ML20050A947

Discusses Effects of Pressure in Drywell from Hydrogen Burn.Drywell Pressures Predicted by CLASIX-3 Computer Code Should Be Considered Very Conservative

ML20050A947
Person / Time
Site:	Grand Gulf
Issue date:	03/31/1982
From:	Dale L MISSISSIPPI POWER & LIGHT CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
References
NUDOCS 8204020429
Download: ML20050A947 (2)

Text

MISSISSIPPI POWER & LIGHT COMPANY Helping Build A1ississippi EulMdWdiddE P. O. B O X 16 4 O. J A C K S O N, MiSSlSS1PPI 39205 NUCLEAR PRooUCTioN DEPARTMENT '

g U. S. Nuclear Regulatory Commission N Office of Nuclear Reactor Regulation 2 pf.ON ,

Washington, D. C. 20555 2 R Q g y. 3 -

Mr. Harold R. Denton, Director Attention:

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Dear Mr. Denton:

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SUBJECT:

Grand Gulf Nuclear Station O Q Units 1 and 2 Docket Nos. 50-416 and 50-417 File: L-860.0/0756 Effects of Pressure in the Drywell From Hydrogen Burn AECM-82/118

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I. Based on the Combustion and Explosives Research, Inc. (COMBEX) evaluation of hydrogen burning in the drywell, the drywell pressures predicted by the CLASIX-3 computer code should be considered very conservative. The six foot per second (6 fps) burn speed used to establish the drywe

pressurization profiles are assumptions incorporated into the CLASIX-3 evaluation. These pressure profiles are very conservative representations of the drywell response to hydrogen burning. The aalyses assume that hydrogen burning will not occur until the average drywell oxygen concentra-tion reaches 5 volume percent, and then, at the prescribed burn speed, all the availabic oxygen is consumed. The expected drywell hydrogen burn, as predicted by COMBEX, should be considerably slower with the establishment of an oxygen-limited flame at the outlet ducts of the drywell purge conpressors and post-LOCA vacuum breakers. The drywell pressurization resulting from this flame should occur over minutes rather than seconds as modelled by CLAS1X-3. Hence pool swell concurrent with drywell hydrogen burning is not expected.

II. Drywell Structural Capability  ;

II As previously discussed in AECM 11/336, dated August 31, 1981, the ultimate capacity of the dryvell structure is evaluated to be 67 psig positive (i.e., drywell pressure above containment pressure) based on specified material strengths. The negative pressure capability is higher than the positive pressure capability. Therefore, the pressures reported 1

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O AECM-82/118 MISSISSIPPI PuWER & LIGHT COMPANY for the 6 fps burn speed case should have no adverse effects on the drywell structural capability.

Yours truly, M

L. F. Dale Manager of Nuclear Services RMS /SHil/JDR: rg cc: Mr. N. L. Stampley Mr. R. B. McGehee Mr. T. B. Conner Mr. G. B. Taylor Mr. Richard C. DeYoung, Director Office of Inspection & Enforcement U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Mr. J. P. O'Reilly, Regional Administrator Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission Region Il 101 Marietta St., N.W., Suite 3100 Atlanta, Georgia 30303