Preliminary Public Dose Evaluation in Support of the Development of
November , 2012
Rare Element Resources, Inc. Bear Lodge Project
10
Engineering controls will mitigate dust emissions from the process. Much of the PUG process
will be wet and enclosed. In addition, and as shown in Figure 2.1, dust collectors will be used —
prior to ventilation— at the drying component of the process.
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, sodium carbonate is used to precipitate
REEs. 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 potentially 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.
