ML19332A542

Second Revised Final Deficiency Rept Re Possible Structural Failure of Spent Fuel Pool Gate During Seismic Event.Problem to Be Corrected by Administratively Requiring Gate to Remain in Storage Location During Normal Plant Operations

ML19332A542
Person / Time
Site:	Sequoyah
Issue date:	09/08/1980
From:	Mills L TENNESSEE VALLEY AUTHORITY
To:
References
10CFR-050.55E, 10CFR-50.55E, NCR-SQN-NEB-801, NUDOCS 8009160372
Download: ML19332A542 (3)

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400 Chectnut Street Tower II Sentriber 3, 1980 Fr. Jr es ?. O'Reilly, Directo" Cffica of Ia?> ,ct!on and Erforcenent U.S. huclea - ?? 'O.atv y Cc =i331on

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Dear 1:

r. O'.Seiliy:

.tEQUOYAH ::UCLFAR ?LANT UNITS 1 AND 2 - SPENT FUEL PCCL GATES - NCE SCN

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The cub,' set deficiere/ :.aa initially reportec to NRC-0IE Ir.spector J . L . *di l e c : en h" ' . 1'if 0, in accordanc-r '. it" 10 CFR 50.55(o).

Ar frt e-it re pe: t ':.u rut aitt ed : n "n~ 79, 1?CO. a final rcpert mc cubmitted cr Jur.e 16, 1960, and a :evised final report :me cutnitte i en July 2, irc0. The fina'. raport : ac been further reviced at the recuest of F. S. Cr.trell to correct the statements about ni:! heir;ht restrainta en '.ha Callefonte !!nclent ?lant cpent fuel pcol gatos.

If you '.r ave any questions, picace get in teuen with D. L. Lambert nt L . .,;,,. . b '; I ~<.~. c .- . e. .

Very tr::ly : cure,

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L. -i. ".i'_la, Manarer l Nuclear Regulaticn and Safety ir.c;ccure cc: F.r. Victcr 3tello, Directcr (Er.clocure)

Cffice of In.spection end ir.forcement u.a. ..uc. ear aequ_ater-; ,.c.m:':isaicr.

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8009160 3 72 3

ENCLOSURE-

'SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2

. SPENT FUEL POOL. GATES

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H NCR_SQN NEB 8012 10CFR50.55 (e) -

- SECOND REVISED FINAL itEPORT

' Description of Deficiency The NCR states.that the spent fuel pool gates- (one to the transfer canal and one'to the cask loading area) are not designed-to Seismic Category I require =ents in accordance'with Regulatory Guide 1.13.

Similar.NCR's.were written on Watts Bar (WBNNEBS005) and Bellefonte (SLT.;E38005) Nuclear Plants.

Safetv !=clications Stru:tural failure of the gates during a seismic event could result in ds= age to stored spent fuel elements. This could result in radiation levels in the spent fuel pool area higher than those assu=ed

.in the plant safety analysis, and thus could result in doses to plant persennel and the public' greater than has been analyzed. This safety-related function results in a-Seismic Category I(L) classification of the gates. There was .a question within TVA as to whether the gates also have a pri:ary safety-function of caintaining sufficient water level above the-spent fuel. This function, if verified, would have

, =ade the gates Seismic Category I and would require QA program coverage

.cf the ;ates' fabrication. It.was found by analyses of pool water level drops due to leaking gates that this is not a required function of the gates; the water level will not drop sufficiently in any case to permit excessive radiation ' levels in the pool area.

Corrective Action The spent fuel pool gates for~ all three plants were designed by TVA, considering seismic loadings. 'The fabrication was contracted out with the design ensuring the seismic integrity _ of the gates although the procure =ent documents did not otherwise~specify the seismic requirements.

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Quality assurance program coverage was not specified because the original l desi;ns considered that the gates'would normally be stored, and would be installed only~ when it would be necessary. to dewater the transfer canal i of the cask loading area for maintenance.  ;

Eecause of increasing QC and QA documentation emphasis within TVA in the

. l years since the gate fabrication was contracted out, the-QA aspects of the gates' integrity is.to be verified'for all three plants. This will be dene thtcugh the_ evaluation of inspection and repair records at the fabricators' facilities and at the sites if possible. Alternatively, certificates of compliance will be obtained .from the fabricators to verify that the specified materials and construction standards were used in the gates' fabrication. Failing both ' of the ^ above, the verification

' will be obtained through testing and inspection of the materials and l welds in the gates. Any required corrective actions wilI'be taken. This l work-does not affect the reportability to NRC of the three NCR's dis- ~

o cussed above. --

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The Sequoyah and Watts Bar gate designs were analyzed later for the case

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. . of water en both sides of the installed gates, and it was for this case that the Sequoyah cask leading area gate ~was found to- be inadequate. This

- was the only' case. of potential . failure among the four gates at the two plants. The , transfer canal and the cask loading area gates.at Sequoyah

~ and 'n'atts Bar were' designed with paired restraints attached to the pool wall.at the top and at the bottom of the gates. At Watts Bar, restraints 2 .

account fer _ these gates being seismically qualified. The midheight restraints were omitted at Sequoyah.- This problem will be corrected by

- administratively requiring lthe gate to remain in it's storage locatien '

during normal plant operaticns. The gate will only be susceptible to seismic events when it'is in place for lowering or raising a spent fuel shipping cask or- for dewatering the cask- loading area. It is believed that the'short time these events would occur are insignificant and that-a modification to the cask loading area gate -is not required.- The

- Sellerente gates were ' designed after tne analysis was made including the

} case of water en both sides of the gates. The resultant loads were

, therefere considered in the design, and no midheight restraints were

!- needed.

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