ML20035H136

Clarifies Question Raised Re Max Authorized Enrichment Levels

ML20035H136
Person / Time
Site:	Westinghouse
Issue date:	04/27/1993
From:	Adensam E NRC OFFICE OF NUCLEAR MATERIAL SAFETY & SAFEGUARDS (NMSS)
To:	Koga R WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
References
NUDOCS 9305030189
Download: ML20035H136 (2)

Text

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o UNITED STATES 8

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p WASHINGTON, D. C. 20555 i

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i APR 2 71993 1

Docket 70-1151 i

License SNM-1107 Mr. R. H. Koga Columbia Plant Manager Westinghouse Electric Corporation Commercial Nuclear Fuel Division P.O. Drawer R l

Columbia. S.C.

29250

SUBJECT:

CLARIFICATION REGARDING MAXIMUM AUTHORIZED ENRICHMENT LEVELS The purpose of this letter, which is being sent to ABB Combustion Engineering (Hematite, M0); Babcock and Wilcox Fuel Company (Lynchburg, VA); General Electric Company (Wilmington, NC); Siemens Power Corporation (Richland, WA);

and Westinghouse Electric Corporation (Columbia, SC), is to clarify a question raised about maximum enrichment levels. Specifically, the question is whether a licensee can legitimately possess uranium that has a measured U-235 enrichment value (used by the licensee for accounting purposes) that is slightly higher that the maximum authorized level, and, if so, how much higher? To clarify the Nuclear Regulatory Commission's position on this matter, the following example is given.

EXAMPLE:

A licensee that is authorized to possess uranium having a maximum U-235 enrichment (or isotopic distribution) of 5.0 weight percent, receives a shipment of uranium that the shipper assays to be 4.997 weight percent U-235 (relative to the total uranium element content) and the receiver's (i.e.,

the licensee's) measurement is 5.012 weight percent.

Furthermore, in this example, the receiver's measurement uncertainty is plus or minus 0.40 percent relative (or plus or minus 0.020 absolute weight percent enrichment), and the difference between shipper's and receiver's measurements is within statistical agreement at the 95 percent confidence level (C.L.).

In the above example, the licensee could use its 5.012 weight percent enrich-ment value for accounting purposes and not be in violation of its maximum authorized enrichment level. The rationale for such conclusion is that:

(1) based on the licensee's ur.:ertainty, the hypothesis that the true enrichment level is 5.0 weight percent or less can not be rejected at the 0.05 level of significance; i

(2) the licensee's enrichment measurement uncertainty (i.e., limit of error) is no greater than 0.50 percent relative (at the 95 percent i

C.L.); and

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2 (3) the difference between shipper's and receiver's enrichment measurements is within statistical agreement (i.e., within the combined limit of error at the 95 percent C.L.) ---NOTE: if the shipper limit of error is not known, it can be assumed to be the same as that of the receiver's when calculating the combined limit of error.

I In summary, it should be noted that receipt and use of uranium that has a measured enrichment in excess of the maximum authorized level (as stated in the license) is permissible only if conditions (1), (2), and (3), above, are true. Additionally, the licensee should review the criticality safety limits to assure that operations at the license enrichment limit takes into account the maximum uncertainty so that such operations will not result in inadequate i

safety margins.

Should you have any questions regarding this matter, please contact either Charles Emeigh or Donald Joy of my. staff at (301) 540-2396 or (301) 504-2352, respectively.

j Sincerely, Original signed by Elinor G. Adensam, Acting Chief Licensing Branch Division of fuel Cycle Safety and Safeguards, NMSS DISTRIBUTION:

Docket File 70-1151' PDR NRC File Center Region 11 RCJones, NRR JPStohr, RII NMSS r/f JGreeves TWenck FCSS r/f ETenEyck FCLB r/f EKeegan FCLSI r/f CNSmith SH0 CBassett, Ril

[A:\\CLARIFIC]

• See previous concurrence OFC FCLB C

FCLB C

FCLB N

FCLB C

OGC N

Ff28 NAME DJoy*

RMilstein*

RWilson*

CEmeigh*

RFonner*

EMm DATE 3/25/93 3/25/93 3/25/93 3/25/93 4/1/93 4'/47 h3 C = COVER E = COVER & ENCLOSURE N = NO COPY OFFICIAL RECORD COPY