Fire Risks for Fuel Cycle Facilities
For fuel cycle facilities, two principal risks to health and safety are nuclear criticality events and the release/dispersal of hazardous chemicals and radioactive material as a result of a fire or explosion.
Fire-induced nuclear criticality events may include failures of "geometric control," which involves the set of measures used to maintain nuclear materials in a subcritical condition during storage, transportation, and disposal, to prevent the occurrence of a self-sustaining nuclear chain reaction. Such criticality events may result from (1) collapse of structures that are designed to maintain spacing, (2) addition of a moderator through automatic or manual fire suppression activities, or (3) movement of containers during manual fire-fighting efforts.
By contrast, hazardous releases and dispersal events are most likely to result from fire-induced breaches of airborne particle filtration systems or other systems/components that contain hazardous chemicals or radioactive material. They may also result from fire-induced expansion of uranium hexafluoride (UF6) in the 14-ton cylinders used for storage and transportation. (This may occur as the heat of a fire transforms the UF6 from a solid to a gas.)
These risks have been demonstrated in significant fires that have occurred thus far in nuclear fuel cycle facilities. One particularly notable example, in April 1996, involved a fire in the incinerator ductwork on the roof of the Nuclear Fuel Services facility in Erwin, Tennessee. Another, in December 1998, involved a fire in the enrichment cascade cells at the Portsmouth Gaseous Diffusion (uranium enrichment) plant in Portsmouth, Ohio. Neither of these fires involved a significant dose to either facility workers or the public. Nonetheless, to minimize the occurrence of fires, and mitigate the consequences of those that do occur, the U.S. Nuclear Regulatory Commission (NRC) administers a fire protection program for fuel cycle facilities.