The four steel cylinders carrying granular uranium hexafluoride fell Thursday at around 10 p.m., setting off a short-lived radiation scare at the Ceres terminal in the city's north end.
Firefighters determined there wasn't a leak of radioactive material when the cylinders encased in concrete, each weighing about 4.5 tonnes, fell from a pallet as they were being lifted off the ship and landed in a contained area of the vessel.
Phil McNulty, the city's executive fire officer, said one of the lift's arms failed and sent the cylinders tumbling onto other containers on the ship. There were no injuries and no one was contaminated at the terminal in Fairview Cove.
The granular substance was contained in the cylinders, McNulty added.
"They go to great lengths to ensure the safety of the product because human beings are dealing with it all the way from start to the end user," he said.
District commander Peter Andrews said an evacuation area at the port extended about 150 metres and would remain in place until after a consultant hired by RSB Logistic, the Canadian company responsible for shipping the product, completed examining the area to confirm no containers were compromised.
Andrews said that work was expected to conclude Saturday morning, at which point normal operations at the port would resume and the cylinders would be placed on a truck and continue to their destination in Columbia, S.C.
URENCO said the cylinders came from its enrichment facility in the United Kingdom. Uranium hexafluoride is the chemical compound used in the gas centrifuge process to enrich uranium.
URENCO's website says it is an international supplier of enrichment services for nuclear fuel used to generate electricity.
William Cook, an associate professor of chemical engineering at the University of New Brunswick, said the compound comes in a solid form that is similar to salt crystals and poses a relatively low risk.
"This material shouldn't be highly radioactive anyway," said Cook. "Not much more so than the actual rocks that would have originally been dug out of the ground to process this."
Because the compound is chemically reactive, he said it could form a corrosive mixture if it were to get wet. Problems would also be posed if the solid were to turn to gas, but he said that would require temperatures well above 55 Celsius.
"Unless there was a very hot condition around, the volatility issue shouldn't be too bad," Cook said.
Firefighters evacuated the immediate area as a safety precaution after the accident Thursday night and the crew of the Atlantic Companion — which arrived in Halifax from Liverpool, England — were taken to a local hotel.
McNulty said there was a similar incident at a Halifax port in the late 1990s involving uranium hexafluoride, but there was no leakage.
George Malek, vice-president of business development and operations for the Halifax Port Authority, said shippers are required to file a dangerous goods manifest with federal authorities and to apply to the port so officials know what is arriving.
"Everybody that handles that dangerous goods container in the supply chain has the documentation on what it is and what the hazards are and how to respond," said Malek.
He said about four per cent of traffic handled each year in Halifax is considered to be hazardous material under federal regulations.
Note to readers: This is a corrected story. An earlier version reported that the Canadian Nuclear Safety Commission said the uranium cylinders came from a URENCO enrichment facility in the United Kingdom.
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