ML20154Q113

Requests That Matls Engineering Branch Evaluate Margin for Safety Re Potential LOCA Due to Energized Uncovered Pressurizer Heaters

ML20154Q113
Person / Time
Site:	Rancho Seco
Issue date:	09/19/1988
From:	Cintula T NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD)
To:	Rosenthal J NRC OFFICE FOR ANALYSIS & EVALUATION OF OPERATIONAL DATA (AEOD)
Shared Package
ML20154Q117	List: ML20154Q113 ML20154Q134 ML20154Q232
References
NUDOCS 8810030312
Download: ML20154Q113 (2)

Text

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gr i s met MEMORANDUM FOR: Jack E. Rosenthal, Chief Reactor Operations Analysis Branch Divisicn of Safety Programs Office for Analysis and Evaluation of Operational Data THRU: George F. Lanik, Chlef Reactor Systems Section GE & CE Reactor Operations Analysis Branch Division of Safety Programs Office for Analysis and Evaluation of Operational Data FROM: Theodore C. Cintula, Reactor Systems Engineer Reactor Systems Section GE & CE Reactor Operations Analysis Branch Division of Safety Programs Office for Analysis and Evaluation ,

of Operational Data s t

SUPJECT

POTENTIAL LOCA DUE TO EXERGIZED UNC0VERED PRESSbRIZER HEATERS 2 This study was initiated after a rereview of foreign operating experience from l

the Nuclear inergy Agency Incident Reporting System File. The event at the

- foreign ren. tor culminated in a large bre,1A loss of coolant acctdent from  !

localized overheating and failure of the reactor coolant pressure bnundary from

uncovered immersion heaters. The imersion heaters remained energized through-

'out the event because a vcided liquid level sensor refererce leg caused its associated centrol function to continuously activate all heater elements. j 1: The event scenario may t,e applicable to the immersion-type prest.urizer heaters  ;

at'all domestic PWRs. A review of operating experience found b ee events of  !

i the pressurizer heaters vncovering. In one plant, Rancho Sec . the uncovered pressurizer heaters did Mt all burn out and led to localized en 9ating,  ;

with a hot spot temperatere of 1000F, of the reactor coolant systein pressure ,

boundary. At the time of the localized overhecting, the reac ar pressure was F

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l Jack E. Rosenthal  :

very low, so the stress safety analysis did not ir.clude an internal pressure contribution to the weakening of the reactor pres;ure boundary. There appears

to be no explicit preventive limitation from this event recurring at the more unfavorable conditions associated with normal reactor operations. Accordingly, it is requested that the Materiais Engineering Branch, Division of Engineering, Office of Nuclear Regulatory Research evaluate the margin for safety for the un

nalyzed condition of localized overheating to 1000F coincident with a

maximum primary system pressure of 2485 psig to determine whether this issue i merits further regulatory pursuit.

/*/

Theodore C. Cintula, Reactor Systems Engineer Reactor Systems Section GE & CE i Reactor Operations Analysis Branch Division of Safety Programs Office for Analysis and Evaluation of Operational Data I

Enclosure:

l As stated 4

1 l

Distribution:

PDR ROAB R/F Glanik TCintula JRosenthal Thovak VBenaroya KBlack VWilliams JPartlow, OSP MTaylor, CHeltemes EJordan WLanning ,

ROAB:DSP:AE00 RC SP:AEOD R AB:DSP:AEOD TCintula:md GLTn k J sc.. thal 7/$1/88 7/AA'88 * /// /88

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