ML20197G674

Informs That NRC Cannot Endorse Usecs Use of Scale 4.3 Codes & Cross Sections at Present Time.Nrc Suggests That Technical Meeting Be Scheduled to Discuss Stated Issues in Detail

ML20197G674
Person / Time
Site:	07003089
Issue date:	12/04/1998
From:	Pierson R NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
To:	Woolley R UNITED STATES ENRICHMENT CORP. (USEC)
References
TAC-L32076, NUDOCS 9812100062
Download: ML20197G674 (2)

Text

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/d g/"% '4 UNITED STATES g j NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 30666 0001 t

. m , *# December 4, 1998 Mr. Robert Woolley Manager, AVLIS Nuclear Regulatory Policy  !

and Licensing  ;

U.S. Enrichment Corporation '

Two Democracy Center 6903 Rockledge Drive Bethesda, MD 20817

SUBJECT:

AVLIS CRITICALITY CODE VAllDATION REPORT (TAC NO. L32076)

Dear Mr. Woolley:

i in a letter dated October 22,1998, "AVLIS Criticality Code Validation," L-98-011, the United States Enrichment Corporation (USEC) provided further discussion of the applicability of the Atomic Vapor Laser Isotope Separation (AVLIS) Criticality Code Validation Report submitted to the U. S. Nuclear Regulatory Commission (NRC) on April 22,1998, and the general rules of  :

practice for AVLIS criticality safety analyses that will be incorporated into the nuclear criticality l safety chapter of the AVLIS license application. USEC concluded that the selected  ;

benchmarks adequately cover AVLIS materials, configurations of interest, and ranges of

• applicability, including the intermediate fission energy spectrum. Based upon these  ;

conclusions, USEC requested endorsement of the SCALE 4.3 codes and cross sections as  :

applied to AVLIS materials and systems.

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t On November 4,1998, NRC technical staff toured the AVLIS Demonstration Pilot located at the Lawrence Livermore National Laboratory. This tour served to greatly facilitate the understanding of AVLIS-specific issues; however, NRC cannot endorse USEC's use of the SCALE 4.3 codes and cross sections at this time, Although NRC finds merit with USEC's philosophy and approach to criticality safety, NRC has concluded that further information from USEC is necessary to determine the acceptability of the report for the proposed area of applicability. NRC recognizes that it is not necessary or currently possible for a benchmark set i to cover every parameter over the full range of possibilities. However, it is NRC's expectation j that USEC evaluate sufficient experimental evidence to support statistically significant trends for ,

the areas of requested operation or limit the validation range to those areas where sufficient data exists. NRC has identified the following general areas that require further USEC review ,

and discussion:  !

-(1) Analysis and review of process conditions occurring in the intermediate energy range and the adequacy of current experimental evidence to support these cases; (2) Application of appropriate bias and margins of safety for the extension of enrichment i values in the range of 5 - 10 weight percent; (3) Review of multiple parameter interdependence and perturbation for those parameters specific to the AVLIS process; and ,

6O (4) Adequacy of available cross-sections for high temperature metals and systems that are part of the AVLIS process or supporting rationale that such conditions are not possible.

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R. L. Woolley, USEC 2 g4 g i

a in regard to item 4 above, the October 22nd letter concluded that high temperature systems were not of concern to the AVLIS validation since moderation was required for criticality and the introduction of such material would reduce operating temperatures to values where the SCALE 4.3 cross sectich sets are adequately validated. NRC finds that such a conclusion is not reasonable for all possible scenarios since final system temperatures would depend upon mass rate inflow and reaction rate dynamics. Thus, NRC believes that further review of high temperature cross section set validation is warranted.

NRC suggests that a technical meeting be scheduled to discuss these issues in detail. Should you have any questions or wish to schedule such a meeting, please contact Jack Davis of my staff i at (301) 415-7256.

Sincerely, 05.alsignedey Robert C. Pierson, Chief Special Projects Branch l

Division of Fuel Cycle Safety and Safeguards, NMSS Docket No. 70-3089 cc: Mr. Ronald P. Koopman, LLNL

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DISTRIBUTION Docket 70-3089 JPCJlc..ComeerdFCSS 3 r/f PUBLIC APersinko, FSPB FSPB r/f PTing, FCOB NMSS r/f CEmeigh, FCLB c:\ Davis'amaster\avlis\ val.rpt OFC SPB C SPB 6 SPB C SPB n NAME hN) JDavis JMuszkie b 3hh RPi< Eson DATE 12/ l B8 12/3 Bd 12/ hS8 12/ 4 B8 Cm Cover E= Cover & Enclosure I N= No Copy OFFICIAL RECORD COPY