United States Nuclear Regulatory Commission - Protecting People and the Environment

Scenarios and Analytical Methods for UF6 Releases at NRC-Licensed Fuel Cycle Facilities NUREG/CR-3139)

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Publication Information

Manuscript Completed: January 1983
Date of Issue: June 1984

Prepared by:
M. Siman-Tov
J. Dykstra
D. D. Holt
W. P. Huxtable
R. A. Just
W.R. Williams

Oak Ridge National Laboratory
Oak Ridge, Tennessee 37831
Under Interagency Agreement
DOE 40-550-75

S. Bernstein, NRC Project Manager

NRC FIN B0495

Prepared for:
U.S. Nuclear Regulatory Commission
Office of Nuclear Regulatory Research
Division of Risk Analysis
Transportation and Materials Risk Branch
Washington, DC 20555

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Abstract

This report identifies and discusses potential scenarios for the accidental release of UF 6 at NRC-licensed. UF6 production and fuel fabrication facilities based on a literature review, site visits, and DOE enrichment plant experience. Analytical tools needed for evaluating source terms for such releases are discussed, and the applicability of existing methods is reviewed. Accident scenarios are discussed under the broad headings of cylinder failures, UF6 process system failures, nuclear criticality events, and operator errors and are categorized by location, release source, phase

of UF 6 Prior to release, release flow characteristics, release causes,.initiating events, and UF6 inventory at risk.* At least three types of releases are identified for further examination: (1) a release from a liquid-filled cylinder: outdoors, (2) a release from a pigtail or cylinder in a steam chest, and (3) an indoor release from either (a) a pigtail or liquid-filled cylinder or (b) other indoor source depending on facility design and operating procedures. Indoor release phenomena may be analyzed to determine input terms for a ventilation model by using a time-dependent homogeneous compartment model or a more complex hydrodynamic model if time-dependent, spatial variations in concentrations, temperature, and pressure are important. Analytical tools for modeling directed jets and explosive releases are discussed as well* as some of the complex phenomena to be considered in analyzing UF6 releases both indoors and outdoors.

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