Measurements of Distribution Coefficient for Sm on Tuff and Granodiorite in Synthesized Sea Water and Distilled Water

Morooka, Koichi*; Nakazawa, Toshiyuki*; Yoshihiko, Saito,; Suyama, Tadahiro*; Shibata, Masahiro ; Sasamoto, Hiroshi   

Japan Nuclear Cycle Development Institute (JNC) has developed a sorption database for bentonite and rocks in order to assess the retardation property of important radioactive elements in natural and engineered barriers in the H12 report. However, there are not enough distribution coefficient data for some radioactive elements in the database. Thus the batch sorption tests for tuff and granodiorite were performed for Samarium (Sm) in synthesized sea water and distilled water under reducing conditions. For Samarium, there are little registration numbers of JNC database and it is important element for performance assessment of HLW disposal system. The results of the experiments are summarized below;(1)Kd for tuff were approximately 0.6 m/kg in rock - distilled water leachate (Eh=-320 - -270mV) adjusted to pH 7 after 10000 MWCO filtration.(2)Kd for tuff were approximately 0.4 m/kg in rock - synthesized sea water leachate (Eh=-304 - -265mV) adjusted to pH 7 after 10000 MWCO filtration.(3)Kd for granodiorite at 1 week were approximately 3.9 m/kg in rock - distilled water leachate (Eh=-279 - -242mV) adjusted to pH 9 after 10000 MWCO filtration. Kd had a tendency to rise with time in the period of 1 week through 4 week.(4)Kd for granodiorite at 1 week were approximately 0.3 m/kg in rock - synthesized sea water leachate (Eh=-237 - -206mV) adjusted to pH 9 after 10000 MWCO filtration. Kd had a tendency to rise with time in the period of 1 week through 4 week.