Radiochemical investigation of TENORM waste associated with non-nuclear industries: iron and steelmaking – case study

The industry of iron and steel production is considered as one of the global economic backbones, and has been worldwide ranked as one of the largest industrial sources of environmental contamination. The radiometric measurements by γ - and α -spectroscopy indicated that the steel waste samples contain natural radionuclides ( 226 Ra and 228 Ra) below the exemption safe limits set by the ICRP and IAEA. The estimated radiological hazard indices as external hazards ( I γ 1 , I γ 2 & I γ 3 ) and internal hazard ( I α ) were below the maximum safe limit (i.e., <1). The estimated ecological risk indices of Cr, Fe, Mn and Ni in the steel waste as single indices (EF, CF and E r ) and integrated indices (CD, PLI and RI) revealed that the accumulated steel waste in its physical state has low ecological risk to the surrounded environment (RI < 150). Moreover, the mobilization behavior of radionuclides and heavy metals in steel waste was investigated using two standard leaching methods (TCLP and EU) to simulate the natural wetting conditions such as rain or groundwater. It is found that natural γ -emitters (e.g., 228 Ra, 226 Ra, 214 Pb, 214 Bi and 210 Pb) and α -emitters (e.g., 232 Th, 238 U, 226 Ra, 210 Po and 222 Rn) are detected in the extraction solution@1 of TCLP test with low activity levels below the safe limits (<10 Bq/L). Also, the concentrations of Fe and Cr were 17.5 and 2.2-folds above the recommended safe limits in drinking water set by the WHO, respectively. Regarding to speciation diagrams, 226 Ra in the steel waste samples can be mobilized out as soluble acetate species (CH 3 COO– 226 Ra–OH and/or 226 Ra(CH 3 COO) 2 ), while the highly toxic Cr 6+ is leached out as soluble anionic species of chromates (HCrO 4 − and CrO 4 2− ) and/or dichromate (HCr 2 O 7 − ) and Cr 2 O 7 2− . Thus, these wastes can be managed to prevent or minimize their hazards; either long-term storage in designated landfills (i.e., engineered), or recycled in civil engineering applications as additives in the cement industry, and roadbed construction…etc.