B. Tucker .

PFG/php Attachment ec: Document Control Desk U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Mr. J. C. Bryant NRC Resident Inspector Oconee Nuclear Station INPO Records Center Suite 1500

-1100 Circle 75 Parkway Atlanta, Georgia 30339 Ms. Helen Nicolaras Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission

- Washington, D. C. 20555 OFFICIAL COP'l 84 6190205 P

406 Mb I ADOCK 0 7 I g S pg

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Oconee Nuclear Station i Special Report I

Unit 3 Refueling Operations i

'" Fuel Handling Incident ,

L Fuel Assembly Damaged during Fuel Reshuffling {

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l Description of Occurrence:

(ht April 19, 1984, during fuel reshuffling for Unit 3 Cycle 8, Fuel. Assembly number (FA No.) 0297 became stuck in fuel location E-10, while being inserted into this location. This FA was grappled by the auxiliary bridge fuel mast.

1 Numerous attempts were made to free this fuel assembly (FA) in.accordance with procedure, with no success. During one such attempt the FA in Location E-9

(FA No . 01MC) was lifted approximate 1y'one foot when its upper end fitting Jcaught a spacer grid on FA No. 0297. On April 24,,1984. FA No. 01MC was +-

. grappled by the control rod drive crane while FA.No. 0297 was still grappled to the auxiliary bridge fuel mast. Both fuel assemblies were raised simultaneously until they were verified to have separated. 'FA No.;0297 was raised out of the core while FA No. 01MC was lowered back into core location E-9.

Cause of-Occurrence:

- Problems withithe main bridge control mast resulted.in a procedure change to the refueling procedure in order to provide-a sequence of fuel shuffling with the auxiliary bridge: fuel mast while repairs were being made to'the main bridge control mast. At 2350 hours0.0272 days <br />0.653 hours <br />0.00389 weeks <br />8.94175e-4 months <br /> on April 18 1984 while utilizing the auxiliary bridge fuel mast, FA No. 033A was removed.from core location E-10. 'The next step in the revised procedure was'to remove FA No. 029Q from core location 0-3; however. the FA was stuck and would not move. As in the past when this situation occurs, four alternate steps were written to remove. adjacent fuel assemblies so that'FA No. 029Q'could be removed. FA No. 029Q was relocated to core location E-11.

'To verify full insertion'of a FA, the Z-Z tape reading, which gives vertical

' displacement, is utilized. The Z-Z tape reading was ' correct, and thus the FA

-was assumed to be properly aligned. However, FA No. 029Q was not properly set

.in the lower grid. The. lower end fitting of FA No. 029Q straddled the lower-grid ' structure of the core in such a manner that the FA was partially occupying -

core. location E-10.. Furthermore, FA No. 029Q was sufficiently bowed to give the impression that the FA was properly positioned in core location E-11.

Then FA No. 0297 was set in core location E-10, it scraped the lower south side of FA No. 029Q and became stuck approximately one foot from the bottom of the

-core. Figure 1 is a schematic of the positions of the. fuel assemblies at the time of the incident.

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' Analysis of' Occurrence:

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Visual inspections'were made of the fuel assemblies involved to assess the damage. . The primary concern was with FA No. 029Q since this FA was scheduled to be reinserted for Cycle 8, while the others were to be discharged. FA No. 029Q

-was found to have approximately eight inch long scrapes on all fifteen fuel

' rods on the lower south side, between the lowest spacer grid and the lower end fitting. A detailed visual inspection of FA No. OlMC and No.-0297 was not per-

' formed because they were scheduled to be discharged. An initial visual inspection of FA No. 0297 found a pin hole in one of the rods. No other significant damage to the other fuel assemblies was observed.

' The damage to FA No. 029Q has been extensively evaluated and the FA was determined to be acceptable for.use for another cycle. Even if the fifteen damaged rods of this assembly were to fail, the resulting reactor coolant activity would be less r than 1% failed fuel.

.Section 15.11 of the Final Safety Analysis Report for Oconee Nuclear Station l

. addresses fuel handling accidents. The assumptions made in that analysis bound  :

the conditions that existed during the evaluation of this incident. .Also, since. .

this event occurred in the Reactor Building, filtering of all off-site releases 'l would have occurred which is more conservative than that which was assumed in l the analysis. Therefore, the health and safety of. the public were not affected  ;

.by this incident. ,

Corrective Actions:

Upon determining that fuel assemblies Nos. 0297 and 01MC had become interlocked with each other, both were lowered back into the core and steps were taken to

• separate them.- Precautions to minimize any potential release that might have T occurred during the course of events were taken. A visual inspection of the fuel assemblies involved that were to be discharged to the spent fuel pool for ,

permanent storage was performed. A detailed visual inspection and evaluation l of FA No. 029Q were performed to assess the impact that the damage to the assembly l might have on its use for one more cycle.  :

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. . neuaE i i SHEET 1 of 2 ,

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FUEL ASSEMBLIES ARRANGEMENT AT THE TIME OF THE ,.

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D 0339 01L3 032F l

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E .. 01MC 0297 029Q .,.

a a F 0335 01MA 033L l 9 10 11 (

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FIGURE 1 SHEET 2 of 2 FA FA 0297 FA 01MC 0290 a

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' ' ' ^ ' +-- LOWER GRID STRUCTURE E-9 E-10 E-11 FA 0290 STRADDLING SECTION A-A LOWER GRID

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