Nukewatch Quarterly Winter 2014
In November, the Honeywell corporation’s Metropolis Works (HMW) uranium processing factory in southern Illinois reported a “plant emergency” when it began spewing clouds of poisonous gas that have since been declared harmless by the Nuclear Regulatory Commission.
Uranium hexafluoride (UF6) leaked from inside the site’s Feed Materials Building at 8:24 p.m. on Oct. 26. Uranium hexafluoride is extremely toxic, is corrosive to most metals and reacts violently with water.
The facility processes raw uranium, or yellowcake, into uranium hexafluoride, or UF6, which is enriched at other facilities into uranium fuel for commercial nuclear reactors.
According to the Nuclear Regulatory Commission’s accident report, on Sunday Oct. 26, an employee “put on a respirator and confirmed the leak at 8:24 p.m.” Onsite emergency responders shut down operations, and Honeywell declared a “plant emergency” rather than an official “Alert”—the lowest NRC emergency classification for fuel facilities. The Nov. 13 report by the NRC says that the leak began at 7:24 p.m. Sunday, that, “No one was injured and Honeywell declared ‘all clear’ status at 2:16 a.m. Monday,” Oct. 27.
People outside the factory reported that a cloud was visible coming from the building well before mitigation spray towers were activated, the NRC reported. Indeed, the United Steel Workers posted a video online that shows clouds of gas billowing from the building for six long minutes before fire hoses were used to douse the plume.
Honeywell and the NRC claim that the gas spewing from the Feed Materials Building was not uranium hexafluoride but hydrogen fluoride gas, produced when UF6 reacts with water or water vapor.
(The Honeywell factory is on the Ohio River just downstream from the notoriously contaminated Paducah Gaseous Diffusion Plant in Paducah, Kentucky.)
After interviewing Honeywell employees, reviewing records and examining the affected areas, the NRC concluded:
1) The leaking UF6 vaporized and interacted with moisture inside the Feed Building, which converted it into UO2F2 (a solid form of uranyl fluoride, a yellow powder).
2) The uranyl fluoride was contained within the Feed Building and settled within a few feet of the cold trap leak.
3) The chemical conversion process also produced hydrogen fluoride gas, some of which was visible emanating from the building.
4) A potential violation was identified related to the emergency classification of the event and remains under agency review.
In response to questions raised by community members and the United Steel Workers Union, the NRC said Nov. 14, “[T]he leaking UF6 vaporized and solidified and fell to the floor near the leak inside the [Feed Materials Building]. Note that Honeywell is not a zero release facility. All [radiation] readings taken at the fence line and at the nearest residence were well within Honeywell’s regulatory limits. There are HF and radiation monitors onsite and the readings from them were carefully analyzed by the NRC.”
NRC inspectors concluded that Honeywell failed to recognize that the release of hydrogen fluoride gas warranted an emergency classification of “Alert.” Honeywell eventually agreed to the correction. The NRC also reported that Honeywell “determined that if any hydrogen fluoride travelled beyond their property it would have been of such low concentration as to pose no public safety hazard.” After that the NRC reviewed Honeywell’s calculations on the amount of HF released and its subsequent plume estimate, the agency concluded Honeywell’s assessment “reasonable.”
Since 1958, the Metropolis Works has been the nation’s only uranium conversion factory.
—JL
