ML20149J080
| ML20149J080 | |
| Person / Time | |
|---|---|
| Issue date: | 08/26/1996 |
| From: | Blaha J NRC OFFICE OF THE EXECUTIVE DIRECTOR FOR OPERATIONS (EDO) |
| To: | Boyle R, Coplan S, Lubenau J NRC COMMISSION (OCM) |
| Shared Package | |
| ML20149J042 | List: |
| References | |
| FOIA-97-68 NUDOCS 9707280033 | |
| Download: ML20149J080 (3) | |
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B UNITED STATES E
NUCLEAR REGULATORY COMMISSION wAsamoton, o.c. aoss> moi
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August 26, 1996 NOTE TO COMMISSIONER ASSISTANTS OCM/SJ OCM/KR OCM/GD Marylee Slosson Myron Karman
_ Brad Jones Annette Vietti-Cook Mort Fleishman
_ Terence Chan Mitzi Young Jack Sorensen
_ Anthony Markley James Johnson L Seth Coplan L Joel Lubenau Brian Holian g Lynn Deering g Keith McDaniel
_L Regis Boyle Lil Vancise
_ Donna Smith Bob Mc0sker Ann Haikalis Jackie Silber
_ Joanne Field Janice Dunn Lee
_ Joel Lubenau Chris Miller g Scott Moore Gerry Schuetze Evelyn Williams Judy Ledbetter Pat Celenza Leslie Hill Y
nl FROM:
James L. Blaha Assistant for Operations, OEDO t
SUBJECT:
STAFF RESPONSES TO CHAIRMAN'S QUESTIONS CONCERNING ENVIROCA The Chairman's office verbally communicated five questions concerning the Envirocare facility to staff. Attached are the responses to those questions.
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Attachment:
As stated
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J. Taylor, EDO (w/o attachment) cc:
J. Milhoan, DEDR (w/o attachment)
H. Thompson, DEDS (w/o attachment)
J. Blaha, A0/0ED0 (w/ attachment) i K. Stablein, OED0 (w/o attachment)
L. Person, NHSS (w/o attachment)
SECY (w/ attachment)
OGC (w/ attachment)
OCA (w/o attachment)
OPA (w/o attachment) 9707280033 970721
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lESPONSE TO OCM/SJ QUESTIONS ON '
STAFF'S MAY 13,1996 MEMORANDUM TO THE COMMISSION i
REGARDING CRITICALITY SAFE CONCENTRATION LIMITS FOR DIFFUSE WASTE OUESTION 1:
Should the staff initiate actions with the State of Utah concerning an exemption for Envirocare to possess amounts of special nuclear material (SNM) in soil greater than the mass limits in 10 CFR l
Part 150 prior to completing its analysis of SNM~ reconcentration after disposal?
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BACKGROUND:
1 Issue was raised as a result of the Commission's review of a memorandum to the Commission dated May 13,1996, " Exemption for Envirocare of Utah to Possess U-235 in Excess of Current Regulatory Limits." In a February 7,1996, memorandum to the EDO, Chairman Jackson directed, 3
"...the staff should complete its analyses of determining a safe concentration limit for diffuse waste i
before granting the exemption to Envirocare." As indicated in the May 13 memorandum, the
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proposed order to Envirocare would be based on a " criticality safe" level for special nuclear material i
(SNM) in diffuse waste while the waste is in the licensee's possession above ground. The.
memorandum states that staff is examining separately the issue of reconcentration of below ground wt.ste. Resolution of the reconcentration issue will not impact the order to Envirocare and q
resolution of the possession limit issue for SNM in diffuse waste, as desenbed in staff's November 13,1995 memorandum to the Commission.
Jj' DISCUSSION:
1 Limits in 10 CFR 150 apply to above ground possession, not to waste af ter disposal.
Limit proposed by the staff in the May 13,1996. memo would have the same application.
s NRC re0ulations do not limit SNM concentrations while in a licensee's possession (separate limits are applied to transuranic concentrations in waste for radiation protection purposes j,
under NRC's land disposal regulations in 10 CFR 61,55).
4' Limit of 770 pCilg for 235U imposed by Utah license condition.
Limit proposed by staff (400 pCilg 235U) is less than Utah limit.
Reconcentration processes are long term in nature (tens of thousands of years) and are not expected to occur while the containers are temporarily above ground.
Concentration limit for above ground possession is t.nrelated to a limit that would be developed for disposal.
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Disposallimit must address conditions and processes that do not occur during possession of the waste above ground.
As a practical matter, actual disposals of diffuse waste at Envirocare do not pose a criticality concern during possession or after disposal because of very low average enrichment of 235U in the waste.
Under contract with NRC, Oak Ridge National Laboratory completed criticality calculations under possession and disposal conditions for Envirocare last Fall and is currently completing a consequence analysis of potential cr.~ticality af ter disposal. The consequence analysis should be completed by October 1996.
i CONCLUSION:
Potential reconcentration of SNM in diffuse waste after disposal will not impact the order to Envirocare.
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l QUESTION 2 Why does the mass concentration decrease by a factor of 20 when the enrichment increases by a factor of 107 i
5 ANSWER:
The Bolzmann neutron transport equation, used to determine the criticality safe concentrations for SNM in diffuse waste, is not a linear function. The complexity of the equation defies a simple explanation of its derivation or its terms. A very simplistic explanation is that as enrichment increases (i.e., the ratio of 235U/g U increases) there is less 238U in the mixture. 238U not only absorbs neutrons, but it also acts to physically separate the 235U atoms. Therefore, as the amount of 238U decreases, more soilis needed per gram of U.
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