The US Nuclear Regulatory Commission (NRC) has launched a special inspection at Honeywell Metropolis Works in Illinois to assess a uranium hexafluoride (UF6) leak that occurred during maintenance activities on 1 August. The Metropolis uranium conversion facility had declared an alert, the lower of the NRC’s two emergency classification levels for fuel facilities, at 5:55pm that day.
The Metropolis plant is owned and operated by Honeywell. It converts uranium oxide powder into gaseous UF6 suitable for enrichment, which is then marketed by Converdyn, a joint venture of Honeywell and General Atomics.
In a statement yesterday, the NRC said Honeywell had reported that a valve installed during maintenance activities had begun to leak. No one at the facility was injured and the company reported that no material was released past the site boundary, the NRC added. The leak – on the sixth floor of the plant’s Feed Materials Building – was reported to have been stopped at 7.48pm.
The facility’s mitigation towers, which are large water sprays, were activated, and according to Honeywell, no UF6 left the plant site. Monitoring devices located at the site boundaries detected no radiological release beyond regulatory limits.
Victor McCree, the NRC’s Region II administrator, said that while no workers were affected and there was no offsite release, any release of UF6 is a potentially serious event.
The plant also suffered a leak on 26 October last year, which plant operators said was contained by prompt action including water sprays. Honeywell said then that the incident followed “an apparent equipment failure in the main production building”. The NRC later said it had occured on the fourth floor of the Feed Materials Building.
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