ML20028H801

LER 90-002-01:on 900116,determined That 891211 Reconstitution of More than One Spent Fuel Assembly Per Time in Violation of Fuel Handling Incident Safety Analysis. Caused by Deficient procedure.W/910124 Ltr

ML20028H801
Person / Time
Site:	Calvert Cliffs
Issue date:	01/24/1991
From:	Denton R, Muth D BALTIMORE GAS & ELECTRIC CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-002, LER-90-2, NUDOCS 9101300134
Download: ML20028H801 (5)

Text

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, B ALTIMORE GAS AND ELECTRIC CHARLES CENTER e P.O. BOX 1475 o BALTIMORE, MARYLAND 21203 1475 n E DENTON o[NLRAL MANAGER CALvtRt CLWFS January 24, 1991 U.S. Nuclear Regulatory Commission Washington, D.C. 20555 ATTENTION: Document Control Desk

SUBJECT:

Calvert Cliffs Nuclear Power Plant Unit Nos. I or 2; Docket Nes. 50 317 or 318; License No. DPR 53 or DPR 69 Licensee F*?ent Report 90 002. Revision 01 Centlemen:

The attached report is being sent to you as required under 10 CFR 50.73 guidelines. Should you have any questions re6arding this report, we will be pleased to discuss them with you.

Very truly yours, r h4 i

RED /DWM/bj d Attachment ec: D. A. Brune, Esquire J. E. Silberg, Esquire R. A. Capra, NRC D. G. Mcdonald, Jr. , NRC T. T. Martin, NRC L. E. Nicholson, NRC R. I. McLean, DNR Director, Office of Management Information and Program Control 9101300134 910124 PDR ADOCK 05000317 /

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t,'o N,'.Ae B.L E I I I I I I I I  ! l !  ! I I I I I I I I l l l ! ! I I l SUP9ttMINT AL R EPOR T t RPECT10114> MONie C air vt&D Sv t w ' 58 'ON 4 i E 09 von tome,ere 9 k9tCTfD $v0w3310% C,A rto No l l l 4.887 R ACT IL,=f to P dM speces . e . sapeoemere e f.*resa pay e spece r,pennreen 1,aest t16 On December 11, 1989, with Unit 1 in MODE 5 and Unit 2 defueled, we determined that our previous practice of reconstituting more than one spent fuel assembly at a time was not bounded by the assumptions of the Fuel llandling Incident safety analysis, which assumes that only one fuel assembly could be damaged in the event of a fuel handling incident. On January 16, 1990 this practice was j determined to place the plant in a condition outside its design basis as described in the Updated Final Safety Analysis Report (UFSAR).

The root cause of this condition was a deficient procedure which did not prevent movement and placement of fuel assemblics such that more than one could be damaged in the event of a fuel handling incident.

Fuel handling procedure FH-48 has been revised to require that only one assembly at a time be placed in a designated location for reconstitution.

This change ensures that no more than one assembly could be danaged in a fuel handling incident.

All fuel handling procedures have been reviewed against the UF3AR with no l discrepancies identified. Future changes to fuel handling precedures will be reviewed against UFSAR accident analysis assumptions.

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LICENSEE EVENT REPORT (LER) TEXT CONTINUATION F ACIUTV NAME DOCKET NUMBER tf R NUMBER PAQt Calvert Cliffs, Unit 1 05000317 90 002 01 0 2 0F 0 4 n a e mm m. w.s u suwm I. DESCRIPTION OF EVENT On December 11, 1989, with Unit 1 in MODE 5 and Unit 2 defueled, we determined that our previous practice of reconstituting more than one spent fue) assembly at a time was not bounded by the assumptions of the Fuel Handling Incident safety analysis in the Updated Final Safety Analysis Report (UFSAR). Reconstitution of more than one assembly in the Spent Fuel Pool (SFP) at a time opens the possibility that more than one assembly could be damaged in the event of a fuel handling incident. The UFSAR assumes that only one fuel assembly could be damaged in the event of a fuel handling incident. On January 16, 1990 this practice was determined to place the plant in a condition outside its design basis as described in the UFSAR. This item is reportabic under 10 CFh 50.73(a)(2)(ii)(B).

Section 14.18 of the UFSAR describes the fuel handling incident safety analysis.

The analysis assumes a fuel assembly is dropped during fuel handling, striking the Spent Fuel Fool (SFP) floor vertically and rotating to a horizontal attitude, striking a protruding structure. Only one assembly is assumed to be damaged.

All other assemblies in the SFP are assumed to be stored within the spent fuel l storage rcchs at the bottom of the SFP. The top of the rack extends at least ten inches above the top of the stored fuel assemblies. A dropped assembly could impact a stored assembly only in an end-on fashion. Analysis indicates that the force of this impact could be absorbed with no fuel rod failures.

In order to reconstitute fuel assemblics in the SFP these assemblies are placed in a single row of designated spent fuel storage rack locations at the bottom of which are placed 20 1/2 inch tall rack spacers upon which the assemblies to be repaired are set. The assemblics, having been placed on top of the spacers, protrude roughly ten inches above the top of the spent fuel storage racks.

Reconstitution requires the removal of the upper end fittings from the l assemblies. Placing the assemblics such that they protrude above the level of the spent fuel racks allows the removal of the upper end fittings, l In the past, there were no procedural controls to prevent the movement of fuel assemblies in the vicinity of the assemblies protruding above the top edge of the storage racks. Past practice has been to work on several assemblics at one time.

This called for assemblies to be moved to storage rack locations directly adjacent to locations containing protruding assemblies. Movement was allowed into locations adjacent to assemblies the upper end fittings of which had been removed.

This inadequacy was found during the revision of fuel handling procedure PH-48, which governs the inspection, testing and repair of fuel assemblies in the SFP.

PH 48 is revised prior to each refueling outage during which these activities are scheduled to occur. A new, more stringent procedure review process used for revising this procedure required the comparison of the procedure against the i

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LICENSEE EVENT REPORT (LER) VEXT CONTINUATION F ACluTY NAME DOCKET N'JMBER LER NUMBER PAGE Calvert Cliffs, Unit 1 05000317 90-002-01 0 3 0F 0 4 nxr v w. .vu. N r wa. m uma u,m.e UFSAR. As a result of this review, FH-48 was revised to prevent reconstitution of more than one assembly at a time. The revised procedure was used for the Unit 2's eighth refueling outage.

II. CAUSE OF CONDITION The root cause of this condition was a deficient procedure which did not prevent I movement and placement of fuel assemblies such that more than one could be damaged in the event of a fuel handling incident in the SFP. The procedure methodology was developed prior to the first Unit I refueling outage in 1977 and has been reviewed every refueling outage since then. This inadequacy was not identified during initial development of the methodology or in any previous revision of the procedure. This inadequate issue discovery is a contributing cause of this event.

III. ANALYSIS OF CONDITION The manner in which fuel reconstitution was performed prior to the Unit 2's eighth refueling created the possibility of more than one assembly being damaged in the event of a fuel handling incident. Given the fuel reconstitution practices in use, the worst case fuel har.dling incident would involve an assembly being dropped next to the fuel reconstitution platform and falling across all of the fuel assemblies being reconstituted. That an assembly would fall in exactly this manner is highly unlikely.

A review of fuel reconstitution history found that the maximum number of assemblics that could have been damaged was 11 and that the minimum time between unit shutdown and reconstitution of any assemblies was 15 days. The site boundary dose resulting from the clad failure of one assembly (feilure of all 176 fuel rods) removed from the core 15 days after shutdown is 4.55E-3 REM Whole Body and 9.308-2 REM Thyroid. Assuming clad failure of all fuel rods in all 11 assemblies (which is highly unlikely) site boundary dose is 0.050 REM Whole Body and 1.023 REM Thyroid, These values are significantly lower than the 10 CFR 100 site boundary limits of 6.25 REM Whole Body and 75 REM Thyroid.

IV. CORRECTIVE ACTIONS Fuel handling procedure, FH-48, which governs the inspection, testing and repair of core components in the SFP, has been revised to require that on1;. one assembly at a time be placed in a designated location for reconstitution. The procedure requires that once an assembly is in the reconstitution station, the Spent Fuel Handling Machine (SFHM) is moved to a remote location in the SFP and l

'de energized. The SFHM may only be re-energized when it has no fuel assembly grappled and is directed by the procedure to retrieve the assembly from the

reconstitution station. While an assembly is protruding above the top level of the storage racks, no other assemblies may be moved in the SFP, This change l

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r LICENSEE EVENT REPORT (LER) TEXT CONTINUATION F ACIUTY MAME DoCKE1 NUMBER LIR NUMBER PAGE Calvert Cliffs, Unit 1 05000317 90 002 01 0 4 0F 0 4 te a r . .p.c. . meg .aoe.i ensures that no more than one assembly could be damaged in a fuel handling incident.

All fuel handling procedures currently in une have been reviewed under the ongoing Procedure Upgrade Froject. This review includes a comparison of each procedure against the accident assumptions of the UFSAR with no discrepancies identified. Future changes to these procedures are governed by Calvert Cliffs Instruction CCI 101, which requires review against portinent documents, including UFSAR accident analysis assumptions.

V. ADDITIONAL INFORMATION A similar event was documented in LER 88-15, Movement of Heavy Loads Over the Spent Fuel Pool. In that LER, an administrative control was not properly maintained and a heavv load was moved over the SFP.

IEEE 803 IEEE 805 Component EIIS Funct System ID SFP N/A DB Spent Fuel Storage Rack RK DB SHHM FHM DF

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