Challenge of 90Sr separation in environmental samples collected from the Fukushima exclusion zone

Fukushima Daiichi nuclear power plant (FDNPP) accident caused radioactive contamination with fission products (I, Te, Be, Cs, Sr isotopes, etc.). The fission products are neutron rich isotopes therefore beta particles will be released from the nucleus to reach stable isotope configuration. Since decay process is accomplished with gamma ray emission, gamma-ray spectroscopy is applied mainly for fission products determination in samples affected by nuclear accident. However, some fission products such as 90Sr, 89Sr are pure beta emitters. Since the energy distribution of the emitted electrons in the beta decay is continuous, element specific separation from the interfering beta emitters is essential for qualitative radioisotopes identification and subsequent measurement.The most important step for reliable 90Sr determination is the highly effective radionuclide separation. Even after five years of the Fukushima accident, there is radioactive contamination in environmental samples caused by radiocaesium isotopes (134Cs and 137Cs) around the Fukushima exclusion zone. The contamination of 90Sr is significantly lower, by four or five magnitudes than radiocaesium isotopes. Under this condition, the decontamination factor of caesium should be higher around six figures in order to eliminate interfering beta particles from radiocaesium isotopes during 90Sr analysis.In recent publication for chemical separation of 90Sr, extraction chromatography is preferred using Sr specific resin (crown ether). Therefore, caesium decontamination factor (DF) was determined in Sr resin using soil samples from the Fukushima exclusion zone with elevated 137Cs contamination (over 3,000 Bq g-1). The caesium separation was not adequate in every case (DF = 104 105), presence of radiocaesium affected the results of 90Sr measurement. Consequently, additional separation steps were required. Caesium purification, with classical selective oxalic acid precipitation method , was achieved with DF range from 50 to 100. However, applying oxalic precipitation combining with Eichrom Sr resin separation, interfering radiocaesium isotopes can be removed with high efficiency (DF>106). The details of this procedure will be discussed during the presentation.International Nuclear Chemistry Congress(INCC 2017