The influence of temperature on the diffusion of ¹²⁵I⁻ in Beishan Granite

Abstract

Abstract China has planned to deal with the high-level radioactive wastes (HLW) in the middle of this century with deep geologic disposal method. The release of heat from HLW may cause the rise of temperatures in the surrounding backfilling materials or even the host rock of a repository. This brings about the concerns that the temperature elevation in the host rock may change the diffusion characteristics of key radionuclides and have some unpredictable effects in the performance assessment. In this paper, the influence of temperature on the diffusion of 125 I − in Beishan Granite is studied by through diffusion method. The effective diffusion coefficients ( D e ) of 125 I − in the granite from 27 to 50 °C are obtained and analyzed as a function of temperature. Our result indicated that the relationship between D e and temperature can be described by the modified Nernst equation, and the formation factors ( F f ) of the granite from 27 to 50 °C is constant with an average value of 1.03×10 −4 .