ML20084U623

AO 50-254/75-4:on 750212,fuel Assembly Found in Proper Core Location But Misoriented 180 Degrees.Caused by Misloaded Bundle.Misoriented Assembly & Spring Clips Replaced

ML20084U623
Person / Time
Site:	Quad Cities
Issue date:	02/21/1975
From:	Kalivianakis N COMMONWEALTH EDISON CO.
To:	Oleary J Office of Nuclear Reactor Regulation
Shared Package
ML20084U597	List: ML20084U593 ML20084U623 ML20084U639
References
AO-50-254-75-4, NUDOCS 8306290148
Download: ML20084U623 (3)

Text

Comm:nwalth Edison y

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February 21, 1975 Ey #3/ a; 8c

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Y Mr. John F. O' Leary, Director Directorate of Licensing Regulation U. S. NUCLEAR REGULATORY C0ftMISS10N Washington, D. C. 20545

REFERENCE:

Quad-Cities Nuclear Power Station Docket No. 50-254, DPR-29 Appendix A, Sections 1.0.A.8, 6.6.B.I.a

Dear Mr. O' Leary:

Enclosed please find Abnormal Occurrence Report No. 50-254/75-4 for Quad-Cities Nuclear Power Station. This occurrence was previously reported to Region 111, Directorate of Regulatory Operations by telephone on February 12 and February 13, 1975, and to you and Region lil, Directorate of Regu-latory Operations by telecopy on February 13, 1975 This report is submitted to you in accordance with the requirements of Technical Specification 6.6.B.I.a.

Very truly yours, COMMONWEALTH EDISON COMPANY QUAD-CITIES NUCLEAR POWER STATION s Y

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N. J. Kalivianakis Station Superintendent NJK:SRH/dkp cc: Region ill, Directorate of Regulatory Operations J. S. Abel 5D' p s 2138 8306290148 750325 PDR ADOCK 05000254 S PDR y SENT ItEGION m mg e ~- .

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• REPORT NUMBER: A0-50-254/75-4 -

REPORT DATE: February 21, 1975 OCCURRENCE DATE: February 12, 1975 FACILITY: Quad-Cities Nuclear Power Station Cordova, IL 61242 IDENTIFICATION OF OCCURRENCE:

Fuel mispositioned in Unit I cycle 2 core.

CONDITIONS PRIOR TO OCCURRENCE:

At the time the abnormal occurrence was discovered, Unit I was shutdown for piping repairs. Prior to this time the unit had experienced six months of normal power operation with the fuel mispositioned. There were no measurable indications of abnormal fuel performance in the core power distribution or unit off gas release rates observed.

DESCRIPTION OF OCCURRENCE:

On February 12, 1975, while performing a core verification prior to replace-ment of the reactor head, a fuel assembly was found to be in its proper core location but misoriented 180 degrees. Then, during the process of reviewing video tapes of the core verification to assure there were no other loading errors, three peripheral fuel assemblies were found not fully seated due to spring clips being hung-up on the core upper grid.

DESIGNATION OF APPAREllT CAUSE OF OCCURRENCE:

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Operator Error - In the case of the fuel assembly rotated 180 degrees, at least two errors occurred. The bundle was misloaded and the loading error was not discovered in the core verification.

In the case of the fuel assemblies that were hung up on the upper core grid, station personnel were not aware of any spring clip design problem that would allow this to occur. The small difference in the relative bundle height was not recognized in the core verification.

ANALYSIS OF OCCURRENCE: ,

The fuel assembly that was misoriented was an initial cycle (7X7) fuel assembly that, at the beginning of Cycle 2, had approximately 8000 MWD /T of exposure.

For a fuel assembly in this exposure range, with the local peaking factor in-creased by as much as 35% due to the misorientation, it is estimated that the peak linear heat generation rate (LHGR) was about 17 Kw/Ft. There is no possi-bility that either 1% plastic strain or departure from nucleate boiling limits were reached.

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The fuel. assemblies that were not fully seated in the lower grid are located on the core periphery and therefore run at approximately 60% of the power level ,

of an average assembly. At the reduced power level of a peripheral assembly there is no possibility of departure from nucleate boiling even if the assembly received no forced circulation.

1 It is therefore concluded that no safety limit was exceeded as a result of this t

abnormal. occurrence and that there were no effects on the health and safety of the public.

CORRECTIVE ACTION:

The misoriented assembly was replaced with an assembly of the same type that was removed from the core during the last refueling. The three spring clips on the i peripheral assemblies were replaced and the assemblies returned to the core.

These reloaded assemblies were subsequently verified for proper identification, orientation, and seating.

4 The present core verification procedure requires verification of proper assembly

} orientation, location, and seating during one video taping of the core. Per-j forming all three verifications simultaneously may have contributed to the failure to detect the mispositioned fuel. To prevent repetition of this and similar occurrences, the core verification procedure will be changed to require a sep-arate verification of bundle orientation and bundle heights before the assembly ID numbers are verified.

I The misoriented assembly that was removed from the core will be sipped to de-termine if there were any gross failures of the fuel cladding. Based on the-i fact that the operational off gas release rates were not excessive, it is felt that there were no gross failures of this or any other assembly in the Core.

FAILURE DATA:

i There has been no previous case of fuel misloading that was not detected during the core verification. Therefore, there are no safety implications resulting from cumulative experience.

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