| Popis: |
Nickel and uranium loadings from oxidized sulphide-bearing waste rock have been estimated at three successive scales: laboratory columns, a 320 m 3 -constructed pile (CPE) and the Claude waste rock pile. The Claude waste rock pile is approximately 20 years old and is composed of waste rock from the Claude open pit, which was mined for uranium on the Cluff Lake site, Northern Saskatchewan, Canada. The Claude waste rock pile is about 29 m high at its highest point and covers an area of 29.5 ha. It contains roughly 7.9 million tonnes of waste rock. Operational groundwater monitoring has been in place in the Claude pile area since 1991 with monthly hydraulic head and groundwater chemistry measurements. An assessment of the existing contaminant plume suggests that between 12% and 30% of the nickel and uranium inventory has been released to the groundwater system since initial construction of the pile. Based on sequential leach tests and unsaturated column leach tests results, these leached masses range from 25% and 45% of the total leachable mass for uranium and from 31% to 58% of the total leachable mass for nickel. This metal load was estimated be released during the first pore volume replacement of the waste rock pile. Field loading estimates for the CPE also suggested that a significant portion of the uranium and nickel mass was released during the first pore volume replacement of the waste rock mass, with calculated leached fractions on the order of 80% and 24% for uranium and nickel, respectively. For both the Claude waste rock and the waste rock used to construct the CPE, it is suspected that these high leached fractions are the result of a large quantity of readily soluble products that the waste rock has accumulated from a rapid weathering and oxidation of the sulphides. Subsequently, this suggests that the cover of the Claude pile should target an efficient reduction of infiltration rather than a reduction of oxygen ingress within the pile Additional |
