ML20210Q959
| ML20210Q959 | |
| Person / Time | |
|---|---|
| Issue date: | 08/13/1997 |
| From: | Paperiello C NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS) |
| To: | Terri Mclaughlin LOS ALAMOS NATIONAL LABORATORY |
| References | |
| NUDOCS 9709020226 | |
| Download: ML20210Q959 (3) | |
Text
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NUCLEAR REGULATORY COMMISSION WASHINGTON D.C. 9066Mnet o
%,,,,,# August 13, 1997 i
Dr. Thomas P. McLaughlin Group Leader. Nuclear Criticality Safety Chairman, ANSl/ANS 8 Committee Los Alamos National Laboratory los Alamos. NM 87545
Dear Dr._McLaughlin:
The Nuclear Regulatory Commission desires either the extension of a current or development of a new ANSI /ANS standard concerning the possession, use.
storage, and processing of enriched uranium between 5 and 20 wt.% U 235 at fuels and materials facilities. The standard should address the necessary elements of a nuclear criticality safety arogram which would provide an adequate safety basis and rationale for t1e safe use and handling of this material. Even though the NRC will partici) ate in the standard's working group. it is expected that industry will tace the lead in this matter by
- providing the technical basis necessary to support standard development.
The NRC believes that there may be difficulties in analyzing systems utilizing between 5 and 20 wt % U 235. These difficulties were not encountered when the systems were previously analyzed for enriched material at 5 wt.% U-235.
ANSI /ANS 8.1 section 4.3.2 refers to extending the range of applicability of data: and section 4.3.3 refers to determining the subtritical margin taking into account the uncertainties in the bias and in the extension of the range of applicability. Thus criticality safety margins should be based on critical experiments in the range of applicability for the process being evaluated including calculational biases and uncertainties.
Based on our review of the issue to date the NRC staff has identified the following difficulties in determining the safety basis at the enrichment range l0 of 5 to 20 wt.% U 235: (1) lack of needed criticality experiments. (2) inability to economically operate a fuels and materials facility based on data extrapolated from high enrichments (e.g. 93 wt.% U-235), and (3) lack of .
u general agreement on the methods using data extrapolated from less than 5 wt.% 49,3 U 235. These difficulties are especitlly significant when recognizing the pualitativevariationsbetweensystemslessthan5wt.%U-235andgreaterthan a wt.% U-235 which affect criticality safety (e.g. at greater than 6 wt.%
U-235, a system does not need moderation to become critical).
- Possible resolutions include
- (1) performing needed criticality experiments.
i (2) developing acceptable extrapolation schemes, and (3) exteriding enrichment-
! dependent criticality safety margin curves or tables to the 5 and 20 wt %
U-235 range. 0;,y a g I. II. I! ,Il ,l l,. .
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l Dr. Thomas McLaughlin The commercial nuclear industry has expressed interest in the use of uranium fuel with enrichments greater than 5 wt.% U 235. In anticipation of any su.h requests, the NRC believes an ANSI /ANS standard addressing the use of uranium enriched between 5 and 20 wt.% U 235 at fuels and materials facilities would be desirable and contribute to ensuring the safety of these o)erations. Since ANSl/ANS 8.1 was recently revised and the next revision will se in several years, the NRC requests the committee's determination on the feasibility and practicality of developing interim guidance on the use of between 5 and 20 wt.% U 235 at fuels and materials facilities. We appreciate your assistance.
If you have any questions, please contact me at (301) 415 7800 or Mrs. Elizabeth Ten Eyck. Director. Division of fuel Cycle Safety and l Safeguards, at (301) 415 7212. 1 Sincerely.
Original signed by W.F. Kane for i
Carl J. Pa)eriello. Director Office of luclear Material Safety and Safeguards Qistribution NRC File Center PUBLIC FCSS R/F FCLB R/F NMSS R/F NMSS Dir Off r/f
[GAgrt5std9. doc)
- See previous concurrence cpienooret>Avoust 7.1987 OFC FCLB' FCLB' FCLB' FCLB*
NAME HFelsher PShea KHardin MWeber DATE 7/23/97 7/23/97 7/23/97 7/23/97 summuseumsmuuuuuuuuuuumuma useum a musansmusummuumuu musus a museuumummumuseum muss u .
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OFC FRIB* FCSS* FCSS* NMSSn j NAME TSherr EBrach ETen Eyck CkaNelb DATE 8/6/97 8/7/97 8/7/97 8/8 /97 C = COVER E = COVER & ENCLC'SURE N = NO COPY OFFICIAL RECORD COPY
. i Dr. Thomas McLaughlin 2-The commercial nuclear industry has expressed interest in the use of uranium fuel with enrichments greater than 5 wt.% U 235. In anticipation of any such requests the NRC believes an ANSl/ANS standard addressing the use of uranium enriched between 5 and 20 wt.% U 235 at fuels and materials facilities would .
be desirable and contribute to ensuring the safety of these operations. Since !
ANSI /ANS 8.1 was recently revised and the next revision will be in several years, the NRC requests the committee's determination on the feasibility and practicality of developing interim guidance on the use of between 5 and 20 wt.% U 235 at fuels and materials facilities. We appreciate your assistance, if you have any questions, please contact me at (301) 415 7800 or Mrs. Elizabeth Ten Eyck. Director. Division of Fuel Cycle Safety and Safeguards, at (301) 415 7212.
Sincerely.
Carl J. Pa)eriello Director Office of luclear Material Safety and Safeguards ,
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