Field Tests of ²³⁷Np, ²³⁸Pu, ²⁴¹Am and ⁹⁰Sr Migration in Bentonite From China and Japan

Under natural and artificial rainfall conditions, field tests of ²³⁷Np, ²³⁸Pu, ²⁴¹Am and ⁹⁰Sr migration in bentonite from China and Japan at aerated zone were conducted in the field test site of China Institute for Radiation Protection during the period from June 25,1997 to July 11,2000. The specimen with the dimension of 150mm×150mm is composed of bentonite and sand(bentonite∶sand=15∶85(wt)).Tests show that radionuclide distribution and migration trend in two types of specimen are similar under both natural and artificial rainfall conditions. ^238Pu and ²⁴¹Am have not remarkable movement under two rainfall conditions in three years. Under natural rainfall condition, concentration peak of ²³⁷Np and ⁹⁰Sr in specimen show to be widen. ²³⁷Np and ⁹⁰Sr move down wards 1.5mm and 2.0mm in specimen separately after 1106d under artificial rainfall condition. This indicates that nuclide movement in bentonite/sand is dominated by diffusion.