Radium-226 removal by precipitation and sedimentation in settling ponds

CIM Bulletin, Vol. 74, No. 832, 1981

D. MOFFETT and E. BARNES, Rio Algom Ltd. Elliot Lake, Ontario, J.N. HILTON, McLaren Engineers, Planners and Scientists Inc. Willowdale, Ontario

A recent pilot-plant program carried out at Rio Algom's Quirke uranium mine at Elliot Lake, Ontario is described. The goal of the research was the production of tailings basin effluents which were low in total radium-226. The process tested involved precipitation of radium with barium chloride and sedimentation in plastic-lined settling ponds. Adjustment of the tailings basin overflow from its normal value of pH9.5 by addition of sulphuric acid to about pH 7.5 was found to give approximately a five-fold improvement in total radium-226 removal. A five-month demonstration test resulted in an effluent with a mean total radium-226 activity of 44 pCi/L after 2.5 days settling time and 29 pCi/L after 5 days. The results from the demonstration program are used to propose a schedule of achievable total radium-226 activities where precipitation and sedimentation are employed. The maximum suggested values for 5 days nominal settling time are: 30 pCi/L in an annual mean, 45 pCi/L in a monthly mean, 60 pCi/L in a weekly mean and 80 pCi/L in any single grab sample.

Keywords: Radium, Precipitation, Sedimentation, Settling ponds, Uranium milling, Tailings, Environmental control, Barium chloride.