ML20216G443

Forwards Open Items Associated W/Steam Explosion SER for AP600

ML20216G443
Person / Time
Site:	05200003
Issue date:	03/13/1998
From:	Joseph Sebrosky NRC (Affiliation Not Assigned)
To:	Liparulo N WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
References
NUDOCS 9803190413
Download: ML20216G443 (3)

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March 13,1998 Mr. Nicholas J. Liparulo, Manager Nuclear Safety and Regulatory Analysis Nuclear and Advanced Technology Division Westinghouse Electric Corporation '

P.O. Box 355 Pittsburgh, PA 15230

SUBJECT:

OPEN ITEMS ASSOCIATED WITH THE STEAM EXPLOSION SAFETY EVALUA-TION REPORT (SER) FOR THE AP600 i

Dear Mr. Liparulo:

The Containment Systems and Severe Accident Branch has provided an SER for their review associated with in-vessel, and ex-vessel, steam explosions for the AP600. However, the SER contained some open items. These open items have been extracted from the SER and can be found in the enclosure to this letter. ,

if you have any questions regarding this matter, you may contact me at (301) 415-1132. ,

Sincerely, original signed by:

Joseph M. Sebrosky, Project Manager Standardization Project Directorate Division of Reactor Program Management Office of Nuclear Reactor Regulation Docket No.52-003 Enc'osure: As stated cc w/ encl: See next page plSTRIBUTION:

Docket File PDST R/F TQuay PUBLIC TKenyon WHuffman JSebrosky DScaletti JNWilson ACRS (11) JMoore,0-15 B18 RPalla, O-8 H7 JKudrick,0-8 H7 MSnodderly,0-8 H7 s

,o C3 1 DOCUMENT NAME: A:FCl.RAI *See previous concurrence To receive a copy of this document, indicate in the box: "C" = Copy without ettagh, ment / enclosure "E" = Copy with attachment / enclosure "N" = No copy , /(/

OFFICE PM:PDST:DRPM l SCSB:DSSA l D:PDST:DRPM i (A)$:DRPM l NAME JMSebrosky:sg fWi MSnodderly* TRQuay -tyiv JWhoe DATE 03/ l V98 03/12/98 03/ o /98 ' 03/ h/98 OFFICIAL RECORD COPY 9803190413 980313 o" ^

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Mr. Nicholas J. Liparuto Docket No.52-003 )

Westinghouse Electric Corporation AP600 l

l cc: Mr. B. A. McIntyre Mr. Russ Bell Advanced Plant Safety & Licensing Senior Project Manager, Programs Westinghouse Electric Corporation Nuclear Energy institute l Energy Systems Business Unit 1776 i Street, NW P.O. So,t 355 Suite 300 Pittsburgh, PA 15230 Washington, DC 20006-3706 Ms. Cindy L Haag Ms. Lynn Connor Advanced Plant Safety & Licensing Doc-Search Associates  !

Westinghouse Electric Corporation Post Office Box 34 Energy Systems Business Unit Cabin John, MD 20818 l Box 355 Pittsburgh, PA 15230 Dr. Craig D. Sawyer, Manager  :

Advanced Reactor Programs i Mr. Sterling Franks GE Nuclear Energy U.S. Department of Energy 175 Curtner Avenue, MC-754 NE-50 San Jose, CA 95125 19901 Germantown Road Germantown, MD 20874 Mr. Robert H. Buchholz GE Wuclear Energy Mr. Frank A. Mss 175 Curtner Avenue, MC-781 U.S. Department of Energy, ME-42 San Jose, CA 95125 Office of LWR Safety and Technology 19901 Germantown Road Barton Z. Cowan, c!sq.

Germantown,MD 20874 Eckert Seamans Cherin & Mellott 600 Grant Street 42nd Floor Mr. Charies Thompson, Nuclear Engineer Pittsburgh, PA 15219 AP600 Certification NE-50 Mr. Ed Rodwell, Manager 19901 Germantown Road PWR Design Certification Germantown, MD 20874 Electric Power Research Institute 3412 Hillview Avenue Mr. Robert Malers, P.E. Palo Alto, CA 94303 Pennsylvania Department of Environmental Protection Bureau of Radiation Protection Rachel Carson State Office Building P.O. Box 8469 Harrisburg, PA 17105-8469

Steam Explosion Questions 720.466F in response to RAI 720.426F, which considered the likelihood of downward reloca-tion resulting from crust failure, Westinghouse offered qualitative arguments that any secondary explosion would involve a complex relocation process, and would not be conducive to producing an explosion load to threaten the containment. The ac-knowfadgment that the relocation process may be complex makes the qualitative arguments less convincing in absence of some quantifications. For example, how much melt mass will likely be released from the crucible upon primary er.,losion induced failure, how much will the lower plenum coolant inventory be at the time, what would be the estimate of explosion load for that combination of melt and water.

These are the types of quantifications that would add credibility to the qualitative stguments. In the absence of such infom:stion, the staff believes that the downward relocation issue remains an open item.

720.467F During a meeting with Westinghouse on January 22,1998, the staff communicated its concem with the values chosen for the number and diameter of the Jets as input for the hinged failure case. Specifically, the hinged failure case was modeled as 236 coherent jets with a diameter of .068 m, and the model was chosen to represent the upper metallic layer spilling from the " unzipped" lower crucible. The concem was not necessarily that the values were inappropriate but that sufficient information on how Westinghouse had arrivtsd at these peculiar input parameters had not been pro-vided. it is the staffs contontion thst a process of trial and error must have taken place to arrive at these two values that would result in TEXAS calculating a signifi-cant explosion. The staff believes this process should be documented and that this issue is an open item.

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