Design and Application of Materials for Sequestration and Immobilization of ⁹⁹Tc

Abstract

99Technetium (99Tc) is a hazardous radionuclide that poses a serious environmental threat. The wide variation and complex chemistries of liquid nuclear waste streams containing 99Tc often create unique, site specific challenges when sequestering and immobilizing the waste in a matrix suitable for long-term storage and disposal. Therefore, an effective management plan for 99Tc containing liquid radioactive wastes (such as storage (tanks) and decommissioned wastes) will likely require a variety of suitable materials/matrixes capable of adapting to and addressing these challenges. In this review, we discuss and highlight the key developments for effective removal and immobilization of 99Tc liquid waste in inorganic waste forms. Specifically, we review the synthesis, characterization, and application of materials for the targeted removal of 99Tc from (simulated) waste solutions under various experimental conditions. These materials include (i) layered double hydroxides (LDHs), (ii) metal–organic frameworks (MOFs), (iii) ion-exchange resins (IERs) as well as cationic organic polymers (COPs), (iv) surface modified natural clay materials (SMCMs), and (v) graphene-based materials (GBMs). Second, we discuss some of the major and recent developments toward 99Tc immobilization in (i) glass, (ii) cement, and (iii) iron mineral waste forms. Finally, we present future challenges that need to be addressed for the design, synthesis, and selection of suitable matrixes for the efficient sequestration and immobilization of 99Tc from targeted wastes. The purpose of this review is to inspire research on the design and application of various suitable materials/matrixes for selective removal of 99Tc present globally in different radioactive wastes and its immobilization in stable/durable waste forms.

Advanced Porous Materials as Designer Platforms for Sequestering Radionuclide Pertechnetate

“…To put this into perspective, a nuclear reactor with a 1 GWe capacity produces about 21 kg of 99 Tc each year. Since the dawn of nuclear power, this has culminated in a global total of approximately 400 metric tonnes of 99 Tc. − The primary form of 99 Tc in the environment is pertechnetate (TcO 4 – ), an anion known for its high solubility and poor ability to form complexes. , These properties allow it to move swiftly through various environments, bypassing minerals and organic substances with ease. Such mobility poses substantial concerns regarding the contamination of groundwater and the potential risks to aquatic ecosystems, especially in locations with legacy radioactive waste from historical power production and military activities.…”

“…), an anion known for its high solubility and poor ability to form complexes. 22,23 These properties allow it to move swiftly through various environments, bypassing minerals and organic substances with ease. Such mobility poses substantial concerns regarding the contamination of groundwater and the potential risks to aquatic ecosystems, especially in locations with legacy radioactive waste from historical power production and military activities.…”