ML18127A651

LER 1978-025-00 for St. Lucie Unit 1, on 07/24/78 Concerning an Error in the Analysis for the Cask Drop Accident Which Makes the Technical Specification 3.9.14 Non-Conservative

ML18127A651
Person / Time
Site:	Saint Lucie
Issue date:	08/07/1978
From:	Schmidt A Florida Power & Light Co
To:	O'Reilly J NRC/RGN-II, NRC/IE
References
PRN-LI-78-219 LER 1978-025-00
Download: ML18127A651 (5)

Text

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DXSTRIBUTION FOR INCOMING NATERIAL 50-335 REC: OREXLLY J P, GRG; SCHMIDT A D DOCDATE: 08/07/78 NRC FL PWR 8( LIGHT DATE RCVD: 08/15/78 DOCTYPE: LETTER NOTARIZED: NO COPIES RECEIVED

SUBJECT:

LTR 1 ENCL 1 LICENSEE EVENT REPT 50-335/78-25 ON 07/24/78 CONCERNING AN ERROR IN THE ANALYSIS FOR Tl-IE CASK DROP ACCIDENT WHICI.I MAKES TFIE TECH SPEC 3. 9. 14 NGI4-CONSERVATI VI:.

PLANT MANE: ST LUCXE REVIEWER INITIAL: XBT

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FLORIDA POPOVER 5 LIGHT COMPANY August 7, 197g-P RN" L I 219m~

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n Mr. James P. O'Reilly, Director, Region II CA Office of Inspection and Enforcement, U. S. Nuclear Regulatory Commission Peachtree Street, N. M., Suite 1217

'30 Atlanta, Georgia 30303

Dear Mr. O'Reilly:

REPORTABLE OCCURRENCE 335-78-25 ST. LUCIE UNIT 1 DATE OF OCCURRENCE: JULY 24 1978 CASK DROP ANALYSIS The attached Licensee Event Report is being submitted in accordance with Technical Specification 6.9 to provide prompt notification of the subject occurrence.

Very truly yours, JiP A. D. Schmidt Vice President Power Resour ces MAS/ms Attachment cc: Harold F. Reis, Esquire Director, Office of Inspection and Enforcement (40)

Director, Office of Management Information and Program Control (3) 782230377 PLOPLF . ~ . SERVING PFOPI.F

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3.9. 1 4 i s .non-conservati ve. It has been determined that a dro ed cask could impact a larger radius, therefore, a longer decay time is needed before a cask. can be moved into the spent fuel pool cask compartment.

There are no adverse conse uences because of the small amount of fuel in the pool and the high degree of conservatism in the analysis.

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Reportable Occurrence 335-78-25 Licensee Event Report Pa e Two Additional Event Descri tion During power operation, the Architect/Engineer found an error in the accident analysis for the drop of a spent fuel cask into the spent fuel pool. As a result of the error; Specification 3.9.14 on spent fuel handling is non-conservative. The analysis was originally performed assuming a single pendu-lum, which gave a drop radius of 133 inches. The FSAR methodology, however, specifies a double pendulum, which gives a drop radius of 248 inches. This means that a dropped cask could impact more, fuel elements, therefore, "fresh" spent fuel must be stored farther from the cask area and/or allowed to decay longer before the cask can be moved into the spent fuel pool. The probable consequences of the occurrence are not signifi cant because fuel was stored in the pool for only 2 months before the error was found, and there is considerable conservatism in the dose rate analysis for the cask drop acci-dent. This was the first occurrence involving a calculational error associated with a spent fuel system.