@article{fdi:010078054,
  title = {{G}eochemical characterization of uranium mill tailings ({B}ois {N}oirs {L}imouzat, {F}rance) highlighting the {U} and {R}a-226 retention},
  author = {{C}hautard, {C}. and {B}eaucaire, {C}. and {G}{\'e}rard, {M}artine and {R}oy, {R}. and {S}avoye, {S}. and {D}escostes, {M}.},
  editor = {},
  language = {{ENG}},
  abstract = {{A}s with other metals, the management of tailings from former uranium ({U}) mines requires a good knowledge of the geochemical mechanisms governing the retention of radioelements of interest: {U} and {R}a-226. {T}his article presents the results of the study of the bearing phases featuring these two radioelements within the {B}ois {N}oirs {L}imouzat tailings storage facility ({L}oire), the only site in {F}rance where the tailings (a sandy silt facies and a clayey silt facies) are currently stored only under water. {T}he aim is to gain a better understanding of their respective mobility under current storage conditions. {F}or this purpose, a multi-scale approach was adopted combining historical research and airborne image analysis to select the core location, chemical and radiological analyses, mineralogical characterizations supplemented by sequential extractions (two specifically developed protocols). {T}he results show that {U} and {R}a-226 are mainly found in the clayey silt facies with an average {U} concentration of 243.3 ppm (132.3 ppm in the sandy silt facies) and an average {R}a-226 mass activity of 64.7{B}q/g (18.0{B}q/g in the sandy silt facies). {T}hese results are in accordance with the initial {U} grade of the ore (2 parts per thousand), the extraction efficiency of the ore processing plant (95%) and the age of mineralization (305 {M}a). {T}he approach adopted made it possible to highlight several mineralogical traps available for each radioelement, regardless of the facies type. {T}hus, a significant part of the {U} is still trapped within the primary phases, resistant to treatment and therefore relatively immobile under current storage conditions (49.6%-77.8% for the sandy silt facies and 27.2%-36% for the clayey silt facies). {M}ost of the leached {U} is mainly associated with weakly crystalised iron oxyhydroxides (8.7%-42.4% for the sandy silt facies and 50.9%-71.8% for the clayey silt facies) and to a lesser extent with clay minerals (5%-12.3% for the sandy silt facies and 0.8%-11.5% for the clayey silt facies). {F}or the {R}a-226, irrespective of the facies type, a significant part remains trapped within phosphate phases, resistant to the leaching process and therefore also relatively immobile under storage conditions (24.4%-38.9% for the silty sandy silt facies and 39.9%-98.9% for the clayey silt facies). {S}equential extractions revealed a different geochemistry of {R}a-226 depending on the facies. {F}or the silty sandy silt facies, most of the {R}a-226 is mainly associated with the clay minerals (6.4%-69.2%) and to a lesser extent with iron oxyhydroxides, barite or aluminum phosphate sulphate minerals ({APS}) (6.4%-33.9%). {F}or the clayey silt facies, most of the {R}a-226 is mainly associated with iron oxyhydroxides, barite or {APS} (6.4%-53.3%) and to lesser extent clay minerals (0.4%-6.8%). {T}he leaching process did not allow the differentiation between the contributions of each of these phases to the retention of {R}a-226. {A}t last, all the identified bearing phases demonstrate that the {U} is relatively immobile under the current storage conditions, irrespective of the facies. {F}or the {R}a-226, the bearing phases differ according to the facies. {W}ithin the sandy silt facies, the {R}a-226 is mainly borne by clay minerals and can be mobilised more easily. {H}owever, the sandy silt facies represents only one third of the tailings currently.},
  keywords = {{M}ill tailings ; {U} ; {R}a-226 ; {S}equential extractions ; {R}etention ; {FRANCE}},
  booktitle = {},
  journal = {{J}ournal of {E}nvironmental {R}adioactivity},
  volume = {218},
  numero = {},
  pages = {art. 106251 [16 ]},
  ISSN = {0265-931{X}},
  year = {2020},
  DOI = {10.1016/j.jenvrad.2020.106251},
  URL = {https://www.documentation.ird.fr/hor/fdi:010078054},
}