237Np,238Pu,241Am和90Sr在中国和日本膨润土中迁移的野外试验

从1997年6月25日到2000年7月11日在中国辐射防护研究院试验场，在天然降雨和人工喷淋（15mm/d）两种条件下，在包气带黄土中进行了²³⁷Np,²³⁸Pu,²⁴¹Am和⁹⁰Sr在中国膨润土和日本膨润土中迁移的野外试验。试块由膨润土和砂子以质量比为15∶85组成，试块大小为150mm×150mm。试验结果表明，在两种条件下，核素在两种膨润土试块中分布状态和变化趋势相似，²³⁸Pu和²⁴¹Am在3a内没有明显移动，²³⁷Np和⁹⁰Sr在天然降雨条件下，分布曲线有所展宽；在人工喷淋条件下经1106d后，²³⁷Np和⁹⁰Sr在试块内分别向下迁移15mm和20mm，呈现出扩散为主的迁移。

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.