Occupational Dose Evaluation in Support of the Development of the
October, 2012
Rare Element Resources, Inc. Bear Lodge Project
12
2.3
Hydrometallurgical Plant
The Hydromet plant contains two parallel circuits to process the expected range of pre-
concentrate production. The pre-concentrate from the PUG is first leached with hydrochloric
acid. Iron then is precipitated from the leachate, using a pH adjustment. Calcium and manganese
are extracted from the leachate via ion exchange. Finally, REEs are precipitated as carbonates
using sodium carbonate. The hydrochloride acid is regenerated. The carbonate concentrate will
have an approximate rare earth equivalent content of 45 percent by weight.
The Hydromet process is the first point where radionuclides in the pre-concentrate can be
preferentially concentrated based on chemical characteristics. Preliminary tests indicate that
thorium oxides in the pre-concentrate are not leached by hydrochloric acid; thus are retained in
the tailings and conveyed to the TSF.
Uranium is present in the pre-concentrate at lower levels than thorium. Tests have shown that the
hydrochloric acid only partially leaches uranium oxides, which then could be conveyed to the
TSF or occur in the carbonate product (RER, 2010).
The Hydromet process will be enclosed. Additionally, potential emissions from the plant,
including dust and vapor, will be controlled by dust collectors and wet scrubbers as indicated in
Figure 2.1.
2.3.1
Tailings Storage Facility
Tailings will be stored in an engineered, lined facility west of the plant. The TSF is designed to
meet the regulatory requirements of the Wyoming Department of Environmental Quality. Details
of the TSF preliminary design are presented in
Technical Report on the Mineral Reserves and
Development of the Bull Hill Mine
(RER, 2012).
The tailings are designed to be 5 percent solids slurry. The solids will be comprised of sulfate
sludge (72 percent), iron hydroxide (7 percent), and compounds not leached by the Hydromet
process (RER, 2012). The tailings flow rate is estimated at 116 gallons per minute.
Currently, the TSF has a designed footprint of 157 acres with a storage capacity of 5.2 x 10
6
tons. Its construction is expected to be staged holding approximately 1 million tons of tailings.
2.4
Radionuclide Content of Ore and Concentrates
Three general types of material will be produced by the BLP and include ore mined from the
BHM, a pre-concentrate generated from the PUG, and a carbonate concentrate product from the
Hydromet.
2.4.1
Bull Hill Ore
Ore from the BHM can be grouped into four general types including:
