Leaching of uranium and ²²⁶ra from low‐level radioactive waste from port hope, ontario

Abstract

Uranium and radium were leached from a low-level radioactive soil sample neutralized with limestone from Port Hope, ON, in single stage and multistage leaching tests. The leachants used were alkaline EDTA, sodium citrate, sodium potassium tartrate, acidic ferric chloride, hydrochloric acid, nitric acid and hydrochloric or nitric acid plus boric acid mixtures, All leaching tests except the two-stage acid leachings proved ineffective in yielding leach residues with low residual 226Ra concentrations of < 100 pCi/g. Leaching with 4 mol/L HNO, in the first stage followed by treatment with 4 moliL HNO, plus 0.05 moVL boric acid in the second stage proved effective and gave a leach residue with 85 pCiig 226Ra and I6 ppm uranium.

Characterization and remediation of soils contaminated with uranium

“…According to the USEPA [47], natural attenuation is the "use of natural processes to contain the spread of the contamination from chemical spills and reduce the concentration and amount of pollutants at contaminated sites". It can also be termed as intrinsic remediation, bio-attenuation and intrinsic bioremediation [164,165,166]. Natural attenuation is considered to be the least invasive approach to environmental remediation.…”

“…Several investigations on the removal of uranium from artificially contaminated soils as well as from anthropogenic sources, such as mine tailings and DU processing facilities, revealed that the application of any remedial technology for soils contaminated with uranium must take into account the potential of exposure to workers (as a consequence of the presence of radionuclides and the type and energy of radiation emitted) and the need to keep the exposure as low as reasonable achievable [147,[162][163][164]. The ultimate goal is to develop technologies that can further reduce risks, reduce cleanup costs and reduce the volume of remaining contaminated soil [15].…”

Removal of depleted uranium from contaminated soils

“…As the pH increases, the tendency is for uranium hydroxide complexes to dominate under oxidizing conditions (positive Eh). No U(IV) cations are pre- After analysis of the Eh-pH diagram for a U system, it appears that the experimental conditions under which Nirdosh [8] performed extractions were optimal for the UO 2 2+ cation to exist. The low pH and high Eh conditions prevented the formation of solid compounds such as uraninite and schoepite.…”

“…Another method of DU extraction was reported by Nirdosh [8]. A two-stage acid leaching procedure was developed for treatment of radioactive soil waste.…”

“…As a result, there is strong interest in re-mediation of depleted uranium (DU) laden areas. Several investigations into the removal of uranium from artificially contaminated soils as well as from anthropogenic sources, such as mine tailings and DU processing facilities, have been published [3,5,6,8]. Several chemical processes used for extracting U from contaminated soils are summarized in Table 1.…”