ML19326C341

Requests Analysis of Potential for Consequences of Boron Dilution Accident.Response Should Include Proposals for Design or Procedural Corrective Actions If Required to Preclude Accident or to Mitigate Accident Consequences

ML19326C341
Person / Time
Site:	Arkansas Nuclear
Issue date:	09/15/1977
From:	Desiree Davis Office of Nuclear Reactor Regulation
To:	Cavanaugh W ARKANSAS POWER & LIGHT CO.
Shared Package
ML19326C335	List: ML19326C333 ML19326C341
References
NUDOCS 8004220888
Download: ML19326C341 (3)

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Docket b

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,ccket !:o. 5D-313 CNelson s

u SEP 151977 RPSnaider RMDiggs DEisenhut Attorney, OELD L

Arkansas Power & Light Conpany I&E(3)

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Mr., Willian Cavanauch, III

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TJCarter Executive Director,' Generation JRBuchanan and Construction TBAbernathy P. O. Sox 551 ACRS(16)

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Little Rock, Arkansas 72203 p

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'iecently at an operating P2 f acility, a lietited baron ciletion incident occurred cue to the inadvertent injection of a portion of the contents of the tja0H tank into the reactor ccclant system while the reactor was in the cold shutdown condition. While perfoming surveillance testing (valve cycling) of the HaOH tank isolation valve, with the Decay Heat f.

Removal (DnR) systen lined up for reactor coolant recirculation, a portion f"

of the tank's contents drained into the DHR system.

Upon resumption of I

coolant recirculation this !!acil was injected into the reactor coolant

[i systen.

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In the above-nentioned case, only a limited anount of fin 0i! (apprcxiactely 600 gallons) was injected and the reactor renained suberiti' cal ny a large E

cargin. HowcVer, this event highlighted the fact that a postulated single failure at this facility (i.e., e.isposition of the isolation valve for che !lach tank then the DhR system is lined un for recirculation er operating in the recirculation Nde) could result in u nederator dilution incident which had not been previously considereo. Subsequent analysis Dy the licensee and his vendor revealed that, for certain conservative assunptions (c.c., reactor in the cold siiutdo tn condition, vessel tomrcture less than 100T, besinning of core life charccteristics, vessel drained to a level approxinately equal to the height of the outlet nozzle, lowst inital boron concentration allowed by Technical Specifications, tbc raxinum worth control rod stuct in_ ti,e fully cut position, and no credit assured for operater action), the injection of the !:aOH tan % contents into the reactor coolant systen due to the nisrosition of a single isolation valve cculd result in

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reactor criticality with tne control roJs insertec.

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t Arkansas Power & Light Company SEP 151977 Based upon our review of this particular incident, we concluded that the assumption that operator action would not be taken in suf-

.;;; s ficient tine to tominate the event prior to reactor criticality

=4 would be overly conservative. This detemination was influenced by the length of the dilution time necessary before return to criticality E

and by the number of indications and alaras available to the operator at this facility.

Due to plant-specific system design and instrumen-tation cifferences, we are not able at this time to reach a similar con-l clusion for all PWR's. Furthemore nost Pt R boron dilution analyses have been limited to addressing a nalfunction in the makeun and purification systen (chemical and volusc control systera). The incident discussed above is an example of a bcron dilution accident not covered by these analyses. Therefore ue are requesting that each licensee of a PWR f acility provide an analysis of the potential for and consequences of r+=

boron dilution accidents at his facilitye You are requested to perfom and submit the results of such an analysis within 90 deys of receipt of this letter.

Your analysis should be based

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upon conservative assu~ptions consistent with the design of your facility and your Technical Specifications and should include the assuaption of the most 11aiting single failure. The analysis should also ir,clude an assess-nont of the factors which affect the capability of the operator to take corrective action which would teminate the postulated events prior to achieving reactor criticality.

If, based on the results of this analysis, you deternine that corrective actions (desien or procedurai) are rcquired to preclude the occurrence or uitigate the consequences of postulated boron dilution accicents, your j'

response should include proposals for such octions.

Sincerely, sw Original sgned by v

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00n h. Davis, /.cting Chief Operating Reactors Branch #2 Division of Operating Reactors cc: Sec nnt page

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3-September 15, 1977 Arkansas Power & Light Compan/

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Phillip K. Lyon, Esauire House, Holms & Jewell 1550 Tower Building Little Rock, Arkansas 72201 Mr. Donald Rueter

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Manager, Licensing

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Arkansas Power & Light Company Post Office Box 551 2;

Little Rock, Arkansas 72201 Arkansas Polytechnic College Russellville, Arkansas 72801

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Mr. John W. Anderson, Jr.

Plant Superintendent Arkansas fiuclear One Post Office Box 608

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Russellville, Arkansas 72801

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