ML18227A467

Letter Reporting Abnormal Occurrence No. 251-75-4 of Lateral Restraints for Spent Fuel Racks Broken, in Unit 4 on 3/12/1975

ML18227A467
Person / Time
Site:	Turkey Point
Issue date:	03/21/1975
From:	Schmidt A Florida Power & Light Co
To:	Case E Office of Nuclear Reactor Regulation
References
Download: ML18227A467 (8)

Text

OF ABNORMAL OGGURRENGE AND/OR INGIDENI'RC

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FLORIDA POWER 8L LIGHT COMPANY March 21 Mr. Edson G. Case, Acting Director Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission Washington, D. C. 20555

Dear Mr. Case:

ABNORMAL OCCURRENCE NO. 251-75-4 OCCURRENCE DATE: MARCH 12, 1975 TURKEY POINT UNIT NO. 4 LATERAL RESTRAINTS FOR SPENT FUEL RA'CKS'ROKEN A. CONDITIONS PRIOR TO OCCURRENCE Unit No. 4 was at steady-state power operation at 99% rated power.

The Unit No. 4 spent fuel pool was drained and being cleaned in preparation for the first refueling.

B. DESCRIPTION OF OCCURRENCE During the spent fuel pool cleaning on March 6, 1975, found that one of the 116 stainless steel seismic restraint it was springs (see Sketches No. 1 and 2) on the spent fuel racks had broken into two pieces and was lying on the pool floor. The re-maining springs were all noted to be in place. However, a more careful examination of each of the remaining 115 springs was completed on March 12, 1975 and revealed that 5 additional springs were similarly broken, but were held in place by the nuts used to fasten the spring to the stud used for preloading the spring (see Sketch No. 1).

C. DESIGNATION OF APPARENT CAUSE OF OCCURRENCE The investigation to date has not conclusively determined the cause of the broken springs. One of the broken springs has been sent to a laboratory for metallurgical analysis, but the results are not, yet available.

D. ANALYSIS OF OCCURRENCE The springs provide restraint for the spent fuel racks in the event of a seismic event. Inasmuch as there was no spent fuel in the Unit No. 4 spent fuel pool, the broken springs clearly presented no nuclear safety problem, and posed no potential danger to the public health and safety.

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Mr. Edson G. Case, Acting Director Page Two March 21, 1975 E. CORRECTIVE ACTION The broken springs will be replaced with new springs of the same functional design. A supplement to this report will be issued in the event that additional corrective action is required as a result of the continuing investigation.

f P. FAILURE DATA There has been one other instance of a broken spring at the Turkey Point Plant. On March 10, 1975, one of the 116 springs installed in Unit No. 3 spent fuel pool was found to have broken.

The springs are manufactured by Unistrut Corporation, Wayne, Michigan, and are designated as part number 115792.

Very truly yours, D. Schmidt Vice President Power Resources HNP/cpc cc: Mr. Norman C. Moseley Jack R. Newman, Esquire

STAINLESS STEEL SPRING (USED FOR LATERAL RESTRAINT OF FUEL RACKS),.

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'OP OF POOL HORIZONTAL MEMBER OF SPENT FUEL RACK SPENT FUEL STUD AND NUTS USED FOR POOL WALL PRELOADING,OF SPRING BOTTOM OF POOL P

SPRING INSTALLATION IN TURKEY POINT SPENT FUEL POOL SKETCH NO. 1

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FRACTURE LINE

, STAINLESS STEEL SPRING USED FOR LATERAL RESTRAINT OF SPENT FUEL RACKS AT TURKEY POINT PLANT SKETCH NO. 2

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