Two of the companies involved in the transport of a nuclear compound that was mishandled at the port of Halifax, forcing the closure of a terminal, had been implicated in previous shipping mishaps.
The Fairview terminal, one of two containers processing points of the Halifax harbour, shut down for an investigation Friday after dock workers dropped four canisters containing uranium hexafluoride while unloading them from a ship Thursday evening.
Used to produced nuclear fuel, uranium hexafluoride (UF6) only emits low levels of radiation but it reacts violently to water, creating a highly corrosive gas.
The material was packed in barrel-like canisters called 30B cylinders.
The cylinders fell about six metres to the ground, Calvin Whidden, a vice-president at Cerescorp, the operator of the terminal, said in an interview. They were not breached.
The cylinders are supposed to survive a drop of nine metres, according to safety standards of the Canadian Nuclear Safety Commission.
In a statement, the CNSC said that its inspectors were heading to Halifax and that there was no radiation risks for workers or the public.
The 30B cylinders came from a British enrichment facility and had been transported on the freighter Atlantic Companion, a vessel of the New Jersey-based shipping firm Atlantic Container Line.
They were to be trucked away to South Carolina by RSB Logistic, a Saskatchewan transporter.
Both firms had close calls recently.
Last August, an RSB Logistic trailer rig was carrying UF6 from Ontario to Kentucky when the truck overheated and a blaze started. The truckers managed to disconnect the trailer before it caught fire.
In May, another Atlantic Container Line freighter, the Atlantic Cartier, caught fire while docked in Hamburg. It was carrying nine tonnes of UF6. There was no leak but it took 200 firefighters to extinguish the flames.
Neither company would comment when contacted Friday.
The incidents should make the Canadian Nuclear Safety Commission think twice about its plans to allow the use of similar containers to transport highly enriched liquid uranium from the reactor in Chalk River, Ont., to the United States, said John Bennett, executive director of Sierra Club Canada.
"This should give us pause," Mr. Bennett said in an interview. "So far we have been lucky that there have been no major breaches with those containers."
The UF6 in the Halifax incident came from the UK company Urenco Ltd. and was being transported to the Columbia, S.C., facility of Westinghouse Electric Co., both firms confirmed.
"Initial investigations have confirmed there has not been any breach to the cylinders. The (CNSC) have been notified and we are working closely with them," Urenco said in a statement Friday.
Urenco frequently transports UF6 from Liverpool to Halifax on Atlantic Container Line vessels, according to records filed with the U.S. Nuclear Regulatory Commission.
The documents say that the UF6 is transported in 30B cylinders that are loaded on flat racks and secured by bolts.
"The cylinders are designed to withstand significant impact," Urenco said in its communiqué.
Mr. Whidden said the cylinders were held in flat racks, the term for containers without walls or roof.
Stevedores were using a lifting device called a spreader to pull the flat racks out of the ship.
"We were discharging a 20-foot flat rack and it separated from our spreader," Mr. Whidden said.
"It won't take very long to determine what failed," he said. "The evidence is still there. The smashed-up container is there, the spreader is still there... We'll keep that crane out of service until we determine whether it was the crane or not."
Dropping a container happens less than once a year at the terminal, which handles about 200,000 containers annually, he said.
In Canada, regulations require that nuclear transport containers such as 30B cylinders be able withstand the cumulative effects of a nine-metre drop, a 30-minute exposure to 800 Celsius temperature and an hour-long immersion under 15 metres of water.
During transport, 30B cylinders are supposed to be placed in a protective outer packaging, according to a training manual of the International Atomic Energy Agency.
Furthermore, a small breach while the cylinder is immersed wouldn't necessarily flood its interior, the document said. The chemical reaction creates intermediate chemicals that are highly viscuous and could "act as an effective sealing compound."