Sorption distribution coefficients of selenium on a sandy mudstone under reducing conditions of underground

Abstract

  Sorption of radionuclides on rocks is an important factor for safety assessments of geologic disposal of radioactive wastes. Batch sorption tests were conducted to investigate effects of concentrations of NaNO₃ and NaCl on sorption distribution coefficients (K_d) of selenium on a sandy mudstone under reducing environment of underground. The rock and groundwater used in the tests were sampled from depths of 129-156 m with special care minimizing contact with air. Selenium was spiked as HSe^-to the test solutions and kept reducing conditions (Eh, pH) of the solutions throughout the test periods. Obtained log K_d (m³ kg^-1) values were in a range of -1.84 to -1.44, which were as high as those for Cs.