锕系核素烧绿石模拟固化体化学稳定性研究

Chemical Durability of Actinide Simulated Pyrochlore Immobilization

以La2Zr2O7为固化基材,Nd为锕系核素模拟核素,通过溶胶凝胶法制备了(La1-yNdy)2Zr2O7(0≤y≤1.0)系列烧绿石模拟固化体。样品经过高能γ辐照,辐照剂量为233.78 k Gy。通过PCT粉末浸出测试方法对固化体化学稳定性进行了测试,辐照前后样品的La,Nd,Zr均保持了较低的化学浸出率10-4(g·m-2·d-1),锆基烧绿石具有可靠的化学稳定性主要取决于稳定的Zr-O键。当模拟锕系核素Nd的掺杂量达到相变区域(0.6≤y≤0.8)时,元素浸出率有明显增加,主要可能是结构的无序化导致。γ辐照后样品Zr的浸出率在相变区域也出现明显的增加,可能是由于γ辐照导致固化体Zr-O48f键结构的变化。

La2Zr2O7pyrochlore doped with Nd have been synthesized by sol- spray pyrolysis method,Nd is used as surrogated element for actinides.（ La1- yNdy）2Zr2O7（ 0≤y≤1. 0） samples have been irradiated by60 Co γ- ray source with 233. 78 k Gy dose. Leaching studies of unirradiation and irradiation pyrochlore samples were performed through the PCT method in deionized water. The leaching rate of La,Nd,Zr in these samples are extremely low about 10- 4（ g·m- 2·d- 1）,which suggests that zircontae pyrochlore is chemical stable in contact with water. The leaching rate appears to increase significantly as Nd content increase from 0. 6 to 0. 8,which results from the structure disorder of（ La1- yNdy）2Zr2O7pyrochore. The leaching rate of Zr in irradiation samples also increase with increasing Nd content,it is maybe that the Zr- O48 fbond is changed under the γ- irradiation condition.