ML20210K242

Forwards Safety Evaluation & TER-C5506-418, Structural Evaluation of Vacuum Breakers (Mark I Containment Program), Cooper Nuclear Station, Supporting Analytical Method Used to Evaluate Critical Stresses

ML20210K242
Person / Time
Site:	Cooper
Issue date:	09/25/1986
From:	Long W Office of Nuclear Reactor Regulation
To:	Pilant J NEBRASKA PUBLIC POWER DISTRICT
Shared Package
ML20210K247	List: ML20210K242 ML20210K249 ML20212A824
References
NUDOCS 8610010346
Download: ML20210K242 (3)

Text

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September 25 1986 0

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Docket No. 50-298 Mr. J. M. Pilant, Technical Staff Manager Nuclear Power Group Nebraska Public Power District Post Office Box 499 Columbus, Nebraska 68601

SUBJECT:

MARK I CONTAINMENT DRYWELL VACUUM BREAKERS Re:

Cooper Nuclear Station In December of 1979, the General Electric Company issued Service Information Letter (sR) No. 321 informing customers of unanticipated cycling and damage to drywell vacuum breakers during LOCA tests in a Mark I containment full-scale test facility. The SIL addressed the possibility of vacuum breaker failure due to chugging.

Failure due to pool swell was determined to be not applicable to Mark I containments (Ref: Safety Evaluation, Letter from Vassallo to Pfefferlen, dated May 5, 1983).

To assure that drywell vacuum breakers would be capable of withstanding chugging loads, the staff issued Generic Letter 83-08 on February 2,1983, requesting licensees of Mark I BWRs to submit results of calculations which provide bases for either (1) modifications to the vacuum breakers, or (2) justification that the as-built vacuum breakers are acceptable.

In your letter dated April 29, 1983 you provided the requested information, describing the results of your analysis which concluded that no modifications are necessary as the valves had been modified earlier. Your analysis was based on the Mark I containment generic load determination methodology described in (CDI) Tech Note 82-31 of October, 1982.

In SIL No. 321, Supplement 1 of August 24, 1984, GE announced the availability of plant specific methodology. The plant specific methodology is described in an enclosure (CDI Report No. 81-2) to a letter from H.C. Pfefferlen to D. B. Vassallo, dated September 26, 1984. The Staff Evaluation of the plant specific methodology was completed on December 24, 1984 (Letter from Vassallo to Pfefferlen dated December 24,1984). The Evaluation describes restrictions and conditions on the use of the model. These conditions and restrictions ensure conservatism in determination of the pallet impact velocity loads on the vacuum breakers during chugging.

On February 14,19E6 we sent you a Request for Additional Information (RAI).

The purpose of this RAI was to obtain verification that the pallet impact velocity used in your vacuum breaker stress analysis was determined using the approved methodology consistent with the conditions and restrictions prescribed by the staff. Your initial reply dated April 7, 1986 did not confirm that you used the approved methodology. However, in your subsequent 8610010346 860925 PDR ADOCK 05000298 P

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l*a w letter dated August 21, 1986, you provided additional information which indicates that the stress calculations were based on use of conservative values of pallet impact velocity.

The staff's technical assistance contractor, Franklin Research Center (FRC),

has reviewed the results of the stress analysis to verify that the vacuum breaker stresses are within the ASME code allowable values for the materials used. Their Technical Evaluation Report is appended to our Safety Evaluation which is enclosed for your information.

Based on our review, we conclude that the analyses performed to predict the drywell vacuum breaker impact velocities and resulting stresses, were performed using acceptable trethodology and that the vacuum breakers will not be subjected to excessive stress as a result of LOCA chugging and condensation oscillation loads.

This completes our review of Multiplant Action Item D-20 for Cooper fiuclear Station.

If ycu have any questions concerning our review, please contact the NRR Project Manager, Bill Long at (301) 492-9477.

i Sincerely, g,,,kcdi 1A.J.LJ William 0. Long, Project Manager EWR Project Directorate #2 Division of BWR Licensing

Enclosure:

As stated cc w/ enclosure:

See next page Distribution: Docket File

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Mr. J. M. Pilant Nebraska Public Power District Cooper Nuclear Station cc:

Mr. G. D. Watson,. General Counsel Nebraska Public Power District P. O. Box 4999 Columbus, Nebraska 68601 Mr. Arthur C. Gehr, Attorney Snell & Wilmer 3100 Valley Center Phoenix, Arizona 85073 Cooper Nuclear Station ATTN: Mr. c. Horn, Division Manager of Nuclear Operations P. O. Box 98 Brownville, Nebraska 68321 Director Nebraska Department of Environmental Control P. O. Box 94877 State House Station Lincoln, Nebraska 68509 Mr. William Siebert, Comissioner Nemaha County Board of Comissioners g

Nemaha County Courthouse t

Auburn, Nebraska 68305 i

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Resident inspector i

U.S. Nuclear Regulatory Comission P. O. Box 218 l

Brownville, Nebraska 68321

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Regional Administrator, Region IV U.S. Nuclear Regulatory Comission bl li ton xa 9,

H. Ellis Simons, Director Division of Radiological Health i

Department of Health 301 Centennial Hall, South P. O. Box 95007 Lincoln, Nebraska 68509

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