A Nuclear Criticality Safety Assessment of the Loss of Moderation Control in 2 1/2 and 10-ton Cylinders Containing Enriched UF₆

Conference · Fri Aug 16 00:00:00 EDT 1991

OSTI ID:5274606

Newvahner, R. L. ^[1]; Pryor, W. A. ^[2]

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1. Portsmouth Gaseous Diffusion Plant, Piketon, OH (United States)
2. PAI Corp., Oak Ridge, TN (United States)

Moderation control for maintaining nuclear criticality safety in 2-1/2-ton, 10-ton, and 14-ton cylinders containing enriched uranium hexafluoride (UF₆) has been used safely within the nuclear industry for over thirty years, and is dependent on cylinder integrity and containment. This assessment evaluates the loss of moderation control by the breaching of containment and entry of water into the cylinders. The first objective of this study was to estimate the required amounts of water entering these large UF₆ cylinders to react with, and to moderate the uranium compounds sufficiently to cause criticality. Hypothetical accident situations were modeled as a uranyl fluoride (UO₂ F₂) slab above a UF₆ hemicylinder, and a UO₂ sphere centered within a UF₆ hemicylinder. These situations were investigated by computational analyses utilizing the KENO V.a Monte Carlo Computer Code. The results were used to estimate both the masses of water required for criticality, and the limiting masses of water that could be considered safe. The second objective of the assessment was to calculate the time available for emergency control actions before a criticality would occur, i.e., a "safetime,'' for various sources of water and different size openings in a breached cylinder. In the situations considered, except the case for a fire hose, the safetime appears adequate for emergency control actions. The assessment shows that current practices for handling moderation-controlled cylinders of low enriched UF₆, along with the continuation of established personnel training programs, ensure nuclear criticality safety for routine and emergency operations.

• Research Organization: Portsmouth Gaseous Diffusion Plant, Piketon, OH (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA), Nuclear Criticality Safety Program (NCSP)
• DOE Contract Number: AC05-76OR00001
• OSTI ID: 5274606
• Report Number(s): POEF-T--3574; CONF-9110117--6; ON: DE91018896
• Country of Publication: United States
• Language: English

Related Subjects

050900 -- Nuclear Fuels-- Transport
Handling
& Storage
11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS
42 ENGINEERING
420204* -- Engineering-- Shipping Containers
ACCIDENTS
ACTINIDE COMPOUNDS
Assessment Findings
COMPUTER CODES
CONTAINMENT
CRITICALITY
CYLINDERS
Enriched Uranium Hexafluoride
FLUORIDES
FLUORINE COMPOUNDS
HALIDES
HALOGEN COMPOUNDS
Hypothetical Accident Situations
K CODES
KENO V.a Monte Carlo Computer Code
MATERIALS HANDLING
Moderation Control
Nuclear Criticality Safety Program (NCSP)
RELIABILITY
SAFETY
SAFETY ANALYSIS
STORAGE
TRANSPORT
UF-6
URANIUM COMPOUNDS
URANIUM FLUORIDES
URANIUM HEXAFLUORIDE
Water Mass Estimation