ML20058F884

Forwards Response to NRC 931029 Questions 2 & 3 Re Technical Basis for Position on Use of lighter-than-air Noncondensible Gas in Std BWR Test Program & Date for Submittal of Technical Basis for Position Re Severe Accident

ML20058F884
Person / Time
Site:	05200004
Issue date:	11/30/1993
From:	Leatherman J GENERAL ELECTRIC CO.
To:	Joshua Wilson NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation
References
MFN-214-93, NUDOCS 9312090035
Download: ML20058F884 (3)

Text

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GENuclear Energy nne,a wcawwy feb l

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November 30,1993 MFh No.214-93 '

Docket STN 52-004 Document Control Desk U.S. Nuclear Regulatory Commission Washington DC 20555 Attention: Jerry N. Wilson, Director Standardization Project Directorate

Subject:

Transmittal of Responses to NRC Ouestions

Reference:

NR.C Letter to GE Nuclear Energy," Summary of Meeting on Octcher 25 and 26,1993... Japan," dated November 18.1993. ,

i During our October 29,1993 telecon, responding to staff concerns, Questions 2 and 3 were deferred until now for response. Attachment I to this letter consists of responses to these questions. ,

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Sincerely ..

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/W < (MITRv J. E. leatherman SRWR Certification Manager MC-781, (408)925-2023 1

I cc: M. Malloy, Project Manager (NRC) (2 attachments)

F. W. IIasselberg, Project Manager (NRC) (1 attachment) l Of.50072 i

h j urmaage a

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Attachment 1 to MFN No.214-93 Question 2:

Please provide the staff with a date for the submittal of GE's technictd basis for its i position regarding the use oflighter-than-air non-condensable gas in SBWR test  ;

program. j Response to Question 2: l The GIRAFFE test >rogram was specifically designed to address long-term containment coolin following a Design Basis Accident (DBA). The only source of-  ;

hydrogen during a A is from radiolysis. The amount of hydrogen potentially i liberated by radiolysis de, ends on the time period considered. The design basis for the performance of the S BWR passive containment cooling system is 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. A j conservative calculation of the amount of hydrogen liberated by radiolysis over 77 *

. hours gives about 51 standard cubic meters (SCM) or 4.6 kg. The liberated  !

hydrogen mass is produced from the same source, and in proportion to, the decay r heat steam. It is to be expected that the steam and hydrogen will be well mixed as  !

. they leave the RPV and nse to enter the Passive Containment Condensers (PCCs). l About 1400 metric tons of steam are produced by decay heat over a 72-hour time  ;

period. This means that the radiolytic hydrogen is about 0.0003% by mass of the i decay heat steam with which it is mixed. GE concludes that this amount of i hydrogen would have a negligible effect on the PCC heat transfer perfoimance. 1 The 4.6 kg of hydrogen may also be compared with the roughly 10,000 kg of l containment nitrogen inventory. In summary, radiolytic hydrogen was judged not  !

to be necessary for accurate simulation of a DBA because: (1) its rate of production is negligible in comparison to decay heat steam production, and (2) the l total production of hydrogen is a small fraction of the amount of nitrogen in the i inerted containment atmosphere.  !

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h Attachment I to MFN No.214-93 Question 3:

Please provide the staff with a date for the submitti of GE's technical baais for its  !

70sition that severe accident considerations (such as high concentrations of .I lydrogen) need not to be included in any of the SBWR design certification test '

programs.

Response to Question 3:

The GENE position regarding testing with large concentrations of a light gas, simulating hydrogen, is that the effect can be adequately evaluated by analysis.

The quesn,on is to evaluate the consequence of the hydrogen release associated  ;

with a 100% fuel-clad / water reaction. This results in the production of about 1000  !

kg of hydrogen. The potential effects of the hydrogen are to increase the inventory of non-condensable gas in the Wetwell (WW) and to cause a period of degraded operation of the Passive Containment Cooling Systems (PCCS). A boundmg calculation of the first effect can be made by simply assuming that all of the hydrogen is in the WW along with the total mventory of nitrogen (about 10,000 kg).

The potential effect of the hydrogen on PCCS heat removal can also be evaluated.

The earliest time at which the PCCS is required to assume the decay heat load is somewhere between 2000 seconds and one hour from the instant of LOCA. This corresponds to the time at which the flow of subcooled Gravity Driven Cooling System (GDCS) water to the Reactor Pressure Vessel (RPV) ceases to be the dominant heat sink. Assume that at 2000 seconds the entire inventory of hydroge-n i is stratified at the top of the Drywell(DW) and must be urged to the WW before l

any decay energy can be removed from the DW via the 1 CCS. Under these conditions, the DW pressure will quickly rise to open the top Loss of Coolant Accident (LOCA) vent. It can be shown that the corresponding DW to WW pressure difference will cause the stratified hydrogen to be purged to the WW in ,

about 400 seconds. The decay energy transferreg to the suppression pool over this j time period will raise its temperature by about 3 K. j The 100% metal / water reaction case is in the severe accident category. This l means that the appropriate basis for evaluating the consequences of the accident for containment mtegrity is the Service Level C pressure. It can be shown that the combination of all the hydrogen m the WW (in addition to the nitrogen), and -

i com,lete degradation of the PCCS heat removal during hydrogen purging, will not i resu t in a containment pressure in ucess of Service 12 vel C.

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