LEACHABILITY OF BARIUM-RADIUM SULFATE SLUDGES
P. M. Huck, Associate Professor
B. Anderson, Research Assistant
Faculty of Engineering
University of Regina
Regina, Saskatchewan S4S 0A2
In the milling of uranium ore, only a small amount of product called yellow cake is
produced, while almost the entire mass of ore is transformed into a waste product called
tailings. These tailings are typically conveyed in slurry form to an impoundment area where
the solids settle. In the climatic conditions that prevail in the uranium producing areas in
Canada, there is a net water or decant discharge from the tailings area. This water includes
the water used to transport the tailings as well as any precipitation falling on the tailings
basin. Because the tailings contain all the radioactive isotopes from the uranium, actinium
and thorium decay series, the decants contain a number of dissolved species; of particular
concern for environmental protection is the amount of 226Ra being discharged to the
aquatic environment.
Uranium mine/mill tailings decants are treated with barium chloride to remove 226Ra.
Historically this has been accomplished in ponds which provide an opportunity for a barium-
radium sulfate precipitate to form and subsequently settle (Figure 1). The treated effluent
is discharged, and the barium-radium sulfate sludge accumulates in the pond.
Because the Canadian Atomic Energy Control Board does not consider the ponds to be
suitable final disposal locations for the sludge, alternative disposal sites must be found.
Alternatives that have been suggested include placing the sludge in special chambers in
worked-out mine areas or placing it back in the tailings area. In any event, information
must be available on the leachability of 2J6Ra from the sludge so that appropriate containment can be provided. In the case of disposal in tailings areas, of particular importance
are the relative leachabilities of tailings and sludge.
The information available on (Ba,Ra)S04 sludge leachability is very limited, in contrast
to the large amount of work that has been performed in defining radium releases from
tailings. This study was designed to fill this information gap.
OBJECTIVE
This chapter presents the initial phase of a research program designed to examine the
leachability of 6Ra from barium-radium sulfate sludges. The objective of this first phase
was to survey a number of leaching variables to determine those most critical for radium
release. The first phase was also designed to provide results that could be compared to those
obtained by other workers for radium leaching from uranium tailings.
Figure I. Schematic of uranium tailings
basin and effluent treatment pond.
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