A Study on Formation and Growing Processes of the Colloids Containing Long-Lived Radionuclides by Means of Laser Induced Photoacoustic Spectroscopy

用直线加速器产生的韧致辐射辐照高锝酸盐水溶液，研究了二氧化锝水合物胶体的辐解形成。透射电子显微镜显示的胶体的粒径分布在50和130 nm之间。通过色散X-射线光谱法证实了胶体的组成。通过电子衍射分析发现胶体为非晶态结构。溶液中溶解的气体对胶体的产率有很大的影响。在用氧气或一氧化二氮气体饱和的溶液中，没有形成胶体，而在Ar饱和的溶液中，发现90%的Tc作为胶体。在二氧化锝胶体的前驱体Tc（IV）物种的形成过程中，水合电子在高锝酸根离子的还原过程中起着重要作用，随后Tc（VI）和Tc（V）的还原反应也随之发生。对硫化锝胶体颗粒光声信号的分析表明，硫化锝在胶体颗粒表面的沉积增加了胶体颗粒的尺寸，而不是胶体颗粒的凝聚。

Radiolytic formation of the colloids of technetium dioxide hydrate was investigated by irradiation of aqueous pertechnetate solutions with bremsstrahlung generated from a linear accelerator. Transmission electron microscopy revealed the size distribution of the colloids between 50 and 130 nm. The composition of the colloids was confirmed by dispersive x-ray spectrometry. An amorphous structure of the colloids was found by electron diffraction analysis. The yield of the colloids was strongly affected by dissolved gases in solutions. In the solutions saturated with oxygen gas or nitrous oxide gas, no colloids were formed, while 90 % of Tc was found as the colloids for the Ar-saturated solutions. In the formation of Tc(IV) species as a precursor of technetium dioxide colloids, it was found that hydrated electrons played an important role on the reduction processes of pertechnetate ions followed by successive disproportionation reactions of Tc(VI) and Tc(V).Laser induced photoacoustic spectroscopy was applied to a study on the formation and growing processes of technetium sulfide colloids. Analysis of the photoacoustic signals from technetium sulfide colloid particles revealed that the colloid particle the size of colloid particles increased by deposition of technetium sulfide on the particle surfaces, not by coagulation of colloid particles.