Influence of γ-irradiation and oxygen conditions on the diffusion of I-125 in crushed Beishan granite. (September 2020)

• Record Type: Journal Article
• Authors: He, Jiangang; Li, Yao; Su, Yin; Yang, Junqiang; Hou, Xiaolin; Wu, Wangsuo; Shi, Keliang
• Is Part Of: Applied radiation and isotopes. Volume 163(2020:Sep.)
• Publication Date: 2020-09
• Subjects: Capillary method -- Irradiation -- Diffusion -- 125I -- Beishan granite; Radiology -- Periodicals; Radiation -- Industrial applications -- Periodicals; Nuclear chemistry -- Periodicals; Internet resource; Periodical; 660.298
• DOI: 10.1016/j.apradiso.2020.109224
• Languages: English
• ISSNs: 0969-8043

Abstract

Abstract: The diffusion of iodine (labeled with 125 I - ) in compacted Beishan granite (BsG) was investigated using the in-diffusion capillary method at pH ~2.0 to ~11.0 under oxygen and irradiation conditions. With the advantages of simple and easy operation of the capillary diffusion devices, this work makes a preliminary investigation on the irradiation condition that cannot be performed by the traditional diffusion experiment. In this study, D a values of 125 I as a tracer in the form of iodide were determined to investigate and assess the influence of irradiation and oxygen conditions, which must be considered in-situ environment of the geologic repository. The results indicate that capillary method is a simple and efficient method to study the diffusion behavior of radionuclides, which is a relatively feasible to quickly obtain the diffusion coefficient, especially for some special conditions, e.g., oxygen and irradiation conditions. The diffusion results showed that D a values of 125 I - range from 1.4 × 10 -10 to 1.5 × 10 -9 m 2 ∙s -1, which was much faster than other nuclides, such as 79 Se (10 -11 m 2 ∙s -1 ). The batch adsorption experiments in this paper and related studies showed that the sorption could be neglected, i.e., 125 I - is a weak adsorbent nuclide. Its diffusion and sorption process were hardly affected by pH、oxygen and irradiation conditions, which is very different from 79 Se. Besides, ionic strength has a significant impact on the diffusion rate of 125 I -, which is closely related to the double electric layer. Overall, this study indicates that natural BsG couldn't greatly attenuate the mobility of 125 I - in the deep geologic repository and new retardation method or materials need to be explored. Highlights: The capillary method is a simple and highly efficient way to investigate some special conditions, such as γ-irradiation. This work is the first attempt to study the influence of irradiation and oxygen conditions on I-129 diffusion using capillary method. The diffusion of 125 I - was much faster than other nuclides, which was hardly affected by irradiation and oxygen irradiation conditions.