Seeing Clearly Through the Cloud – Assessing a Leak at Honeywell

Joey Ledford
Public Affairs Officer
Region II


The sound of alarms during the evening of Oct. 26 at the Honeywell Metropolis Works alerted workers and those living closest to the Metropolis, Ill., site that something out of the ordinary had occurred.

Honeywell MetropolisThe plant, a fixture in the southern Illinois river town since 1958, is the nation’s only uranium conversion plant. It converts raw uranium, or yellowcake, into uranium hexafluoride, or UF6, which is enriched at other facilities into fuel for commercial nuclear power plants.

That Sunday evening, Honeywell experienced a leak of UF6. The leak occurred in a cold trap inside the Feed Materials Building. (A cold trap is a large tank where raw UF6 accumulates so it can be cooled and solidified and later heated and drained during normal plant operations.) The leak occurred while the cold trap was heated and was being drained.

An operator put on a respirator and confirmed the leak at 7:24 p.m. local time. Plant emergency responders were dispatched to shut down operations and account for all personnel. Honeywell declared a “plant emergency,” but did not declare an “Alert,” the lowest NRC emergency classification for fuel facilities. Honeywell advised the NRC the cold trap was isolated, vacuum devices were being used to collect leakage, and the material in the device was cooling by 8:15 p.m.

 No one was injured and Honeywell declared “all clear” status at 2:16 a.m. Monday.

People outside the plant reported that a cloud was visible, coming from the building even before mitigation spray towers were activated. Those towers generate gigantic streams of water and water vapor into the air inside and outside the plant, and contributed to clouds that were seen after they were activated.

The NRC quickly dispatched a senior fuel facilities inspector to Honeywell to independently assess what had occurred and how Honeywell had responded. Another inspector later travelled to the facility to gather more information.

After reviewing records, interviewing Honeywell employees and examining the affected areas, the NRC has reached a number of preliminary conclusions:

  • 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).
  • The uranyl fluoride was contained within the Feed Building and settled within a few feet of the cold trap leak.
  • The chemical conversion process also produced hydrogen fluoride gas, some of which was visible emanating from the building.
  • The mitigating sprays outside the building were aimed at the windows in an effort to keep the hydrogen fluoride from getting offsite.
  • Honeywell implemented their emergency plan, assessing the event and taking the actions spelled out in the plan, including stopping the leak.
  • A potential violation was identified related to the emergency classification of the event and remains under agency review.
  • The hydrogen fluoride gas that left the building had no health effects for workers or nearby residents.

Honeywell plant management has agreed to the terms of a Confirmatory Action Letter issued by the NRC to not restart the facility until the NRC is satisfied that the company has appropriately addressed the emergency classification issues raised during and after the event. Honeywell has also agreed to a number of corrective actions, including revised training and emergency procedures. The NRC is monitoring an emergency exercise at Honeywell to ensure that corrective measures are in place.

The NRC will remain vigilant and will closely inspect the corrective actions made by Honeywell this week under the CAL. As well, the NRC will consider potential enforcement actions stemming from the event.

Update: You can read the latest Preliminary Notification here.

Author: Moderator

Public Affairs Officer for the U.S. Nuclear Regulatory Commission

7 thoughts on “Seeing Clearly Through the Cloud – Assessing a Leak at Honeywell”

  1. I would like to see some serious financial and criminal charges placed for the improper reporting, aka attempted coverup

  2. No real time monitoring? Shame on all involved. Real time monitoring must be implemented, if the NRC is interested in protecting the public instead of the nuclear industry’s bottom line.

  3. Safety and security are always the NRC’s top priorities. We dispatched an inspector to the site based on the technical details of the leak, and before the first videos were available. The NRC inspector’s only job was to ensure that Honeywell met all regulatory safety and security requirements.

    The “fence line” radiation readings were taken when Honeywell removed target filters from sample locations permanently installed on the fence and scanned them for radiation and none were above any regulatory limit. In addition, the Illinois Emergency Management Agency collected their targets from monitors located outside the fence (one was relatively downwind from the Feed Material Building) and they indicated no elevated radiation readings. In addition, Honeywell conducted radiation surveys on nearby private property with permission from the property owner and did not detect any radiation readings above background.

    With respect to HF, the NRC concluded that the visible cloud on the YouTube video was probably HF from the leak inside the Feed Materials Building. The NRC staff concluded that the details of the event should have led Honeywell to declare an ALERT. Our conclusion was based on detailed interviews of both on-site workers and off-site members of the public, Honeywell’s modeling of the leak and subsequent plume, NRC independent modeling (which was consistent with the Honeywell modeling) and a review of all videos of the event. HF detectors mounted on the fence did not detect any measurable increase in HF but were not located optimally to detect this release. Results of fluorine testing of off-site vegetation samples have not yet been received but modeling of the release indicate that concentrations of HF should fall below regulatory limits. All of these indirect measurements support a leak of approximately six pounds of UF6 resulting in less than two pounds of HF and no off-site consequences which would have required protective actions for nearby residents.

    The spray down system is designed to quickly enable the conversion of HF to Hydrofluoric acid and minimize the release of HF off-site.

    The technical basis for our conclusions will be documented in the 4th quarter Honeywell inspection report which should be available in January 2015.

    Joey Ledford

  4. Moderator, please ensure a exhaustive response to Mr. Morgan’s query, or this blog is irrelevant.

  5. What were the “fence line” radiation and HF readings at each monitoring point during the accident? What were the radiation and HF monitor readings at the building vent emission points? HF vapor is clearly seen in this You Tube video, and. If not HF vapor what is it? Quote from Region 2 NRC – “might have been released as a gas…did not detect HF gas…” This is problematic as the HF plume can be clearly seen in the video The hazardous gas release continued on for several minutes prior to water dampers being activated. Do the water dampers create a problem as to the formation of Hydrofluoric Acid? There is the appearance that some of the workers videoing the event have a different story than Honeywell and the NRC. According to news reports residents are saying,”… our safety is not being taken into consideration.”

    Emission vent and perimeter monitor readings at the time of the accident, prior to the accident and 1 day post accident should be made public..

  6. 1. No workers were injured and they were the only individuals potentially endangered by this release. We have carefully reviewed the licensee’s records and calculations on the amount of material released and found them reasonable. Six pounds of UF6 would yield less than 2 pounds of HF. Our plume modeling shows extremely low concentrations of HF beyond the fences, all above 50 feet in height and dissipating well below regulatory limits at ground level. An alert does not prompt protective actions such as sheltering downwind, etc., therefore there was no need for additional downwind sampling or monitoring.

    2. That statement on release of radioactive material is primarily based on the visual indication surrounding the leak site and the chemical properties of UF6. There was a well-defined concentration of UO2F2 deposited within a few feet of the leak site. This material is very heavy and will not migrate very far. As we noted, the leaking UF6 vaporized and solidified and fell to the floor near the leak inside the facility. Note that Honeywell is not a zero release facility. All 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.

    Joey Ledford

  7. CDC says – “Hydrogen fluoride is a highly dangerous gas, forming corrosive and penetrating hydrofluoric acid upon contact with tissue, water and air. The gas can also cause blindness by rapid destruction of the corneas. Swallowing only a small amount of highly concentrated hydrogen fluoride will affect major internal organs and may be fatal. Often, patients exposed to low concentrations of hydrogen fluoride on the skin do not show effects or experience pain immediately. Exposure to hydrogen fluoride can result in severe electrolyte problems. People who survive after being severely injured by breathing in hydrogen fluoride may suffer lingering chronic lung disease.” CDC info on this deadly gas –

    Regarding this statement in the blog article: “The hydrogen fluoride gas that left the building had no health effects for workers or nearby residents. NRC also confirmed there was no indication that detectable radioactive material was released into the environment.”
    Questions – 1. How can the NRC declare there were “no health effects for workers or nearby residents” this soon? Did the NRC or county health officials survey all workers and residents within a 25 mile area of the contamination plume? What was the exact plume path of the Hydrogen Fluoride poison gas? Are public health officials or Honeywell doing surveys and follow-up to determine no cornea damage, respiratory, skin, or other health effects? Where may the official report be found as to no ill health effects and the methodology of patient/victim screening and testing?

    2. How did they monitor to determine “there was no indication that detectable radioactive material was released into the environment”? Where are the monitors located? What kind of monitors are used and when were they last calibrated? What level of radioactivity were the set to record as “detectable”? Were they monitoring for the possible emissions from this particular accident and their radioactive prodigy? Was Honeywell monitoring in real time or is TLD monitoring accomplished? Are the monitoring results available to the public at this time, if so, where may they be found?

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