Study of cesium sorption by a Brazilian bentonite

Daisy Mary Marchezini Dos Santos,Clédola Cássia Oliveira De Tello

doi:10.15392/bjrs.v9i1a.1519

Abstract

Engineered and natural barriers compose the disposal system of near surface repository to store low and intermediate level radioactive wastes. Waterproofing barriers are constituted of clays, such as the bentonite, in order to avoid or to limit the release of radionuclides to with consequences to the environment and humans. Characteristics such as high cation exchange capacity, high adsorption capacity and high sealing capacity, are taken into consideration for choosing this material. The migration of radionuclides through protection barriers can occur in a variety of ways, such as surface water infiltration, groundwater intrusion, among others. Diffusion is the process which governs the contaminant transport through soil barriers. Adsorption is one of the processes that could be considered in the diffusion mechanism, and sorption isotherms are obtained from values measured in the batch-adsorption experiments. Therefore, such experiments were carried out in order to estimate the cesium sorption by the bentonite. The quantitative analysis was performed using atomic absorption and the energy dispersive X-ray fluorescence spectrometry. With the purpose to calculate the true value of cesium sorption, a mass-balance was made considering all the steps of the batch experiment, and it was found a 6% loss in the whole process. The quantity of cesium sorbed by the bentonite was 66.7 mg.g-1. At the moment, eight additional experiments are being performed, using solutions with different cesium concentrations, leading to all the necessary data for the isotherm.

Highlights

The management of radioactive waste aims to ensure the safe storage of such wastes, in order to protect the environment and humans
Additions of N2 gas were made at a temperature of -196 °C, which were adsorbed through condensation on the surface and in the pores of the bentonite
When sorption of inorganic cations occurs in a medium with a high pH value, there is an increase in their sorption capacity

Summary

Introduction

The management of radioactive waste aims to ensure the safe storage of such wastes, in order to protect the environment and humans. During the management of these wastes, storage can be done in different types of deposits, and the final storage is carried out in repositories. Low and intermediate level radioactive wastes are stored in near surface repository [1, 2, 3]. The near surface repository is used in several countries and, in order to assure public safety and confidence, the institutional controls is carried out after the end of the operation stage of the repository. Deposition areas consist of several barriers in order to avoid or to limit the release of radionuclides into the environment until their decay at a safe level of radiation to humans and the environment [7]

Methods

Results

Conclusion