Radionuclide Concentrations in Vegetation at a Solid Radioactive Waste‐Disposal Area in Southeastern Idaho

Abstract

Abstract Concentrations of 238 Pu, 239,240 Pu, and 241 Am in crested wheatgrass ( Agropyron cristatum (L.) Gaertn) and Russian thistle ( Salsola kali L.) samples collected at a solid radioactive waste‐disposal area in southeastern Idaho were significantly ( P ± 0.05) greater than concentrations in control vegetation. No significant differences were found for 90 Sr or 137 Cs concentrations between the waste‐disposal and control‐area vegetation. Russian thistle had more radionuclide contamination than crested wheatgrass, presumably because of its greater rooting depth and spreading growth. The total radionuclide inventory of 90 Sr, 137 Cs, 238 Pu, 239,240 Pu, and 241 Am in vegetation at the 36‐ha waste‐disposal area (77 µ Ci) was not significantly ( P > 0.05) greater than the 17 µ Ci in control‐area vegetation. Ninety percent of the radioactivity in waste‐disposal area vegetation and 99% in control‐area vegetation were attributed to 90 Sr and 137 Cs. The Pu inventory in Subsurface Disposal Area (SDA) vegetation was only 0.02% of the quantity of Pu estimated to occur in SDA surface soils in 1974. Accumulation of radionuclides by vegetation is not considered a major mode of radionuclide transport through the environment surrounding this radioactive‐waste‐disposal area.