Cigar Lake successfully plugged

20 February 2008

A concrete plug required to dewater the flooded Cigar Lake uranium mine has been proven effective, according to Cameco, 50% owner of the mine. The 7000 tonne per year mine could operate in 2011.


Cigar Lake underground 
How Cigar Lake tunnels looked
before the flood. (Image: Cameco)
Describing 'significant progress' at Cigar Lake, Cameco detailed how it had tested a plug poured near the site of a rockfall that led to a dramatic flood late in 2006 when the underground uranium mine was 60% complete.


Cameco drilled 465 metres underground and poured several layers of concrete, designed to harden underwater, to form a plug which was then grouted by a further high-pressure pumping of cement. To test the plug Cameco pumped out water down to a level of 100 metres and measured the time taken for groundwater to refill the mine to a certain level. Between 12-18 February it was demonstrated that "the seal is effective with no indication of plug deterioration."


Approval from the Canadian Nuclear Safety Commission (CNSC) would be required before Cameco could pump all the water out of the mine and begin to prepare the mine for completion and eventual operation. The company is preparing a submission to the CNSC now, and expects to gain approval and complete dewatering in the second half of 2008. 


Two other areas of the mine could require 'depressurization, reinforcement or other precautionary measures.' Cameco is investigating this and will make decisions on further action in the first quarter of this year.


The start of production at the northern Saskatchewan mine is predicted for 2011 "at the earliest." It is owned by Cameco (50%), Areva Resources Canada (37%), Idemitsu Canada Resources (8%) and Tepco Resources (5%).