Investigators determined that the probable cause of the event is a combination of several factors including the lack of agitation of the nitrite-based mixture as well as the delay in cation regeneration commencement following sodium hydroxide addition. They determined that this delay may have allowed sodium hydroxide to settle in the heel of the waste tank instead of being used in the regeneration process. Although there were no adverse safety or health problems and no radiological release, exposure to nitrogen dioxide fumes can be harmful to the respiratory and cardiovascular systems. The short-term exposure limit for nitrogen dioxide recommended by the National Institute for Occupational Safety and Health is 1 ppm, with an immediately dangerous to life or health limit of 50 ppm. EH has reported similar events.
Some examples follow.
Approximately 2.5 ounces of the slurry was released, spraying the contractor and the ceiling. He was preparing waste containers for shipment to an off-site waste disposal facility, and violated procedures by adding water to the container. The water reacted with the Raney nickel releasing hydrogen and pressurizing the container. Raney nickel is a finely-divided alloy of nickel and aluminum, suspended in water. This event is significant because improper handling of hazardous chemicals can cause serious personnel injury.