Weakley and 3 co-authors, reported in 1981 that in order to meet the increased demands for uranium oxide (U308) that will occur in the future, new low-grade domestic deposits may have to be mined. This study examined the type and level of wastes that would be generated in the mining and milling of U308 from four potential domestic sources of uranium. The estimated costs of the technology to control these wastes to different degrees of stringency are presented.
The incremental cost for the control of waste from U30S production could vary not only with the level of control but from site to site (see Table 1). The minimum incremental cost of environmental control technology per pound of U308 ranges from $22 at the Thomas Caldera and the Chattanooga shale deposits to $11 at the Florida phosphate deposit. These figures represent the minimum cost of meeting present regulations. The maximum incremental
cost of environmental control technology per pound of U308 ranges from $1,343 at the Florida phosphate and Thomas Caldera deposits to $903 at the
Chattanooga shale deposit. The major difference between the minimum and maximum costs are the methods used to control the mill tailings. The minimum cost alternative is a clay core dam without any pond liner while the maximum cost alternative is to dewater the tailings, blend them with 40% asphalt, and pump the mixture to a landfill pit or mound.
The annual cost of the latter method is very high due to the cost of the asphalt material. The differences between the costs at the four sites at both the maximum and minimum levels of control are caused by the amount of ore processed and the treatment process for the tailings from the mine and mill. These differences, as well as many others among the other sites, cause the environmental control technology costs to be highly site-and-process-specific.
The major wastes generated at most sites would be similar in type (dust, water, etc.), but the radioactive content would vary, depending on the ore
grade. The major cost would be for controlling the waste water and tailings from the mines and mills. The type of control method that would be used
depends on the water volume and its radioactivity level. Waste water control consists of tailings ponds, pond covers, beach dust control, and, in some
cases, dewatering and material additions to immobilize the radioactive constituents.
This study indicated that most of the environmental control technology costs (up to 90%) at each site would be for the control of mill tailings. The unit costs would be lower in all cases if the throughput rates and/or ore grades were higher. It could cost over an order of magnitude more to reduce the amount of a specific waste released by the last 1 or 2%. The technologies examined in this study have the potential to effectively hold the discharge of
wastes to very low levels.
There is a lack of data dealing with the wastes from low-grade uranium mining and milling. Most of the environmental control technology data deals with much more radioactive waste streams than are present in this study. If the development of the above deposits becomes probable, research should be
undertaken to:
• Obtain site-specific data from the deposit to be developed (e.g., ore analysis, hydrology, ecology, etc.).
• Define flow sheet and processes for the specific sites more accurately.
• Analyze the radon concentrations and retention parameters likely to be encountered in mines and tailings piles at these deposits. Perhaps less stringent methods than assumed in this study may be used for the low-grade ore tailings.
• Evaluate the performance characteristics of environmental control technology at the waste levels to be encountered at the sites under study.
• Assess the technology and environmental control effectiveness of backfilling underground mines with tailings in greater detail.
• Develop lower cost technologies for long-term storage and stabilization of mill tailings.
• Develop milling processes and tailings control technology that reduce water consumption in arid mining regions.
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