ML19326C018

Advises That Proposed Decay Heat Removal Sys High Pressure Alarm Does Not Provide Protection Equal to Automatic Closure Sys.Plans & Schedule to Modify Sys Valving Design to Include Automatic Closure Sys Requested

ML19326C018
Person / Time
Site:	Arkansas Nuclear
Issue date:	11/01/1972
From:	Deyoung R US ATOMIC ENERGY COMMISSION (AEC)
To:	Phillips J ARKANSAS POWER & LIGHT CO.
References
NUDOCS 8004180705
Download: ML19326C018 (2)

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Docket No. 50-313 Mr. J. D. Phillipe Vice Pr==&=t & Chief Engineer Arkeness Power & Light Conquay j

Si::th and Pine Streets Pine Bluff, Arkanans 71601

Dear !!r. Phillips:

Your resposee to our Information Request No. 9.1 indicated that so devine is being provided to close autenatically the motor-eparated iso-latica valves in the auction lines of the Decay Bent Meroval System (DIRS) when reactor coolant preenwra exceeds a selected fraction of the design pressure of the DERS. You have proposed a DI2S high pressure alarm t.o ' alert the operator abould the valves be left open when raising RC pressure. You have sentended that the rate of pressexe increosa which is possible in sufficiently low that the enerator enn react in 1

time to protect the DHRS.

We have evaluated your proposed alarm sehene and do not regard it as providing a degree of protection eauivalent to an automatie closure system. First, and more importantly, the alarm would not wirn of a condition where the root valve (RC side) is closed and the other valve open. This single velve isolation poseihility askes the plant vulner-able to a grievous failure if the plant ranches power and that aine.le valve fails. Secondly, analysia presented for another plant of this type indicates the potential, durinc presseure faeressing transionen, for reaching en overpressure caxlition in less than 10 minutes tedess correct operator action is taken.

Cemeequently, the proposed alaru scheme is not rararded as providing a degree of protection equivalent to en automatic silosure system. " Please indicate your plans and schedulo to redify the desis of the DHRS valving to loclude the preferred automatic closure feature or to coninr.s to other criteria that provide an equivalent degree of protection. In addition, the interlocka provided to prevent. valve opening at high pressure sboeld be independent and diverse.

Both the valva autcutatic closure and 1

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l Form AEC-StS (Rev. 9 53) AECM 0240 o u s covannweur peinri%o oarics. ter : -44e -t se

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l Mr. J. D. Phf111pm gay yg peepentime-i_ r,--t== systeen should comply with all the requir-*=

(met merely the intent) of IEEE-279.

Simeerely.

Original signed by R. C. DeYoung R. C. DeYoung, Assistant Director for Pressurised ifator Emmeters Directorate of Limensing se w/unal l'

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