Lance Moore
WC Monitor
8/07/2015
A senior fuel facility inspector from the Nuclear Regulatory Commission (NRC) is expected this weekend to complete a weeklong assessment of the uranium hexafluoride (UF6) leak that occurred during maintenance activities at the Honeywell Metropolis Works facility in Illinois last Saturday.
The amount of UF6 that leaked from a valve installed during maintenance has not been determined fully. The NRC said the incident caused no injuries and that no material escaped the uranium conversion facility. The leak was cleaned by a water mitigation system — basically powerful water cannons.
“When UF6 is released into the air, the humidity present in the air causes it to break down into UO2F2 and HF (hydrogen fluoride). UO2F2 is heavier than air and falls to the ground. HF is a gas that rises. The most effective way to mitigate an HF cloud is to spray it with water both to knock down the cloud and to dilute the HF,” Honeywell spokesman Peter Dalpe said by email. “HF is water soluble, so you end up with small amounts of fluoride diluted in water. It is not dangerous in this form. Indeed, public water systems regularly add fluoride to water. Any UO2F2 that is present is collected and disposed of.”
Roger Hannah, senior publications officer from NRC Region II, detailed what the inspection would look like: “The inspector will look at the sequence of events leading up to the unplanned release; verify that Honeywell classified the event appropriately and notified other agencies in accordance with their procedures and regulatory requirements; verify that Honeywell actions to stop or mitigate the release were done in accordance with procedures; validate the estimate of material released and that it remained inside the plant boundary; examine the performance of the plant’s detection systems for such a release as well as results of air sampling and other surveys; and review Honeywell’s corrective actions.”
NRC said it expects to release a report documenting the findings within 45 days after the inspection is completed.
The leak was noticed by plant personnel who were monitoring the room in which it occurred via a video surveillance system. The plant uses a number of methods to determine if a leak has breached the site boundary, including video surveillance and sensors that are located within the plant and along the plant’s fence line. The facility previously experienced leaks of UF6 in 2003 and 2014. In both incidents, there were no injuries and Honeywell resumed UF6 production after making improvements to the plant’s emergency response procedures. Pending the inspection and approval to resume operations, the plant is not in production and there is currently no timeline for resuming work.
The site, in cooperation with the NRC, is doing a root-cause analysis of the equipment failure, as well as working on a response to the incident. This will determine what corrective actions will be made.
“The NRC and other regulatory agencies were alerted to the incident promptly and the plant’s emergency equipment and response teams worked as designed to contain and stop the leak without injuries,” Dalpe said. “The company has made numerous improvements to its emergency response procedures over the last several years and continues to invest significantly in upgrades to the plant, including more than $60 million in projects that directly support health, safety and the environment. “
Although no material has been found beyond the boundary of the facility, Hannah emphasized the seriousness of such a leak. “UF6 is hazardous, both from a chemical and radiological perspective. It can be dangerous to workers in the area of a release or to people living close by if there is enough material involved. Honeywell reported to the NRC that there were no exposures to workers at the plant or people living nearby.”
Honeywell Metropolis Works is the sole U.S. plant to conduct conversion of uranium ore into uranium hexafluoride, which is used on production of enriched uranium used to fuel atomic energy facilities.
