Cameco remediate Cigar Lake delay

11 January 2007

Cameco has begun remediation work to remove water from the Cigar Lake uranium mine following a rockfall and water inflow that eventually flooded the entire complex.

Originally, the Canadian mine which will exploit the second-largest known uranium deposit, would have begun operation in early 2008. Now, according to company statements, Cameco expect the project to suffer a one year delay and "significantly higher" capital costs - to be estimated when remediation measures have been fully developed. Cameco previously costed the project at C$ 660 million ($572 million).

On 23 October a rockfall in the underground production area of the mine led to water ingress. Mine operator Cameco expected that closing bulkhead doors would contain the water inflow and protect mine shaft 1, the future processing area, pumps, a refuge station and a heat exchanger for ore freezing.

Unfortunately one of the doors did not seal properly, allowing water to enter the processing area while worker attempts to fully seal the door were unsuccessful. Furthermore, the rate of water ingress far exceeded the speed water could be pumped out. Finally, Cameco managers decided there was no option but to allow the water to overtake the mine. All staff were evacuated with no injuries and there was no impact on the environment.

The first phase of remediation involves drilling 465 m down to the tunnels immediately downstream of the point water was entering the complex. Concrete will be pumped into the tunnels to form a plug, which will be grouted by a further high-pressure pumping of cement. Then the area of the rockfall itself will be filled with grout.

Cameco said that 40-50 workers were currently participating in the phase 1 drilling, working in three shifts per day, seven days per week.

The second phase would see water in the remainder of the complex pumped out before the concrete plug could be verified and bulkhead doors, underground pumps and ventilation systems be repaired. In later phases Cameco envisage freezing the area of water inflow, restoring some other underground areas and recommencing mine development. Each phase must be approved by the Canadian Nuclear Safety Commission and Saskatchewanian authorities.

Cigar Lake is located 660 km north of Saskatoon, Saskatchewan, Canada. It is expected to produce about 18 million pounds of U3O8 per year for joint venture partners Cameco (50%), Areva Resources Canada (37%), Idemitsu Uranium Exploration Canada (8%) and Tepco Resources (5%).

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