Investigation on chemical effects on GMZ bentonite used as buffer materials

Abstract

GMZ bentonite has been selected as a buffer/backfill material for the design of Chinese HLW repository due to its suitable properties. Investigations have been conducted on this material to have a better understanding of its engineering behavior. In this paper, a review of the studies on the chemical effects in GMZ bentonite is presented. The adsorption of radionuclides Ni(II), Cr(III) and Eu(III) etc. on GMZ bentonite is investigated and the influences of external chemical agents are assessed. Some modifications on GMZ bentonite have been implemented to improve its adsorption properties. In the meantime, the influences of NaOH solutions with variations in concentration and pH values on hydraulic conductivity, mechanical behavior and mineralogy of GMZ bentonite are investigated with consideration of temperature. Effects of salt solutions are also assessed in different studies using solutions of Na+ and Ca2+, which are the predominant cations in the groundwater of Beishan area. It is observed that both cations influence the buffering behavior of bentonite at a different degree. Further investigations should be done for better understanding the influences of coupling factors and time on the chemical behavior of material.