ML20009A748

Final Deficiency Rept Re Overstressed Condition in Letdown Cooler Supports.Three Addl Holes Will Be Drilled for Attachment Bolts in Cooler Support Bracket.Support Platform Will Be Modified to Fully Contact Support Bracket

ML20009A748
Person / Time
Site:	Midland
Issue date:	06/30/1981
From:	Jackie Cook CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
10CFR-050.55E, 10CFR-50.55E, 12034, NUDOCS 8107140097
Download: ML20009A748 (2)

Text

O Consumers Power James W Cook nce PressJent - Projects, Lngsne. nng and Construction General offices- 1945 West Pernell Road. Jackson. MI 49201 * (517) 788 0453 80-01 #7 June 30,1981 U '

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Mr J G Keppler, Regional Director .7 } g\

Office of Inspection and Enforcement 9[ 3g7d US Iluelear Regulatory Conni 3sion Region III 3 Jg 1 yoo -

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799 Roosevelt Road #

Glen Ellyn, IL 60137 7 MILLAIiD PROJECT N DOCKET NOS .'M-329, 50-330 LE"DOWN C00LFR SUFFORTS FILE: 0.L.9.38 UFI: 73*10*01, 152h0(E), 02312(S) SE:u! L : 1203h

References:

CFCo letters to J G Keppler, Same

Subject:

(1) Serial Howe-6h-80, dated March 27, 1980 (2) Serial 9180 dated June 19, 1980

( 3) Serial 9769 dated October 10, 1980 l (h) Serial 1099h dated December 30, 1980 (5) Serial 11177 dated January 30, 1981 i (6) Serial 11967 dated April 15, 1961 The referenced letters were interim 50 55(e) reports concerning the overstressed condition in the letdown cooler supports. Corrective action has now been determined, and its implementation scheduled. This letter is therefore the final report on letdown cooler support overstress.

As it was originally determined, a deficiency existed in the design of the letdown cooler supports such that the application of design (specification) nozzle loade to the cooler would result in overstress of the lower support bracket , which is an integral part of the letdovn cooler. The overstrest resulted because the support platfom, which mates the letdown cooler support bracket to the supporting structure, did not fully contact the letdown cooler l

support bracket, in effect rendering it a cantilever beam and thereby requiring it to sustain moments in excess of its capability. A detailed description of the deficiency is included in the attachment to reference 1.

Since the actual loads applied to the cooler would be less than the design loads, the possibility existed that the application of the actual loads would not cause an overstress condition. An analysis done by the equipment manufacturer later confirmed that this was not the case (reference 2) .

In subsequent analysis, actual piping loads calculated by Bechtel were used.

l Actual piping loads were provided to the letdown cooler manufacturer i

(reference 3) who used them in combination with the loads due to the cooler 2 Y3@

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s 2 Ser!.al 1203h 81-01 07 0

itself to analyze the cooler support bracket. These loads were then provided to Bechtel (reference h and 5) by B&W for use in designing the support platform.

B&W and the letdown cooler manufacturer also informed Bechtel of their require-nent that the fixed cooler support bracket be encompassed by the support platform, to eliminate the cantilever condition, and that complete contact between the bracket and the platform be maintained. To accorplish this, three additional attachment bolts will be used.

Bechtel has determined that the support platform can be modified to meet these requirements.

The action to 2 taken to correct this deficiency is to drill three additional holes for attachment bolts in the letdown cooler support bracket, and to modify the support p]atform to fully contact the support bracket, and provide bolt holes and bolts to aatch the additional holes to the bracket. The design details are presently beit, finalized, and the installation of the support modifications is scheduled to be complete by February 26, 1982.

HWD/lr CC: Director of Office of Inspection & Enforcement Att Mr Victor Stello, USNRC (15)

Director, Office of Management Information & Program Control, USNRC (1)

RJCook, USNRC Resident Inspector Midland Nuclear Plant (1)

CBechhoefer, ASLB RSDecker, ASLB FPCowan, ASLB AS&L Appeal Panel MMCherry, Esq MSinclair BStamiris CRStephens, USNRC WDPaton, Esq, USNRC FJKelly, Esq, Attorney General l SHFreeman, Esq, Asst Attorney General GTTaylor, Esq, Asst Attorney General WHMarshall GJMerritt, Esq, TNK&J