CNSC requests action by licensees with tailings facilities

19 August 2014

The Canadian nuclear regulator has requested action from licensees of uranium mines and mils with tailings facilities in response to a recent tailings dam breach at a copper/gold mine in British Columbia.

The tailings pond dam at the Mount Polley open pit mine breached on 4 August, and released an estimated 10 million cubic metres of water and 4.5 million cubic metres of fine sand into Polley Lake. The event was described as 'extremely rare' by the Ministry of Energy and Mines (MEM), which does not recall an incident of this magnitude in at least the last 40 years.

In response, the Canadian Nuclear Safety Commission (CNSC) has asked licensees with tailings facilities to review the causes of the tailings dam breach at Mount Polley mine and confirm that the safety case for the tailings dam at their facility remains valid.

They have also been asked to "confirm and demonstrate" that all necessary operations, inspections and monitoring have been conducted in compliance with their licence and licence conditions handbook.

Licensees must also confirm that the measures are in place to mitigate breach accidents and report on any gaps and the associated plans to address them.

"This is a reminder that vigilance must be maintained by ensuring that tailings dams continue to be properly designed, constructed, operated, maintained and monitored to prevent such occurrence," CNSC said in a letter to the licensees.

In Canada, tailings are currently deposited in tailings management facilities at Cameco Corporation's Key Lake and Rabbit Lake operations, as well as AREVA's McClean Lake operation. There are also two inactive above-ground TMFs located at the Rabbit Lake and Key Lake Operations, as well as 20 facilities located at closed or decommissioned mines in Canada.

Seven licensees are affected: AREVA, Cameco Corporation, Rio Algom Limited, Willet Green Miller Ctr, P.J. Brugger and Associates, EWL Management Ltd. and Denison Mines Inc. They have until 15 September 2014 to respond to CNSC's request for action.

During its next inspection, the regulator also plans to conduct walk down inspections of above-ground tailings management facilities to independently verify that the safety control measures for tailings dams are in place and remain adequate.

Photo: Tailings management facility at AREVA's McClean Lake, northern Saskatchewan (Source: CNSC)

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