The immobilization of low- and intermediate-level radioactive waste (LILW) is crucial for its final disposal in repositories. While cementitious waste forms have conventionally been used for immobilizing various LILWs, they suffer from several issues, including poor durability, low resistance to leaching, and limited waste loading capacity. As an alternative, alkali or acid-activated geopolymer waste forms have garnered global attention. Unlike cementitious waste forms, geopolymer waste forms exhibit excellent physicochemical characteristics due to their three-dimensional amorphous structure and low calcium content. In this work, we provide an overview of geopolymer waste form research being conducted in countries such as Japan, the United Kingdom, the European Union, and South Korea. We specifically focus on the immobilization of soil waste, spent ion exchange resins, organic liquid waste, and evaporator concentrate (borate waste). We also identify the factors influencing the physicochemical characteristics of geopolymer waste forms and their immobilization performance. We propose a guide for optimizing the molar mixing formulations of geopolymer waste forms, including the selection of appropriate precursor materials. Additionally, we discuss the future prospects and significant challenges in the field of geopolymer waste forms that need to be addressed for their application in radioactive waste management.

Prussian blue is known as a superior material for selective adsorption of radioactive cesium ions; however, the separation of Prussian blue from aqueous suspension, due to particle size of around several tens of nanometers, is a hurdle that must be overcome. Therefore, this study aims to develop granule type adsorbent material containing Prussian blue in order to selectively adsorb and remove radioactive cesium in water. The surface of granular activated carbon was grafted using a covalent organic polymer (COP-19) in order to enhance Prussian blue immobilization. To maximize the degree of immobilization and minimize subsequent detachment of Prussian blue, several immobilization pathways were evaluated. As a result, the highest cesium adsorption performance was achieved when Prussian blue was synthesized in-situ without solid-liquid separation step during synthesis. The sample obtained under optimal conditions was further analyzed by scanning electron microscope-energy dispersive spectrometry, and it was confirmed that Prussian blue, which is about 9.7% of the total weight, was fixed on the surface of the activated carbon; this level of fixing represented a two-fold improvement compared to before COP-19 modification. In addition, an elution test was carried out to evaluate the stability of Prussian blue. Leaching of Prussian blue and cesium decreased by 1/2 and 1/3, respectively, compared to those levels before modification, showing increased stability due to COP-19 grafting. The Prussian blue based adsorbent material developed in this study is expected to be useful as a decontamination material to mitigate the release of radioactive materials.