Radiolytically-induced novel materials and their application to waste processing

Massimo Bertino, Akira Tokuhiro, Tadashi Tokuhiro

关键词: AFFINITY;    AQUEOUS SOLUTIONS;    CATIONS;    DIFFUSION;    FUNCTIONALS;    HYDROGELS;    LIQUID WASTES;    NATURAL CONVECTION;    NUCLEAR FUELS;    PARTICULATES;    POLYMERS;    SILICA;    SILICA GEL;    SILVER;   

DOI  :  10.2172/920382
RP-ID  :  final report
PID  :  OSTI ID: 920382
Others  :  TRN: US0800947

学科分类：核能源与工程

美国|英语

来源: SciTech Connect

【 摘 要 】

In the present NEER project we investigated two different types of gel materials with respect to potential applications in environmental remediation, including mixed waste generated from the nuclear fuel cycles. The materials under study were: (1) silica-polymer based aerogel composites into which specific metallic cations diffuse into and remain, and (2) polymer gels made of thermo-sensitive polymer networks, whose functional groups can be ''tailored'' to have a preferred affinity for specific cations, again diffusing into and remaining in the network under a volumetrically, contractive phase-transition. The molecular, diffusion of specific cations, including those of concern in low-level waste streams, into the gel materials studied here indicates that a scaled, engineered system can be designed so that it is passive; that is, minimal (human) intervention and risk would be involved in encapsulating LLW species. In addition, the gel materials hold potential significance in environmental remediation of and recovery of metallic cations identified in respective domains and physico-chemical processes. In brief, silica gels start as aqueous/liquid solutions of base catalyzed silica hydrogels and metal ions (targeted species), such as silver. The metal ions are reduced radiolytically and migrate through the solution to form clusters. Upon post-irradiation processing, aerogel monoliths, extremely lightweight but mechanically strong, that encapsulate the metals are produced. Interestingly the radiolytic or photonic source can be gamma-rays and/or other rays from ''artificial sources'', such as reactors, or ''inherent sources'' like those characterizing mixed waste. Polymer gels, in contrast exhibit thermally-induced volumetric contraction at 20-50 C by expelling water from the gels physical state. Further, some functional groups that capture di- or tri-valent cations from aqueous solutions can be incorporated into the polymer networks on synthesis, including by radiolytic means. These polymer gels retain cations after volumetric contraction and have the ability to trap solid particulates in liquid waste streams. With both silica and polymer gels, functional design of a prototypic ''recovery'' systems, such as by natural convection in a rectangular cell, appears possible. Additional and specific details are provided in the rest of this Final Report.