ML19320B078

Revised Final Deficiency Rept Re Spent Fuel Pool Gates. Gates Are Not Designed to Seismic Category 1 Requirements Per Reg Guide 1.13.QA Aspects of Gate Integrity Will Be Verified for All Three Plants

ML19320B078
Person / Time
Site:	Sequoyah
Issue date:	07/02/1980
From:	TENNESSEE VALLEY AUTHORITY
To:
Shared Package
ML19320B075	List: ML19320B074 ML19320B078
References
NCR-SQN-NEB-801, NUDOCS 8007090258
Download: ML19320B078 (2)

Text

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-ENCLOSURE

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'SEQUOYAH NUCLEAR PLANT UNITS 1 AND 2 SPENT FUEL POOL GATES NCR SQN NEB 8012 .

10CFR50.55(e)

REVISED FINAL REPORT Descriotion of Deficiency The NCR states that the spent -fuel pool gates (one te 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 (WBNNEB8005) and Bellefonte

_(BLNNE38005) Nuclear Plants.

Safety Implications Structural failure of the gates during a seismic event could result in damage'to stored spent fuel elements. This could result in *.

. radiation levels in the spent fuel pool area higher than those assumed

'in the plant safety analysis, and thus could result in doses to plant personnel 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: primary safety function of =aintaining sufficient water level above the spent fuel. This function, if verified, would have made the gates Seismic Category I and would require QA progran coverage

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of the gates' fabrication. It was found by analyses of pool water icvel

- 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 parait.

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 procurement documents did not otherwise specify the seismic requirements.

-Quality _ assurance program coverage was not specified because the original

- designs considered that the gates could normally be stored, and would be-

installed only when it would be necessary to dewater the transfer canal of'the: cask loading area for maintenance.

Because of increasing QC and QA documentation emphasis within TVA in the -

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 done through the evaluation of inspectiot, and repair records at the Ifabricators. 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 z in'the gates' fabrication. Failing both of the above, the verification

.will'be obtained through testing and inspection of the materials and

-welds;in the gates. Any required corrective' actions will be caken. 't .is work does 'not affect..the reportability to NRC of the three NCR's dis-cussed abovel

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IThe!gateidesfens were analyzed later for the case of water on both

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sides of-the lastalled gates, and it was for this case that.the Sequoyah cask loading area gate was found-to be inadequate." This was the only case'of potential failure among the six gates at the three plants. The transfer canal and -the cask loading area gates at Sequoyah.and Watts Bar were derigned with paired restraints attached to the pool wall at the top ar.t at the bottom of the gates. At Watts Bar, restraints were later added at midheight to correct a leakage problem encountered. on testing of the gates in the nool. These restraints, and similar ones added at Bellefonte,.; count for these gates being seismically qualified. The midheight restraints were omitted at Sequoyah. This problem will be corrected by administratively requiring the gate to remain in iis storage location during normal plant

-operations. The gate will only be rusceptible 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 anC that a' modification to the cask loading area gate is not required.

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